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  • 151.
    Mouzon, Johanne
    et al.
    Luleå University of Technology.
    Lindbäck, Ture
    Luleå University of Technology.
    Odén, Magnus
    Luleå University of Technology.
    Influence of Agglomeration on the Transparency of Yttria Ceramics2008In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 10, no 91, p. 3380-3387Article in journal (Refereed)
    Abstract [en]

     In this work, five yttria powders with slightly different states of agglomeration, inherited from various procedures of dewatering the same precursor, were densified by a combination of vacuum sintering followed by hot isostatic pressing (HIP). In order to relate the densification behavior of each powder to its state of agglomeration, all powders were characterized by tap density measurements, X-ray diffraction, nitrogen adsorption, and laser scattering, while the microstructures of the corresponding densified samples were studied by optical and scanning electron microscopy. The five yttria powders produced sintered samples that differed remarkably from each other in terms of transparency. These discrepancies were related to the degree of fineness in the powders at two different levels. At the level of primary particles, fine and weakly agglomerated powder was very sinterable, causing abnormal grain growth to occur only in the very late stage of sintering. However, the resulting entrapped pores and reduction due to vacuum sintering were responsible for poor optical properties. At the agglomerate level, a bimodal size distribution was identified for all powders. For powders showing severe agglomeration of the primary particles, increasing the relative content of the smaller size population of agglomerates was found to trigger abnormal grain-growth earlier during presintering. This was attributed to the density around large agglomerates exceeding a critical threshold in the green bodies. Finally, transparency was achieved in samples for which presintering was stopped before grain growth became abnormal. This confirmed that the key to successfully obtaining transparency was to keep porosity intergranular, which could be removed subsequently by HIP treatment.

  • 152.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
    Reverse martensitic transformation and resulting microstructure in a cold rolled metastable austenitic stainless steel2008In: Steel Research International, ISSN 1611-3683, Vol. 79, no 6, p. 433-439Article in journal (Refereed)
    Abstract [en]

    The reverse martensitic transformation in cold-rolled metastable austenitic stainless steel has been investigated via heat treatments performed for various temperatures and times. The microstructural evolution was evaluated by differential scanning calorimetry, X-ray diffraction and microscopy. Upon heat treatment, both diffusionless and diffusion-controlled mechanisms determine the final microstructure. The diffusion reversion from α′-martensite to austenite was found to be activated at about 450°C and the shear reversion is activated at higher temperatures with Af′ ∼600°C. The resulting microstructure for isothermal heat treatment at 650°C was austenitic, which inherits the α′-martensite lath morphology and is highly faulted. For isothermal heat treatments at temperatures above 700°C the faulted austenite was able to recrystallize and new austenite grains with a low defect density were formed. In addition, carbo-nitride precipitation was observed for samples heat treated at these temperatures, which leads to an increasing Ms-temperature and new α′-martensite formation upon cooling.

  • 153.
    Mouzon, J.
    et al.
    Luleå University of Technology.
    Dujardin, C.
    Claude Bernard/Lyon1 University.
    Tillement, O.
    Claude Bernard/Lyon1 University.
    Odén, Magnus
    Luleå University of Technology.
    Synthesis and optical properties of Yb0.6Y1.4O3 transparent ceramics2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 464, no 1-2, p. 407-411Article in journal (Refereed)
    Abstract [en]

     Transparent yttrium oxide ceramics doped with 30 at.% ytterbium were successfully produced by a combination of pre-sintering and hot isostatic pressing. The influence on the final transparency of different densification states and porosity configurations obtained by varying pre-sintering conditions were investigated by optical and electron microscopy. Our results show that densification prior to the final stage of sintering is necessary to limit final porosity. Samples showing open porosity were found to lead to pore entrapment because of the diffusion of argon inside the glass capsule during hot isostatic pressing. Transmittance measurements showed that the valence charge of the ytterbium ions was 3+ at the end of the process, indicating no effect of reduction when pre-sintering in vacuum was employed. 

  • 154.
    Knutsson, Axel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Johansson, M.P.
    Seco Tools AB, SE-73782 Fagersta, Sweden.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Thermal decomposition products in arc evaporated TiAlN/TiN multilayers2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 14, p. 143110-Article in journal (Refereed)
    Abstract [en]

    Cubic metastable Ti0.34Al0.66 N/TiN multilayers were grown by reactive arc evaporation using Ti33-Al67 and Ti cathodes in a N2 atmosphere. X-ray diffractometry and high resolution transmission electron microscopy revealed that metastable c-Ti 0.34Al0.66N partly decomposes after annealing at 900 °C into c-TiN rich and c-AlN rich phases with retained lattice coherency. Elemental mapping by energy dispersive x-ray spectroscopy showed a homogenous distribution of Ti and Al in the as-deposited 25 nm Ti0.34Al 0.66N layers. The annealed Ti0.34Al0.66N layers exhibited coherent 5 nm domains with high Al content surrounded by a high Ti content matrix. This nanostructure formation is discussed in terms of spinodal decomposition. © 2008 American Institute of Physics.

  • 155.
    Hörling, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sjölén, Jacob
    Seco Tools AB, Fagersta, Sweden.
    Willmann, Herbert
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Larsson, T.
    Seco Tools AB, Fagersta, Sweden.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Thermal stability, microstructure and mechanical properties of Ti1 − xZrxN thin films2008In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 516, no 18, p. 6421-6431Article in journal (Refereed)
    Abstract [en]

    Single-phase [NaCl]-structure Ti1 − xZrxN thin films (0 < < 1) have been deposited using cathodic arc plasma deposition. The films were investigated using X-ray diffraction (XRD), transmission electron microscopy, differential scanning calorimetry (DSC), and nanoindentation. Density functional theory calculations on phase stabilities show that the pseudo-binary TiN–ZrN system exhibits a miscibility gap, extending over 0 ≤ ≤ 0.99 at 1000 °C, with respect to phase transformation from a solid solution into a two-phase mixture of [NaCl]-structure TiN and ZrN components. The films were found to retain their as-deposited single-phase structure during post-deposition annealing at 600 °C (18 h), 700 °C (12 h), 1100 and 1200 °C (2 h), and for as long as 195 h at 600 °C. DSC revealed no heat flow during annealing, similar to TiN, and only the = 0.53 film exhibited a slight increase in XRD peak broadening after annealing at 1200 °C, consistent with spinodal decomposition. This effective thermal stability of the alloys is explained by the combination of a limited driving force for phase transformation and an insufficient atom diffusivity. In terms of mechanical properties, films with composition deepest within the miscibility gap showed a hardness of ∼ 30 GPa after annealing at 1100–1200 °C; a value only moderately lower than in the as-deposited condition. The principal hardening mechanism for the Ti1 − xZrxN films is proposed to be solid-solution hardening through local lattice strain fields originating from difference in atomic radius of Ti and Zr. The material system is thus promising for cutting tool applications.

  • 156.
    Mouzon, Johanne
    et al.
    Division of Engineering Materials, Luleå University of Technology, Luleå, Sweden.
    Odén, Magnus
    Division of Engineering Materials, Luleå University of Technology, Luleå, Sweden.
    Alternative method to precipitation techniques for synthesizing yttrium oxide nanopowder2007In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 177, no 2, p. 77-82Article in journal (Refereed)
    Abstract [en]

    Yttrium oxide nano-powder has been successfully synthesized by a novel approach. In the first step, a foamy structure was produced by combustion synthesis using yttrium nitrate and glycine. This was followed by the addition of sulfate ions and calcination at 1100 °C for 4 h. The sulfated and unsulfated powders were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller method (BET). The sinterability of the resulting powders was also studied by dilatometry. The studies indicated that this method not only allows for producing weakly-agglomerated nano-particles, but is also a very time-efficient process in comparison to precipitation techniques. Moreover, the possibility of performing all processing steps in a fully automated batch reactor was also considered.

  • 157.
    Mouzon, Johanne
    et al.
    Luleå University of Technology.
    Nordell, Patricia
    Luleå University of Technology.
    Thomas, Adrien
    Luleå University of Technology.
    Odén, Magnus
    Luleå University of Technology.
    Comparison of two different precipitation routes leading to Yb doped Y2O3 nano-particles2007In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 27, no 4, p. 1991-1998Article in journal (Refereed)
    Abstract [en]

    Two different precipitation routes leading to (YbxY1−x)2O3 nano-particles (with x = 0; 0.027; and 0.31) were compared, namely, precipitation of hydroxynitrate platelets and amorphous carbonate spherical particles. For both methods, the particle morphology was observed by scanning electron microscopy. X-ray diffraction studies of the unit cell, energy dispersive X-ray analysis and inductive coupled plasma spectroscopy were used to check the ytterbium distribution. The precipitation of amorphous carbonate was found to produce particles with uniform morphology and homogeneous distribution of ytterbium, while hydroxide precipitation favours the formation of hard and dense ytterbium-rich agglomerates. These differences are discussed in terms of precipitation, growth and agglomeration behaviour. The sinterability of both resulting powders is also discussed.

  • 158. Söderberg, Hans
    et al.
    Flink, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Beckers, Manfred
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Growth and characterization of TiN/SiN(001) superlattice films2007In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 22, no 11, p. 3255-3264Article in journal (Refereed)
    Abstract [en]

    We report the layer structure and composition in recently discovered TiN/SiN(001) superlattices deposited by dual-reactive magnetron sputtering on MgO(001) substrates. High-resolution transmission electron microscopy combined with Z-contrast scanning transmission electron microscopy, x-ray reflection, diffraction, and reciprocal-space mapping shows the formation of high-quality superlattices with coherently strained cubic TiN and SiN layers for SiN thickness below 7–10 Å. For increasing SiN layer thicknesses, a transformation from epitaxial to amorphous SiNx (x ? 1) occurs during growth. Elastic recoil detection analysis revealed an increase in nitrogen and argon content in SiNx layers during the phase transformation. The oxygen, carbon, and hydrogen contents in the multilayers were around the detection limit (~0.1 at.%) with no indication of segregation to the layer interfaces. Nanoindentation experiments confirmed superlattice hardening in the films. The highest hardness of 40.4 ± 0.8 GPa was obtained for 20-Å TiN with 5-Å-thick SiN(001) interlayers, compared to monolithic TiN at 20.2 ± 0.9 GPa.

  • 159.
    Hultman, Lars
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bareño, Javier
    Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
    Flink, Axel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Söderberg, Hans
    Engineering Materials, Luleå University of Technology, Luleå, Sweden .
    Larsson, Karin
    Department of Materials Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Petrova, Vania
    Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA .
    Odén, Magnus
    Engineering Materials, Luleå University of Technology, Luleå, Sweden.
    Greene, J. E.
    Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
    Petrov, Ivan
    Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
    Interface structure in superhard TiN-SiN nanolaminates and nanocomposites: film growth experiments and ab initio calculations2007In: Physical Review. B, ISSN 1098-0121, Vol. 75, no 15, p. 155437-Article in journal (Refereed)
    Abstract [en]

    Nanostructured materials—the subject of much of contemporary materials research—are defined by internal interfaces, the nature of which is largely unknown. Yet, the interfaces determine the properties of nanocomposites and nanolaminates. An example is nanocomposites with extreme hardness70–90  GPa, which is of the order of, or higher than, diamond. The Ti-Si-N system, in particular, is attracting attention for the synthesis of such superhard materials. In this case, the nanocomposite structure consists of TiN nanocrystallites encapsulated in a fully percolated SiNx “tissue phase” (1 to 2 monolayers thick) that is assumed to be amorphous. Here, we show that the interfacial tissue phase can be crystalline, and even epitaxial with complex surface reconstructions. Using in situ structural analyses combined with ab initio calculations, we find that SiNx layers grow epitaxially, giving rise to strong interfacial bonding, on both TiN(001) and TiN(111) surfaces. In addition, TiN overlayers grow epitaxially on SiNx/TiN(001) bilayers in nanolaminate structures. These results provide insight into the development of design rules for new nanostructured materials.

  • 160.
    Söderberg, Hans
    et al.
    Luleå University of Technology.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Odén, Magnus
    Luleå University of Technology.
    RHEED studies during growth of TiN/SiNx/TiN trilayers on MgO(001)2007In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, p. 2352-2356Article in journal (Refereed)
  • 161.
    Hedstrom, Peter
    et al.
    Luleå University of Technology.
    Lienert, Ulrich
    Luleå University of Technology.
    Almer, Jon
    Luleå University of Technology.
    Oden, Magnus
    Luleå University of Technology.
    Stepwise transformation behavior of the strain-induced martensitic transformation in a metastable stainless steel2007In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 56, no 3, p. 213-216Article in journal (Refereed)
    Abstract [en]

    In situ high-energy X-ray diffraction during tensile loading has been used to investigate the evolution of lattice strains and the accompanying strain-induced martensitic transformation in cold-rolled sheets of a metastable stainless steel. At high applied strains the transformation to alpha-martensite occurs in stepwise bursts. These stepwise transformation events are correlated with stepwise increased lattice strains and peak broadening in the austenite phase. The stepwise transformation arises from growth of alpha-martensite embryos by autocatalytic transformation.

  • 162.
    Mouzon, Johanne
    et al.
    Luleå University of Technology.
    Odén, Magnus
    Luleå University of Technology.
    Tillement, Olivier
    Universite´ C. Bernard Lyon I.
    Jorand, Yves
    GEMPPM, INSA Lyon.
    Effect of drying and dewatering on yttria precursors with transient morphology2006In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 89, no 10, p. 3094-3100Article in journal (Refereed)
    Abstract [en]

    The influence of drying and dewatering of a yttrium hydroxynitrate precursor with transient morphology was investigated. The ability of this precursor to form soft agglomerated nanoparticles after calcination is dependent on the dewatering method. Freeze drying leads to finer particles than other dewatering methods that involve removal of the solvent from its liquid state. As water is directly removed by sublimation during freeze drying, this method inhibits the formation of solid bridges between hydroxynitrate platelets. These bridges, which form with the other dewatering methods, destabilize the spheroidization process of the platelets during subsequent firing at high temperatures.

  • 163.
    Soderberg, H.
    et al.
    Söderberg, H., Division of Engineering Materials, Luleå University of Technology, SE-971 87 Luleå, Sweden.
    Odan, M.
    Odán, M., Division of Engineering Materials, Luleå University of Technology, SE-971 87 Luleå, Sweden.
    Larsson, T.
    Ombenning by 14, SE-737 90 Ängelsberg, Sweden.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Molina-Aldareguia, J.M.
    CEIT, TECNUN, Paseo de Manuel Lardizabal 15, 20018 San Sebastián, Spain.
    Epitaxial stabilization of cubic- SiNx in TiN/SiNx multilayers2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 19Article in journal (Refereed)
    Abstract [en]

    The formation of cubic-phase Si Nx is demonstrated in TiNSi Nx multilayers deposited by reactive dual magnetron sputtering. Transmission electron microscopy examination shows a transition from epitaxially stabilized growth of crystalline Si Nx to amorphous growth as the layer thickness increases from 0.3 to 0.8 nm. The observations are supported by ab initio calculations on different polytypes, which show that the NaCl structure has the best lattice match to TiN. Calculations also reveal a large difference in elastic shear modulus between NaCl-Si Nx and TiN. The results for phase structure and shear modulus offer an explanation for the superhardening effect determined by nanoindentation experiments. © 2006 American Institute of Physics.

  • 164.
    Hedström, Peter
    et al.
    Luleå University of Technology.
    Almer, Jon
    Argonne National Laboratory, USA.
    Lienert, Ulrich
    Argonne National Laboratory, USA.
    Odén, Magnus
    Luleå University of Technology.
    Evolution of residual strains in metastable austenitic stainless steels and the accompanying strain induced martensitic transformation2006In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 524-525, p. 821-826Article in journal (Refereed)
    Abstract [en]

    The deformation behavior of metastable austenitic stainless steel AISI 301, suffering different initial cold rolling reduction, has been investigated during uniaxial tensile loading. In situ high-energy x-ray diffraction was employed to characterize the residual strain evolution and the strain induced martensitic transformation. Moreover, the 3DXRD technique was employed to characterize the deformation behavior of individual austenite grains during elastic and early plastic deformation. The cold rolling reduction was found to induce compressive residual strains in the austenite along rolling direction and balancing tensile residual strains in the alpha-martensite. The opposite residual strain state was found in the transverse direction. The residual strain states of five individual austenite grains in the bulk of a sample suffering 2% cold rolling reduction was found to be divergent. The difference among the grains, considering both the residual strains and the evolution of these, could not be solely explained by elastic and plastic anisotropy. The strain states of the five austenite grains are also a consequence of the local neighborhood.

  • 165.
    Terner, Mark R.
    et al.
    Luleå University of Technology.
    Hedström, Peter
    Luleå University of Technology.
    Almer, J.
    Argonne National Laboratory, USA.
    Ilavsky, J.
    Argonne National Laboratory, USA.
    Odén, Magnus
    Luleå University of Technology.
    Residual stress evolution during decomposition of Ti((1-x))Al((x))N coatings using high-energy x-rays2006In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 524-525, p. 619-624Article in journal (Refereed)
    Abstract [en]

    Residual stresses and microstructural changes during phase separation in Ti33Al67N coatings were examined using microfocused high energy x-rays from a synchrotron source. The transmission geometry allowed simultaneous acquisition of x-ray diffraction data over 360 degrees and revealed that the decomposition at elevated temperatures occurred anisotropically, initiating preferentially along the film plane. The as-deposited compressive residual stress in the film plane first relaxed with annealing, before dramatically increasing concurrently with the initial stage of phase separation where metastable, nm-scale c-AlN platelets precipitated along the film direction. These findings were further supported from SAXS analyses.

  • 166.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Inst of New Materials Technology Northeastern University, Shenyang.
    Almer, J
    Advanced Photon Source Argonne National Laboratory.
    Odén, M
    Engineering Materials Luleå Tekniska Universitet.
    Liu, Y D
    Inst of New Materials Technology Northeastern University, Shenyang.
    Zuo, L
    Inst of New Materials Technology Northeastern University, Shenyang.
    Determination of Grain-Orientation-Dependent Stress in Coatings2005In: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Diffusion and defect data, solid state data.. P. B,. Solid state phenomena, Vol. 105, p. 107-112Article in journal (Refereed)
    Abstract [en]

    Quantitative interpretations of the so-called non-linear lattice strain distributions observed in coatings and thin films are important not only for determining the macro- and micro-stress fields, but also for inferring the active mechanisms of grain interactions during various deposition processes. In this paper, we present a method, which determines simultaneously both the macro- and micro-stress fields in the coatings and thin films. This method is extended from the previous stress-orientation distribution function (SODF) analysis method, which has already been used for residual stress analysis in bulk materials subjected to rolling and fatigue deformation. The validity of analysis method is demonstrated through measurements of lattice strains by high-energy x-ray and analysis of grain-orientation-dependent stresses in a CrN coating

  • 167.
    Wang, Y.-D.
    et al.
    Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China.
    Peng, R.L.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Almer, J.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne, IL 60439, United States.
    Oden, M.
    Division of Engineering Materials, Luleå Tekniska Universitet, S-971 87 Luleå, Sweden.
    Liu, Y.-D.
    Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China.
    Deng, J.-N.
    Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China.
    He, C.-S.
    Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China.
    Chen, L.
    Department of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
    Li, Q.-L.
    Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China.
    Zuo, L.
    Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China.
    Grain-to-grain stress interactions in an electrodeposited iron coating2005In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 17, no 10, p. 1221-1226Article in journal (Refereed)
    Abstract [en]

    The distribution of residual stresses, in an iron electrolytic coating with the thickness of 1 mm, was discussed. It was found that the coating minimizes the influence of crystallographic texture and stress gradients. Scanning electron microscopy observations indicate that some cracks are produced in the direct current deposited layer. The results show that the grain size in the electrolytic coating observed by transmission electron microscopy is around 20 nm with an aspect ratio of 5:1.

  • 168.
    Hörling, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Division of Engineering Materials, The Sirius Laboratory, Luleå University of Technology, Luleå, Sweden.
    Sjölén, Jacob
    SECO Tools AB.
    Karlsson, Lennart
    Seco Tools AB.
    Mechanical properties and machining performance of Ti1−xAlxN-coated cutting tools2005In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 191, no 2-3, p. 384-392Article in journal (Refereed)
    Abstract [en]

    The mechanical properties and machining performance of Ti1−xAlxN-coated cutting tools have been investigated. Processing by arc evaporation using cathodes with a range of compositions was performed to obtain coatings with compositions x=0, x=0.25, x=0.33, x=0.50, x=0.66 and x=0.74. As-deposited coatings with x≤0.66 had metastable cubic structures, whereas x=0.74 yielded two-phase coatings consisting of cubic and hexagonal structures. The as-deposited and isothermally annealed coatings were characterised by nanoindentation, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cutting tests revealing tool wear mechanisms were also performed. Results show that the Al content, x, promotes a (200) preferred crystallographic orientation and has a large influence on the hardness of as-deposited coatings. The high hardness (∼37 GPa) and texture of the as-deposited Ti1−xAlxN coatings are retained for annealing temperatures up to 950 °C, which indicates a superior stability of this system compared to TiN and Ti(C,N) coatings. We propose that competing mechanisms are responsible for the effectively constant hardness: softening by residual stress relaxation through lattice defect annihilation is balanced by hardening from formation of a coherent nanocomposite structure of c-TiN and c-AlN domains by spinodal decomposition. This example of secondary-phase transformation (age-) hardening is proposed as a new route for advanced surface engineering, and for the development of future generation hard coatings.

  • 169.
    Söderberg, Hans
    et al.
    Luleå Tekniska Universitet.
    Odén, Magnus
    Luleå Tekniska Universitet.
    Molina-Aldareguia, Jon M.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Nanostructure formation during deposition of TiN SiNx nanomultilayer films by reactive dual magnetron sputtering2005In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, no 11, p. 114327-Article in journal (Refereed)
    Abstract [en]

    Multilayer thin films consisting of titanium nitride (TiN) and silicon nitride (SiNx) layers with compositional modulation periodicities between 3.7 and 101.7 nm have been grown on silicon wafers using reactive magnetron sputtering. The TiN and SiNx layer thicknesses were varied between 2-100 nm and 0.1-2.8 nm, respectively. Electron microscopy and x-ray diffraction studies showed that the layering is flat with distinct interfaces. The deposited TiN layers were crystalline and exhibited a preferred 002 orientation for layer thicknesses of 4.5 nm and below. For larger TiN layer thicknesses, a mixed 111002 preferred orientation was present as the competitive growth favored 111 texture in monolithic TiN films. SiNx layers exhibited an amorphous structure for layer thicknesses ≥0.8 nm, however, cubic crystalline silicon nitride phase was observed for layer thicknesses ≤0.3 nm. The formation of this metastable SiNx phase is explained by epitaxial stabilization to TiN. The microstructure of the multilayers displayed a columnar growth within the TiN layers with intermittent TiN renucleation after each SiNx layer. A nano-brick-wall structure was thus demonstrated over a range of periodicities. As-deposited films exhibited relatively constant residual stress levels of 1.3±0.7 GPa (compressive), independent of the layering. Nanoindentation was used to determine the hardness of the films, and the measurements showed an increase in hardness for the multilayered films compared to those for the monolithic SiNx and TiN films. The hardness results varied between 18 GPa for the monolithic TiN film up to 32 GPa for the hardest multilayer, which corresponds to the presence of cubic SiNx. For larger wavelengths, ≥20 nm, the observed hardness correlated to the layer thickness similar to a Hall-Petch dependence, but with a generalized power of 0.4. Sources of the hardness increase for shorter wavelengths are discussed, e.g., epitaxial stabilization of metastable cubic SiNx, coherency stress, and impeded dislocation activity. © 2005 American Institute of Physics.

  • 170.
    Peng, Ru
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Wang, Y D
    Studsvik Neutron Research Laboratory, Uppsala universitet, Nyköping , Sweden.
    Odén, Magnus
    Engineering Materials, Luleå University, Luleå, Sweden.
    Almer, J
    Advanced Photon Source Argonne National Laboratory, Argonne, IL, USA.
    Residual Stress Analysis in both As-deposited and Annealed CrN Coatings2005In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 490-491, p. 643-648Article in journal (Refereed)
    Abstract [en]

    In this paper, we report on residual stress analysis in physical vapour deposited (PVD) CrN coatings. Two 9 µm thick coatings were grown on tool steel substrates with bias voltages of - 50 V and -300 V, respectively. High-energy (E=80 keV) synchrotron radiation measurements have been performed to investigate residual stresses in both as-deposited and annealed CrN coatings. To understand the origins of non-linear distribution of lattice strain versus sin2ψ for certain (hkl) planes in both coatings, a stress orientation distribution function (SODF) analysis has been carried out, which yields grain-orientation-dependent residual stresses. The results are compared to previous analyses using Reuss and Vook-Witt models on the as-deposited coatings.

  • 171.
    Schlauer, Christian
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Div of Enginnering Materials, Luleå University.
    Residual stress evolution and near-surface microstructure after turning of the nickel-based superalloy Inconel 7182005In: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 96, no 4, p. 385-392Article in journal (Refereed)
    Abstract [en]

    Turning experiments have been carried out with the cutting speed and feed as variables that were systematically varied between 10 m min−1 and 1200 m min−1, and 0.1 mm and 0.5 mm, respectively, while all other cutting parameters were held constant. The arising residual stress distributions are presented and the influence of the varied machining parameters is investigated. Compressive residual stresses dominate the depth profiles but are often accompanied by a thin tensile residual stress layer at the surface. Microstructural investigations of near-surface cross-sections by means of transmission electron microscopy showed a zone where the grains had undergone plastic deformation, indicated by slip bands. On top of this layer, a surface layer exists where the grain size has radically decreased to only 50 nm to 130 nm. The grain size of the nanocrystalline layer is fairly constant for a certain cutting speed and feed, but depends on these cutting parameters. An increase in cutting speed and feed leads to larger grains in the nanocrystalline layer.

  • 172.
    Larsson, Cecilia
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hardness profile measurements in functionally graded WC–Co composites2004In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 382, no 1-2, p. 141-149Article in journal (Refereed)
    Abstract [en]

    Micro- and nanoindentation were used to determine hardness as a function of depth in two functionally graded WC–Co composites. The gradients were continuous (extended over ∼70 and ∼40 μm, respectively) and consisted of varying WC and Co phase volume fractions. Five comparable homogeneous samples with different Co contents and different average WC grain sizes were also used for direct comparison. A relationship between hardness and Co content was established for both the graded and the homogeneous samples wherein the hardness decreased with increasing Co content. The magnitude of the hardness was the same (for a given Co content) for the functionally graded and the homogeneous materials. The hardness measurements were also correlated with X-ray diffraction studies of thermal residual stresses and the absence of any major influence explained. It is generally concluded that the hardness values are dominated by the local Co content. Additionally, the examination of surface cracks around indents suggests that compositional gradients in WC–Co composites offer increased toughness.

  • 173. Almer, J
    et al.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
    Hakansson, G
    Microstructure and thermal stability of arc-evaporated Cr-C-N coatings2004In: PHILOSOPHICAL MAGAZINE, ISSN 1478-6443, Vol. 84, no 7, p. 611-630Article in journal (Refereed)
    Abstract [en]

    The role of C incorporation in the microstructure and thermal stability of arc-evaporated Cr-C-N coatings is explored via reactive growth in a mixed C2H4-N-2 environment. C is found to react more readily than N at both the Cr cathode and the coating surfaces, so that a C2H4-to-N-2 flow ratio of only 1% yields a C-to-N ratio of approximately 10% within the coatings. The as-deposited microstructures consist primarily of the delta-Cr(C, N) phase and possess high compressive residual stresses, which decrease with increasing C content. Post-deposition annealing up to 700degreesC results in depletion of lattice defects, and concomitant reductions in stress and coating hardness, together with phase transformations which suggest metastable phase formation during growth. Apparent activation energies for this lattice defect are found to be in the range expected for bulk diffusion of N and C (2.4-2.8 eV). The results suggest that inclusion of small amounts of C in this system offers the ability to reduce internal stresses while maintaining defect-related hardness increases, permitting growth of thicker and thus more wear-resistant coatings.

  • 174.
    Larsson, Cecilia
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    X-ray diffraction determination of residual stresses in functionally graded WC–Co composites2004In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 22, no 4-5, p. 177-184Article in journal (Refereed)
    Abstract [en]

    X-ray diffraction was used to determine the thermal residual stresses that develop in a functionally graded WC–Co composite. Stresses were measured in both WC and Co phases at various depths. Pole figures were obtained in order to determine optimal sample orientations that provided adequate intensity for measurements in the Co phase. For WC, the in-plane compressive residual stresses varied approximately between −300 and −500 MPa with depth below the surface. For the low volume fraction Co phase, the tensile residual stresses were approximately 600 MPa. The microstresses in the graded zone were attributed to the thermal mismatch between the WC and the Co phase during cooling from the liquid phase sintering temperature (1450 °C). The microstresses determined were in reasonable agreement with a prediction using Eshelby theory. The compressive macrostresses were attributed to the compositional gradient, a result further substantiated by the fact that no significant macrostresses were measured in a comparable homogeneous sample, i.e., without the compositional gradient. Thus, varying compositional gradients in WC–Co composites during fabrication can be expected to directly influence the macrostress component of the overall residual stress state.

  • 175.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Rode, Nils
    Intitute of Materials Technolgy University of Kassel.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Gibmeier, Jens
    Institute of Materials Technology University of Kassel.
    Scholtes, B
    Institute of Materials Technology University of Kassel.
    Characterisation of residual stress distribution in clinching joints of carbon steel by diffraction methods2003In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 19, no 3, p. 336-342Article in journal (Refereed)
    Abstract [en]

    Sheet joints of carbon steel fabricated by two different clinching methods, namely TOX and Eckold, have been investigated. The holding force of the joints was determined by shear tension tests and the deformation microstructure was characterised using optical microscopy. The surface residual stress and mean residual stress distributions as a function of increasing distance from the outer diameter of the interlock button were mapped by X-ray and neutron diffractometry, respectively.The Eckold joints showed more severe joint distortion in the form of global sheet bending, but nevertheless possessed higher shear tension strength than the TOX joints. Characteristic residual stress distributions depending on the clinching method were found in both the TOX and Eckold joints. The observed residual stress distributions have been attributed to the different die construction employed by the two methods, which permitted different degrees of plastic deformation during clinching.

  • 176. Jensen, J.A.D.
    et al.
    Persson, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Pantleon, K.
    The Technical University of Denmark, Inst. of Manufacturing Eng./Mgmt., Lyngby DK-2800, Denmark.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Somers, M.A.J.
    The Technical University of Denmark, Inst. of Manufacturing Eng./Mgmt., Lyngby DK-2800, Denmark.
    Electrochemically deposited nickel membranes, process-microstructure-property relationships2003In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 172, no 1, p. 79-89Article in journal (Refereed)
    Abstract [en]

    This paper reports on the manufacturing, surface morphology, internal structure and mechanical properties of Ni-foils used as membranes in reference-microphones. Two types of foils, referred to as S-type and 0-type foils, were electrochemically deposited from a Watts-type electrolyte, with (S-type) or without (0-type) the use of the sulfur-containing additive sodium saccharin. Both types of Ni-foils appeared perfectly smooth when investigated with scanning electron microscopy (SEM), while atomic force microscopy (AFM) and transmission electron microscopy (TEM) revealed differences in the surface morphologies and a smaller grain-size in the S-type foils. X-Ray diffraction showed a <311> texture component in both types of Ni-foils, most pronounced for 0-type foils. A minor <111> texture component observed in both foil types was strongest in the S-type foils. Mechanically 0-type foils proved more ductile than S-type foils during thin film tensile testing, due to microstructural defects caused by sodium saccharin during deposition. Tensile strengths in the order of 700-1000 MPa were observed - highest for the more ductile 0-type foils. A hardness in the order of 6 GPa (590 HV) was found by nanoindentation. © 2003 Elsevier Science B.V. All rights reserved.

  • 177.
    Palmquist, J.-P.
    et al.
    Uppsala University.
    Czigany, Zs.
    Research Institute for Technical Physics and Materials Science, Budapest.
    Odén, Magnus
    Luleå University of Technology.
    Neidhardt, Jörg
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, U.
    Uppsala University.
    Magnetron sputtered W-C films with C60 as carbon source2003In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 444, no 1-2, p. 29-37Article in journal (Refereed)
    Abstract [en]

    Thin films in the W–C system were prepared by magnetron sputtering of W with coevaporated C60 as carbon source. Epitaxial deposition of different W–C phases is demonstrated. In addition, nanocrystalline tungsten carbide film growth is also observed. At low C60/W ratios, epitaxial growth of α-W with a solid solution of carbon was obtained on MgO(001) and Al2O3(001) at 400 °C. The carbon content in these films (10–20 at.%) was at least an order of magnitude higher than the maximum equilibrium solubility and gives rise to an extreme hardening effect. Nanoindentation measurements showed that the hardness of these films increased with the carbon content and values as high as 35 GPa were observed. At high C60/W ratios, films of the cubic β-WC1−x (x=0–0.6) phase were deposited with a nanocrystalline microstructure. Films with a grain size <30 Å were obtained and the hardness of these films varied from 14 to 24 GPa. At intermediate C60/W ratios, epitaxial films of hexagonal W2C were deposited on MgO(111) at 400 °C. Polycrystalline phase mixtures were obtained on other substrates and hexagonal WC could be deposited as minority phase at 800 °C.

  • 178.
    Gorishnyy, T.Z.
    et al.
    Department of Mechanical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States.
    Olson, L.G.
    Department of Mechanical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States.
    Oden, Magnus
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Aouadi, S.M.
    Department of Physics, Southern Illinois University, Carbondale, IL 62901-4401, United States.
    Rohde, S.L.
    Department of Mechanical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, United States.
    Optimization of wear-resistant coating architectures using finite element analysis2003In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 21, no 1, p. 332-339Article in journal (Refereed)
    Abstract [en]

    The design of successful wear-resistant coating architectures requires simultaneous consideration of several factors. In particular, coatings which consist of CrN layers of varying thickness separated by thin Cr layers have the highest wear resistance for both aluminum and steel substrate materials, but a methodology was needed to optimize both the overall coating design and the individual layer thicknesses. This paper provides an initial step toward the development of future application specific coating designs and improved coating design methodologies.

  • 179.
    Almer, J.
    et al.
    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois.
    Lienert, U
    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois.
    Peng, Ru
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Schlauer, Christian
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Engineering Materials Luleå University of Technology.
    Strain and texture analysis of coatings using high-energy x-rays2003In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, no 1, p. 697-702Article in journal (Refereed)
    Abstract [en]

    We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 ψ strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed.

  • 180.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Anisotropic high cycle fatigue behaviour of duplex stainless steels: influence of microstresses2002In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 93, no 1, p. 7-11Article in journal (Refereed)
    Abstract [en]

    The anisotropic high cycle fatigue behaviour has been investigated for a duplex stainless steel in as-received and prestrained condition. It was found that the anisotropy of the fatigue limit is different from the anisotropy of yield strength. The main reason for this is the influence of microstresses on fatigue crack initiation. Fatigue cracks are seen to nucleate preferably in the austenite phase, which has tensile microstresses. Prestraining alters the microstresses from being higher in the transverse direction to being higher in the rolling direction. At the same time, the fatigue limit is changed from being higher in the rolling direction to being higher in the transverse direction.

  • 181.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Deformation behaviour of a prestrained duplex stainless steel2002In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 337, no 1-2, p. 25-38Article in journal (Refereed)
    Abstract [en]

    The anisotropic flow behaviour due to a change in strain path during uniaxial deformation of a duplex stainless steel has been investigated. The anisotropic flow behaviour of the as-received material could be predicted from the crystallographic texture. However, it was found that prestraining introduces a transient work hardening behaviour during the second stage deformation, which causes an anisotropic flow behaviour immediately after yielding that cannot be described by the crystallographic texture. Samples subjected to a coaxial second stage deformation show a small increase in flow stress and similar work hardening rate as in the monotonic loading. Samples subjected to noncoaxial second stage deformation show a pronounced transient stage characterised by early yielding and a high work hardening rate in the first part of the transient stage. Beyond the earliest stage of deformation a higher flow stress and a lower work hardening rate compared to monotonic loading is observed for the noncoaxial samples. The transient phenomena are discussed based on the measured internal stresses and the differences in dislocation structures in the two different phases.

  • 182.
    Molina-Aldareguia, J.M.
    et al.
    Dept. of Mat. Sci. and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, United Kingdom.
    Lloyd, S.J.
    Dept. of Mat. Sci. and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, United Kingdom.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
    Joelsson, Torbjörn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Clegg, W.J.
    Dept. of Mat. Sci. and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, United Kingdom.
    Deformation structures under indentations in TiN/NbN single-crystal multilayers deposited by magnetron sputtering at different bombarding ion energies2002In: Philosophical magazine. A. Physics of condensed matter. Defects and mechanical properties, ISSN 0141-8610, Vol. 82, no 10 SPEC., p. 1983-1992Article in journal (Refereed)
    Abstract [en]

    Work elsewhere has suggested that multilayer films with layer thicknesses of a few nanometres can be much harder than monolithic films, although there is considerable variation in the observed magnitude of this effect. To investigate this, multilayer TiN/NbN films have been deposited by reactive magnetron sputtering on to MgO single crystals. The hardnesses measured were similar to those of the TiN and NbN alone, which is consistent with the observation by transmission electron microscopy (TEM) that deformation across the interfaces was not prevented. Varying the electrical potential at which the film was grown from -10 to -200 V and the corresponding ion energy from 10 to 200 eV increased the hardness from 19 to 25 GPa, further decreases in the potential caused the hardness to decrease. Using TEM, deformation was observed to occur along the apparent columnar boundaries within the films, suggesting that the effect of the electrical potential on the measured hardness was caused by changes in the apparent strength of the columnar boundaries, possibly associated with the variations in the volume fraction of voids that were observed on these boundaries.

  • 183.
    Larsson, Cecilia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Determination of Thermal Residual Stresses in a Functionally Graded WC-Co composite2002In: Denver X-ray Conference,2002, 2002Conference paper (Refereed)
  • 184.
    Odén, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Gall, D
    Dept of Materials Science University of Illinois.
    Shin, C-S
    Dept of Materials Science University of Illinois.
    Spilla, T
    Dept of Materials Science University of Illinois.
    Senna, M J H
    Dept of Materials Science University of Illinois.
    Greene, J E
    Dept of Materials Science University of Illinois.
    Petrov, I
    Dept of Materials Science University of Illinois.
    Growth of single-crystal CrN on MgO(001): Effects of low-energy ion-irradiation on surface morphological evolution and physical properties2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, no 6, p. 3589-3597Article in journal (Refereed)
    Abstract [en]

    CrN layers, 0.5 ╡m thick, were grown on MgO(001) at Ts=570-775░C by ultrahigh vacuum magnetically unbalanced magnetron sputter deposition in pure N2 discharges at 20 mTorr. Layers grown at Ts=700░C are stoichiometric single crystals exhibiting cube-on-cube epitaxy: (001)CrN(001)MgO with [100]CrN[100]MgO. At higher temperatures, N2 desorption during deposition results in understoichiometric polycrystalline films with N fractions decreasing to 0.35, 0.28, and 0.07 with Ts=730, 760, and 775░C, respectively. The surface morphologies of epitaxial CrN(001) layers were found to depend strongly on the incident ion-to-metal flux ratio JN2+/JCr which was varied between 1.7 and 14 with the ion energy maintained constant at 12 eV. The surfaces of layers grown with JN2+/JCr=1.7 consist of self-organized square-shaped mounds, due to kinetic roughening, with edges aligned along orthogonal <100> directions. The mounds have an average peak-to-valley height =5.1 nm and an in-plane correlation length of =0.21 ╡m. The combination of atomic shadowing by the mounds with low adatom mobility results in the formation of nanopipes extending along the growth direction. Increasing JN2+/JCr to 14 leads, due to increased adatom mobilities, to much smoother surfaces with =2.5 nm and =0.52 ╡m. Correspondingly, the nanopipe density decreases from 870 to 270 ╡m-2 to <20 ╡m-2 as JN2+/JCr is increased from 1.7 to 6 to 10. The hardness of dense CrN(001) is 28.5▒1 GPa, but decreases to 22.5▒1 GPa for layers containing significant nanopipe densities. The CrN(001) elastic modulus, 405▒15 GPa, room-temperature resistivity, 7.7╫10-2 cm, and relaxed lattice constant, 0.4162▒0.0008 nm, are independent of JN2+/JCr. ⌐ 2002 American Institute of Physics.

  • 185. Talyzin, AV
    et al.
    Dubrovinsky, LS
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
    Le Bihan, T
    Jansson, U
    In situ x-ray diffraction study of C-60 polymerization at high pressure and temperature2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 16Article in journal (Refereed)
    Abstract [en]

    The C-60 polymerization was studied by x-ray diffraction in situ in the pressure range 13-18 GPa and at temperatures up to 830 K and nonhydrostatic conditions. Quenched samples were studied ex situ by Raman spectroscopy. The results of the high-pressure and high-temperature treatment are strongly dependent on the history of the sample and stress. An inaccurate increase of the pressure leads to the formation of internal stresses in the sample which gives elliptical Debye-Scherrer diffraction rings already at room temperature. During the subsequent heat treatment a soft amorphous phase is formed. At certain conditions no elliptical diffraction patterns were observed at 13 GPa and 830 K. Samples with a relatively low internal stress showed a transformation to a phase with decreased c-cell parameter compared to the known two-dimensional rhombohedral phase. The observed phase can be described as distorted cubic, but a better fit is achieved using a rhombohedral cell. It is suggested that this phase is a three-dimensional polymer with each C-60 molecule bonded to eight neighbors. This phase showed an increased hardness (about 37 GPa) and a Raman spectrum distinctly different from previously known polymeric phases.

  • 186.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of elastic and plastic anisotropy on the flow behavior in a duplex stainless steel2002In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 33, no 1, p. 57-71Article in journal (Refereed)
    Abstract [en]

    The load partitioning between two phases in a cold-rolled duplex stainless steel has been experimentally studied in situ by X-ray diffraction, for different loading directions. It was found that the load partitioning between the two phases is dependent on the loading direction. For loading in the rolling direction, both phases deform plastically to the same degree, while more plastic deformation occurs in the austenitic phase during loading in the transverse direction. For loading in the 45-deg direction, more plastic deformation occurs in the ferritic phase. The strong crystallographic texture in the ferritic phase makes the material anisotropic, with a higher stiffness and yield strength in the transverse direction compared to the rolling direction. The measured texture was used as input to theoretical predictions of both elastic and plastic anisotropy. The plastic anisotropy was predicted by assuming intragranular slip as the main deformation mechanism. The predicted anisotropic material properties were then used in finite-element simulations to study the flow behavior of the material in different directions. The predicted flow behavior was found to be in good agreement with the experimentally observed load partitioning between the phases for loading in the rolling and transverse directions. However, the yield strength of the ferritic phase during loading in the 45-deg direction was found to be lower than what was predicted. The reason for this is the difference in slip characteristics in different sample directions, because of the morphological texture.

  • 187.
    Moverare, Johan
    et al.
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
    Influence of Microstresses on Anisotropic High Cycle Fatigue Behaviour of Duplex Stainless Steels2002In: Proc. 8th International Fatigue Congress, 2002, p. 541-548Conference paper (Other academic)
  • 188.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Studsvik Neutron Research Lab Uppsala University.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Intergranular strains and plastic deformation of an austenitic stainless steel2002In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 334, no 1-2, p. 215-222Article in journal (Refereed)
    Abstract [en]

    Intergranular strains due to tensile plastic deformation were investigated in a sheet material of austenitic stainless steel. The objective was to study the development of residual intergranular strains in samples unloaded from the intermediate and large plastic deformation regimes for which few theoretical and experimental studies were available. By using neutron diffraction, residual lattice strain distribution as a function of sample direction was mapped for a number of crystallographic planes. Deformation microstructures were examined by both transmission electron microscopy and the electron back scattering pattern technique. Residual intergranular strains were observed in samples deformed significantly beyond the elastic limit and the strains varied with sample directions as well as the amount of applied plastic strain. In addition, a different tendency of intergranular strain evolution was observed after large plastic deformation, which could be attributed to the change of dominant plastic deformation mode from slip to mechanical twinning. The results are discussed based on the observed deformation microstructure studies. ⌐ 2002 Elsevier Science B.V. All rights reserved.

  • 189.
    Gibmeier, Jens
    et al.
    Institute of Materials Technology University of Kassel.
    Peng, Ru
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Scholtes, B
    Institute of Materials Technology University of Kassel.
    Residual Stress Distributions around Clinched Joints2002In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 404-407, p. 617-622Article in journal (Refereed)
    Abstract [en]

    Clinching is a mechanical press joining method, which has become of growing interest in recent time since it has the potential to replace other conventional joining methods like e.g. spot welding. However, there still exists a lack of knowledge in terms of the mechanical behavior of clinched joints under quasistatic or cyclic loading. For that reason clinching is usually used for applications in structures which are not subjected to external loads. In particular the residual stress distribution in the vicinity of clinched joints and its influence on the mechanical behavior of the joints is unknown. Here diffraction methods are used for the determination of characteristic residual stress distributions in undismantled clinched samples. A combined residual stress determination by X-ray and neutron diffraction has been used to get a well-founded assessment of the residual stress distributions in the immediate vicinity of clinched joints. The residual stress analysis is supplemented by characterizations of the microstructures and the mechanical properties of single clinched joints. Two materials with different strain hardening behavior were used for clinching, a micro alloyed steel (ZStE340) and a non age hardenable aluminum base alloy (AlMg5). In addition two different common clinching techniques were applied - the TOX- [5] and the Eckold-technique [6]. Characteristic residual stress distributions were found for the combinations of clinching techniques and joined sheet materials investigated here. It has been determined that the clinching process induces predominantly compressive residual stresses inside the clinch and in the immediate vicinity of the clinch. The near surface residual stress distributions determined by X-ray diffraction measurements tend to reveal somewhat different residual stresses than measured by neutron diffraction, indicating a possible stress gradient through the sheet thickness. Further evaluation of the FWHM-values of the respective interference profiles shows that for both clinching techniques the largest amount of plastic deformation occurs in the clinch lock region.

  • 190.
    Gibmeier, Jens
    et al.
    Institute of Materials Technology University of Kassel.
    Rode, Nils
    Institute of Materials Technology University of Kassel.
    Peng, Ru
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Scholtes, B
    Institute of Materials Technology University of Kassel.
    Residual stress in clinched joints of metals2002Article in journal (Refereed)
    Abstract [en]

    Diffraction methods are used for the determination of characteristic residual stress (RS) distributions in undismantled clinched samples for the assessment of the influence of RS on the mechanical behaviour of clinched joints. While X-ray diffraction enables merely the determination of near-surface RS distributions, the higher penetration depth of neutron radiation allows the determination of triaxial RS states inside the material. In addition, the complex geometry of clinched joints restricts the application of X-ray RS analysis. Therefore a combined RS determination by X-ray and neutron diffraction has been used to obtain an expressive assessment of the RS distributions in the immediate vicinity of clinched joints. Two different materials with different mechanical behaviour were used for clinching, as well as two different common clinching techniques.

  • 191.
    Schlauer, Christian
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Peng, Ru
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Residual Stresses in a Nickel-based Superalloy Introduced by Turning2002In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 404-407, p. 173-178Article in journal (Refereed)
    Abstract [en]

    Near-surface residual stress distributions in the nickel-based superalloy Inconel 718 that originate from the machining operation turning are studied. The turning process that is used in the experiments is face grooving which gives quasi-orthogonal cutting conditions. Cutting speed and feed have been varied to investigate their effects on the residual stress state. Tensile residual stresses with a maximum of 1300 MPa were found at the surface that turn rapidly into compressive residual stresses of up to -800 MPa. The depth distributions of the residual stresses are presented and discussed with respect to observations made by optical and transmission electron microscopy.

  • 192.
    Hörling, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Sjölén, Jacob
    SECO Tools AB.
    Karlsson, Lennart
    SECO Tools AB.
    Thermal stability of arc evaporated high aluminum-content Ti1−xAlxN thin films2002In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 20, no 5, p. 1815-1823Article in journal (Refereed)
    Abstract [en]

    The thermal stability of Ti1−xAlxN films deposited by arc evaporation from Ti–Al cathodes with 67 and 75 at. % aluminum, respectively, has been investigated. The microstructure of as-deposited and isothermally annealed samples were studied using scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The chemical composition and elemental distribution were determined by energy dispersive x ray (EDX), Rutherford backscattering spectrometry, and EDX mapping. Transmission electron micrographs revealed a dense and columnar microstructure in the as-deposited condition. Films deposited from the 67 at. % cathodes were of cubic NaCl-structure phase, whereas films deposited from the 75 at. % cathodes exhibited nanocrystallites of wurzite-structure hexagonal-phase AlN in a cubic (c)-(Ti,Al)N matrix. Both films were stable during annealing at 900 °C/120 min with respect to phase composition and grain size. Annealing at 1100 °C of films deposited from the 67 at. % cathodes resulted in phase separation of c-TiN and h-AlN, via spinodal decomposition of c-TiN and c-AlN. (Ti,Al)N films undergo extensive stress relaxation and defect annihilation at relatively high temperatures, and aspects of these microstructural transformations are discussed.

  • 193.
    Shin, C.-S.
    et al.
    Materials Science Department, Frederick Seitz Mat. Res. Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Gall, D.
    Materials Science Department, Frederick Seitz Mat. Res. Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Kim, Y.-W.
    Materials Science Department, Frederick Seitz Mat. Res. Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Desjardins, P.
    Materials Science Department, Frederick Seitz Mat. Res. Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Petrov, I.
    Materials Science Department, Frederick Seitz Mat. Res. Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Greene, J.E.
    Materials Science Department, Frederick Seitz Mat. Res. Laboratory, University of Illinois, 104 South Goodwin Avenue, Urbana, IL 61801, United States.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Epitaxial NaCl structure d-TaNx(001): Electronic transport properties, elastic modulus, and hardness versus N/Ta ratio2001In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, no 6, p. 2879-2885Article in journal (Refereed)
    Abstract [en]

    While metastable Bl-NaCl-structure d-TaNx. is presently used in a variety of hard coating, wear-resistant, and diffusion barrier applications, it is a complex material exhibiting a wide single-phase field, x?0.94-1.37, and little is known about its fundamental properties. Here, we report physical properties of epitaxial d-TaNx. layers grown as a function of x on MgO(00) by ultrahigh vacuum reactive magnetron sputter deposition. The room-temperature resistivity (? = 225 µO cm), hardness (H = 30.9 GPa), and elastic modulus (E = 455 GPa) of d-TaNx(001) are independent of x over the range 0.94-1.22. However, changes in the electronic structure associated with increasing x>1.22 lead to an increase in ? with a decrease in H and E. All d-TaNx(001) layers exhibit negative temperature coefficients of resistivity between 20 and 400 K due to weak carrier localization. d-TaNx is superconducting with the highest critical temperature, 8.45 K, obtained for layers with the lowest N/Ta ratio, x=0.94. Based upon the above results, combined with the fact that the relaxed lattice constant a0 shows only a very weak dependence on x, we propose that the wide phase field in d-TaNx is due primarily to antisite substitutions of Ta on N (and N on Ta) sites, rather than to cation and anion vacancies. To first order, antisite substitutions in TaNx are isoelectronic and hence have little effect on charge carrier density. At sufficiently high N/Ta ratios, however, simple electron-counting arguments are no longer valid since large deviations from stoichiometry alter the character of the band structure itself. © 2001 American Institute of Physics.

  • 194.
    Högberg, H
    et al.
    Ångström Lab Uppsala university.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Malm, J-O
    National Center of HREM Lunds university.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Jansson, U
    Ångström lab Uppsala university.
    Growth, structure and mechanical properties of transition metal carbide superlattices2001In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 16, no 5, p. 1301-1310Article in journal (Refereed)
  • 195.
    Almer, J
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Håkansson, G
    Bodycote Värmebehandling AB Linköping.
    Microstructure, stress and mechanical properties of arc-evaporated Cr-C-N coatings2001In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 385, no 1-2, p. 190-197Article in journal (Refereed)
    Abstract [en]

    The relationships between coating microstructure and properties in the Cr-C-N system have been investigated as a function of composition and post-deposition annealing. Coatings of varying compositions were grown using arc-evaporation, by varying the reactive gas flow ratio fR = f(C2H4)/f(N2) from 0 to 0.2, and were found to consist primarily of the cubic d-Cr(C,N) phase. Changes in both the unstressed lattice parameter, ao, and X-ray diffraction background intensity indicate that both the carbon concentration within the d-phase and amorphous/crystalline content increases with fR. Increasing fR also decreases the magnitude of the compressive biaxial residual stress, from approximately 6 to 1 GPa, while increasing both the inhomogeneous stress and thermal stability. The elastic modulus and hardness of as-deposited coatings were determined from nanoindentation to be 320 and 23 GPa, respectively, for moderate carbon concentrations (fR=0.05). Concurrent variations in microstructure and hardness with post-deposition annealing indicate that the as-deposited hardness is significantly enhanced by the microstructure, primarily by lattice defects and related stresses (microstresses) rather than average stresses (macrostresses).

  • 196.
    Talyzin, A V
    et al.
    Dept of Inorganic Chemistry , Ångström Lab Uppsala university.
    Dubrovinsky, L S
    Theoretical Geochemistry Program; Inst of Eart Sciences Uppsala university.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Jansson, U
    Dept of Inorganic Chemistry, Ångström Lab Uppsala University.
    Superhard and superelastic films of polymeric C602001In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 10, no 11, p. 2044-2048Article in journal (Refereed)
    Abstract [en]

    The C60 thin film deposited on steel substrate was transformed by high pressure-high temperature treatment to a superhard and superclastic material. The films were studied by Raman spectroscopy in situ at 20 GPa after heating at 300░C and ex situ after the quenching. The hardness and elastic properties of the high-pressure phases have been characterized with nanoindentation. The hardness of the films were determined to be 0.5 ▒ 0.1 GPa and 61.9 ▒ 9 GPa for unmodified C60 and HPHT treated films, respectively. The hardness of the pressurized film is higher than for cubic BN but lower than hardness values reported for ultrahard fullerite samples prepared from powders. An interesting observation was that the HPHT treated film showed an extreme elastic response with an elastic recovery of approximately 90%. ⌐ 2001 Elsevier Science B.V. All rights reserved.

  • 197.
    Moverare, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Influence of Texture and Anisotropy on Microstresses and Flow Behavior in a Duplex Stainless Steel During Loading2000In: Advances in X-ray Analysis, Vol. 44, 2000, p. 229-234Conference paper (Other academic)
    Abstract [en]

    The load partitioning between the two phases in a cold rolled duplex stainless steel sheet have been experimentally studied in situ during loading, via X-ray diffraction, for different loading directions. The microstresses in the two phases were found to decrease when loading in the transverse direction, while they increase during loading in the rolling and 45°-direction. Due to strong crystallographic texture in the ferritic phase the material is anisotropic with a higher stiffness and yield strength in the transverse direction compared to the rolling direction. The texture have been measured and used as input to theoretical predictions of both elastic and plastic anisotropy. The predicted anisotropic material properties have then been used in finite element simulations to study the flow behaviour of the material in different directions. The predicted flow behaviour was found to be in good agreement with the experimentally observed load partitioning between the phases for loading in the rolling and transverse direction. However, the yield strength of the ferritic phase during loading in the 45°-direction was found to be lower than what can be predicted by the crystallographic texture.

  • 198.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Studsvik Neutron Research Lab Uppsala university.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Integranular Strains in a Deformed Austenitic Stainless Steel2000In: ICRS-6,2000, London: IOM Communications , 2000Conference paper (Refereed)
  • 199.
    Johansson (Moverare), Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Load sharing between austenite and ferrite in a duplex stainless steel during cyclic loading2000In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 31, no 6, p. 1557-1570Article in journal (Refereed)
    Abstract [en]

    The load sharing between phases and the evolution of micro- and macrostresses during cyclic loading has been investigated in a 1.5-mm cold-rolled sheet of the duplex stainless steel SAF 2304. X-ray diffraction (XRD) stress analysis and transmission electron microscopy (TEM) show that even if the hardness and yield strength are higher in the austenitic phase, more plastic deformation will occur in this phase due to the residual microstresses present in the material. The origin of the microstresses is the difference in coefficients of thermal expansion between the two phases, which leads to tensile microstresses in the austenite and compressive microstresses in the ferrite. The microstresses were also found to increase from 50 to 140 MPa in the austenite during the first 100 cycles when cycled in tension fatigue with a maximum load of 500 MPa. The cyclic loading response of the material was, thus, mainly controlled by the plastic properties of the austenitic phase. It was also found that initial compressive macrostresses on the surface increased from −40 to 50 MPa during the first 103 cycles. After the initial increase of microstresses and macrostresses, no fading of residual stresses was found to occur for the following cycles. A good correlation was found between the internal stress state and the microstructure evolution. The change in texture during cyclic fatigue showed a sharpening of the deformation texture in the ferritic phase, while no significant changes were found in the austenitic phase.

  • 200.
    Hultman, Lars
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Engström, Carl
    Volvo Teknisk Utveckling AB Göteborg.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Mechanical and thermal stability of TiN/NbN superlattice thin films2000In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 133-134, p. 227-233Article in journal (Refereed)
    Abstract [en]

    High-temperature stability and mechanical deformation mechanisms of TiN/NbN superlattice structures have been investigated. Single-crystal TiN/NbN superlattices were deposited by reactive dual-cathode unbalanced magnetron sputtering in an Ar/N2 discharge onto MgO(001) substrates held at a temperature of 700 ░C. The thermal stability was studied by X-ray measurements of superlattice satellite peak intensity variation during and after annealing at up to 950 ░C. The apparent activation energy for metal interdiffusion in the TiN-NbN diffusion couple is temperature-dependent, with values ranging from 2.6 to 4.5 eV. Film hardness as measured by nanoindentation was observed to decrease during annealing, as the result of effective alloying of the nitride layers. TiN/NbN superlattices are ductile at room temperature and exhibit dislocation glide limited to within individual layers in scratching experiments.

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