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  • 1.
    Abrikosov, Igor A.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Steneteg, Peter
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Hultberg, Lasse
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Yu Mosyagin, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Department of Theoretical Physics and Quantum Technologies, National Research, Technological University MISiS, Moscow, Russia.
    Lugovskoy, Andrey V.
    Department of Theoretical Physics and Quantum Technologies, National Research, Technological University MISiS, Russia.
    Barannikova, Svetlana A.
    Institute of Strength Physics and Materials Science, Siberian Branch of Russian Academy of Science, Tomsk, Russia; Department of Physics and Engineering, Tomsk State University, Tomsk, Russia.
    Finite Temperature, Magnetic, and Many-Body Effects in Ab Initio Simulations of Alloy Thermodynamics2013In: TMS2013 Supplemental Proceedings, John Wiley & Sons, 2013, p. 617-626Chapter in book (Refereed)
    Abstract [en]

    Ab initio electronic structure theory is known as a useful tool for prediction of materials properties. However, majority of simulations still deal with calculations in the framework of density functional theory with local or semi-local functionals carried out at zero temperature. We present new methodological solution.s, which go beyond this approach and explicitly take finite temperature, magnetic, and many-body effects into account. Considering Ti-based alloys, we discuss !imitations of the quasiharmonic approximation for the treatment of lattice vibrations, and present an accurate and easily extendable method to calculate free ,energies of strongly anharmonic solids. We underline the necessity to going beyond the state-of-the-art techniques for the determination of effective cluster interactions in systems exhibiting mctal-to-insulator transition, and describe a unified cluster expansion approach developed for this class of materials. Finally, we outline a first-principles method, disordered local moments molecular dynamics, for calculations of thermodynamic properties of magnetic alloys, like Cr1-x,.AlxN, in their high-temperature paramagnetic state. Our results unambiguously demonstrate importance of finite temperature effects in theoretical calculations ofthermodynamic properties ofmaterials.

  • 2.
    Adegoke, Olutayo
    et al.
    Univ West, Sweden.
    Polisetti, Satyanarayana Rao
    Univ West, Sweden.
    Xu, Jinghao
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Andersson, Joel
    Univ West, Sweden.
    Brodin, Hakan
    Siemens Ind Turbomachinery, Sweden.
    Pederson, Robert
    Univ West, Sweden.
    Harlin, Peter
    Univ West, Sweden; Sandvik Addit Mfg, Sweden.
    Influence of laser powder bed fusion process parameters on the microstructure of solution heat-treated nickel-based superalloy Alloy 247LC2022In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 183, article id 111612Article in journal (Refereed)
    Abstract [en]

    In this study, Alloy 247LC samples were built with different laser powder bed fusion (L-PBF) process parameters. The samples were then subjected to solution heat treatment at 1260 degrees C for 2 h. The grain size of all the samples increased significantly after the heat treatment. The relationship between the process parameters and grain size of the samples was investigated by performing a design of experiment analysis. The results indicated that the laser power was the most significant process parameter that influenced the grain height and aspect ratio. The laser power also significantly influenced the grain width. The as-built and as-built + heat-treated samples with high, medium, and low energy densities were characterized using a field emission gun scanning electron microscope equipped with an electron backscatter diffraction detector. The micrographs revealed that the cells present in the as-built samples disappeared after the heat treatment. Isolated cases of twinning were observed in the grains of the as-built + heat-treated samples. The disappearance of cells, increase in the grain size, and appearance of twins suggested that recrystallization occurred in the alloy after the heat treatment. The occurrence of recrystallization was confirmed by analyzing the grain orientation spread of the alloy, which was lower and more predominantly <1 degrees in the as-built + heat-treated conditions than in the as-built conditions. The microhardness of the as-built + heat-treated samples were high which was plausible because gamma precipitates were observed in the samples. However, the L-PBF process parameters had a very low correlation with the microhardness of the as-built + heat-treated samples.

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  • 3.
    Almyras, Georgios
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr Univ Bochum, Germany.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System2019In: Materials, E-ISSN 1996-1944, Vol. 12, no 2, article id 215Article in journal (Refereed)
    Abstract [en]

    We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1-xAlxN (0 x 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the models predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of approximate to 40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1-xAlxN (0 amp;lt; x amp;lt; 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.

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  • 4.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Jaladurgam, Nitesh Raj
    Chalmers Univ Technol, Sweden.
    Kumara, Chamara
    Univ West, Sweden.
    Hansson, Thomas
    Univ West, Sweden; GKN Aerosp Sweden AB, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Univ West, Sweden.
    Gardstam, Johannes
    Qunitus Technol AB, Sweden.
    Pederson, Robert
    Univ West, Sweden.
    On the Microstructure of Laser Beam Powder Bed Fusion Alloy 718 and Its Influence on the Low Cycle Fatigue Behaviour2020In: Materials, E-ISSN 1996-1944, Vol. 13, no 22, article id 5198Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing of Alloy 718 has become a popular subject of research in recent years. Understanding the process-microstructure-property relationship of additively manufactured Alloy 718 is crucial for maturing the technology to manufacture critical components. Fatigue behaviour is a key mechanical property that is required in applications such as gas turbines. Therefore, in the present work, low cycle fatigue behaviour of Alloy 718 manufactured by laser beam powder bed fusion process has been investigated. The material was tested in as-built condition as well as after two different thermal post-treatments. Three orientations with respect to the building direction were tested to evaluate the anisotropy. Testing was performed at room temperature under controlled amplitudes of strain. It was found that defects, inclusions, strengthening precipitates, and Youngs modulus influence the fatigue behaviour under strain-controlled conditions. The strengthening precipitates affected the deformation mechanism as well as the cycle-dependent hardening/softening behaviour. The defects and the inclusions had a detrimental effect on fatigue life. The presence of Laves phase in LB-PBF Alloy 718 did not have a detrimental effect on fatigue life. Youngs modulus was anisotropic and it contributed to the anisotropy in strain-life relationship. Pseudo-elastic stress vs. fatigue life approach could be used to handle the modulus-induced anisotropy in the strain-life relationship.

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  • 5.
    Balachandramurthi, Arun Ramanathan
    et al.
    Univ West, Sweden.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Univ West, Sweden.
    Dixit, Nikhil
    Univ West, Sweden.
    Deng, Dunyong
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Pederson, Robert
    Univ West, Sweden.
    Microstructural influence on fatigue crack propagation during high cycle fatigue testing of additively manufactured Alloy 7182019In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 149, p. 82-94Article in journal (Refereed)
    Abstract [en]

    A study of the microstructure of additively manufactured Alloy 718 was performed in order to better understand the parameters that have an influence on the fatigue properties of the material. The specimens were manufactured using two powder bed fusion techniques - Electron Beam Melting (EBM) and Selective Laser Melting (SLM). Four point bending fatigue tests were performed at room temperature with a stress ratio of R = 0.1 and 20 Hz frequency, on material that was either in hot isostatically pressed (HIP) and solution treated and aged (STA) condition or in STA condition without a prior HIP treatment. The grains in the SLM material in the HIP + STA condition have grown considerably both in the hatch and the contour regions; EBM material, in contrast, shows grain growth only in the contour region. Fractographic analysis of the specimens in HIP + STA condition showed a faceted appearance while the specimens in STA condition showed a more planar crack appearance. The crack propagation occurred in a transgranular mode and it was found that precipitates such as NbC, TiN or 8-phase, when present, did not affect the crack path. The areas with larger grains corresponded to the faceted appearance of the fracture surface. This could be attributed to the plastic zone ahead of the crack tip being confined within one grain, in case of the larger grains, which promotes single shear crack growth mode.

  • 6. Order onlineBuy this publication >>
    Barrirero, Jenifer
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Department of Material Science, Saarland University, Saarbrücken, Germany.
    Eutectic Modification of Al-Si casting alloys2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Aluminum alloys with silicon as the major alloying element are the most widely used aluminum casting alloys. The eutectic phase in these alloys is formed by hard and brittle silicon plates in an aluminum matrix. Such silicon plates can act as crack propagation paths deteriorating the toughness of the material. To enhance ductility, silicon can be modified to a coral-like microstructure by addition of a modifying agent. Amongst the elements proposed as modifiers, only strontium, sodium and europium induce a plate-tocoral transition, while others such as ytterbium, only refine the silicon plates. The exact mechanism for the remarkable plate-to-coral change, and the reason why certain elements only refine the structure, is still not completely understood.

    In this investigation, atom probe tomography and transmission electron microscopy were used to analyze and compare the crystal structure and the distribution of solute atoms in silicon at the atomic level. An unmodified alloy and alloys modified by strontium, sodium, europium and ytterbium were studied. Elements inducing silicon plate-to-coral transition were found to contain nanometer sized clusters at the defects in silicon with stoichiometries corresponding to compounds formed at the ternary eutectic reaction of each system. In contrast, the addition of ytterbium, that only refines the silicon plates, is unable to form clusters in silicon. We propose that the formation of ternary compound clusters AlSiNa, Al2Si2Sr and Al2Si2Eu at the silicon / liquid interface during solidification restrict silicon growth. The formation of clusters on silicon facets create growth steps and increase growth direction diversity. The incorporation of clusters in silicon explains the high density of crystallographic defects and the structural modification from plates to corals.

    The parallel lattice plane-normals 011Si // 0001Al2Si2Eu, 011Si // 610Al2Si2Eu and 111Si // 610Al2Si2Eu were found between Al2Si2Eu and silicon, and absent between Al2Si2Yb and silicon. We propose a favorable heterogeneous formation of Al2Si2Eu on silicon. The misfit between 011Si and 0002Al2Si2X interplanar spacings shows a consistent trend with the potency of modification for several elements such as strontium, sodium, europium, calcium, barium, ytterbium and yttrium.

    List of papers
    1. Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
    Open this publication in new window or tab >>Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
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    2014 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 611, p. 410-421Article in journal (Refereed) Published
    Abstract [en]

    The mechanical properties of Al-7 wt.% Si can be enhanced by structural modifications of its eutectic phase. Addition of low concentrations of certain elements, in this case 150 wt-ppm Sr, is enough to cause a transition from a coarse plate-like Si structure to a finer coralline one. To fully understand the operating mechanism of this modification, the composition of the eutectic Si phase in unmodified and Sr-modified alloys was analysed and compared by atom probe tomography and (scanning) transmission electron microscopy. The unmodified alloy showed nanometre sized Al-segregations decorating defects, while the Sr-modified sample presented three types of Al-Sr segregations: (1) rod-like segregations that promote smoothening of the Al-Si boundaries in the eutectic phase, (2) particle-like segregations comparable to the ones seen in the unmodified alloy, and (3) planar segregations favouring the formation of twin boundaries. Al and Sr solubilities in Si after solidification were determined to be 430 +/- 160 at-ppm and 40 +/- 10 at-ppm, respectively. Sr predominantly segregates to the Si phase confirming its importance in the modification of the eutectic growth.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Aluminium-silicon alloys; Strontium modification; Atom probe tomography; Transmission electron microscopy; Microstructure
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-109356 (URN)10.1016/j.jallcom.2014.05.121 (DOI)000338932400064 ()
    Available from: 2014-08-15 Created: 2014-08-15 Last updated: 2020-03-19Bibliographically approved
    2. Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
    Open this publication in new window or tab >>Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
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    2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 117, p. 16-19Article in journal (Refereed) Published
    Abstract [en]

    Atom probe tomography was used to compare Na and Sr modified Al-Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 +/- 0.46 and an Al:Na ratio of 1.07 +/- 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at the Si/liquid interface and take part in the modification process by altering the eutectic Si growth.

    Place, publisher, year, edition, pages
    PERGAMON-ELSEVIER SCIENCE LTD, 2016
    Keywords
    Eutectic solidification; Atom probe tomography; Aluminium alloys; Eutectic modification; Transmission electron microscopy
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-127548 (URN)10.1016/j.scriptamat.2016.02.018 (DOI)000373547500004 ()
    Note

    Funding Agencies|German Federal Ministry of Economics and Technology [AiF 17204 N]; European Regional Development Fund (AME-Lab) [C/4-EFRE-13/2009/Br]; German Research Foundation (DFG); Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Doctoral Programme DocMASE of the European Commission [FPA 2011-0020]; VINNOVA Strategic Faculty Grant VINNMER Marie Curie Chair [2011-03464]; Major International (Regional) Joint Research Project from China [51420105005]

    Available from: 2016-05-04 Created: 2016-05-03 Last updated: 2020-03-19
    3. Eutectic modification by ternary compound cluster formation in Al-Si alloys
    Open this publication in new window or tab >>Eutectic modification by ternary compound cluster formation in Al-Si alloys
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    2019 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, article id 5506Article in journal (Refereed) Published
    Abstract [en]

    Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

    Place, publisher, year, edition, pages
    NATURE PUBLISHING GROUP, 2019
    National Category
    Metallurgy and Metallic Materials
    Identifiers
    urn:nbn:se:liu:diva-156563 (URN)10.1038/s41598-019-41919-2 (DOI)000462990000048 ()30940873 (PubMedID)
    Note

    Funding Agencies|European Regional Development Fund (ERDF); DFG; Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Programme of the European Commission within the Doctoral Programme DocMASE; Major International (Regional) Joint Research Project from China [51420105005]; Overseas, Hong Kong, Macao Scholars Cooperative Research Fund from China [51728101]

    Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2022-09-15
    4. Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition
    Open this publication in new window or tab >>Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition
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    2015 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 46, no 3, p. 1300-1311Article in journal (Refereed) Published
    Abstract [en]

    Al-5 wt pct Si-based alloys with Na additions (19 and 160 ppm) have been produced by controlled sand casting and melt spinning. Entrained droplet technique and differential scanning calorimetry were employed to investigate the nucleation behavior of eutectic Si. High-resolution transmission electron microscopy and atom probe tomography were used to investigate the distribution of Na atoms within eutectic Si and at the interfaces between eutectic Si and eutectic Al. It was found that (i) only 19 ppm Na addition results into a high undercooling (49 K (49 °C)) of the entrained eutectic droplet. However, further increasing Na addition up to 160 ppm exerts no positive effect on the nucleation of eutectic Si, instead a decreased undercooling (29 K (29 °C)) was observed. (ii) Na addition suppresses the growth of eutectic Si due to the Na segregation at the interface between eutectic Si and eutectic Al, and (iii) Na addition promotes significant multiple Si twins, which can be attributed to the proposed adsorption of Na atoms at the intersection of Si twins and along the 〈112〉Si growth direction of Si. The present investigation demonstrates, for the first time, a direct observation on the distribution of Na atoms within eutectic Si and thereby provides strong experimental supports to the well-accepted impurity-induced twinning growth mechanism and poisoning of the twin plane re-entrant edge growth mechanism.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-160234 (URN)10.1007/s11661-014-2702-6 (DOI)
    Available from: 2019-09-12 Created: 2019-09-12 Last updated: 2019-09-13
    5. Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography
    Open this publication in new window or tab >>Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography
    2019 (English)In: Praktische metallographie, ISSN 0032-678X, E-ISSN 2195-8599, Vol. 56, no 2, p. 76-90Article in journal (Refereed) Published
    Abstract [en]

    We present how the conventional focused ion beam (FIB) lift-out method can be modified to obtain phase selective specimens for atom probe tomography (APT). The modified method combines selective deep etching with site-specific lift-out using a micromanipulator in a FIB/SEM workstation. This method is used for phase-selective sample preparation in alloys with complex microstructures such as the coral- and plate-like silicon structures in the eutectic phase of Al-Si castings. The method proves to be both, practical and robust, with a high success rate of high-quality phase-specific APT specimens.

    Place, publisher, year, edition, pages
    CARL HANSER VERLAG, 2019
    National Category
    Analytical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-154847 (URN)10.3139/147.110557 (DOI)000458507500002 ()
    Note

    Funding Agencies|EU; DFG; Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Programme of the European Commission within the Doctoral Programme DocMASE

    Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-09-13
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  • 7.
    Barrirero, Jenifer
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany.
    Pauly, C.
    Saarland Univ, Germany.
    Engstler, M.
    Saarland Univ, Germany.
    Ghanbaja, J.
    Univ Lorraine, France.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Li, J.
    Univ Leoben, Austria.
    Schumacher, P.
    Univ Leoben, Austria.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Muecklich, F.
    Saarland Univ, Germany.
    Eutectic modification by ternary compound cluster formation in Al-Si alloys2019In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, article id 5506Article in journal (Refereed)
    Abstract [en]

    Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

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  • 8.
    Berntsson, Fredrik
    et al.
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Wikström, Patrik
    SSAB Europe, Sweden.
    Thermal tracking of a ladle during production cycles2023In: International Journal for Computational Methods in Engineering Science and Mechanics, ISSN 1550-2287, E-ISSN 1550-2295, Vol. 24, no 6, p. 406-416Article in journal (Refereed)
    Abstract [en]

    Temperature control is important for the steel making process. Knowledge of the amount of thermal energy stored in the ladle allows for better predictions of the steel temperature during the process. This has a potential to improve the quality of the steel. In this work, we present a mathematical model of the heat transfer within a ladle during the production process. The model can be used to compute the current, and also the future, thermal status of the ladle. The model is simple and can be solved efficiently. We also present results from numerical simulations intended to illustrate the model.

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  • 9.
    Bi, Yanyan
    et al.
    Sandvik Int Trading, Peoples R China.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Mat Technology, Sweden.
    Forsberg, Urban
    Sandvik Mat Technology, Sweden.
    Darkey, Glenn
    Sandvik Int Trading, Peoples R China.
    Investigation of cold-forming properties of Sanicro 25-a potential candidate for superheater and reheaters in high efficiency A-USC fossil power plants2017In: PROCEEDINGS OF THE ASME POWER CONFERENCE JOINT WITH ICOPE-17, 2017, VOL 1, AMER SOC MECHANICAL ENGINEERS , 2017, article id UNSP V001T01A008Conference paper (Refereed)
    Abstract [en]

    Sanicro 25 material is approved for use in pressure vessels and boilers according AMSE code case 2752, 2753 and VdTuN blatt 555. It shows good resistance to steam oxidation and flue gas corrosion, and has higher creep rupture strength than any other austenitic stainless steels available today. It is a candidate material for superheater and reheaters, enabling higher steam parameters of up to about 650 degrees C steam (ie about max 700 degrees C metal) without the need for expensive nickel based alloys. The effect of cold-forming on time and temperature-dependent deformation and strength behavior has been examined in a comprehensive study. The objective was to determine the maximum allowable degree of cold-forming to be used without additional heat treatment. The findings of these investigations indicate that the maximum allowed cold deformation could be possible to increase from todays maximum 20 % (VdTuV 555), 15 % (540-675 degrees C) and 10 % (higher than 675 degrees C) respectively (ASME 2011a Sect I PG19). A solution annealing after the cold bending will recover creep ductility but will also at the same time increase manufacturing costs. Higher allowed degree of cold-forming without the need for post bend heat treatments, would allow for more narrow bending radii and thereby a more compact construction that would result in a significant decrease in production costs. This paper presents the findings in the mentioned study and is to be a background for possible coming discussions with involved entities on a revision of the max allowed deformation of this material without the need for solution annealing.

  • 10.
    Brandtberg, Sebastian
    Linköping University, Department of Management and Engineering, Engineering Materials.
    Microstructural inhomogeneity and anisotropicproperties in IN-718 structures fabricated byElectron Beam Melting: Mikrostrukturell inhomogenitet och anisotropa egenskaper i strukturerav IN-718 tillverkade genom Electron Beam Melting2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Additive Manufacturing, or 3D printing, provides an opportunity to manufacture advanced 3D geometrieswith little material waste and reduced need for tooling compared to conventional methods. There are,however, challenges remaining regarding anisotropy in the mechanical properties of built components.

    The aim of this project is to investigate the anisotropy of additive manufactured material and the effect ofdifferent build directions. The material used is Inconel 718, which was manufactured by Electron BeamMelting as vertical and horizontal rods. The tests performed are microstructural investigations about thegrains, precipitates and porosities, but also include hardness testing and tensile testing. The material istested in its as-built state.

    The results show that the material consist of an anisotropic microstructure with elongated grains in thebuild direction. The build height has a bigger influence on the properties of the material than the builddirection for the specimens. The top pieces are consistently different from the others and are the leasthomogeneous. The microstructure consists of large quantities of delta-phase, and solidification pores arefound throughout the material. The hardness of the material differs from 324 HV to 408 HV depending onthe part of the build. The tensile testing shows that the vertically built specimens have a higher yieldstrength and ultimate tensile strength while the horizontally built specimens have a greater ductility.

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    Microstructural inhomogeneity and anisotropic
  • 11. Order onlineBuy this publication >>
    Calmunger, Mattias
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    On High-Temperature Behaviours of Heat Resistant Austenitic Alloys2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Advanced heat resistant materials are important to achieve the transition to long term sustainable power generation. The global increase in energy consumption and the global warming from greenhouse gas emissions create the need for more sustainable power generation processes. Biomass-fired power plants with higher efficiency could generate more power but also reduce the emission of greenhouse gases, e.g. CO2. Biomass offers no net contribution of CO2 to the atmosphere. To obtain greater efficiency of power plants, one option is to increase the temperature and the pressure in the boiler section of the power plant. This requires improved material properties, such as higher yield strength, creep strength and high-temperature corrosion resistance, as well as structural integrity and safety.

    Today, some austenitic stainless steels are design to withstand temperatures up to 650 °C in tough environments. Nickel-based alloys are designed to withstand even higher temperatures. Austenitic stainless steels are more cost effective than nickel-based alloys due to a lower amount of expensive alloying elements. However, the performance of austenitic stainless steels at the elevated temperatures of future operation conditions in biomass-red power plants is not yet fully understood.

    This thesis presents research on the influence of long term high-temperature ageing on mechanical properties, the influence of very slow deformation rates at high-temperature on deformation, damage and fracture, and the influence of high-temperature environment and cyclic operation conditions on the material behaviour. Mechanical and thermal testing have been performed followed by subsequent studies of the microstructure, using scanning electron microscopy, to investigate the material behaviours.

    Results shows that long term ageing at high temperatures leads to the precipitation of intermetallic phases. These intermetallic phases are brittle at room temperature and become detrimental for the impact toughness of some of the austenitic stainless steels. During slow strain rate tensile deformation at elevated temperature time dependent deformation and recovery mechanisms are pronounced. The creep-fatigue interaction behaviour of an austenitic stainless steel show that dwell time gives shorter life at a lower strain range, but has none or small effect on the life at a higher strain range.

    Finally, this research results in an increased knowledge of the structural, mechanical and chemical behaviour as well as a deeper understanding of the deformation, damage and fracture mechanisms that occur in heat resistant austenitic alloys at high-temperature environments. It is believed that in the long term, this can contribute to material development achieving the transition to more sustainable power generation in biomass-red power plants.

    List of papers
    1. Long Term High-Temperature Environmental Effect on Impact Toughness in Austenitic Alloys
    Open this publication in new window or tab >>Long Term High-Temperature Environmental Effect on Impact Toughness in Austenitic Alloys
    2015 (English)In: / [ed] Key Engineering Materials Vol 627 (2015),pp 205-208., 2015, p. 205-308Conference paper, Published paper (Refereed)
    Series
    KEY ENGINEERING MATERIALS, ISSN 1662-9795 ; 627
    Keywords
    high-temperature environment, precipitation, impact toughness, austenitic stainless steel, nickel-base alloy
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-109512 (URN)10.4028/www.scientific.net/KEM.627.205 (DOI)
    Conference
    13th International Conference on Fracture and Damage Mechanics, Azorerna, 23-25 September 2014
    Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2018-03-09
    2. Damage and Fracture Behaviours in Aged Austentic Materials During High-Temperature Slow Strain Rate Testing
    Open this publication in new window or tab >>Damage and Fracture Behaviours in Aged Austentic Materials During High-Temperature Slow Strain Rate Testing
    2014 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Biomass power plants with high efficiency are desired as a renewable energy resource. High efficiency can be obtained by increasing temperature and pressure. An upgrade of the material performance to high temperature material is therefore required in order to meet the increased demands due to the higher temperature and the more corrosive environment. In this study, the material’s high-temperature behaviours of AISI 304 and Alloy617 under slow deformation rate are evaluated using high-temperature long-term aged specimens subjected to slow strain rate tensile testing (SSRT) with strain rates down to 10-6/s at 700°C. Both materials show decreasing stress levels and elongation to fracture when tensile deformed using low strain rate and elevated temperature. At high-temperature and low strain rates cracking in grain boundaries due to larger precipitates formed during deformation is the most common fracture mechanism.

    Place, publisher, year, edition, pages
    Trans Tech Publications Inc., 2014
    Series
    Key Engineering Materials, ISSN 1662-9795
    Keywords
    High-temperature, ageing, slow strain rate, biomass power plant, austenitic stainless steel, nickel base alloy and dynamic strain ageing
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-96028 (URN)10.4028/www.scientific.net/KEM.592-593.590 (DOI)000336694400133 ()
    Conference
    MSMF7 Materials Structure & Micromechanics of Fracture , July 13, Brno, Czech Republic
    Available from: 2013-08-13 Created: 2013-08-13 Last updated: 2015-11-30Bibliographically approved
    3. Advanced Microstructure Studies of an Austenitic Material Using EBSD in Elevated Temperature In-Situ Tensile Testing in SEM
    Open this publication in new window or tab >>Advanced Microstructure Studies of an Austenitic Material Using EBSD in Elevated Temperature In-Situ Tensile Testing in SEM
    Show others...
    2014 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    In this study an advanced method for investigation of the microstructure such as electron backscatter diffraction (EBSD) together with in-situ tensile test in a scanning electron microscope (SEM) has been used at room temperature and 300°C. EBSD analyses provide information about crystallographic orientation in the microstructure and dislocation structures caused by deformation. The in-situ tensile tests enabled the same area to be investigated at different strain levels. For the same macroscopic strain values a lower average misorientation in individual grains at elevated temperature indicates that less residual strain at grain level are developed compared to room temperature. For both temperatures, while large scatters in grain average misorientation are observed for grains of similar size, there seems to be a tendency showing that larger grains may accumulate somewhat more strains.

    Place, publisher, year, edition, pages
    Trans Tech Publications Inc., 2014
    Series
    Key Engineering Materials, ISSN 1662-9795
    Keywords
    Austenitic stainless steel, electron backscatter diffraction, in-situ tensile test, Schmid factor, grain wsize and slip system
    National Category
    Engineering and Technology Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-97015 (URN)10.4028/www.scientific.net/KEM.592-593.497 (DOI)000336694400111 ()
    Conference
    MSMF7 Materials Structure & Micromechanics of Fracture, July 1-3, Brno, Czech Republic
    Available from: 2013-09-03 Created: 2013-09-03 Last updated: 2015-11-30Bibliographically approved
    4. Mechanical Behaviours of Alloy 617 with Varied Strain Rate at High Temperatures
    Open this publication in new window or tab >>Mechanical Behaviours of Alloy 617 with Varied Strain Rate at High Temperatures
    2014 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 783-786, p. 1182-1187Article in journal (Refereed) Published
    Abstract [en]

    Nickel-base alloys due to their high performances have been widely used in biomass and coal fired power plants. They can undertake plastic deformation with different strain rates such as those typically seen during creep and fatigue at elevated temperatures. In this study, the mechanical behaviours of Alloy 617 with strain rates from 10-2/s down to 10-6/s at temperatures of 650°C and 700°C have been studied using tensile tests. Furthermore, the microstructures have been investigated using electron backscatter detection and electron channeling contrast imaging. At relatively high strain rate, the alloy shows higher fracture strains at these temperatures. The microstructure investigation shows that it is caused by twinning induced plasticity due to DSA. The fracture strain reaches the highest value at a strain rate of 10-4/s and then it decreases  dramatically. At strain rate of 10-6/s, the fracture strain at high temperature is now smaller than that at room temperature, and the strength also decreases with further decreasing strain rate. Dynamic recrystallization can also be observed usually combined with crack initiation and propagation. This is a new type of observation and the mechanisms involved are discussed.

    Keywords
    Nickel-base superalloy, twinning, Dynamic strain ageing, elevated temperature
    National Category
    Engineering and Technology Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-98241 (URN)10.4028/www.scientific.net/MSF.783-786.1182 (DOI)
    Conference
    THERMEC '2013, International Conference on Processing & Manufacturing of Advanced Materials. Processing, Fabrication, Properties, Applications. December 2-6, Las Vegas, USA
    Available from: 2013-10-04 Created: 2013-10-04 Last updated: 2017-12-06Bibliographically approved
    5. Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature
    Open this publication in new window or tab >>Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature
    2014 (English)In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 4, no 041004Article in journal (Refereed) Published
    Abstract [en]

    In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650°C.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2014
    Keywords
    dynamic strain ageing, slow strain rate tensile testing, fracture, damage
    National Category
    Materials Engineering Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-109511 (URN)10.1063/2.1404104 (DOI)
    Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2017-12-05Bibliographically approved
    6. Characterization of austenitic stainless steels deformed at elevated temperature
    Open this publication in new window or tab >>Characterization of austenitic stainless steels deformed at elevated temperature
    Show others...
    2017 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, no 10, p. 4525-4538Article in journal (Refereed) Published
    Abstract [en]

    Highly alloyed austenitic stainless steels are promising candidates to replace more expansive nickel-based alloys within the energy-producing industry. The present study investigates the deformation mechanisms by microstructural characterisation, mechanical properties and stress-strain response of three commercial austenitic stainless steels and two commercial nickel-based alloys using uniaxial tensile tests at elevated temperatures from 400 C up to 700 C. The materials showed different influence of temperature on ductility, where the ductility at elevated temperatures increased with increasing nickel and solid solution hardening element content. The investigated materials showed planar dislocation driven deformation at elevated temperature. Scanning electron microscopy showed that deformation twins were an active deformation mechanism in austenitic stainless steels during tensile deformation at elevated temperatures up to 700 C.

    Place, publisher, year, edition, pages
    Springer-Verlag New York, 2017
    Keywords
    Austenitic stainless steel, Nickel-based alloy, Microstructural characterization, Deformation twinning, Stress-strain response
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-122942 (URN)10.1007/s11661-017-4212-9 (DOI)000408884300012 ()
    Note

    Previous status of this publication was manuscript

    Funding agencies: AB Sandvik Materials Technology in Sweden; Swedish National Energy Administration through the Research Consortium of Materials Technology for Thermal Energy Processes [KME-701]; AFM Strategic Faculty Grant SFO-MAT-LiU at Linkoping University [2009-00971]

    Available from: 2015-11-30 Created: 2015-11-30 Last updated: 2017-09-22Bibliographically approved
    7. Characterisation of creep deformation during slow strain rate tensile testing
    Open this publication in new window or tab >>Characterisation of creep deformation during slow strain rate tensile testing
    2015 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The strain-rate dependent deformation of the superalloy Haynes 282 during slow strain-rate tensile testing (SSRT) at 700 C has been investigated. The stress-strain response is remarkably well described by a simple constitutive model over a wide range of different strain-rates. The microstructure development is characterised and related to the influence of both strainrate dependent and independent deformation. Damage and cracking similar to what has been observed previously during conventional creep testing of Haynes 282 was found and explained. The model and the microstructure investigations show that the deformation and damage mechanisms during SSRT are essentially the same as under creep.

    Keywords
    Slow strain-rate tensile testing, Creep, Norton equation, Constitutive modelling, Cavity
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-122943 (URN)
    Available from: 2015-11-30 Created: 2015-11-30 Last updated: 2015-11-30Bibliographically approved
    8. Creep and Fatigue Interaction Behavior in Sanicro 25 Heat Resistant Austenitic Stainless Steel
    Open this publication in new window or tab >>Creep and Fatigue Interaction Behavior in Sanicro 25 Heat Resistant Austenitic Stainless Steel
    2016 (English)In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 69, no 2, p. 337-342Article in journal (Refereed) Published
    Abstract [en]

    Sanicro 25 is a newly developed advanced high strength heat resistant austenitic stainless steel. The material shows good resistance to steam oxidation and flue gas corrosion, and has higher creep rupture strength than other austenitic stainless steels available today. It is thus an excellent candidate for superheaters and reheaters for advanced ultra-super critical power plants with efficiency higher than 50 %. This paper provides a study on the creep–fatigue interaction behavior of Sanicro 25 at 700 °C. Two strain ranges, 1 and 2 %, and two dwell times, 10 and 30 min, were used. The influences of dwell time on the cyclic deformation behavior and life has been evaluated. Due to stress relaxation the dwell time causes a larger plastic strain range compared to the tests without dwell time. The results also show that the dwell time leads to a shorter fatigue life for the lower strain range, but has no or small effect on the life for the higher strain range. Fracture investigations show that dwell times result in more intergranular cracking. With the use of the electron channeling contrast imaging technique, the influences of dwell time on the cyclic plastic deformation, precipitation behavior, recovery phenomena and local plasticity exhaustion have also been studied.

    Place, publisher, year, edition, pages
    Springer, 2016
    Keywords
    Sanicro 25, advanced ultra-super critical power plant, creep, low cycle fatigue, cyclic plastic deformation
    National Category
    Metallurgy and Metallic Materials
    Identifiers
    urn:nbn:se:liu:diva-123646 (URN)10.1007/s12666-015-0806-3 (DOI)000368032700027 ()
    Conference
    7th International Conference on Creep, 19-22 January 2016, IGCAR, Kalpakkam, India
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Funding agencies: AB Sandvik Materials Technology in Sweden; Swedish National Energy Administration through the Research Consortium of Materials Technology for Thermal Energy Processes [KME-701]; AFM Strategic Faculty Grant SFO-MAT-LiU at Linkoping University [2009-00971]

    Available from: 2016-01-04 Created: 2016-01-04 Last updated: 2017-12-01
    9. Surface Phase Transformation in Austenitic Stainless Steel Induced by Cyclic Oxidation in Humidified Air
    Open this publication in new window or tab >>Surface Phase Transformation in Austenitic Stainless Steel Induced by Cyclic Oxidation in Humidified Air
    Show others...
    2015 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 100, p. 524-534Article in journal (Refereed) Published
    Abstract [en]

    The formation of α’ martensite at the surface of an AISI 304 stainless steel subjected to cyclic heating in humidified air is reported. The α’ martensite formed during the cooling part of the cyclic tests due to local depletion of Cr and Mn and transformed back to austenite when the temperature again rose to 650 °C. The size of the α’ martensite region increased with increasing number of cycles. Thermodynamical simulations were used as basis for discussing the formation of α’ martensite. The effect of the α’ martensite on corrosion is also discussed.

    Place, publisher, year, edition, pages
    Pergamon Press, 2015
    Keywords
    Stainless steel, thermal cycling, SEM, oxidation, high temperature corrosion
    National Category
    Metallurgy and Metallic Materials
    Identifiers
    urn:nbn:se:liu:diva-122008 (URN)10.1016/j.corsci.2015.08.030 (DOI)000363070100049 ()
    Note

    Funding agencies: AB Sandvik Materials Technology in Sweden; Swedish National Energy Administration through the Research Consortium of Materials Technology for Thermal Energy Processes [KME-701]; Agora Materiae and AFM Strategic Faculty Grant SFO-MAT-LiU at Linkoping Unive

    Available from: 2015-10-15 Created: 2015-10-15 Last updated: 2017-12-01
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  • 12.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology,Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Creep and Fatigue Interaction Behavior in Sanicro 25 Heat Resistant Austenitic Stainless Steel2016In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 69, no 2, p. 337-342Article in journal (Refereed)
    Abstract [en]

    Sanicro 25 is a newly developed advanced high strength heat resistant austenitic stainless steel. The material shows good resistance to steam oxidation and flue gas corrosion, and has higher creep rupture strength than other austenitic stainless steels available today. It is thus an excellent candidate for superheaters and reheaters for advanced ultra-super critical power plants with efficiency higher than 50 %. This paper provides a study on the creep–fatigue interaction behavior of Sanicro 25 at 700 °C. Two strain ranges, 1 and 2 %, and two dwell times, 10 and 30 min, were used. The influences of dwell time on the cyclic deformation behavior and life has been evaluated. Due to stress relaxation the dwell time causes a larger plastic strain range compared to the tests without dwell time. The results also show that the dwell time leads to a shorter fatigue life for the lower strain range, but has no or small effect on the life for the higher strain range. Fracture investigations show that dwell times result in more intergranular cracking. With the use of the electron channeling contrast imaging technique, the influences of dwell time on the cyclic plastic deformation, precipitation behavior, recovery phenomena and local plasticity exhaustion have also been studied.

    Download full text (pdf)
    fulltext
  • 13.
    Calmunger, Mattias
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials.
    Eriksson, Robert
    Siemens AG, Huttenstr. 12, 10553 Berlin, Germany.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandviken, Sweden.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Phase Transformation in Austenitic Stainless Steel Induced by Cyclic Oxidation in Humidified Air2015In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 100, p. 524-534Article in journal (Refereed)
    Abstract [en]

    The formation of α’ martensite at the surface of an AISI 304 stainless steel subjected to cyclic heating in humidified air is reported. The α’ martensite formed during the cooling part of the cyclic tests due to local depletion of Cr and Mn and transformed back to austenite when the temperature again rose to 650 °C. The size of the α’ martensite region increased with increasing number of cycles. Thermodynamical simulations were used as basis for discussing the formation of α’ martensite. The effect of the α’ martensite on corrosion is also discussed.

    Download full text (pdf)
    fulltext
  • 14.
    Calmunger, Mattias
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Wärner, Hugo
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Alleima AB, Stragetic research, Sandviken, Sweden.
    Segersäll, Mikael
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Thermomechanical Fatigue of Heat Resistant Austenitic Alloys2023In: Procedia Structural Integrity, ISSN 2452-3216, Vol. 43, p. 130-135Article in journal (Refereed)
    Abstract [en]

    Rising global energy consumption and the increase in emissions of greenhouse gases (e.g. CO2) causing global warming, make need for more sustainable power generation. This could be accomplished by increasing the efficiency of the biomass-fired power plants, which is achieved by increasing the temperature and pressure. In addition, flexible generation of power is critical if only renewable power generation is to be achieved and this will increase the number of start-and stop cycles. Cyclic condition in a long-term high temperature environment is an operation process that such materials must withstand, in order to satisfy the needs for future power generation.

    Commonly austenitic stainless steel are used for critical components of power plants. Because of future change in operating conditions, further investigations are needed to verify that the demands on safety for cyclic long-term usage is fulfilled. This work includes investigation of two commercial austenitic steels: Esshete 1250 and Sanicro 25. The materials were exposed to thermomechanical fatigue (TMF) in strain control under In-Phase and Out-of-Phase conditions and main testing temperature ranges of 100-650°C and 100-800°C respectively. Some of the specimens were pre-aged to simulate prolonged service condition. Mechanical test data were obtained and analysed in order to define the TMF performance of the investigated alloys. The differences in performance were discussed in relation to mechanical and microstructural characterization.

  • 15.
    Ceschini, Lorella
    et al.
    Dept of Industrial Engineering (DIN), University of Bologa, Italy.
    Morri, Alessandro
    Dept of Industrial Engineering (DIN), University of Bologa, Italy.
    Morri, Andrea
    Industrial Research Centre for Advanced Mechanics and Materials, University of Bologna, Italy.
    Toschi, Stefania
    Dept of Industrial Engineering (DIN), University of Bologna, Italy.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Seifeddine, Salem
    Dept of Materials and Manufacturing, Jönköping University.
    Effect of Microstructure and Overaging on the Tensile Behavior at Room and Elevated Temperature of C355-T6 Cast Aluminum Alloy2015In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 83, p. 626-634Article in journal (Refereed)
    Abstract [en]

    The present study was focused on the microstructural and mechanical characterization of the Al–Si–Cu–Mg C355 alloy, at room and elevated temperature. In order to evaluate the influence of microstructural coarseness on mechanical behavior, samples with different Secondary Dendrite Arm Spacing (SDAS) (20–25 μm for fine microstructure and 50–70 μm for coarse microstructure), were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated at T6 condition and at T6 with subsequent high temperature exposure (41 h at 210 °C, i.e. overaging), both at room and elevated temperature (200 °C). Microstructural investigations were performed through optical and electron microscopy.

    The results confirmed the important role of microstructure on the tensile behavior of C355 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Larger SDAS, related to lower solidification rates, modify microstructural features, such as eutectic Si morphology and size of the intermetallic phases, which in turn influence elongation to failure. Overaging before tensile testing induced coarsening of the strengthening precipitates, as observed by STEM analyses, with consequent reduction of the tensile strength of the alloy, regardless of SDAS. A more sensible decrease of tensile properties was registered at 200 °C testing temperature.

  • 16.
    Ceschini, Lorella
    et al.
    Dept of Industrial Engineering (DIN), University of Bologa, Italy.
    Morri, Alessandro
    Dept of Industrial Engineering (DIN), University of Bologna, Italy.
    Toschi, Stefania
    Dept of Industrial Engineering (DIN), University of Bologna, Italy.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Seifeddine, Salem
    Dept of Materials and Manufacturing, Jönköping University.
    Microstructural and Mechanical Properties Characterization of Heat Treated and Overaged Cast A354 Alloy with Various SDAS at Room and Elevated Temperature2015In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 648, p. 340-349Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to carry out a microstructural and mechanical characterization of the A354 (Al–Si–Cu–Mg) cast aluminum alloy. The effect of microstructure on the tensile behavior was evaluated by testing samples with different Secondary Dendrite Arm Spacing, (SDAS) values (20–25 μm and 50–70 μm for fine and coarse microstructure, respectively), which were produced through controlled casting conditions. The tensile behavior of the alloy was evaluated both at room and elevated temperature (200 °C), in the heat treated and overaged (exposure at 210 °C for 41 h, after heat treatment) conditions. Optical, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) were used for microstructural investigations.

    Experimental data confirmed the significant role of microstructural coarseness on the tensile behavior of A354 alloy. Ultimate tensile strength and elongation to failure strongly increased with the decrease of SDAS. Moreover, solidification rate influenced other microstructural features, such as the eutectic silicon morphology as well as the size of the intermetallic phases, which in turn also influenced elongation to failure. Coarsening of the strengthening precipitates was induced by overaging, as observed by STEM analyses, thus leading to a strong reduction of the tensile strength of the alloy, regardless of SDAS. Tensile properties of the alloy sensibly decrease at elevated temperature (200 °C) in all the investigated heat treatment conditions.

  • 17.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Materials Technology,Sandviken, Sweden .
    Hernblom, Johan
    Sandvik Materials Technology,Sandviken, Sweden .
    Peltola, Timo
    Sandvik Materials Technology,Sandviken, Sweden .
    Forsberg, Urban
    Sandvik Materials Technology,Sandviken, Sweden .
    Creep Behavior in A Newly Developed Heat Resistant Austenitic Stainless Steel2015In: Berg- und Huttenmännische Monatshefte (BHM), ISSN 0005-8912, E-ISSN 1613-7531, Vol. 160, no 9, p. 400-405Article in journal (Refereed)
    Abstract [en]

    UNS S31035 austenitic stainless steel grade is a newly developed advanced heat resistant material for use in coal fired boilers at metal temperatures up to 700 °C. This new grade that has recently got two AMSE code cases shows good resistance to steam oxidation and flue gas corrosion and high creep rupture strength. This paper will mainly focus on the characterization of long term structure stability and performances such as the creep behaviors at different temperatures for up to 86,000 h at high temperatures. The creep damage mechanisms were studied using electron transmission microscopy, electron backscatter diffraction, and electron channeling contrast image analysis. The results show that the creep strength is related to the intragranular nano particles that act as obstacles for dislocation movements. Plastic deformation and transgranular fracture is the main creep fracture mechanism in the creep test samples of UNS S31035. The material has good creep ductility by formation of twins during the creep test. This material has been installed and tested in several European power plants, and has shown good performance. The material is an excellent alternative for superheaters and reheaters in future high-efficient coal fired boilers with design material temperatures up to 700 °C, instead of more costly nickel based alloy. 

  • 18.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Alleima AB, Sweden.
    Lautrup, L.
    Alleima AB, Sweden.
    Gustavsson, F.
    Swerim AB, Sweden; Vattenfall, Sweden.
    Extra-long creep rupture life of Alleima 3R60™ (316/316L) stainless steel2024In: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 41, no 1, p. 169-176Article in journal (Refereed)
    Abstract [en]

    Alleima 3R60 (TM) is an AISI 316/316 L type of stainless steel. This alloy shows extra-long creep lives. At 700 degrees C with an applied stress of 45 MPa, the specimen broke first after 240 131 hours, a 140% longer creep life than the predicted. The reasons have been studied using SEM/EDS, EBSD, ECCI and TEM. Two unexpected phenomena have been observed. One is the presence of homogeneously dispersed small Mo2Fe4CrSi(Ni-0.5)f063type of precipitates in the matrix. According to the thermodynamic calculation, this phase should not form in this alloy at 700 degrees C. The other is the fine grains formed in the matrix during the creep-testing at 700 degrees C for such an extra-long time. It is believed that both small precipitates and fine grain size contribute to this extra-long creep life of the steel. With the microstructural study and thermodynamic simulation, the mechanisms to form precipitates and fine grains have been discussed.

  • 19.
    Chai, Guocai
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Mat Technol, Sweden.
    Siriki, Raveendra
    Sandvik Mat Technol, Sweden.
    Nordström, Joakim
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Sandvik Mat Technol, Sweden.
    Dong, Zhihua
    KTH, Sweden; Chongqing Univ, Peoples R China.
    Vitos, Levente
    KTH, Sweden.
    Roles of Nitrogen on TWIP in Advanced Austenitic Stainless Steels2023In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 94, no 10, article id 2200359Article in journal (Refereed)
    Abstract [en]

    The influence of nitrogen on the mechanical properties of two high Ni containing advanced austenitic stainless steels with low stacking fault energies is investigated. The results show that increase of nitrogen content greatly increases both strength and elongation of the steel at the same time. At the cryogenic temperature, the steels show a twin induced plasticity behavior. Ab initio calculations indicate that the increase of nitrogen slightly increases the stacking fault energy and consequently the critical shear stress for twin initiation in the steel. However, addition of nitrogen significantly increases the flow stress. This leads to a smaller critical strain for twin initiation and promotes deformation twinning in the high nitrogen steel. This is confirmed by the microstructure investigation. Deformation in steels is a competitive process between slip and twinning. Dislocation slip is dominant at low strain range, but formation of stacking fault and twinning become important in the later stages of deformation. At cryogenic temperature, it is mainly deformation twinning. The influence of nitrogen addition on magnetic property and its effect on deformation twinning are also discussed. The present study increases the understanding for the development of high-performance and low-cost advanced austenitic stainless steels.

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  • 20.
    Chalapathi, Darshan
    et al.
    Laboratory for Mechanics of Microstructures, Department of Metallurgical and Materials Engineering, IIT Madras, Chennai, India.
    Nordström, Joakim
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Alleima, Sandviken, Sweden.
    Siriki, Raveendra
    Alleima, Sandviken, Sweden.
    Lautrup, Lisa
    Alleima, Sandviken, Sweden.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Alleima, Sandviken, Sweden.
    Kanjarla, Anand K.
    Laboratory for Mechanics of Microstructures, Department of Metallurgical and Materials Engineering, IIT Madras, Chennai, India.
    Deformation twinning and the role of stacking fault energy during cryogenic testing of Ni-based superalloy 6252024In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 898, article id 146404Article in journal (Refereed)
    Abstract [en]

    Ni-based superalloys play a crucial role in various high-temperature applications, where their exceptional mechanical properties and resistance to corrosion are highly desirable. However, their response to low temperatures, especially concerning strain hardening, microstructural evolution, and deformation mechanisms, requires further scrutiny. In this study, we investigate the influence of temperature on the stacking fault energy (SFE) and its implications on deformation twinning in Alloy 625. Uniaxial tensile tests are performed at 298 K, 173 K and 77 K. The study reveals a notable increase in strain hardening at intermediate strain levels, suggesting the activation of a secondary deformation mechanism. To gain deeper insights, crystal plasticity-based simulations using the DAMASK framework are employed, complementing the experimental outcomes. Deformation twins are consistently observed at all temperatures, albeit with a small volume fraction and thickness. The critical strain for twinning decreased with decreasing temperature. Based on the numerous literature studies, experimental and computational observations, the SFE of the material is estimated to be constant over the studied temperature range.

  • 21.
    Charalampopoulou, Evangelia
    et al.
    SCK CEN, Belgium; Univ Antwerp, Belgium.
    Lambrinou, Konstantina
    SCK CEN, Belgium; Univ Huddersfield, England.
    Van der Donck, Tom
    Katholieke Univ Leuven, Belgium.
    Paladino, Boris
    Ist Italiano Tecnol, Italy.
    Di Fonzo, Fabio
    Ist Italiano Tecnol, Italy.
    Azina, Clio
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mraz, Stanislav
    Rhein Westfal TH Aachen, Germany.
    Schneider, Jochen M.
    Rhein Westfal TH Aachen, Germany.
    Schryvers, Dominique
    Univ Antwerp, Belgium.
    Delville, Remi
    SCK CEN, Belgium.
    Early stages of dissolution corrosion in 316L and DIN 1.4970 austenitic stainless steels with and without anticorrosion coatings in static liquid lead-bismuth eutectic (LBE) at 500 degrees C2021In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 178, article id 111234Article in journal (Refereed)
    Abstract [en]

    This work addresses the early stages (<= 1000 h) of the dissolution corrosion behavior of 316L and DIN 1.4970 austenitic stainless steels in contact with oxygen-poor (C-O < 10(-8) mass%), static liquid lead-bismuth eutectic (LBE) at 500 degrees C for 600-1000 h. The objective of this study was to determine the relative early-stage resistance of the uncoated steels to dissolution corrosion and to assess the protectiveness of select candidate coatings (Cr2AlC, Al2O3, V2AlxCy). The simultaneous exposure of steels with intended differences in microstructure and thermomechanical state showed the effects of steel grain size, density of annealing/deformation twins, and secondary precipitates on the steel dissolution corrosion behavior. The findings of this study provide recommendations on steel manufacturing with the aim of using the steels to construct Gen-IV lead-cooled fast reactors.

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  • 22.
    Chen, Yu-Hsiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Rongström, L.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Ostach, D.
    HZG, Germany.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Johansson-Jöesaar, Mats P
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden.
    Schell, N.
    HZG, Germany.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Effects of decomposition route and microstructure on h-AlN formation rate in TiCrAlN alloys2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 691, p. 1024-1032Article in journal (Refereed)
    Abstract [en]

    The phase evolution of cubic (c), solid solution TixCr-0.37Al1-0.37-x N alloys with x = 0.03 and 0.16, and the kinetics of the hexagonal (h)-AlN formation are studied via in situ wide angle x-ray scattering experiments during high temperature (1000-1150 degrees C) annealing. Spinodal decomposition was observed in Ti0.16Cr0.36Al0.48N while Ti0.03Cr0.38Al0.59N decomposes through nucleation and growth of h-AlN, c-TiN and c-CrAlN. h-AlN is formed from c-CrAlN domains in both cases and the formation rate of h-AlN depends on the stability of the c-CrAlN domains. In Ti0.16Cr0.36Al0.48N, the c-CrAlN domains are stabilized by crystallographic coherency with the surrounding c-TiCrN in a microstructure originating from spinodal decomposition. This results in lower formation rates of h-AlN for this composition. These differences are reflected in higher activation energy for h-AlN formation in Ti0.16Cr0.36Al0.48N compared to Ti0.03Cr0.38Al0.59N. It also points out different stabilities of the intermediate phase c-CrAlN during phase decomposition of TiCrAlN alloys. Additional contributions to the low activation energy for formation of h-AlN in Ti0.03Cr0.38Al0.59N stems from precipitation at grain boundaries. (C) 2016 Elsevier B.V. All rights reserved.

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  • 23. Order onlineBuy this publication >>
    Chen, Zhe
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Surface Integrity and Fatigue Performance of Nickel-based Superalloys2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to global warming, the demand for more efficient gas turbines has increased. A way to achieve this, is by increasing the operating temperature of the gas turbine. Therefore, nickel-based superalloys have been developed to withstand these extreme temperatures and loads, especially in the hot sections. Today, the way of operating land-based gas turbines is changing. Instead of running for long periods of time, the operation is becoming more flexible, with ever-increasing cyclic loads and number of start and stop cycles. To handle the increased stress and cycles, component resistance to fatigue failures need to be improved.

    Surface integrity is critical to fatigue performance, since fatigue cracks normally initiate at a surface. Machining changes the surface integrity which can result in worse fatigue resistance. The work presented in this Ph.D. thesis was conducted in collaboration with Siemens Industrial Turbomachinery AB in Finspång, Sweden. Surface integrity changes which are induced during machining and their effects on fatigue performance have been studied on the alloy Inconel 718. Inconel 718 is a widely-used nickel-based superalloy for high temperature applications in modern gas turbines.

    Broaching, milling, and wire electrical discharge machining, related to component manufacturing in turbo machinery industries, were included in this study. Machining induced surface defects provide preferential sites for fatigue crack initiation which influence the fatigue performance of the alloy. If compressive residual stresses are induced during machining, they benefit the fatigue life by retarding fatigue crack initiation away from surface regions. Shot peening was performed on machined Inconel 718, by which high compressive residual stresses are deliberately induced. It results in enhanced fatigue performance.

    The high temperatures in gas turbines generally deteriorate the surface integrity. Recrystallization often occurs in the highly deformed surface layer. Microstructural degradation, in the form of α-Cr precipitates, have also been frequently observed in the deformed surface and sub-surface microstructure. Oxidation at elevated temperatures degrades the surface integrity and thereby also the fatigue performance. Fatigue cracks are preferably initiated at oxidized surface carbides, if thermal exposure has been made prior to the test. It is even worse when high temperatures relax the beneficial surface compression induced by shot-peening and thereby lowering the fatigue resistance.

    Machinability of a newly developed nickel-based superalloy, AD 730TM, and the surface integrity induced during turning have also been studied in this thesis project. AD 730TM is a candidate for turbine disc applications with an operating temperature above 650 °C. At such high temperatures, Inconel 718 is no longer stable and its mechanical properties start to degrade.

    To summarize, the results from this thesis work show the importance of understanding surface integrity effects for fatigue applications, especially in harsh environments. Moreover, the knowledge gained through this work could be used for surface enhancement of turbine components which are subjected to a high risk of fatigue failure. These will contribute to more efficient and flexible power generation by gas turbines.

    List of papers
    1. Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
    Open this publication in new window or tab >>Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
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    2016 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47A, no 7, p. 3664-3676Article in journal (Refereed) Published
    Abstract [en]

    The current study focused on the surface integrity issues associated with broaching of Inconel 718 and the structural stability of the broached specimen at high temperatures, mainly involving the microstructural changes and residual stress relaxation. The broaching operation was performed using similar cutting conditions as that used in turbo machinery industries for machining fir-tree root fixings on turbine disks. Thermal exposure was conducted at 723 K, 823 K, and 923 K (450 A degrees C, 550 A degrees C, and 650 A degrees C) for 30, 300, and 3000 hours, respectively. Surface cavities and debris dragging, sub-surface cracks, high intensity of plastic deformation, as well as the generation of tensile residual stresses were identified to be the main issues in surface integrity for the broached Inconel 718. When a subsequent heating was applied, surface recrystallization and alpha-Cr precipitation occurred beneath the broached surface depending on the applied temperature and exposure time. The plastic deformation induced by the broaching is responsible for these microstructural changes. The surface tension was completely relaxed in a short time at the temperature where surface recrystallization occurred. The tensile layer on the sub-surface, however, exhibited a much higher resistance to the stress relief annealing. Oxidation is inevitable at high temperatures. The study found that the surface recrystallization could promote the local Cr diffusion on the broached surface.

    Place, publisher, year, edition, pages
    Springer, 2016
    Keywords
    Structural integrity, Broaching, Inconel 718, Plastic deformation, Residual stresses, Thermal exposure, Superalloy
    National Category
    Materials Engineering Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-111056 (URN)10.1007/s11661-016-3515-6 (DOI)000377434700041 ()
    Funder
    Linköpings universitet, 2009-00971
    Note

    The original title of this article when published in manuscript form was Structural integrity of broached Inconel 718 subjected to thermal exposure.

    Available from: 2014-10-06 Created: 2014-10-06 Last updated: 2018-02-27Bibliographically approved
    2. On the Conjoint Influence of Broaching and Heat Treatment on Bending Fatigue Behavior of Inconel 718
    Open this publication in new window or tab >>On the Conjoint Influence of Broaching and Heat Treatment on Bending Fatigue Behavior of Inconel 718
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    2016 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 671, p. 158-169Article in journal (Refereed) Published
    Abstract [en]

    In this study, the conjoint effect of a broaching operation, similar to that used for machining fir-tree slots on turbine discs, and subsequent heat treatments at 550 °C and 650 °C on the fatigue performance and corresponding crack initiation behavior of forged Inconel 718 has been investigated. Four-point bending fatigue tests were conducted under load control on specimens of two groups, i.e. a polished group and a broached group, with totally six different surface conditions. Compared to the as-polished specimens, a beneficial effect of the broaching operation was found on the fatigue life due to the high compressive residual stresses on the broached surface which transfer the fatigue crack initiation from surface to sub-surface regions. Introducing a heat treatment generally deteriorated the fatigue performance of the alloy because of the oxidation assisted crack initiation, while the reduction in fatigue life was found to be more remarkable for the broached specimens, in particular when heat treated at 650 °C, as the thermal impact also led to a great relaxation of the compressive residual stresses; the combined effect, together with the substantial anomalies created by broaching on the surface, such as cracked carbides and machining grooves, caused an increased propensity to surface cracking in fatigue and consequently a loss of the lifetime. Furthermore, it was found that the occurrence of surface recrystallization at elevated temperatures in machined Inconel 718 could lead to intergranular oxidation, creating micro-notches as preferable sites for the fatigue crack initiation.

    Keywords
    Broaching, Inconel 718, Surface integrity, thermal impact, Fatigue, Crack initiation
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-129843 (URN)10.1016/j.msea.2016.06.030 (DOI)000381165400016 ()
    Note

    Funding agencies: Faculty grant SFO-MAT-LiU at Linkoping University [2009-00971]; Siemens Industrial Turbomachinery AB

    Available from: 2016-06-29 Created: 2016-06-29 Last updated: 2017-11-28
    3. Nano-scale characterization of white layer in broached Inconel 718
    Open this publication in new window or tab >>Nano-scale characterization of white layer in broached Inconel 718
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    2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 684, p. 373-384Article in journal (Refereed) Published
    Abstract [sv]

    The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.

    TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2017
    Keywords
    Surface integrity; White layer; Broaching; Inconel 718; Adiabatic shear band; Mechanically-based subgrain rotation
    National Category
    Materials Chemistry Inorganic Chemistry Other Materials Engineering Paper, Pulp and Fiber Technology Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-134123 (URN)10.1016/j.msea.2016.12.045 (DOI)000393938300045 ()
    Note

    Funding agencies: AForsk Foundation [15-334];  [2009-00971]

    Available from: 2017-01-24 Created: 2017-01-24 Last updated: 2017-11-29Bibliographically approved
    4. Surface Integrity and Fatigue Performance of Inconel 718 in Wire Electrical Discharge Machining
    Open this publication in new window or tab >>Surface Integrity and Fatigue Performance of Inconel 718 in Wire Electrical Discharge Machining
    2016 (English)In: 3RD CIRP CONFERENCE ON SURFACE INTEGRITY, 2016, Vol. 45, p. 307-310Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents a study to characterize the surface integrity in wire electrical discharge machining (EDM) of Inconel 718 and investigate its effect on the fatigue performance of the alloy in a four-point bending fatigue mode at room temperature. The EDM process generates a rough recast surface with multi-types of defects. Surface craters, micro-cracks and micro-voids within the recast layer have been found to be most detrimental from the point of view of fatigue as they could provide many preferential initiation sites for fatigue cracks. As a consequence, the specimens with an EDM cut surface show an approximately 30% decrease in fatigue life compared to those with a polished surface, and multiple crack origins were observed on the fracture surface. The high tensile residual stresses generated on the EDM cut surface, on the other hand, are also believed to be partly responsible for the loss in fatigue life of the alloy machined by EDM.

    Series
    Procedia CIRP, ISSN 2212-8271
    Keywords
    wire electrical discharge machining (wire EDM), surface integrity, fatigue, crack initiation, Inconel 718
    National Category
    Materials Engineering Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-130582 (URN)10.1016/j.procir.2016.02.053 (DOI)000417326500077 ()
    Conference
    3rd CIRP Conference on Surface Integrity (CIRP CSI)8-10 June, 2016, Charlotte, USA
    Note

    Funding agencies: Siemens Industrial Turbomachinery AB; Strategic Faculty Grant AFM at Linkoping University

    Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2022-09-28
    5. Effect of Cooling and Shot Peening on Residual Stresses and Fatigue Performance of Milled Inconel 718
    Open this publication in new window or tab >>Effect of Cooling and Shot Peening on Residual Stresses and Fatigue Performance of Milled Inconel 718
    Show others...
    2017 (English)In: Residual Stresses 2016 ICRS 10 / [ed] T.M. Holden, O. Muránsky, and L. Edwards, 2017, Vol. 2, p. 13-18Conference paper, Published paper (Refereed)
    Abstract [en]

    The present study highlights the effect of cooling and post-machining surface treatment of shot peening on the residual stresses and corresponding fatigue life of milled superalloy Inconel 718. It was found that tensile residual stresses were created on the milled surface, regardless of the use of coolant, however, the wet milling operation led to a lower surface tension and a reduced thickness of the tensile layer. The shot peening performed on the dry-milled specimens completely annihilated the surface tensile residual tresses and introduced a high level of surface compression. A comparable fatigue life for the wet-milled specimens was obtained as compared with the specimens prepared by dry milling. This is very likely attributed to that the milling-induced surface damage with respect to cracked non-metallic inclusions is the predominant cause of the fatigue failure. The presence of the compressive layer induced by shot peening resulted in a significant increase of the fatigue life and strength, while the extent to which the lifetime was prolonged was decreased as the applied load was increased.

    Series
    Materials Research Proceedings, ISSN 2474-395X
    Keywords
    Residual stresses, surface integrity, milling, shot peening, superalloys, fatigue
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-132001 (URN)10.21741/9781945291173-3 (DOI)000401041500003 ()978-1-9452-9116-6 (ISBN)
    Conference
    10th International Conference on Residual Stresses ICRS-10, Sydney, Australia, 3-8 July 2016
    Note

    Funding agencies: Linkoping University [2009-00971]; Ytstruktur Arboga AB; Siemens Industrial Turbomachinery AB

    Available from: 2016-10-13 Created: 2016-10-13 Last updated: 2017-06-13Bibliographically approved
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  • 24.
    Dinsdale, Alan
    et al.
    Hampton Thermodynam Ltd, England.
    Khvan, Alexandra
    NUST MISiS, Russia.
    Smirnova, Ekaterina A.
    NUST MISiS, Russia.
    Ponomareva, Alena V.
    NUST MISiS, Russia.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. NUST MISiS, Russia.
    Modelling the thermodynamic data for hcp Zn and Cu -Zn alloys-an ab initio and calphad approach2021In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 72, article id 102253Article in journal (Refereed)
    Abstract [en]

    The phase diagrams of systems between zinc and elements such as Cu, Ag and Au show two distinct hcp phases on the Zn side of the system. Because of this, it is difficult to model the thermodynamic properties of these phases within a single dataset. As a result it is common to assess the data for these systems with two hexagonal phases, a phase HCP_A3 with a near ideal c/a ratio and the terminal solid solution of Zn with an anomalously high value for this ratio designated as HCP_ZN. We have examined the effect of additions of Cu on the enthalpy of mixing and lattice parameters of HCP_ZN in order to verify, using ab initio calculations, the origin of the above mentioned thermodynamic model for the alloy. The analysis of the calculations allows us to suggest a possible alternative to the state-of-the-art two hcp phases approach akin to the magnetic model used with success within the CALPHAD modelling.

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  • 25.
    Dong, Zhihua
    et al.
    KTH Royal Inst Technol, Sweden; Chongqing Univ, Peoples R China.
    Huang, Shuo
    KTH Royal Inst Technol, Sweden; Uppsala Univ, Sweden.
    Strom, Valter
    KTH Royal Inst Technol, Sweden.
    Chai, Guocai
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. AB Sandvik Mat Technol R& D Ctr, Sweden.
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Hungary.
    Eriksson, Olle
    Uppsala Univ, Sweden; Orebro Univ, Sweden.
    Vitos, Levente
    KTH Royal Inst Technol, Sweden; Uppsala Univ, Sweden; Wigner Res Ctr Phys, Hungary.
    MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 high entropy alloys for magnetocaloric refrigeration near room temperature2021In: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 79, p. 15-20Article in journal (Refereed)
    Abstract [en]

    High entropy alloys (HEAs) based on transition metals display rich magnetic characteristics, however attempts on their application in energy efficient technologies remain scarce. Here, we explore the magnetocaloric application for a series of MnxCr0.3Fe0.5Co0.2Ni0.5Al0.3 (0.8 < x < 1.1) HEAs by integrated theoretical and experimental methods. Both theory and experiment indicate the designed HEAs have the Curie temperature close to room temperature and is tunable with Mn concentration. A non-monotonic evolution is observed for both the entropy change and the relative cooling power with changing Mn concentration. The underlying atomic mechanism is found to primarily emerge from the complex impact of Mn on magnetism. Advanced magnetocaloric properties can be achieved by tuning Mn concentration in combination with controlling structural phase stability for the designed HEAs. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

  • 26.
    Ek, David
    Linköping University, Department of Management and Engineering, Engineering Materials.
    Material parameter study for aheavy-vehicle exhaust manifoldusing the finite element method: to increase component lifetime and decrease its environmental impact2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thesis originates from a need to meet stricter environmental regulations for Scania, to reduce fuel consumption and emission from heavy-vehicles. Scania aims to fulfil these requirements by increasing combustion pressure and temperature. These conditions are tougher for the engine components and they shorten their lifetime. This thesis aims to improve Scania’s ability to increase the lifetime of a heavy-vehicle exhaust manifold, an engine component that collects exhaust from several engine cylinders into one pipe.

    This was done by conducting a material comparison and a parameter study, both used the FEM software Abaqus CAE. The material comparison consisted of three ferritic and austenitic ductile cast irons (SiMo51, SiMo1000 and Ni-resist) subjected to thermal stress. Their max stress was compared for two thermo-mechanical fatigue cases, out-of-phase and in-phase. A parameter study was also conducted to clarify the influence of thermal conductivity, thermalexpansion, Young’s modulus and yield strength on max stress for OP and IP in the exhaust manifold. The FEM simulation results from the parameter study were used to create functions that can be used to decide how to treat/process a material to minimise the stress in the exhaust manifold. They can also be used in material selection to choose a material that minimises stress. The research questions and their shortened answers can be seen below.

    1. Which of SiMo51, SiMo1000 and Ni-resist produces the lowest tensile stresses? ForOP, SiMo1000 produced a slightly lower max principal stress than SiMo51. For IP, Ni-resistproduced the lowest max principal stress by a large margin.

    2. How do different material properties affect the maximum stress during operation of thegiven component? Thermal conductivity has a decreasing relation to max stress. Thermalexpansion and Young’s modulus have a similar relation to max stress, stress increases forboth properties as they increase. A decreased yield strength decreases the max stress forstresses above the yield limit but has no effect on stress below it.

    3. How should an objective function to minimise max stress in the component with regard to material properties be expressed?

    functions of OP and IP can be seen in the actual abstract.

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  • 27.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Mechanical and thermodynamical study of a macroscopically coherent phase transition.Case of the martensitic transformation1991In: Journal de Physique IV, ISSN 1155-4339, Vol. 1, p. C4-89-C4-94Article in journal (Refereed)
    Abstract [en]

    In the general framework of a macroscopically coherent phase transition, the mechanical and thermodynamical behaviour of a two-phase volume element under structural evolution will be investigated and discussed. The identification of internal entropy production will then allow to formulate a general evolution condition for such a system and the internal stress state will appear to influence strongly the transformation behaviour, via the interface. The case of a martensitic transformation is considered. From that rigourous mechanical approach, we obtain the thermodynamical balance equation used for martensitic transformation.

  • 28.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Micromechanical simulation of a martensitic transformaation by Finite Elements1991In: Journal de Physique IV, ISSN 1155-4339, Vol. 1, p. C4-77-C4-82Article in journal (Refereed)
    Abstract [en]

    A micromechanical model describing the martensitic transformation on the grain scale has been developed, using Finite Elements. First results gained from the simulation illustrate how the morphological evolution within the grain is directly controlled by the internal stress state. The reversible and irreversible part of transformation "plasticity" strain and their evolution with the transformation can then be obtained from these calculations.

  • 29.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Sjöström, Sören
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, UA 159 du CNRS, Ecole des Mines, Parc de Saurupt, 54042 Nancy cedex, France.
    Martensitic transformation plasticity simulations by Finite Elements1994In: Journal de Physique IV, ISSN 1155-4339, Vol. 4, p. C3-215-C3-220Article in journal (Refereed)
    Abstract [en]

    The mechanical behaviour associated to the martensitic transformation has been modelled using a 2D FE description. The martensite variants are constituted of different elements of the mesh and four different variants are allowed to transform in the grain. The transformation progress is prescribed using a thermodynamical criterion based on the maximal work associated to the variant formation. Transformation plasticity deformation and plates orientation patterns are obtained for three stress levels. These results are discussed in regard to the model used and the physical parameters introduced in the model.

  • 30.
    Gonzalez, Leny
    Linköping University, Department of Management and Engineering, Engineering Materials.
    Infuence of matrix and alloying on the fatigue crack propagation and fracture toughness of compacted graphite iron for cylinderheads2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The constants modernization in the fuels used request improvements in the combustioneffectiveness, as a consequence the material for components as the cylinder heads mustenhance their properties. Seven different compositions of compacted graphite iron (CGI)are analysed with the aim of characterized and select the most suitable material for thecylinder head service condition. The present master thesis report focuses on the impactof the matrix- either pearlitic or ferritic- and alloying elements such as molybdenum andnickel in the fatigue crack propagation ratedadNand fracture toughness (kIc).Tests to determined the fatigue crack growth rate, according to the ASTM standardE647 and fracture toughness (ASTM E399) were conducted. The equipment utilized was aservo hydraulic machine, for the fatigue crack propagation rate test and a electromechanicalmachine for the fracture toughness. Moreover, for measure the crack length a portablemicroscope camera and a camera connected to a DIC(digital image correlation) softwarewas used. The interpretation of the data obtained from the tests were done by TEMA- aDIC software- and MATLAB.The test results are analysed describing the influence of the composition and the microstructurehave over the mechanical properties achieved. Furthermore, an analyse forrelating the graphite average length and the hardness with the fatigue crack growth rateand the fracture toughness of the materials is performed.

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    Govik, Alexander
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Finite Element Analysis of Sheet Metal Assemblies: Prediction of Product Performance Considering the Manufacturing Process2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the development of methodologies to be used to simulate complete manufacturing chains of sheet components and the study of how different mechanical properties propagate and influence succeeding component performance.

    Since sheet metal assemblies are a major constituent of a wide range of products it is vital to develop methodologies that enable detailed evaluation of assembly designs and manufacturing processes. The manufacturing process influences several key aspects of a sheet metal assembly, aspects such as shape fulfilment, variation and risk of material failure.

    Developments in computer-aided engineering and computational resources have made simulation-based process and product development efficient and useful since it allows for detailed, rapid evaluation of the capabilities and qualities of both process and product. Simulations of individual manufacturing processes are useful, but greater benefits can be gained by studying the complete sequence of a product's manufacturing processes. This enables evaluation of the entire manufacturing process chain, as well as the final product. Moreover, the accuracy of each individual manufacturing process simulation is improved by establishing appropriate initial conditions, including inherited material properties.

    In this thesis, a methodology of sequentially simulating each step in the manufacturing process of a sheet metal assembly is presented. The methodology is thoroughly studied using different application examples with experimental validation. The importance of information transfer between all simulation steps is also studied. Furthermore, the methodology is used as the foundation of a new approach to investigate the variation of mechanical properties in a sheet metal assembly. The multi-stage manufacturing process of the assembly is segmented, and stochastic analyses of each stage is performed and coupled to the succeeding stage in order to predict the assembly's final variation in properties.

    Two additional studies are presented where the methodology of chaining manufacturing processes is utilised. The influence of the dual phase microstructure on non-linear strain recovery is investigated using a micromechanical approach that considers the annealing process chain. It is vital to understand the non-linear strain recovery in order to improve springback prediction. In addition, the prediction of fracture in a dual phase steel subjected to non-linear straining is studied by simulating the manufacturing chain and subsequent stretch test of a sheet metal component.

    List of papers
    1. Finite element simulation of the manufacturing process chain of a sheet metal assembly
    Open this publication in new window or tab >>Finite element simulation of the manufacturing process chain of a sheet metal assembly
    2012 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 212, no 7, p. 1453-1462Article in journal (Refereed) Published
    Abstract [en]

    An increasing number of components in automotive structures are today made from advanced high strength steel (AHSS). Since AHSS demonstrates more severe springback behaviour than ordinary mild steels, it requires more efforts to meet the design specification of the stamped parts. Consequently, the physical fine tuning of the die design and the stamping process can be time consuming. The trial-and-error development process may be shortened by replacing most of the physical try-outs with finite element (FE) simulations of the forming process, including the springback behaviour. Still it can be hard to identify when a stamped part will lead to an acceptable assembly with respect to the geometry and the residual stress state. In part since the assembling process itself will distort the components. To resolve this matter it is here proposed to extend the FE-simulation of the stamping process, to also include the first level sub-assembly stage. In this study a methodology of sequentially simulating each step in the manufacturing process of an assembly is proposed. Each step of the proposed methodology is described, and a validation of the prediction capabilities is performed by comparing with a physically manufactured assembly. The assembly is composed of three sheet metal components made from DP600 steel which are joined by spot welding. The components are designed to exhibit severe springback behaviour in order to put both the forming and subsequent assembling simulations to the test. The work presented here demonstrates that by using virtual prototyping it is possible to predict the final shape of an assembled structure.

    Place, publisher, year, edition, pages
    Elsevier, 2012
    Keywords
    Finite element simulation, Assembly, Sheet metal, Forming, Springback
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-77853 (URN)10.1016/j.jmatprotec.2012.02.012 (DOI)000304020800001 ()
    Note

    Funding Agencies|Swedish foundation for strategic research||ProViking programme||

    Available from: 2012-05-31 Created: 2012-05-31 Last updated: 2017-12-07Bibliographically approved
    2. The effects of forming history on sheet metal assembly
    Open this publication in new window or tab >>The effects of forming history on sheet metal assembly
    2014 (English)In: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 7, no 3, p. 305-316Article in journal (Refereed) Published
    Abstract [en]

    As demand for faster product development increases, physical prototypes are replaced by virtual prototypes. By using finite element simulations to evaluate the functional behaviour of the product as well as its manufacturing process, more design alternatives can be evaluated while a considerably smaller number of physical prototypes are needed. As sheet metal assemblies are common in a wide range of products, reliable methods for predicting their properties are necessary. By sequentially simulating the complete manufacturing process chain of an assembly, early predictions concerning the geometry and material properties of the assembly can be made.

    In this study a simulation-based sensitivity study is performed in order to investigate the influence of the forming history on the predictions of assembly properties. In the study, several simulations of the assembly stage are performed in which different types of forming histories are retained from the forming stage. The simulations of the assembly stage will range from a case with linear elastic conditions without forming history, to a case with the full forming history state and consistent material modelling throughout all simulations. It is found that the residual stress state is the most influential history variable from the forming stage. Especially for more complex geometries in which large residual stresses can be retained.

    Place, publisher, year, edition, pages
    Springer, 2014
    Keywords
    Finite element simulation, Assembly, Sheet metal, Forming, History variables, Chaining of manufacturing processes
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-78765 (URN)10.1007/s12289-013-1128-9 (DOI)000338323600004 ()
    Note

    On the day of the defence date of the Ph.D. thesis the status of this article was Manuscript.

    Available from: 2012-06-20 Created: 2012-06-20 Last updated: 2017-12-07Bibliographically approved
    3. A study of the unloading behaviour of dual phase steel
    Open this publication in new window or tab >>A study of the unloading behaviour of dual phase steel
    2014 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 602, p. 119-126Article in journal (Refereed) Published
    Abstract [en]

    It is important to understand the strain recovery of a steel sheet in order to predict its springback behaviour. During strain recovery, the stress–strain relation is non-linear and the resulting unloading modulus is decreased. Moreover, the unloading modulus will degrade with increasing plastic pre-straining. This study aims at adding new knowledge on these phenomena and the mechanisms causing them. The unloading behaviour of the dual-phase steel DP600 is characterised experimentally and finite element (FE) simulations of a representative volume element (RVE) of the microstructure are performed. The initial stress and strain state of the micromechanical FE model is found by a simplified simulation of the annealing processes. It is observed from the experimental characterisation that the decrease of the initial stiffness of the unloading is the main reason for the degrading unloading modulus. Furthermore, the developed micromechanical FE model exhibits non-linear strain recovery due to local plasticity caused by interaction between the two phases.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Micromechanics; Representative volume element; Dual phase steel; Unloading modulus; Non-linear recovery
    National Category
    Metallurgy and Metallic Materials Applied Mechanics
    Identifiers
    urn:nbn:se:liu:diva-106318 (URN)10.1016/j.msea.2014.02.069 (DOI)000335098500015 ()
    Available from: 2014-05-05 Created: 2014-05-05 Last updated: 2017-12-05Bibliographically approved
    4. Prediction of fracture in a dual-phase steel subjected to non-linear straining
    Open this publication in new window or tab >>Prediction of fracture in a dual-phase steel subjected to non-linear straining
    2014 (English)In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 214, no 11, p. 2748-2758Article in journal (Refereed) Published
    Abstract [en]

    In this work, selected fracture criteria are applied to predict the fracture of dualphase steel subjected to non-linear strain paths. Furthermore, the effects of manufacturing history are studied. Four fracture criteria were calibrated in three tests using standard specimens. The fracture criteria were first validated in the circular Nakajima test. A second validation test case was included in order to validate fracture prediction for non-linear strain paths. In this test a sheet metal component was manufactured and subsequently stretched until it fractured. All fracture criteria included in this study predict fracture during the Nakajima test with reasonable accuracy. In the second validation test however, the different fracture criteria show considerable diversity in accumulated damage during manufacturing which caused substantial scatter of the fracture prediction in the subsequent stretching. This shows that manufacturing history influences the prediction of fracture.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Sheet metal failure, high strength steels, forming limits, non-linear strain paths, forming history
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-105211 (URN)10.1016/j.jmatprotec.2014.05.028 (DOI)000340300400059 ()
    Note

    Funders: SSF ProViking project entitled "SuperLight Steel Structures"

    Available from: 2014-03-13 Created: 2014-03-13 Last updated: 2017-12-05
    5. Stochastic analysis of a sheet metal assembly considering its manufacturing process
    Open this publication in new window or tab >>Stochastic analysis of a sheet metal assembly considering its manufacturing process
    2014 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In order to accurately predict the mechanical properties of a sheet metal assembly it has been shown important to account for how the geometry and material properties are affected by the manufacturing process. It is also of a great interest to predict the variations of important responses, and how these variations depend on the manufacturing process.

    In this study, the variation of properties during the multi-stage manufacturing process of a sheet metal assembly is evaluated and the variability of a response due to loading is studied. A methodology to investigate how variations evolve during the assembling process is presented. The multi-stage assembling process is virtually segmented, such that stochastic analyses of each process stage are performed and coupled to succeeding stages in order to predict the variation in properties of the final assembly. The methodology is applied to an industrial assembly and experimental validations have been conducted. The prediction of the geometry of the final assembly is in good agreement with the experimental results, while the prediction of the variation of this geometry is in fair agreement.

    Keywords
    Finite element simulation, Assembly, Sheet metal, Forming, Monte Carlo analysis, Chaining of manufacturing processes
    National Category
    Metallurgy and Metallic Materials Applied Mechanics
    Identifiers
    urn:nbn:se:liu:diva-106636 (URN)
    Available from: 2014-05-16 Created: 2014-05-16 Last updated: 2014-05-16Bibliographically approved
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    Finite Element Analysis of Sheet Metal Assemblies: Prediction of Product Performance Considering the Manufacturing Process
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  • 32.
    Govik, Alexander
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Nilsson, Larsgunnar
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Moshfegh, Ramin
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Stochastic analysis of a sheet metal assembly considering its manufacturing process2014Manuscript (preprint) (Other academic)
    Abstract [en]

    In order to accurately predict the mechanical properties of a sheet metal assembly it has been shown important to account for how the geometry and material properties are affected by the manufacturing process. It is also of a great interest to predict the variations of important responses, and how these variations depend on the manufacturing process.

    In this study, the variation of properties during the multi-stage manufacturing process of a sheet metal assembly is evaluated and the variability of a response due to loading is studied. A methodology to investigate how variations evolve during the assembling process is presented. The multi-stage assembling process is virtually segmented, such that stochastic analyses of each process stage are performed and coupled to succeeding stages in order to predict the variation in properties of the final assembly. The methodology is applied to an industrial assembly and experimental validations have been conducted. The prediction of the geometry of the final assembly is in good agreement with the experimental results, while the prediction of the variation of this geometry is in fair agreement.

  • 33.
    Govik, Alexander
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Rentmeester, Rikard
    Saab AB, Linköping, Sweden.
    Nilsson, Larsgunnar
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    A study of the unloading behaviour of dual phase steel2014In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 602, p. 119-126Article in journal (Refereed)
    Abstract [en]

    It is important to understand the strain recovery of a steel sheet in order to predict its springback behaviour. During strain recovery, the stress–strain relation is non-linear and the resulting unloading modulus is decreased. Moreover, the unloading modulus will degrade with increasing plastic pre-straining. This study aims at adding new knowledge on these phenomena and the mechanisms causing them. The unloading behaviour of the dual-phase steel DP600 is characterised experimentally and finite element (FE) simulations of a representative volume element (RVE) of the microstructure are performed. The initial stress and strain state of the micromechanical FE model is found by a simplified simulation of the annealing processes. It is observed from the experimental characterisation that the decrease of the initial stiffness of the unloading is the main reason for the degrading unloading modulus. Furthermore, the developed micromechanical FE model exhibits non-linear strain recovery due to local plasticity caused by interaction between the two phases.

  • 34.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    X-ray photoelectron spectroscopy: Towards reliable binding energy referencing2020In: Progress in Materials Science, ISSN 0079-6425, E-ISSN 1873-2208, Vol. 107, article id 100591Article, review/survey (Refereed)
    Abstract [en]

    With more than 9000 papers published annually, X-ray photoelectron spectroscopy (XPS) is an indispensable technique in modem surface and materials science for the determination of chemical bonding. The accuracy of chemical-state determination relies, however, on a trustworthy calibration of the binding energy (BE) scale, which is a nontrivial task due to the lack of an internal BE reference. One approach, proposed in the early days of XPS, employs the C 1s spectra of an adventitious carbon layer, which is present on all surfaces exposed to air. Despite accumulating criticism, pointing to the unknown origin and composition of the adventitious carbon, this is by far the most commonly used method today for all types of samples, not necessarily electrically insulating. Alarmingly, as revealed by our survey of recent XPS literature, the calibration procedure based on the C 1s peak of adventitious carbon is highly arbitrary, which results in incorrect spectral interpretation, contradictory results, and generates a large spread in reported BE values for elements even present in the same chemical state. The purpose of this review is to critically evaluate the status quo of XPS with a historical perspective, provide the techniques operating principles, resolve myths associated with C 1s referencing, and offer a comprehensive account of recent findings. Owing to the huge volume of XPS literature produced each year, the consequences of improper referencing are dramatic. Our intention is to promote awareness within a growing XPS community as to the problems reported over the last six decades and present a guide with best practice for using the C 1s BE referencing method.

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  • 35. Order onlineBuy this publication >>
    Gunnarsson, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Controlling the growth of nanoparticles produced in a high power pulsed plasma2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling.

    If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes.

    When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility.

    The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.

    List of papers
    1. Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    Open this publication in new window or tab >>Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    2015 (English)In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 17, no 9, p. 353-Article in journal (Refereed) Published
    Abstract [en]

    Ti-O nanoparticles have been synthesized via hollow cathode sputtering in an Ar-O-2 atmosphere using high power pulsing. It is shown that the stoichiometry and the size of the nanoparticles can be varied independently, the former through controlling the O-2 gas flow and the latter by the independent biasing of two separate anodes in the growth zone. Nanoparticles with diameters in the range of 25-75 nm, and with different Ti-O compositions and crystalline phases, have been synthesized.

    Place, publisher, year, edition, pages
    Springer Verlag (Germany), 2015
    Keywords
    Titanium dioxide; TiO2; Reactive sputtering; Size control; Composition control; Gas flow sputtering; Aerosols
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-121300 (URN)10.1007/s11051-015-3158-3 (DOI)000360245300002 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg foundation [KAW 2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Available from: 2015-09-16 Created: 2015-09-14 Last updated: 2017-12-21
    2. The influence of pressure and gas flow on size and morphology of titanium oxide nanoparticles synthesized by hollow cathode sputtering
    Open this publication in new window or tab >>The influence of pressure and gas flow on size and morphology of titanium oxide nanoparticles synthesized by hollow cathode sputtering
    Show others...
    2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, no 4, p. 044308-Article in journal (Refereed) Published
    Abstract [en]

    Titanium oxide nanoparticles have been synthesized via sputtering of a hollow cathode in an argon atmosphere. The influence of pressure and gas flow has been studied. Changing the pressure affects the nanoparticle size, increasing approximately proportional to the pressure squared. The influence of gas flow is dependent on the pressure. In the low pressure regime (107 amp;lt;= p amp;lt;= 143 Pa), the nanoparticle size decreases with increasing gas flow; however, at high pressure (p = 215 Pa), the trend is reversed. For low pressures and high gas flows, it was necessary to add oxygen for the particles to nucleate. There is also a morphological transition of the nanoparticle shape that is dependent on the pressure. Shapes such as faceted, cubic, and cauliflower can be obtained. Published by AIP Publishing.

    Place, publisher, year, edition, pages
    AMER INST PHYSICS, 2016
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-131710 (URN)10.1063/1.4959993 (DOI)000382405400029 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg foundation [KAW 2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Available from: 2016-10-03 Created: 2016-09-30 Last updated: 2017-12-21
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  • 36. Order onlineBuy this publication >>
    Gunnarsson, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Titanium oxide nanoparticle production using high power pulsed plasmas2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis covers fundamental aspects of process control when growing titanium oxide nanoparticles in a reactive sputtering process. It covers the influence of oxygen containing gas on the oxidation state of the cathode from which the growth material is ejected, as well as its influence on the particles oxidation state and their nucleation. It was found that a low degree of reactive gases was necessary for nanoparticles of titanium to nucleate. When the oxygen gas was slightly increased, the nanoparticle yield and particle oxygen content increased. A further increase caused a decrease in particle yield which was attributed to a slight oxidation of the cathode. By varying the oxygen flow to the process, it was possible to control the oxygen content of the nanoparticles without fully oxidizing the cathode. Because oxygen containing gases such as residual water vapour has a profound influence on nanoparticle yield and composition, the deposition source was re-engineered to allow for cleaner and thus more stable synthesis conditions.

    The size of the nanoparticles has been controlled by two means. The first is to change electrical potentials around the growth zone, which allows for nanoparticle size control in the order of 25-75 nm. This size control does not influence the oxygen content of the nanoparticles. The second means of size control investigated was by increasing the pressure. By doing this, the particle size can be increased from 50 – 250 nm, however the oxygen content also increases with pressure. Different particle morphologies were found by changing the pressure. At low pressures, mostly spherical particles with weak facets were produced. As the pressure increased, the particles got a cubic shape. At higher pressures the cubic particles started to get a fractured surface. At the highest pressure investigated, the fractured surface became poly-crystalline, giving a cauliflower shaped morphology.

    List of papers
    1. Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    Open this publication in new window or tab >>Synthesis of titanium-oxide nanoparticles with size and stoichiometry control
    2015 (English)In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 17, no 9, p. 353-Article in journal (Refereed) Published
    Abstract [en]

    Ti-O nanoparticles have been synthesized via hollow cathode sputtering in an Ar-O-2 atmosphere using high power pulsing. It is shown that the stoichiometry and the size of the nanoparticles can be varied independently, the former through controlling the O-2 gas flow and the latter by the independent biasing of two separate anodes in the growth zone. Nanoparticles with diameters in the range of 25-75 nm, and with different Ti-O compositions and crystalline phases, have been synthesized.

    Place, publisher, year, edition, pages
    Springer Verlag (Germany), 2015
    Keywords
    Titanium dioxide; TiO2; Reactive sputtering; Size control; Composition control; Gas flow sputtering; Aerosols
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-121300 (URN)10.1007/s11051-015-3158-3 (DOI)000360245300002 ()
    Note

    Funding Agencies|Knut and Alice Wallenberg foundation [KAW 2014.0276]; Swedish Research Council via the Linkoping Linneaus Environment LiLi-NFM [2008-6572]

    Available from: 2015-09-16 Created: 2015-09-14 Last updated: 2017-12-21
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  • 37.
    Gunnarsson Sarius, Niklas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Leisner, Peter
    SP Technical Research Institute of Sweden, Box 857, 501 15 Borås, Sweden/School of Engineering, Jönköping University, Sweden.
    Hald, J.
    ENKOTEC A/S, Denmark.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Electroplating of nickel in grooves under the influence of low and medium frequency ultrasound2011In: Journal for Electrochemistry and Plating Technology, ISSN 1866-7406, Vol. 1, no 3, p. 19-28Article in journal (Refereed)
    Abstract [en]

    The effect of ultrasonics on filling properties has been studied by Ni electroplating from a sulphamate electrolyte in high aspect ratio grooves. The experiments have been performed with two different modes of ultrasound: a) 25 kHz ultrasound with an effect of 225 W directed perpendicular to the substrate surface; b) ultrasonic standing waves of 100 kHz and 400 kHz parallel to the substrate surface. It was found that both methods improve the filling in grooves that are between 0.35 and 1 mm wide with aspect ratios between 0.6 and 3, compared to electroplating with conventional agitation. Under the investigated conditions the 400 kHz standing wave parallel to the surface was most efficient to improve filling of grooves.

  • 38.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Barriers to and Drivers for Improved Energy Efficiency in the Swedish Aluminium Industry and Aluminium Casting Foundries2019In: Sustainability, E-ISSN 2071-1050, Vol. 11, no 7, article id 2043Article in journal (Refereed)
    Abstract [en]

    Industrial energy efficiency is important for reducing CO2 emissions and could be a competitive advantage for companies because it can reduce costs. However, cost-effective energy efficiency measures are not always implemented because there are barriers inhibiting their implementation. Drivers for energy efficiency could provide means for overcoming these barriers. The aim of this article was to study the importance of different barriers to and drivers for improved energy efficiency in the Swedish aluminium industry and foundries that cast aluminium. Additionally, the perceived usefulness of different information sources on energy efficiency measures was studied. The data were collected through a questionnaire covering 39 barriers and 48 drivers, divided into different categories. Both the aluminium and foundry industries considered technological and economic barriers as the most important categories. The most important category of drivers for the aluminium industry was organisational drivers, while the foundries rated economic drivers as the most important. Colleagues within the company, the company group and sector, and the trade organisation were considered the most useful information sources. Important factors for driving work with improved energy efficiency included access to knowledge within the company, having a culture within the company promoting energy efficiency, and networking within the sector. The policy implications identified included energy labelling of production equipment, the law on energy audit in large companies and subsidy for energy audits in small- and medium-sized companies, voluntary agreements that included long-term energy strategies, increased taxes to improve the cost-effectiveness of energy efficiency measures, and EUs Emission Trading System.

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  • 39.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Energy Efficiency in the Supply Chains of the Aluminium Industry: The Cases of Five Products Made in Sweden2019In: Energies, E-ISSN 1996-1073, Vol. 12, no 2, p. 245-Article in journal (Refereed)
    Abstract [en]

    Improved energy efficiency in supply chains can reduce both environmental impact and lifecycle costs, and thus becomes a competitive advantage in the work towards a sustainable global economy. Viewing the supply chain as a system provides the holistic perspective needed to avoid sub-optimal energy use. This article studies measures relating to technology and management that can increase energy efficiency in the supply chains of five aluminium products made in Sweden. Additionally, energy efficiency potentials related to the flows of material, energy, and knowledge between the actors in the supply chains are studied. Empirical data was collected using focus group interviews and one focus group per product was completed. The results show that there are several areas for potential energy efficiency improvement; for example, product design, communication and collaboration, transportation, and reduced material waste. Demands from other actors that can have direct or indirect effects on energy use in the supply chains were identified. Despite the fact that companies can save money through improved energy efficiency, demands from customers and the authorities would provide the additional incentives needed for companies to work harder to improve energy efficiency.

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  • 40.
    Haraldsson, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Johansson, Maria
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Impact analysis of energy efficiency measures in the electrolysis process in primary aluminium production2019In: WEENTECH Proceedings in Energy, 2019, Vol. 4(2), p. 177-184Conference paper (Refereed)
    Abstract [en]

    The Paris Agreement includes the goals of ‘holding the increase in the global average temperature to well below 2°C above pre-industrial levels’ and ‘making finance flows consistent with a pathway towards low greenhouse gas emissions’. Industrial energy efficiency will play an important role in meeting those goals as well as becoming a competitive advantage due to reduced costs for companies. The aluminium industry is energy intensive and uses fossil fuels both for energy purposes and as reaction material. Additionally, the aluminium industry uses significant amounts of electricity. The electrolysis process in the primary production of aluminium is the most energy- and carbon-intensive process within the aluminium industry. The aim of this paper is to study the effects on primary energy use, greenhouse gas emissions and costs when three energy efficiency measures are implemented in the electrolysis process. The effects on the primary energy use, greenhouse gas emissions and costs are calculated by multiplying the savings in final energy use by a primary energy factor, emissions factor and price of electricity, respectively. The results showed significant savings in primary energy demand, greenhouse gas emissions and cost from the implementation of the three measures. These results only indicate the size of the potential savings and a site-specific investigation needs to be conducted for each plant. This paper is a part of a research project conducted in close cooperation with the Swedish aluminium industry.

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  • 41.
    Hasselqvist, Magnus
    et al.
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Moverare, Johan
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Constitutive Behaviour of IN738LC Under TMF Cycling With and Without Intermediate Ageing2007In: Proceedings of the ASME Turbo Expo [Volume 5: Turbo Expo 2007], New York: ASME Press, 2007, p. 131-135Conference paper (Refereed)
    Abstract [en]

    Out of Phase Thermo Mechanical Fatigue (OP TMF) 100–950°C tests with 5 min hold time, some including intermediate ageing for 4000h at 950°C after 25 cycles, have been performed on IN738LC at Siemens Industrial Turbomachinery (SIT) AB. In the standard tests, the variation in stress range during the tests was neutral. When tests with intermediate ageing were added to the analysis, the combination of test data strongly suggest that the neutral response above was because of a fairly even competition between softening due to degradation (particle coarsening etc.) and work hardening. We have concluded that the work hardening occuring for a lab hold time of 5 min. will be insignificant under more realistic, i.e. component-near, hold times. Based on this, we have devised a method for reduction of lab TMF test results, with their too short hold times, to handle actual, i.e. significantly longer, component hold times.

  • 42.
    Hatami, Sepehr
    et al.
    Swerea IVF AB, Mölndal, Sweden.
    Dahl-Jendelin, Anton
    Swerea IVF AB, Mölndal, Sweden.
    Ahlberg, Jörgen
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Termisk Systemteknik AB, Linköping, Sweden.
    Nelsson, Claes
    Termisk Systemteknik AB, Linköping, Sweden.
    Selective Laser Melting Process Monitoring by Means of Thermography2018In: Proceedings of Euro Powder Metallurgy Congress (Euro PM), European Powder Metallurgy Association (EPMA) , 2018, article id 3957771Conference paper (Refereed)
    Abstract [en]

    Selective laser melting (SLM) enables production of highly intricate components. From this point of view, the capabilities of this technology are known to the industry and have been demonstrated in numerous applications. Nonetheless, for serial production purposes the manufacturing industry has so far been reluctant in substituting its conventional methods with SLM. One underlying reason is the lack of simple and reliable process monitoring methods. This study examines the feasibility of using thermography for process monitoring. To this end, an infra-red (IR) camera was mounted off-axis to monitor and record the temperature of every layer. The recorded temperature curves are analysed and interpreted with respect to different stages of the process. Furthermore, the possibility of detecting variations in laser settings by means of thermography is demonstrated. The results show that once thermal patterns are identified, this data can be utilized for in-process and post-process monitoring of SLM production.

  • 43.
    Hedström, Peter
    et al.
    Luleå University of Technology.
    Han, Tong-Seok
    Yonsei University.
    Almer, Jonathan
    Argonne National Laboratory.
    Lienert, Ulrich
    Argonne National Laboratory.
    Odén, Magnus
    Luleå University of Technology.
    Load partitioning between single bulk grains in a two-phase duplex stainless steel during tensile loading2010In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 58, p. 734-744Article in journal (Refereed)
    Abstract [en]

    The lattice strain tensor evolution for single bulk grains of austenite and ferrite in a duplex stainless steel during tensile loading to 0.02 applied strain has been investigated using in situ high-energy X-ray measurements and finite-element modeling. Single-grain X-ray diffraction lattice strain data for the eight austenite and seven ferrite grains measured show a large variation of residual lattice strains, which evolves upon deformation to the point where some grains with comparable crystallographic orientations have lattice strains different by 1.5 × 10−3, corresponding to a stress of 300 MPa. The finite-element simulations of the 15 measured grains in three different spatial arrangements confirmed the complex deformation constraint and importance of local grain environment.

  • 44.
    Horng, Ray-Hua
    et al.
    Natl Yang Ming Chiao Tung Univ, Taiwan.
    Cho, Po-Hsiang
    Natl Yang Ming Chiao Tung Univ, Taiwan.
    Chang, Jui-Che
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Singh, Anoop Kumar
    Natl Chung Hsing Univ, Taiwan.
    Jhang, Sheng-Yuan
    Natl Chung Hsing Univ, Taiwan.
    Liu, Po-Liang
    Natl Chung Hsing Univ, Taiwan; Natl Chi Nan Univ, Taiwan.
    Wuu, Dong-Sing
    Natl Chung Hsing Univ, Taiwan; Natl Chi Nan Univ, Taiwan.
    Bairagi, Samiran
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Chen, Cheng-Hsu
    Natl Chung Hsing Univ, Taiwan.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Growth and Characterization of Sputtered InAlN Nanorods on Sapphire Substrates for Acetone Gas Sensing2024In: Nanomaterials, E-ISSN 2079-4991, Vol. 14, no 1, article id 26Article in journal (Refereed)
    Abstract [en]

    The demand for highly sensitive and selective gas sensors has been steadily increasing, driven by applications in various fields such as environmental monitoring, healthcare, and industrial safety. In this context, ternary alloy indium aluminum nitride (InAlN) semiconductors have emerged as a promising material for gas sensing due to their unique properties and tunable material characteristics. This work focuses on the fabrication and characterization of InAlN nanorods grown on sapphire substrates using an ultra-high vacuum magnetron sputter epitaxy with precise control over indium composition and explores their potential for acetone-gas-sensing applications. Various characterization techniques, including XRD, SEM, and TEM, demonstrate the structural and morphological insights of InAlN nanorods, making them suitable for gas-sensing applications. To evaluate the gas-sensing performance of the InAlN nanorods, acetone was chosen as a target analyte due to its relevance in medical diagnostics and industrial processes. The results reveal that the InAlN nanorods exhibit a remarkable sensor response of 2.33% at 600 ppm acetone gas concentration at an operating temperature of 350 degrees C, with a rapid response time of 18 s. Their high sensor response and rapid response make InAlN a viable candidate for use in medical diagnostics, industrial safety, and environmental monitoring.

  • 45.
    Hu, Ji-Chong
    et al.
    Yantai Univ, Peoples R China.
    Huang, Hai-Liang
    Yantai Univ, Peoples R China.
    Wu, Chong-Chong
    Yantai Univ, Peoples R China.
    Sun, Xiao-Yu
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Wang, Jie
    Yantai Univ, Peoples R China.
    Yang, Yan-Hong
    Chinese Acad Sci, Peoples R China.
    Qu, Jing-Long
    Gaona Aero Mat Co Ltd, Peoples R China.
    Jiang, Liang
    Yantai Univ, Peoples R China.
    Dou, Jin-He
    Shandong First Med Univ & Shandong Acad Med Sci, Peoples R China.
    Chen, Yang
    Yantai Univ, Peoples R China.
    Oxidation behavior of Ni-based superalloy GH4738 under tensile stress2024In: Rare Metals, ISSN 1001-0521, E-ISSN 1867-7185, article id s12598-024-02715-8Article in journal (Refereed)
    Abstract [en]

    Revealing the oxidation behavior of superalloys is crucial for optimizing material properties and extending service life. This study investigated the oxidation behavior of superalloy GH4738 under stress states at 850 degrees C. High-throughput specimens were fabricated to withstand different stresses at the same time. Isothermal oxidation samples were analyzed using the mass gain method to obtain oxidation kinetic curves. The results show that the external stress below 200 MPa could improve the oxidation resistance of the GH4738. With tensile stress increasing, the oxide layer becomes thinner, denser and more complete, while internal oxidation decreases. The tensile stress alters the structure of the external oxide layer from a two-layer to a three-layer configuration. The Cr2O3 oxide layer inhibits the outward diffusion of Ti, leading to Ti enrichment at the oxide-matrix interface and altering the oxidation mechanism of GH4738.

  • 46.
    Hörnmark, Adam
    et al.
    Linköping University, Department of Management and Engineering.
    Andersson, Victor
    Linköping University, Department of Management and Engineering.
    Extruderade längders hållfasthet: Undersökning av samband mellan hållfasthet längs extruderade profiler och olika temperaturgradienter på aluminiumgöt2024Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    During the extrusion of aluminum profiles, a temperature gradient is introduced into the billet to counteract the extra heat generated during the process and is believed to affect the mechanical properties of the profile. This thesis, carried out in collaboration with Hydro Extrusions, examined how the temperature gradient in the billet affects the mechanical properties of extruded aluminum profiles. 

    The work was based on a modified DMAIC methodology where the Control phase was excluded. Tensile tests were conducted to investigate the yield strength, ultimate tensile strength, elongation, and modulus of elasticity of T4- and T6-aged profiles of the alloys EN AW-6060 and EN AW-6082. The profile’s exit temperature, exit speed, and cooling rate was also investigated.

    The results showed that the temperature gradient did not directly affect the mechanical properties of the profiles. Instead, it contributed to maximizing the profile's exit speed. The largest factors influencing the mechanical properties were the aging and cooling methods used.

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  • 47.
    Jiang, Shuang
    et al.
    Northeastern Univ, Peoples R China.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Jia, Nan
    Northeastern Univ, Peoples R China.
    Zhao, Xiang
    Northeastern Univ, Peoples R China.
    Zuo, Liang
    Northeastern Univ, Peoples R China.
    Microstructural and textural evolutions in multilayered Ti/Cu composites processed by accumulative roll bonding2019In: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 35, no 6, p. 1165-1174Article in journal (Refereed)
    Abstract [en]

    Ti/Cu multilayered composites were fabricated via accumulative roll bonding (ARB). During co-deformation of the constituent metals, the hard Ti layers necked preferentially and then fragmented with the development of shear bands. Transmission electron microscopy showed that with increasing ARB cycles, grains in Ti were significantly refined even though dynamic recrystallization has occurred. For Cu the significant grain refinement was only found within the shear banded region when the composite was processed after five ARB cycles. Due to the diffusion of Cu atoms into Ti at the heterophase inter faces, amorphization with a width less than 10 nm was identified even in the composite processed by one cycle. At higher ARB cycles, the width of amorphous region increased and intermetallic compounds CuTi appeared from the region. The lattice defects introduced at the heterophase interfaces under roll bonding was responsible for the formation of the nano-scaled compounds. X-ray diffraction showed that an abnormal {11 (2) over bar0} fiber texture was developed in Ti layers, while significant brass-type textures were developed in Cu layers. Some orientations along the {11 (2) over bar0} fiber favored the prismatic amp;lt;aamp;gt; slip for Ti. Tensile tests revealed the elevated strength without a substantial sacrifice of ductility in the composites during ARB. The unique mechanical properties were attributed to the significantly refined grains in individual metals, the good bonding between the constituent metals, as well as the development of an abnormal {11 (2) over bar0} fiber texture in Ti layers. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science amp; Technology.

  • 48.
    Jiang, Shuang
    et al.
    Northeastern Univ, Peoples R China.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Mathis, Kristian
    Charles Univ Prague, Czech Republic.
    Yan, Hai-Le
    Northeastern Univ, Peoples R China.
    Farkas, Gergely
    Czech Acad Sci, Czech Republic.
    Hegedues, Zoltan
    Deutsch Elektronen Synchrotron DESY, Germany.
    Lienert, Ulrich
    Deutsch Elektronen Synchrotron DESY, Germany.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Zhao, Xiang
    Northeastern Univ, Peoples R China.
    Zuo, Liang
    Northeastern Univ, Peoples R China.
    Jia, Nan
    Northeastern Univ, Peoples R China.
    Wang, Yan-Dong
    Univ Sci & Technol Beijing, Peoples R China.
    Shear banding-induced 〈c + a〉 slip enables unprecedented strength-ductility combination of laminated metallic composites2022In: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 110, p. 260-268Article in journal (Refereed)
    Abstract [en]

    Shear bands in metallic materials have been reported to be catastrophic because they normally lead to non-uniform plastic deformation. Ductility of laminated metallic composites deteriorates with increasing processing strain, particularly for those having hexagonal-close-packed (hcp) constituents due to inadequate slip systems and consequently prominent shear banding. Here, we propose a design strategy that counterintuitively tolerates the bands with localized strains, i.e. the shear banded laminar (SBL) structure, which promotes 〈c + a〉 dislocation activation in hcp metals and renders unprecedented strengthductility combination in hcp-metal-based composites fabricated by accumulative roll bonding (ARB). The SBL structure is characterized with one soft hcp metal constrained by adjacent hard metal in which dislocations have been accumulated near the bimetal interfaces. High-energy X-ray diffraction astonishingly reveals that more than 90% of dislocations are non-basal in Ti layers of the SBL Ti/Nb composite processed by eight ARB cycles. Moreover, 〈c + a〉 dislocations occupy a high fraction of ∼30%, promoting further 〈c + a〉 cross slip. The unique stress field tailored by both shear banding and heterophase interface-mediated deformation accommodation triggers important 〈c + a〉 slip. This SBL design is of significance for developing hcp-based laminates and other heterostructured materials with high performances.

  • 49.
    Johansson, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ektarawong, Annop
    Chulalongkorn Univ, Thailand; Minist Higher Educ Sci Res & Innovat, Thailand.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Theoretical investigation of mixing and clustering thermodynamics of Ti1-xAlxB2 alloys with potential for age-hardening2020In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 128, no 23, article id 235101Article in journal (Refereed)
    Abstract [en]

    Metastable ternary ceramic alloys with clustering tendencies are candidates for hard coating applications. In this work, mixing thermodynamics and structural parameters of ceramic Ti1-xAlxB2 alloys are investigated with theoretical first-principles based techniques. Lattice dynamics and temperature dependent phase stability are explored. The effect of lattice vibrations on the total free energy is investigated and found to not significantly affect phase stability at temperatures below 1200K. The isostructural phase diagram is derived using both cluster expansion-based Monte Carlo simulations and a mean field approach. The phase diagram shows a miscibility gap that does not close at temperatures below the melting or decomposition temperatures of the constituent binaries TiB2 and AlB2. The lattice mismatch between phases in the system is small regardless of their composition even at elevated temperatures. These findings support the prospect of age hardening due to coherent isostructural decomposition, such as spinodal decomposition, in coatings of Ti(1-x)AlxB(2) as diffusion is activated at elevated temperature. (c) 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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  • 50.
    Johansson, Maria
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Haraldsson, Joakim
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Karlsson, Magnus
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.
    Energy efficient supply chain of an aluminium product in Sweden – What can be done in-house and between the companies?2018In: eceee 2018 Industrial Summer Study proceedings / [ed] Therese Laitinen Lindström, Ylva Blume & Nina Hampus, Stockholm, Sweden: European Council for an Energy Efficient Economy (ECEEE), 2018, p. 369-377Conference paper (Refereed)
    Abstract [en]

    According to the Energy Efficiency Directive executed by the European Union, each member state is obliged to set a national target on energy efficiency. This requirement constitutes the basis for governments to formulate policy measures directed towards industrial companies. Such policy measures, along with the demand for cost-effective production to remain competitive on the market, motivates industrial companies to improve their energy efficiency. The aluminium industry is energy intensive and consumes substantial amounts of electricity and fossil fuels, resulting in both direct and indirect greenhouse gas emissions. This paper presents a study of the production of an aluminium product in Sweden in terms of implemented energy efficiency measures in the supply chain and potential areas for further improvement. Most previous studies have focused on energy efficiency measures in individual companies (value chains). However, this paper presents and analyses energy efficiency measures not only in each individual company but also in the entire supply chain of the product. The supply chain studied starts with secondary aluminium production followed by the production of a part of an automobile motor and ends with installing the motor detail in a car. Empirical data were gathered through a questionnaire and a focus group. The study shows the great potential for further energy efficiency improvements in the value chains of each individual company and in the whole supply chain. The work shown here is a part of a larger research project performed in close cooperation with the Swedish aluminium industry.

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