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  • 1.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima AB, Sweden.
    A study on fatigue damage and crack initiation in austenitic steel matrix during very high cycle fatigue2024Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 179, artikel-id 108033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue damage and crack initiation behavior has been studied in an austenitic stainless steel using a novel progressive stepwise load increasing method with a cycle step greater than 108 cycles and investigated with a FIB-SEM. Subsurface crack origin with a fine granular area in the matrix was formed. Heterogeneous plastic deformation causes strain localization and grain fragmentation. Localized plasticity exhaustion induces crack initiation. A crack origin is completed once a short crack reaches the stress intensity factor threshold for stage II crack propagation. This study provides a fundamental discussion how damage and crack initiation in matrix occur during very high cycle fatigue.

  • 2.
    Zhu, Zhenyu
    et al.
    Chengdu Univ, Peoples R China.
    Chen, Maolin
    Chengdu Univ, Peoples R China.
    He, Mingge
    CNPC Chuanqing Drilling Engn Co Ltd, Peoples R China.
    Zhang, Junliang
    PetroChina, Peoples R China.
    Huang, Yanyan
    Chengdu Univ, Peoples R China.
    Chen, Siqi
    PetroChina, Peoples R China.
    Du, Xuanyu
    PetroChina, Peoples R China.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Chengdu Univ, Peoples R China.
    Wang, Qingyuan
    Chengdu Univ, Peoples R China.
    Coupling life prediction of bending very high cycle fatigue of completion strings made of different materials using deep wise separable convolution2024Ingår i: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article predicts bending very high cycle fatigue (VHCF) life of three typical nickel-based alloys SM2550, BG2532, and G3 used for completion strings. Fatigue tests were conducted on the three alloys using an ultrasonic fatigue system at a frequency of 20 kHz. The results showed that the fatigue strength ranges of the three alloys were markedly different, reflecting their different sensitivities to fatigue loading. Scanning electron microscope observations revealed numerous fatigue crack origins with internal decohesion in the fatigue source region. To achieve unified prediction of the fatigue life for the three alloys, a prediction model based on deep learning was built with inputs including fatigue initiation quantity, cleavage facet size, and other fatigue fracture characteristics. It was found that single source feature was insufficient to obtain satisfactory prediction accuracy for all alloys, while multifeature coupling integration could significantly improve the prediction precision, enabling reliable prediction of alloy fatigue life. This study provides new insights into bending VHCF life prediction. This article predicts bending VHCF life for three completion strings. Bending VHCF life model utilizing deep wise separable convolution was established. Deep learning can effectively integrate with bending VHCF analyses.

  • 3.
    Chalapathi, Darshan
    et al.
    Laboratory for Mechanics of Microstructures, Department of Metallurgical and Materials Engineering, IIT Madras, Chennai, India.
    Nordström, Joakim
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima, Sandviken, Sweden.
    Siriki, Raveendra
    Alleima, Sandviken, Sweden.
    Lautrup, Lisa
    Alleima, Sandviken, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. 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 6252024Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 898, artikel-id 146404Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. 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 steel2024Ingår i: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 41, nr 1, s. 169-176Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Ohlin, O.
    et al.
    Alleima, Sweden.
    Siriki, R.
    Alleima, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Medicinska fakulteten. Linköpings universitet, Tekniska fakulteten. Alleima, Sweden.
    Long-term creep behaviours and structural stabilities of austenitic heat-resistant stainless steels2024Ingår i: Materials at High Temperature, ISSN 0960-3409, E-ISSN 1878-6413, Vol. 41, nr 1, s. 61-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For heat resistant alloys, long-term structural stability at high temperatures is a critical issue for alloy design and applications. In this paper, the long-term creep behaviours and structural stabilities of six heat resistant high Ni alloys and austenitic stainless steels have been studied. The longest creep rupture life is up to 359 283 hours. High Ni and Cr alloys show a good combination of high creep and oxidation resistances. Precipitation of nano MX particles with a very low growth rate improves long-term creep resistance at high temperatures. Long-term stable multiple nanoprecipitates of MX, Cu-rich, Laves and M23C6 phases can greatly contribute to the creep strength. Low Ni austenitic stainless steels show comparatively low oxidation and creep resistances. It was first found that at 800 & DEG;C, Cr2N could form in the low Ni steel with a long-term crept by the absorption of nitrogen from the air into the matrix.

  • 6.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima AB, Sweden.
    Siriki, Raveendra
    Alleima AB, Sweden.
    Wang, Qingyuan
    Chengdu Univ, Peoples R China.
    On fatigue crack origin with a fine granular area in matrix without defect2024Ingår i: Materialia, E-ISSN 2589-1529, Vol. 33, artikel-id 102004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue crack initiation in metallic materials during very high cycle fatigue has been characterized by a subsurface crack origin with defect such as an inclusion. In this paper, fatigue damage behavior in an austenitic stainless steel has been studied using a novel progressive stepwise load increasing test method with each cycle step higher than 108 cycles. Subsurface crack origin with a fine granular area has formed in the matrix without defect. This is a new phenomenon. The mechanism has been investigated using Focused Ion Beam crosssectioning and electron channeling contrast imaging techniques. Strain localization, grain fragmentation and local plasticity exhaustion are the main factors that cause fatigue damage and crack initiation in the matrix. This study provides a fundamental understanding how material damage and crack initiation occur in material matrix during very high cycle fatigue.

  • 7.
    Zhu, Zhenyu
    et al.
    Chengdu Univ, Peoples R China.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Chengdu Univ, Peoples R China.
    Zhang, Junliang
    PetroChina Southwest Oil & Gas Field CDB Operating, Peoples R China.
    Li, Xiaotao
    Chengdu Univ, Peoples R China.
    Huang, Yanyan
    Chengdu Univ, Peoples R China.
    Zhang, Jie
    Southwest Jiaotong Univ, Peoples R China.
    Yu, Chao
    Southwest Jiaotong Univ, Peoples R China.
    Wang, Qingyuan
    Chengdu Univ, Peoples R China.
    Origin of prestrain-induced cyclic-strain hardening: Multi-scale experimental characterizations and simulations of 7075 aluminum alloy2024Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 238, artikel-id 112711Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of prefabricated dislocation features induced by rate dependent prestrain on the post-cyclic process in 7075 aluminum alloy exhibits significant variations, which are of great importance in terms of concerns, designs, and discoveries. Considering strain rate dependent prestrain provides diversified hardening stimuli for the subsequent cyclic process. The maximum cyclic stress in the post-cyclic stage was maintained at the same level as the prestress with strain rates ranging from 10-4s-1 to 10-1s-1. Subsequently, by adjusting post-cycling stress amplitude, research was conducted on quasi-plastic amplitude cycle (QPC) and low plasticity amplitude cycle (LPC) loading conditions. Through experimental mechanism analysis, as well as verification through molecular dynamics and crystal plasticity simulations, prestrain induced by rapid strain rates enhanced the hardening during QPC, stemming from the effects of matrix reconstruction strengthening and wavy structured grain boundaries. However, prestrain induced by slow strain rates promoted the hardening during LPC, primarily arising from the non-uniform crystal structures within individual grains, which was achieved through the complex sub-crystal clusters at grain boundaries, along with intracrystal orderly slipping lattice. These findings offer new insights for the optimization of microstructural design through dislocation engineering.

  • 8.
    Nordström, Joakim
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima AB, Sweden.
    Dong, Zhihua
    Department of Materials Science and Engineering, KTH, Sweden; Material Science and Engineering, Chongqing University, China.
    Lautrup, Lisa
    Alleima AB, Sweden.
    Siriki, Raveendra
    Alleima AB, Sweden.
    Vitos, Levente
    Department of Materials Science and Engineering, KTH, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima AB, Sweden.
    Temperature study of deformation twinning behaviour in Nickel-base Superalloy 6252024Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, artikel-id 146628Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Deformation behaviour in the Nickel-base superalloy 625 has been studied by tensile testing at four temperatures: 295, 223, 173 and 77 K. The microstructure has been investigated using TEM, FIB-SEM, EBSD and ECCI techniques. Deformation in the alloy turns out to be a competitive course of events between at least two deformation mechanisms, namely dislocation slip and deformation twinning. Slip is the predominant deformation mechanism at higher temperatures. While at 77 K, deformation induced twinning gives an extra degree of freedom as one of the main deformation mechanisms, i.e., the material shows a twin induced plasticity, TWIP, behaviour. Ab initio calculations indicate that the influence of cryogenic/sub-zero temperatures on the stacking fault energy of this alloy can be limited and that the formation of deformation twins cannot be determined solely by the stacking fault energy. The results implies that it is the critical strain and strain hardening rate that influences the deformation twinning onset and twinning rate.

  • 9.
    Huang, Shuo
    et al.
    China Univ Geosci, Peoples R China; China Univ Geosci, Peoples R China.
    Dastanpour, Esmat
    Royal Inst Technol, Sweden.
    Schonecker, Stephan
    Royal Inst Technol, Sweden.
    Strom, Valter
    Royal Inst Technol, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. AB Sandvik Mat Technol R& D Ctr, Sweden.
    Kiss, Laszlo Ferenc
    Wigner Res Ctr Phys, Hungary.
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Hungary.
    Jin, Hongyun
    China Univ Geosci, Peoples R China.
    Eriksson, Olle
    Uppsala Univ, Sweden; Orebro Univ, Sweden.
    Vitos, Levente
    Royal Inst Technol, Sweden; Wigner Res Ctr Phys, Hungary; Uppsala Univ, Sweden.
    Combinatorial design of partial ordered Al-Cr-Mn-Co medium-entropy alloys for room temperature magnetic refrigeration applications2023Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 123, nr 4, artikel-id 044103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multi-component alloys have received increasing interest for functional applications in recent years. Here, we explore the magnetocaloric response for Al-Cr-Mn-Co medium-entropy alloys by integrated theoretical and experimental methods. Under the guidance of thermodynamic and ab initio calculations, a dual-phase system with large magnetic moment, i.e., Al50Cr19Mn19Co12, is synthesized, and the structural and magnetocaloric properties are confirmed via characterization. The obtained results indicate that the selected alloy exhibits a co-continuous mixture of a disordered body-centered cubic and an ordered B2 phase. The ab initio and Monte Carlo calculations indicate that the presence of the ordered B2 phase is responsible for the substantial magnetocaloric effect. The magnetization measurements demonstrated that this alloy undergoes a second-order magnetic transition with the Curie temperature of similar to 300 K. The magnetocaloric properties are examined using magnetic entropy change, refrigeration capacity, and adiabatic temperature change. The property-directed strategy explored here is intended to contribute to the study of potential multi-component alloys in magnetocaloric applications.

  • 10.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima, Sweden.
    Bergström, Jens
    Karlstad Univ, Sweden.
    Burman, Christer
    Karlstad Univ, Sweden.
    Crack Initiation in Bulk Matrix of Austenitic Stainless Steel during Very High Cycle Fatigue2023Ingår i: Materials Performance and Characterization, ISSN 2379-1365, E-ISSN 2165-3992, Vol. 12, nr 2, artikel-id MPC20220094Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the very high cycle fatigue regime, fatigue crack initiation in high-strength steels is usually correlated to a subsurface inclusion with a fine granular area (FGA). Localized stress-strain concentration at the subsurface inclusion is a critical factor. Fatigue crack initiation with an FGA in the bulk matrix without any defect has rarely been reported. In this paper, a fundamental study on the formation of FGAs in the bulk matrix of an austenitic stainless steel has been carried out using a progressive stepwise load-increasing test with a cycle step of about 108 cycles. FGA formation in the subsurface bulk matrix has been observed. The micro structural damage in the fatigue-tested specimens has been studied using the electron channeling contrast imaging electron microscopy technique. Strain localization and grain fragmentation are the main processes for the formation of FGAs. Local plasticity exhaustion leads to crack initiation due to local stress concentrations. This method can also be used to predict the fatigue damage process, especially the damage rate in individual specimens.

  • 11.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sweden.
    Bergstrom, Jens
    Karlstad Univ, Sweden.
    Burman, Christer
    Karlstad Univ, Sweden.
    Formation of fine granular area in a non-defect matrix of austenitic stainless steel during very high cycle fatigue2023Ingår i: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 46, nr 6, s. 2364-2373Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fine granular area, FGA, is a typical phenomenon observed at the very high cycle fatigue fracture crack origin with a subsurface defect in the material. The FGA has been widely investigated, and different mechanisms have been proposed. In this paper, the formation of FGA in a non-defect matrix of one austenitic steel during very high cycle fatigue was studied using a progressive stepwise load-increasing method and electron scanning microscopy/electron channeling contrast imaging (ECCI) technique. A nano rough surface area or FGA at the fatigue crack origin has been observed in the subsurface matrix without any defect. It is a new phenomenon. A mechanism was proposed using the dislocation plasticity theory. The formation of FGA in a non-defect matrix is a localized plasticity exhausting process by strain localization, grain fragmentation, stress concentration and nano crack initiation and propagation along low-angle grain boundaries.

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  • 12.
    Dong, Han
    et al.
    Shanghai Univ, Peoples R China.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima AB, Sweden.
    Guo, Xiaofei
    Shanghai Univ, Peoples R China.
    High Nitrogen Steels2023Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 94, nr 10, artikel-id 2300505Artikel i tidskrift (Övrigt vetenskapligt)
  • 13.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sweden.
    Siriki, Raveendra
    Sandvik Mat Technol, Sweden.
    Nordström, Joakim
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. 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 Steels2023Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 94, nr 10, artikel-id 2200359Artikel i tidskrift (Refereegranskat)
    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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  • 14.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Wärner, Hugo
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Alleima AB, Stragetic research, Sandviken, Sweden.
    Segersäll, Mikael
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Thermomechanical Fatigue of Heat Resistant Austenitic Alloys2023Ingår i: Procedia Structural Integrity, ISSN 2452-3216, Vol. 43, s. 130-135Artikel i tidskrift (Refereegranskat)
    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.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. AB Sandvik Materials Technology R and D Center, Sandviken, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    High Temperature Fatigue of Aged Heavy Section Austenitic Stainless Steels2022Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 15, nr 1, artikel-id 84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work investigates two austenitic stainless steels, Sanicro 25 which is a candidate for high temperature heavy section components of future power plants and Esshete 1250 which is used as a reference material. The alloys were subjected to out-of-phase (OP) thermomechanical fatigue (TMF) testing under strain-control in the temperature range of 100 ∘C to 650 ∘C. Both unaged and aged (650 ∘C, 3000 h) TMF specimens were tested to simulate service degradation resulting from long-term usage. The scanning electron microscopy methods electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were used to analyse and discuss active failure and deformation mechanisms. The Sanicro 25 results show that the aged specimens suffered increased plastic straining and shorter TMF-life compared to the unaged specimens. The difference in TMF-life of the two test conditions was attributed to an accelerated microstructural evolution that provided decreased the effectiveness for impeding dislocation motion. Ageing did not affect the OP-TMF life of the reference material, Esshete 1250. However, the structural stability and its resistance for cyclic deformation was greatly reduced due to coarsening and cracking of the strengthening niobium carbide precipitates. Sanicro 25 showed the higher structural stability during OP-TMF testing compare with the reference material.

  • 16.
    Öhlin, Oscar
    et al.
    Sandvik Materials Technology, Sandviken.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken.
    Siriki, Raveendra
    Sandvik Materials Technology, Sandviken.
    Structural Stability of Sandvik 3R60™ After 240 131 Hours Ageing and Creep Test at 700 °C2022Ingår i: Transactions of the Indian National Academy of Engineering, ISSN 2662-5415, Vol. 7, nr 2, s. 625-633Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sandvik 3R60™ is an AISI 316/316L type of stainless steel. In this paper, the structural stability of the material under long-term ageing or creep test has been studied. The material had been creep tested with a stress of 45 MPa at 700 °C. The predicted rupture time for the creep specimen was about 100,000 h; however, the specimen broke first after 240,131 h. The oxidation behavior and structural stability in both aged and creep-tested samples were studied using SEM/EDS, EBSD and ECCI techniques. Thin oxide layers near the sample surface are mainly spinel oxides and eskolaite (Cr2O3). Sigma phase, χ-phase, Eta phase, M23C6 and Cr2N have been observed in the matrix of the samples. In the crept sample, the amount of sigma phase has increased, so has Eta phase and χ-phase as well. Thermo-Calc evaluation can reasonably predict precipitation of sigma phase, Eta phase and M23C6, but not χ-phase and Cr2N phases. Creep crack initiation behavior has been studied. It is mainly noticed to start at surface oxide layer or coarse sigma particles at grain boundary or triple point. Additionally, it is also observed that the presence of a thin Cr2O3 layer between the oxide and matrix along with discontinuous sigma phase distribution at grain boundary that will reduce the risk for creep crack initiation. Further, the crack propagation behavior has also been discussed.

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  • 17.
    Mondal, Riya
    et al.
    Dept of Metallurgical Engineering and Materials Science, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Kumar Bonagani, Sunil
    Materials Processing and Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay Mumbai, India.
    Raut, Parvej
    Dept of Mechanical Engineerin, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Kumar, Saurabh
    Dept of Metallurgical Engineering and Materials Science, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Sivaprasad, P. V.
    Sandvik Materials Technology, Sandviken, Sweden.
    Chai, Guocai
    Sandvik Materials Technology, Sandviken.
    Kain, V.
    Materials Processing and Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai, Indiar.
    Samajdar, I.
    Dept of Metallurgical Engineering and Materials Science, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Dynamic Recrystallizatin and Phase-Specific Corrosion Performance in a Super Duplex Stainless Steel2021Ingår i: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, artikel-id 11665Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Super duplex stainless steel specimens were subjected to controlled (in a deformation simulator) thermal and thermal plus deformation treatments. The objective was to relate the corrosion performance with hot (1000-1300°C) deformed microstructures. The microstructural evolutions were quantified with extensive microtextural characterization and measurements of phase-specific micro-hardness. The corrosion behavior was investigated by anodic polarization and phase-specific selective dissolution methods. Though the thermal treatment imposed an increasing degradation in corrosion performance with holding temperature, the associated deformation at that temperature brought a non-monotonic behavior. The best corrosion performance (or the lowest passivation current density) was noted in the specimen deformed at ~1100°C. This superior corrosion behavior was attributed to the grain size refinement in the austenite phase. Finally, a combination of transmission Kikuchi diffraction (TKD) plus transmission electron microscopy (TEM) clearly related the grain size refinement to discontinuous dynamic recrystallization. The overall corrosion behavior was shown to be determined by a balance between decreasing austenite fraction and dynamic recrystallization-induced grain size refinement of the austenite phase.

  • 18.
    Huang, Shuo
    et al.
    Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China;Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Uppsala SE-751 20, Sweden.
    Dong, Zhihua
    State Key Laboratory of Mechanical Transmissions, College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China.
    Mu, Wangzhong
    Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm SE-100 44, Sweden.
    Ström, Valter
    Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm SE-100 44, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. AB Sandvik Materials Technology R&D Center, Sandviken SE-811 81, Sweden.
    Varga, Lajos Károly
    Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest H-1525, Hungary.
    Eriksson, Olle
    Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Uppsala SE-751 20, Sweden;School of Science and Technology, Örebro University, Örebro SE-701 82, Sweden.
    Vitos, Levente
    Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Uppsala SE-751 20, Sweden;Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm SE-100 44, Sweden;Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest H-1525, Hungary.
    Magnetocaloric properties of melt-spun MnFe-rich high-entropy alloy2021Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 119, nr 14, artikel-id 141909Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-entropy functional materials are of great interest in materials science and engineering community. In this work, ab initio electronic structure calculations of the phase stability and magnetic transition temperature of AlxCr0.25MnFeCo0.25−yNiy (x = 0–0.5, y = 0–0.25) alloys were performed to screen for compositions showing promising magnetocaloric properties in the vicinity of room temperature. The selected Al0.44Cr0.25MnFeCo0.05Ni0.2 alloy was synthesized via a rapid solidification technique and systematically characterized with respect to its structural and magnetocaloric properties. The results indicate that this alloy possesses a homogeneous microstructure based on an underlying body-centered cubic lattice and has a Curie temperature of ∼340 K. The temperature dependence of the adiabatic temperature change was evaluated using both direct and indirect methods. The ab initio-assisted design of 3d-metal-based high-entropy alloys, explored here, is intended to contribute to the development of magnetic refrigerators for room-temperature applications. 

  • 19.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Xu, Jinghao
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Microstructural Evolution During High Temperature Dwell-fatigue of Austenitic Stainless Steels2021Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 143, artikel-id 105990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microstructural evolution related to the mechanical response from isothermal dwell-fatigue testing at 700 °C of two austenitic steels, Esshete 1250 and Sanicro 25, is reported. Coherent Cu-precipitates and incoherent Nb-carbides were found to impede dislocation motion, increase hardening and improving the high temperature properties of Sanicro 25. Sparsely placed intergranular Cr- and Nb-carbides made Esshete 1250 susceptible to creep damage and intergranular crack propagation, mainly from interaction of the carbides and fatigue induced slip bands. Dynamic recrystallization of the plastic zone at the crack tip appeared to affect crack propagation of Sanicro 25 by providing an energetically privileged path.

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  • 20.
    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
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. 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 temperature2021Ingår i: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 79, s. 15-20Artikel i tidskrift (Refereegranskat)
    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.

  • 21.
    Huang, Shuo
    et al.
    Faculty of Materials Science and Chemistry, China University, Wuhan, China and Dept of Physics and Astronomy, Div of Materials Theory, Uppsala University.
    Dong, Zhihua
    State of Key Laboratory of Mechanical Transmissions, Chongqing University, China and National Engineering Research Center for Magnesium Alloys, Chongqing University, China.
    Dastanpour, Esmat
    Dept of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Ström, Valter
    Dept of Materials Science and Engineering, KTH, Stockholm.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken.
    Varga, Lajos Károly
    Inst of Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, Hungary.
    Eriksson, Olle
    Dept of Physics and Astronomy, Materials Theory, Uppsala University and School of Science and Technology, Örebro University.
    Vitos, Levente
    Dept of Physics and Astronomy, Materials Theory, Uppsala University and Dept of Materials Science and Engineering, KTH, Stockholm and Inst for Solid State Physics and Optics, Wigner Research Centre for Physics, Budapest, Hungary.
    Vibrational Entropy-enhanced Magnetocaloric Effect in Mn-rich High-entropy Alloys2021Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 119, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the AlxCr0.2MnFe0.5Co0.3Ni0.5 (0.3 <= x <= 0.7) high-entropy alloys by combining experimental and theoretical techniques. X-ray diffraction and magnetization measurements indicate that Al alters the crystal structure and the entropy change upon magnetization-demagnetization while keeping the Curie temperature almost unchanged. First-principles calculations of the vibrational, magnetic, electronic, and configurational entropies show that the leading entropy change is due to the magnetic and vibrational degrees of freedom. The presence of the body-centered-cubic phase, showing a sizable elastic softening upon magnetic transition, brings about the substantial magnetocaloric effect in this family of alloys.

  • 22.
    Mondal, Riya
    et al.
    Dept of Metallurgical Engineering and Materials Science, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Kumar Bonagani, Sunil
    Materials Processing and Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay Mumbai, India.
    Raut, Parvej
    Dept of Mechanical Engineerin, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Sivaprasad, P. V.
    Sandvik Materials Technology, Sandviken, Sweden.
    Chai, Guocai
    Sandvik Materials Technology, Sandviken.
    Kain, V.
    Materials Processing and Corrosion Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai, Indiar.
    Samajdar, I.
    Dept of Metallurgical Engineering and Materials Science, Indian Inst of Technology, Bombay, Powai, Mumbai, India.
    Role of Recovery and Recrystallization on the Post Cold Work Corrosion Performance in a Super Duplex Stainless Steel2020Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 167, nr 10, artikel-id 101501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cold rolled super duplex stainless steel (SDSS) were subjected to recovery (300 °C) and recrystallization (1020 °C) annealing. Annealing related microstructural changes were quantified with microtexture and phase-specific micro-hardness. Subsequent electrochemical characterization included potentiodynamic anodic polarization tests and Mott-Schottky analysis. It was established, for both single and two-phase specimens, that extensive recovery did not affect the electrochemical behavior, while the shortest recrystallization led to significant improvements in corrosion resistance. Improvements in corrosion performance of cold rolled SDSS was thus possible only through recrystallization, and associated removal of large lattice curvatures in the metallic substrate and reduced defect densities in the protective oxide film.

  • 23.
    Dong, Zhihua
    et al.
    KTH Royal Inst Technol, Sweden.
    Li, Wei
    KTH Royal Inst Technol, Sweden.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. AB Sandvik Mat Technol RandD Ctr, Sweden.
    Vitos, Levente
    KTH Royal Inst Technol, Sweden; Uppsala Univ, Sweden; Wigner Res Ctr Phys, Hungary.
    Strong temperature - Dependence of Ni -alloying influence on the stacking fault energy in austenitic stainless steel2020Ingår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 178, s. 438-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using ab initio alloy theory, we calculate the impact of Ni on the stacking fault energy in austenitic stainless steel as a function of temperature. We show that the influence of Ni strongly couples with temperature. While a positive effect on the stacking fault energy is obtained at ambient temperature, the opposite negative effect is disclosed at elevated temperatures. An important rationale behind is demonstrated to be the variation of magneto-volume coupling induced by Ni alloying. The alloy influence on the finite temperature evolution of Ni impact is evaluated for elements Cr, Mo and N. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 24.
    Huang, Shou
    et al.
    Dept of Physics and Astronomy, Materials Theory, Uppsala univ + Dept Materials Science and Eng, KTH, Stockholm.
    Dong, Zhihua
    Dept of Materials Science and Eng, KTH, Stockholm.
    Mu, Wangzhong
    Dept of Materials Science and Eng, KTH, Stockholm.
    Ström, Valter
    Dept of Materials Science and Eng, KTH, Stockholm.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken.
    Vitos, Levente
    Dept of Physics and Astronomy, Materials Theory, Uppsala univ + Dept Materials Science and Eng, KTH, Stockholm + Inst for Solid State Physics ad Optic, Wigner Research Centre for Physics, Budapest, Hungary.
    Thermo-elastic Properties of BCC Mn-rich High-entropy Alloy2020Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Applied Physics Letters, Vol. 117, nr 16, artikel-id 164101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a chemically disordered solid solution, Al0.6Cr0.2MnFe0.5Co0.3Ni0.5, based on a body-centered cubic underlying lattice with the measured Curie temperature of ∼380 K. First-principles alloy theory is employed to investigate the temperature-dependent free energy, elastic constants, and coefficient of thermal expansion at the ferromagnetic and paramagnetic states. Theory and experiment are found to strengthen each other, and the results indicate that the magnetic state has a strong impact on the thermo-elastic properties of the considered alloy. The present advance in the thermo-magneto-elasticity enhances the understanding required for controlling the magnetic and mechanical response of multi-component systems.

  • 25.
    Suo, Jiao
    et al.
    Wuhan Univ, Peoples R China.
    Peng, Zhifang
    Wuhan Univ, Peoples R China.
    Yang, Huachun
    Dongfang Boiler Grp Co Ltd, Peoples R China.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sweden.
    Yu, Mingming
    Dongfang Boiler Grp Co Ltd, Peoples R China.
    Formation of Laves Phase in Sanicro 25 Austenitic Steel During Creep-Rupture Test at 700 degrees C2019Ingår i: METALLOGRAPHY MICROSTRUCTURE AND ANALYSIS, ISSN 2192-9262, Vol. 8, nr 2, s. 281-286Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanisms for the formation of Laves phase located at grain boundaries and in grain interiors in Sanicro 25 steel after creep-rupture test at 700 degrees C and 150/180MPa for 9862/5665h were studied, respectively. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometer, and multi-phase separation technology analysis reveals that Laves phase particles nucleated adjacently either to Si-enriched spots present in the bulky M23C6 carbides or to the grain boundary areas rich in Si, which made the bulky M23C6 carbides gradually divide into small pieces and eventually resulted in the formation of a refined mixture of M23C6 and Laves phase at grain boundaries. Laves phase particles formed independently in austenitic matrix and also dependently at interfaces between austenitic matrix and Z phase in grain interiors. The size and morphology of Laves phase formed at grain boundaries (in M23C6 carbides) and in grain interiors (austenitic matrix) are different. It is hoped that the presented findings will be helpful to understand the Laves phase formation and the grain boundary precipitate refinement correlated with good mechanical properties of this class of austenitic steels/alloys.

  • 26.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Wärner, Hugo
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    High Temperature Properties of Austenitic Stainless Steels for Future Power Plant Applications2019Konferensbidrag (Refereegranskat)
  • 27.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Influence of Ageing on Thermomechanical Fatigue of Austenitic Stainless Steels2019Ingår i: Procedia Structural Integrity / [ed] Elsevier, Elsevier, 2019, Vol. 23, s. 354-359Konferensbidrag (Refereegranskat)
  • 28.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Microscopic Evaluation of Creep-Fatigue Interaction in Heat Resistant Austenic Alloys2019Konferensbidrag (Refereegranskat)
  • 29.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Structural Integrity and Impact Toughness of Austenitic Stainless Steels2019Ingår i: Proceedings of the 13th International Conference on the Mechanical Behaviour of Materials, International Congress on Mechanical Behavior of Materials , 2019, s. 270-275Konferensbidrag (Refereegranskat)
  • 30.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken, Sweden.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Thermomechanical Fatigue Behaviour of Aged Heat Resistant Austenitic Alloys2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, nr 127, s. 509-521Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increasing demands for efficiency and flexibility result in more severe operating conditions for the materials used in critical components of biomass power plants. These operating conditions involve higher temperature ranges, more pronounced environmental effects and cyclic operations. Austenitic stainless steels have shown to possess promising high temperature properties which makes them suitable as candidates for critical components in biomass power plant. However, their behaviour under such conditions is not yet fully understood. This work investigates three commercial austenitic alloys: Esshete 1250, Sanicro 25 and Sanicro 31HT. The alloys were subjected to in-phase (IP) thermomechanical fatigue (TMF) testing under strain-control in the temperature range of 100–800 °C. Both virgin and pre-aged TMF specimens were tested in order to simulate service degradation resulting from long-term usage. The results show that the pre-aged specimens suffered shorter TMF-life compared to the virgin specimens. The scanning electron microscopy methods electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were used to analyse and discuss active failure and deformation mechanisms. The difference in TMF-life produced by the two testing conditions was attributed to an embrittling effect by precipitation, reduced creep properties and oxidation assisted cracking.

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    Thermomechanical Fatigue Behaviour of Aged Heat Resistant Austenitic Alloys
  • 31.
    Nordström, Joakim
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Siriki, Raveendra
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    TWIP and Fracture Behaviour in the Superalloy 625 at Room and Cryogenic Temperatures2019Ingår i: Procedia Structural Integrity / [ed] Elsevier, Elsevier, 2019, Vol. 23, s. 457-462Konferensbidrag (Refereegranskat)
  • 32.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Creep-Fatigue Interaction in Heat Resistant Austenitic Alloys2018Ingår i: MATEC Web of Conferences 165 , 05001 (2018) / [ed] Henaff, G, EDP Sciences, 2018, Vol. 165Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work includes an investigation of two commercial austenitic steels: UNS S21500 (Esshete 1250) and UNS S31035 (Sandvik Sanicro (TM) 25). The materials were exposed to isothermal strain controlled fatigue with load controlled dwell time at maximum strain. The testing temperature used was 700 degrees C and the test cycles were performed in tension. Mechanical test data were obtained and analysed in order to define creep-fatigue damage diagrams at failure for the investigated austenitic alloys. During the given conditions, Sanicro 25 showed superior creep-fatigue life, suffered less amount of creep elongation for the same amount of strain amplitude and dwell times compared to Esshete 1250. Both alloys showed creep-fatigue interaction damage for specific test configurations.

  • 33.
    Nordstrom, Joakim
    et al.
    Sandvik Mat Technol, Sweden.
    Siriki, Raveendra
    Sandvik Mat Technol, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sweden.
    Deformation Twinning Behavior in High Ni-Austenitic Materials2018Ingår i: THERMEC 2018: 10TH INTERNATIONAL CONFERENCE ON PROCESSING AND MANUFACTURING OF ADVANCED MATERIALS, TRANS TECH PUBLICATIONS LTD , 2018, Vol. 941, s. 1591-1596Konferensbidrag (Refereegranskat)
    Abstract [en]

    Deformation twinning behaviors have been studied in high Ni alloys, Alloy 28 or Sanicro 28 and Alloy 625 at RT and at cryogenic temperature. The microstructures were evaluated using SEM-EBSD. Some constitutive approach has also been used in the discussion on the deformation twinning in high Ni-alloys. The results show that deformation twinning can occur in high Ni alloys depending on the chemical composition, strain range and stress conditions. TWIP can occur in the Ni based superalloy Alloy 625 at cryogenic temperature, which increases both strength and ductility. This is the first report of this phenomena for this alloy. Deformation twinning in high Ni alloys occurs heterogeneously in the material, depending on crystallographic parameters such as grain orientation and Schmid factor. Formation of deformation twins can lead to high texture in the material, which will contribute to the increase of strength. The mechanisms for the formation of deformation twins in high Ni alloys have been discussed.

  • 34.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sweden.
    Polak, Jaroslav
    Acad Sci Czech Republ, Czech Republic.
    Petras, Roman
    Acad Sci Czech Republ, Czech Republic.
    Heczko, Milan
    Acad Sci Czech Republ, Czech Republic.
    Kruml, Tomas
    Acad Sci Czech Republ, Czech Republic.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Fracture and Damage Behavior in an Advanced Heat Resistant Austenitic Stainless Steel During LCF, TMF and CF2018Ingår i: ECF22 - LOADING AND ENVIRONMENTAL EFFECTS ON STRUCTURAL INTEGRITY, ELSEVIER SCIENCE BV , 2018, Vol. 13, s. 843-848Konferensbidrag (Refereegranskat)
    Abstract [en]

    Future advanced ultra-supercritical power plant will be run at higher temperature and pressure. New materials will be used to meet the requirements. However, the structure integrity of these materials needs to be evaluated. Sanicro 25 is a newly developed advanced austenitic heat resistant stainless steel with the aim to be used in future 700 degrees C or 650 degrees C power plants to replace part of Ni based alloys. This paper provides an overview on the fracture and damage behavior in this material during LCF, TMF and CF. The cyclic hardening and fatigue life during LCF, TMF and CF will be discussed. The influence of prolonged service degradation has been analyzed by the use of pre-aged material for TMF and CF loading conditions. (C) 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers.

  • 35.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken, Sweden.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan J.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Characterization of austenitic stainless steels deformed at elevated temperature2017Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, nr 10, s. 4525-4538Artikel i tidskrift (Refereegranskat)
    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.

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  • 36.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Influence of Cyclic Oxidation in Moist Air on Surface Oxidation-Affected Zones2017Konferensbidrag (Refereegranskat)
  • 37.
    Bi, Yanyan
    et al.
    Sandvik Int Trading, Peoples R China.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. 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 plants2017Ingår i: PROCEEDINGS OF THE ASME POWER CONFERENCE JOINT WITH ICOPE-17, 2017, VOL 1, AMER SOC MECHANICAL ENGINEERS , 2017, artikel-id UNSP V001T01A008Konferensbidrag (Refereegranskat)
    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.

  • 38.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Robert
    Siemens Industrial Turbomachinery AB, Berlin.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Högberg, Jan
    AB Sandvik Materials Technology R&D Center Sandviken.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Local Surface Phase Stability During Cyclic Oxidation Process2017Konferensbidrag (Refereegranskat)
  • 39.
    Wärner, Hugo
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Thermomechanical Fatigue Behavior of Aged Heat Resistant Austenitic Alloys2017Konferensbidrag (Refereegranskat)
  • 40.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Toughening Behavior in Alloy 617 with Long Term Ageing2017Ingår i: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 258, s. 302-305Artikel i tidskrift (Refereegranskat)
  • 41.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technology, Sweden.
    Analysis of microdamage in a nickel-base alloy during very high cycle fatigue2016Ingår i: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 39, nr 6, s. 712-721Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue damage in a metallic material during very high cycle fatigue can strongly be correlated to the microstructure. This paper provides a review and a discussion on the micro damage behaviours in a nickel-base alloy during very high cycle fatigue using microplasticity and material mechanics. The results show that cyclic plastic deformation in this material can occur very locally even with an applied stress that is much lower than the yield strength. The fatigue damage occurs mainly at grain or twin boundaries because of local impingement and interaction of slip bands and these boundaries. The crystallographic properties, Schmid factors and orientations of grain and boundaries play very important roles to the fatigue damage. Subsurface fatigue crack initiation in the matrix is one of very high cycle fatigue mechanisms. Twinning and detwinning can also occur during the very high cycle fatigue process.

  • 42.
    Calmunger, Mattias
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology,Sandviken, Sweden.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Creep and Fatigue Interaction Behavior in Sanicro 25 Heat Resistant Austenitic Stainless Steel2016Ingår i: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 69, nr 2, s. 337-342Artikel i tidskrift (Refereegranskat)
    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.

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  • 43.
    Kangas, Pasi
    et al.
    Sandvik Materials Technology, Sandviken.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Duplex Stainless Steels for Oil & Gas Applications2016Konferensbidrag (Refereegranskat)
  • 44.
    Polák, Jaroslav
    et al.
    Institute of Physics of Materials, Academy of Sicences of Czech Republic, Brno.
    Petrás, Roman
    Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno.
    Heczko, Milan
    Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno.
    Kruml, Tomás
    Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Sandviken, Sweden.
    Evolution of the Cyclic Plastic Response of Sanicro 25 Steel Cycled at Ambient and Elevated Temperatures2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 83, nr 1, s. 75-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclic plastic response of the austenitic heat resistant steel Sanicro 25 has been studied during strain controlled low cycle fatigue tests performed at ambient and at elevated temperature. Simultaneously with the cyclic hardening/softening curves hysteresis loops during cyclic loading were analyzed using generalized statistical theory of the hysteresis loop. The probability density distribution function of the internal critical stresses, the effective saturated stress and their evolution during cycling were derived for various strain amplitudes. The internal dislocation structure and the surface relief at room and at elevated temperature were studied and correlated with the cyclic stress–strain response and the evolution of the probability density function of the internal critical stresses.

  • 45.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Materials Technology, Strategy research, Sandviken, Sweden.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Odqvist, Joakim
    Sandvik Materials Technology, Strategy research, Sandviken, Sweden.
    Influence of Dynamic Strain Ageing and Long Term Ageing on Deformation and Fracture Behaviors of Alloy 6172016Ingår i: THERMEC 2016 / [ed] C. Sommitsch, M. Ionescu, B. Mishra, E. Kozeschnik and T. Chandra, Trans Tech Publications, 2016, Vol. 879, s. 306-311Konferensbidrag (Refereegranskat)
    Abstract [en]

    Influences of dynamic strain ageing and long term ageing on deformation, damage and fracture behaviors of Alloy 617 material have been studied. Dynamic strain ageing can occur in this alloy at temperature from 400 to 700°C, which leads to a strain hardening and also an increase in fracture strain due to plastic deformation caused by twinning. Long term ageing at 700°C for up to 20 000 hours can cause different precipitation such as γ ́, M6C (Mo-rich) and M23C6 (Cr-rich) carbides. These carbides are both inter-and intra-granular particles. The long term ageing reduces the fracture toughness of the material, but the alloy can still have rather high impact toughness and fracture toughness even with an ageing at 700°C for 20 000 hour. The mechanisms have been studied using electron backscatter detection and electron channeling contrast imaging. It shows that besides dislocation slip, twinning is another main deformation mechanism in these aged Alloy 617 materials. At the crack front, plenty of micro or nanotwins can be observed. The formation of these twins leads to a high ductility and toughness which is a new observation or a new concept for this type of material.

  • 46.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Forsman, Tomas
    R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Gustavsson, Fredrik
    R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Microscopic and Nanoscopic Study on Subsurface Damage and Fatigue Crack Initiation During Very High Cycle Fatigue2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 83, nr 2, s. 288-292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    “Fish eye” is a typical phenomenon of fatigue crack initiation at a subsurface defect such as inclusion during very high cycle fatigue. The formation of a fine grained area and micro-debonding is believed to cause fatigue crack initiation. This paper provides a basic study on the formation of the fine grained area in a martensitic stainless steel during very high cycle fatigue using scanning electron microscopy, SEM, focused ion beam technique, FIB, electron backscatter diffraction, EBSD, and electron channeling contrast imaging, ECCI. The results show that the formation of a fine grained zone is a local behavior. The fine grained zone is very near the fatigue crack initiation origin. In the transversal direction (cross section), the depth of the fine grained zone is only few micrometers. In the longitudinal direction (crack propagation direction), the depth of the fine grain zone is about one micrometer. ECCI analysis shows that in the fine grained area with high retained strain, high plastic deformation can be found. Dislocation slip bands can be observed. They interact with grain boundaries and cause the formation of damage due to impingement cracking. The results indicate that occurrence of plastic deformation in metallic material during very high cycle fatigue is very localized, mainly near the front of the crack tip or a defect.

  • 47.
    Srnivasan, N
    et al.
    IITB-Monash Research Academy,Bombay, Mumbai, India.
    Kain, V
    Materials Science Division, Bhabha Atomic Research Centre, Mumbai, India.
    Birbilis, N
    Department of Materials Science and Engineering, Monash University, Clayton, Victoria, Australia.
    Sunil Kumar, B
    Materials Science Division, Bhabha Atomic Research Centre, Mumbai, India.
    Gandhi, M N
    Centre of Research in Nanotechnology & Science, IIT Bombay, Mumbai, India.
    Sivarprasad, P V
    Sandvik Group, R&D, Sandvik Asia , Dapodi, Pune, India.
    Chai, Guocai
    Sandvik Materials Technology, Sandviken, Sweden.
    Lodh, A
    Department of Metallaurgical Engineering & Materials Science, IIT Bombay, Mumbai, India.
    Ahmedabadi, P M
    Materials Science Division, Bhabha Atomic Research Centre, Mumbai, India.
    Samajdar, I
    Department of Metallurgical Engineering & Materials Science, IIT Bombay, Mumbai.
    Plastic Deformation and Corrosion in Austenitic Stainless Steel: A Novel Approach Through Microtexture and Infrared Spectroscopy2016Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 111, s. 404-413Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The anodic potentiodynamic polarization behaviors of austenitic stainless steels, with varying Cu (copper) and/or Mo (molybdenum) additions, were explored after plane strain compression. Though all the alloys showed developments in deformed microstructures, the presence of Cu + Mo did not result in strain induced martensite formation (SIMF). However, the presence of Cu + Mo revealed the highest degradation in corrosion performance. A combination of microtexture measurements and fourier transform infrared spectroscopy (FTIR)-imaging revealed that the presence of SIMF promoted post-passivation stability or retention of a protective Cr2O3 film.

  • 48.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Hernblom, Johan
    R&D Centre, Sandvik Materials Technology, Sandviken.
    Peltola, Timo
    Global Product Management and Global Technical, Sandviken.
    Forsberg, Urban
    Global Product Management and Global Technical, Sandviken.
    Sanicro 25 - An Advanced High Strength Heat Resistant Austenitic Stainless Steel2016Konferensbidrag (Refereegranskat)
  • 49.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. Sandvik Mat Technol, Sandviken, Sweden.
    Kangas, Pasi
    Sandvik Mat Technol, Sandviken, Sweden.
    Super and hyper duplex stainless steels: structures, properties and applications2016Ingår i: 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21), ELSEVIER SCIENCE BV , 2016, Vol. 2, s. 1755-1762Konferensbidrag (Refereegranskat)
    Abstract [en]

    In oil-gas industry, the exploration and development are now targeted to the deep reservoirs with high pressures, high temperatures and extreme corrosive environments. This requires that the materials used should have a good combination of extra high strength and excellent corrosion resistance. In order to meet these challenges, hyper duplex stainless steels have recently been developed. These materials have nitrogen contents up to about 0.5% and PRE-values close to 50, and show both highest corrosion pitting resistance and highest strength among the existing duplex stainless steels. The purpose of this paper is to provide an overview on hyper duplex stainless steels. It will mainly focus on the material development, microstructures, corrosion properties such as critical pitting corrosion temperature and crevice corrosion resistance, heterogeneous deformation behaviour of duplex stainless steel, and mechanical properties such as tensile properties and fatigue properties. These properties and the ratios of strength/weight will then be compared with those of other type of duplex stainless steels. The potential applications for hyper duplex stainless steels are also discussed. Copyright (C) 2016 The Authors. Published by Elsevier B.V.

  • 50.
    Polák, Jaroslav
    et al.
    Institute of Physics of Materials, Academy of Sciences of Czech Republic, Brno.
    Petrás, Roman
    Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno.
    Chai, Guocai
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Skorik, Viktor
    Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno.
    Surface Profile Evolution adn Fatigue Crack Initiation in Sanicro 25 Steel at Room Temperature2016Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 658, s. 221-228Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Evolution of the surface profile in room temperature cyclic loading has been studied in high alloy austenitic Sanicro 25 stainless steel. The localization of the cyclic plastic strain into persistent slip bands in the volume of the material leads to the formation of the specific surface relief in the form of persistent slip markings (PSMs) consisting of extrusions and intrusions. Evolution of the shape of PSMs was studied during interruption of cycling using SEM and FIB techniques. Three-dimensional information about the PSMs profiles was obtained. The profiles of both extrusions and intrusions and their evolution during cyclic loading were assessed. Generally extrusions grow, intrusions deepen and fatigue cracks initiate from the tip of the deepest intrusions. The experimental observations were compared and discussed in relation to existing physical models of surface relief formation and fatigue crack initiation.

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