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Tarek M. Hatem - One of the best experts on this subject based on the ideXlab platform.

  • dynamic shear strain localization and inclusion effects in lath Martensitic steels subjected to high pressure loads
    Journal of The Mechanics and Physics of Solids, 2010
    Co-Authors: Tarek M. Hatem, Mohammed Zikry
    Abstract:

    Abstract A three-dimensional multiple-slip dislocation-density based crystalline formulation, specialized finite-element formulations, and specialized Voronoi tessellations adapted to Martensitic orientations, were used to investigate shear–strain localization, and dislocation-density evolution in Martensitic Microstructures under dynamic compressive loading conditions. The formulation is based on accounting for variant morphologies and orientations, secondary-phase structures, and initial dislocations-densities that are uniquely inherent to Martensitic Microstructures. The effects of strain rate and inclusions on the evolution of shear–strain localization were investigated. The analysis indicates that variant morphology and orientations have a direct consequence on dislocation-density accumulation and inelastic localization in Martensitic Microstructures, and that lath directions, orientations, and arrangements are critical characteristics of high-strength Martensitic dynamic behavior. It is shown that tensile hydrostatic pressure due to the unloading of the plastic waves at the free boundary and extensive shear–strain accumulation occurs at certain triple junctions. Furthermore, plastic shear-slip accumulation between inclusions and the surrounding Martensitic matrix results in shear–strain localization and increases in the tensile hydrostatic pressure at critical locations, such as trip junctions.

  • Dynamic shear–strain localization and inclusion effects in lath Martensitic steels subjected to high pressure loads
    Journal of the Mechanics and Physics of Solids, 2010
    Co-Authors: Tarek M. Hatem, Mohammed A. Zikry
    Abstract:

    Abstract A three-dimensional multiple-slip dislocation-density based crystalline formulation, specialized finite-element formulations, and specialized Voronoi tessellations adapted to Martensitic orientations, were used to investigate shear–strain localization, and dislocation-density evolution in Martensitic Microstructures under dynamic compressive loading conditions. The formulation is based on accounting for variant morphologies and orientations, secondary-phase structures, and initial dislocations-densities that are uniquely inherent to Martensitic Microstructures. The effects of strain rate and inclusions on the evolution of shear–strain localization were investigated. The analysis indicates that variant morphology and orientations have a direct consequence on dislocation-density accumulation and inelastic localization in Martensitic Microstructures, and that lath directions, orientations, and arrangements are critical characteristics of high-strength Martensitic dynamic behavior. It is shown that tensile hydrostatic pressure due to the unloading of the plastic waves at the free boundary and extensive shear–strain accumulation occurs at certain triple junctions. Furthermore, plastic shear-slip accumulation between inclusions and the surrounding Martensitic matrix results in shear–strain localization and increases in the tensile hydrostatic pressure at critical locations, such as trip junctions.

  • dislocation density crystalline plasticity modeling of lath Martensitic Microstructures in steel alloys
    Philosophical Magazine, 2009
    Co-Authors: Tarek M. Hatem, Mohammed Zikry
    Abstract:

    A three-dimensional multiple-slip dislocation density-based crystalline formulation, specialized finite-element formulations and Voronoi tessellations adapted to Martensitic orientations were used to investigate large strain inelastic deformation modes and dislocation density evolution in Martensitic Microstructures. The formulation is based on accounting for variant morphologies and orientations, retained austenite and initial dislocation densities that are uniquely inherent to Martensitic Microstructures. The effects of parent austenite orientation and retained austenite were also investigated for heterogeneous fcc/bcc crystalline structures. Furthermore, the formulation was used to investigate Microstructures mapped directly from SEM/EBSD images of Martensitic steel alloys. The analysis indicates that variant morphology and orientations have a direct effect on dislocation density accumulation and inelastic localization in Martensitic Microstructures, and that lath directions, orientations and arrangeme...

  • Shear pipe effects and dynamic shear-strain localization in Martensitic steels
    Acta Materialia, 2009
    Co-Authors: Tarek M. Hatem, Mohammed A. Zikry
    Abstract:

    A three-dimensional, multiple-slip, dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to Martensitic orientations were used to investigate dislocation-density activities and shear-strain localization in high-strength Martensitic steels under quasi-static and dynamic loading conditions. The formulation is based on accounting for variant morphologies and orientations, retained austenite, and initial dislocations densities that are uniquely inherent to Martensitic Microstructures. The effects of variant distributions and arrangements, loading directions, and microcracks on the evolution of shear-strain localization are investigated. The analysis indicates that shear-strain localization occurs due to slip-system compatibilities relative to the loading direction and the long direction of laths, which result in shear-strain accumulation. At specific triple junctions, rotation misalignments due to lattice and slip incompatibilities occur, and these incompatibilities are further exacerbated by the presence of defects, such as microcracks.

  • Modeling of Lath Martensitic Microstructures and Failure Evolution in Steel Alloys
    Journal of Engineering Materials and Technology, 2009
    Co-Authors: Tarek M. Hatem, Mohammed A. Zikry
    Abstract:

    A multiple-slip dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to Martensitic orientations were used to investigate dislocation-density activities and crack tip blunting in high strength Martensitic steels. The formulation is based on accounting for variant morphologies and orientations, retained austenite, and initial dislocations densities that are uniquely inherent to Martensitic Microstructures. The effects of variant distributions and arrangements are investigated for different crack and void interaction distributions and arrangements. The analysis indicates that for certain orientations related to specific variant block arrangements, which correspond to random low angle orientations, cracks can be blunted by dislocation-density activities along transgranular planes. For other variant block arrangements, which correspond to random high angle orientations, sharp crack growth can occur due to dislocation activities along intergranular planes.

Mohammed A. Zikry - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural Behavior and Fracture in Crystalline Materials: Overview
    Handbook of Damage Mechanics, 2021
    Co-Authors: Pratheek Shanthraj, Mohammed A. Zikry
    Abstract:

    A dislocation-density-based multiple-slip crystalline plasticity framework, which accounts for variant morphologies and orientation relationships (ORs) that are uniquely inherent to lath Martensitic Microstructures, and a dislocation-density grain-boundary (GB) interaction scheme, which is based on dislocation-density transmission and blockage at variant boundaries, are developed and used to predict stress accumulation or relaxation at the variant interfaces. A microstructural failure criterion, which is based on resolving these stresses on Martensitic cleavage planes, and specialized finite-element (FE) methodologies using overlapping elements to represent evolving fracture surfaces are used for a detailed analysis of fracture nucleation and intergranular and transgranular crack growth in Martensitic steels. The effects of block and packet boundaries are investigated, and the results indicate that the orientation of the cleavage planes in relation to the slip planes and the lath morphology are the dominant factors that characterize specific failure modes. The block and packet sizes along the lath long direction are the key microstructural features that affect toughening mechanisms, such as crack arrest and deflection, and these mechanisms can be used to control the nucleation and propagation of different failure modes.

  • Dynamic shear–strain localization and inclusion effects in lath Martensitic steels subjected to high pressure loads
    Journal of the Mechanics and Physics of Solids, 2010
    Co-Authors: Tarek M. Hatem, Mohammed A. Zikry
    Abstract:

    Abstract A three-dimensional multiple-slip dislocation-density based crystalline formulation, specialized finite-element formulations, and specialized Voronoi tessellations adapted to Martensitic orientations, were used to investigate shear–strain localization, and dislocation-density evolution in Martensitic Microstructures under dynamic compressive loading conditions. The formulation is based on accounting for variant morphologies and orientations, secondary-phase structures, and initial dislocations-densities that are uniquely inherent to Martensitic Microstructures. The effects of strain rate and inclusions on the evolution of shear–strain localization were investigated. The analysis indicates that variant morphology and orientations have a direct consequence on dislocation-density accumulation and inelastic localization in Martensitic Microstructures, and that lath directions, orientations, and arrangements are critical characteristics of high-strength Martensitic dynamic behavior. It is shown that tensile hydrostatic pressure due to the unloading of the plastic waves at the free boundary and extensive shear–strain accumulation occurs at certain triple junctions. Furthermore, plastic shear-slip accumulation between inclusions and the surrounding Martensitic matrix results in shear–strain localization and increases in the tensile hydrostatic pressure at critical locations, such as trip junctions.

  • Shear pipe effects and dynamic shear-strain localization in Martensitic steels
    Acta Materialia, 2009
    Co-Authors: Tarek M. Hatem, Mohammed A. Zikry
    Abstract:

    A three-dimensional, multiple-slip, dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to Martensitic orientations were used to investigate dislocation-density activities and shear-strain localization in high-strength Martensitic steels under quasi-static and dynamic loading conditions. The formulation is based on accounting for variant morphologies and orientations, retained austenite, and initial dislocations densities that are uniquely inherent to Martensitic Microstructures. The effects of variant distributions and arrangements, loading directions, and microcracks on the evolution of shear-strain localization are investigated. The analysis indicates that shear-strain localization occurs due to slip-system compatibilities relative to the loading direction and the long direction of laths, which result in shear-strain accumulation. At specific triple junctions, rotation misalignments due to lattice and slip incompatibilities occur, and these incompatibilities are further exacerbated by the presence of defects, such as microcracks.

  • Modeling of Lath Martensitic Microstructures and Failure Evolution in Steel Alloys
    Journal of Engineering Materials and Technology, 2009
    Co-Authors: Tarek M. Hatem, Mohammed A. Zikry
    Abstract:

    A multiple-slip dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to Martensitic orientations were used to investigate dislocation-density activities and crack tip blunting in high strength Martensitic steels. The formulation is based on accounting for variant morphologies and orientations, retained austenite, and initial dislocations densities that are uniquely inherent to Martensitic Microstructures. The effects of variant distributions and arrangements are investigated for different crack and void interaction distributions and arrangements. The analysis indicates that for certain orientations related to specific variant block arrangements, which correspond to random low angle orientations, cracks can be blunted by dislocation-density activities along transgranular planes. For other variant block arrangements, which correspond to random high angle orientations, sharp crack growth can occur due to dislocation activities along intergranular planes.

Guillermo Requena - One of the best experts on this subject based on the ideXlab platform.

  • Inducing Stable alpha plus beta Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments
    Materials, 2017
    Co-Authors: Pere Barriobero-vila, Joachim Gussone, Jan Haubrich, Stefanie Sandloebes, Julio Cesar Da Silva, Peter Cloetens, Norbert Schell, Guillermo Requena
    Abstract:

    Selective laser melting is a promising powder-bed-based additive manufacturing technique for titanium alloys: near net-shaped metallic components can be produced with high resource-efficiency and cost savings. For the most commercialized titanium alloy, namely Ti-6Al-4V, the complicated thermal profile of selective laser melting manufacturing (sharp cycles of steep heating and cooling rates) usually hinders manufacturing of components in a one-step process owing to the formation of brittle Martensitic Microstructures unsuitable for structural applications. In this work, an intensified intrinsic heat treatment is applied during selective laser melting of Ti-6Al-4V powder using a scanning strategy that combines porosity-optimized processing with a very tight hatch distance. Extensive martensite decomposition providing a uniform, fine lamellar alpha + beta microstructure is obtained along the building direction. Moreover, structural evidence of the formation of the intermetallic alpha(2)-Ti3Al phase is provided. Variations in the lattice parameter of beta serve as an indicator of the microstructural degree of stabilization. Interconnected 3D networks of beta are generated in regions highly affected by the intensified intrinsic heat treatment applied. The results obtained reflect a contribution towards simultaneous selective laser melting-manufacturing and heat treatment for fabrication of Ti-6Al-4V parts

  • Inducing Stable alpha plus beta Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments
    Materials, 2017
    Co-Authors: Pere Barriobero-vila, Joachim Gussone, Jan Haubrich, Stefanie Sandloebes, Julio Cesar Da Silva, Peter Cloetens, Norbert Schell, Guillermo Requena
    Abstract:

    Selective laser melting is a promising powder-bed-based additive manufacturing technique for titanium alloys: near net-shaped metallic components can be produced with high resource-efficiency and cost savings. For the most commercialized titanium alloy, namely Ti-6Al-4V, the complicated thermal profile of selective laser melting manufacturing (sharp cycles of steep heating and cooling rates) usually hinders manufacturing of components in a one-step process owing to the formation of brittle Martensitic Microstructures unsuitable for structural applications. In this work, an intensified intrinsic heat treatment is applied during selective laser melting of Ti-6Al-4V powder using a scanning strategy that combines porosity-optimized processing with a very tight hatch distance. Extensive martensite decomposition providing a uniform, fine lamellar alpha + beta microstructure is obtained along the building direction. Moreover, structural evidence of the formation of the intermetallic alpha(2)-Ti3Al phase is provided. Variations in the lattice parameter of beta serve as an indicator of the microstructural degree of stabilization. Interconnected 3D networks of beta are generated in regions highly affected by the intensified intrinsic heat treatment applied. The results obtained reflect a contribution towards simultaneous selective laser melting-manufacturing and heat treatment for fabrication of Ti-6Al-4V parts

Michaël Peigney - One of the best experts on this subject based on the ideXlab platform.

  • Energy minimizing strains in Martensitic Microstructures
    2013
    Co-Authors: Michaël Peigney
    Abstract:

    This communication is concerned with the theoretical prediction of the energy-minimizing (or stress-free) strains that can be realized by Martensitic Microstructures. Polyconvexification and related notions are used to derive some upper bounds (in the sense of inclusion) on the set of energy-minimizing strains. Lower bounds are obtained from lamination techniques. Three-, four-, and twelve-well problems are considered. In particular, the structure of the set of energy-minimizing strains in cubic to monoclinic transformations is investigated in detail.

  • on the energy minimizing strains in Martensitic Microstructures part 1 geometrically nonlinear theory
    Journal of The Mechanics and Physics of Solids, 2013
    Co-Authors: Michaël Peigney
    Abstract:

    Abstract This paper addresses the theoretical prediction of the quasiconvex hull of energy-minimizing strains that can be realized by Martensitic Microstructures. Polyconvexification and related notions are used to derive some upper bounds (in the sense of inclusion) on the quasiconvex hull. Lower bounds are constructed by lamination techniques. The geometrically nonlinear theory (finite strains) is considered in the present Part 1. Analytical expressions are obtained for a three-well problem which encompasses the cubic to tetragonal transformation as a special case. Twelve-well problems related to cubic to monoclinic transformations are also studied. In that case, sufficient conditions are derived for the microstructure to be restricted to only two of the 12 wells.

  • Energy-minimizing Strains in Martensitic Microstructures
    2013
    Co-Authors: Michaël Peigney
    Abstract:

    Shape memory alloys exhibit a solid/solid phase transformation between different crystallographic structures, known as austenite (stable at high temperature) and martensite (stable at low temperature). That phase transformation is triggered both by thermal and mechanical loading. In terms of crystallographic structure, the austenite has a higher symmetry than the martensite, which leads one to distinguish several symmetry-related Martensitic variants. To each Martensitic variant is attached a transformation strain that describes the deformation between the crystallographic structures of the austenite and the martensite. The number of Martensitic variants as well as the corresponding transformation strains depend on the alloy considered, through the structure of the austenite and martensite lattices. Some common examples include the cubic to tetragonal transformation (MnCu, MnNi), the cubic to orthorombic transformation (CuAlNi) and the cubic to monoclinic transformations (NiTi), corresponding respectively to 3, 6 and 12 Martensitic variants. This talk is concerned with the theoretical prediction of the set of strains that minimize the effective (or macroscopic) energy. Those strains, classically refered to as recoverable strains, play a central role in the shape memory effect. The macroscopic energy is defined as the quasiconvexification (or relaxation) of a multi-well energy function that models the behaviour of the material at a microscopic level. The relaxation procedure essentially consists in finding the austenite/martensite Microstructures which minimize the total energy. The work presented aims at complementing existing results on that problem, essentially through the use of bounds on the set of energy-minimizing strains. Upper bounds are obtained using distinctive properties of Young measures. Lower bounds are constructed using lamination techniques. Both the geometrically nonlinear setting (finite strains) and the geometrically linear setting (infinitesimal strains) are covered, the latter being less accurate but significantly more tractable. In the geometrically nonlinear setting, analytical expressions of both lower and upper bounds are derived for a general three-well problem that encompasses the cubic to tetragonal transformation as a special case. In the geometrically linear setting, the twelve-well problems corresponding to cubic to monoclinic transformations are studied in detail.

  • On the energy-minimizing strains in Martensitic Microstructures-Part 1: Geometrically nonlinear theory
    Journal of the Mechanics and Physics of Solids, 2013
    Co-Authors: Michaël Peigney
    Abstract:

    This paper addresses the theoretical prediction of the quasiconvex hull of energy-minimizing strains that can be realized by Martensitic Microstructures. Polyconvexification and related notions are used to derive some upper bounds (in the sense of inclusion). Lower bounds are constructed by lamination techniques. The geometrically nonlinear theory (finite strains) is considered in the present Part 1. Analytical expressions are obtained for a three-well problem which encompasses the cubic to tetragonal transformation as a special case. Twelve-well problems related to cubic to monoclinic transformations are also studied. In that case, sufficient conditions are derived for the microstructure to be restricted to only two of the 12 wells

  • On the energy-minimizing strains in Martensitic Microstructures—Part 1: Geometrically nonlinear theory
    Journal of the Mechanics and Physics of Solids, 2013
    Co-Authors: Michaël Peigney
    Abstract:

    Abstract This paper addresses the theoretical prediction of the quasiconvex hull of energy-minimizing strains that can be realized by Martensitic Microstructures. Polyconvexification and related notions are used to derive some upper bounds (in the sense of inclusion) on the quasiconvex hull. Lower bounds are constructed by lamination techniques. The geometrically nonlinear theory (finite strains) is considered in the present Part 1. Analytical expressions are obtained for a three-well problem which encompasses the cubic to tetragonal transformation as a special case. Twelve-well problems related to cubic to monoclinic transformations are also studied. In that case, sufficient conditions are derived for the microstructure to be restricted to only two of the 12 wells.

Pere Barriobero-vila - One of the best experts on this subject based on the ideXlab platform.

  • Inducing Stable alpha plus beta Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments
    Materials, 2017
    Co-Authors: Pere Barriobero-vila, Joachim Gussone, Jan Haubrich, Stefanie Sandloebes, Julio Cesar Da Silva, Peter Cloetens, Norbert Schell, Guillermo Requena
    Abstract:

    Selective laser melting is a promising powder-bed-based additive manufacturing technique for titanium alloys: near net-shaped metallic components can be produced with high resource-efficiency and cost savings. For the most commercialized titanium alloy, namely Ti-6Al-4V, the complicated thermal profile of selective laser melting manufacturing (sharp cycles of steep heating and cooling rates) usually hinders manufacturing of components in a one-step process owing to the formation of brittle Martensitic Microstructures unsuitable for structural applications. In this work, an intensified intrinsic heat treatment is applied during selective laser melting of Ti-6Al-4V powder using a scanning strategy that combines porosity-optimized processing with a very tight hatch distance. Extensive martensite decomposition providing a uniform, fine lamellar alpha + beta microstructure is obtained along the building direction. Moreover, structural evidence of the formation of the intermetallic alpha(2)-Ti3Al phase is provided. Variations in the lattice parameter of beta serve as an indicator of the microstructural degree of stabilization. Interconnected 3D networks of beta are generated in regions highly affected by the intensified intrinsic heat treatment applied. The results obtained reflect a contribution towards simultaneous selective laser melting-manufacturing and heat treatment for fabrication of Ti-6Al-4V parts

  • Inducing Stable alpha plus beta Microstructures during Selective Laser Melting of Ti-6Al-4V Using Intensified Intrinsic Heat Treatments
    Materials, 2017
    Co-Authors: Pere Barriobero-vila, Joachim Gussone, Jan Haubrich, Stefanie Sandloebes, Julio Cesar Da Silva, Peter Cloetens, Norbert Schell, Guillermo Requena
    Abstract:

    Selective laser melting is a promising powder-bed-based additive manufacturing technique for titanium alloys: near net-shaped metallic components can be produced with high resource-efficiency and cost savings. For the most commercialized titanium alloy, namely Ti-6Al-4V, the complicated thermal profile of selective laser melting manufacturing (sharp cycles of steep heating and cooling rates) usually hinders manufacturing of components in a one-step process owing to the formation of brittle Martensitic Microstructures unsuitable for structural applications. In this work, an intensified intrinsic heat treatment is applied during selective laser melting of Ti-6Al-4V powder using a scanning strategy that combines porosity-optimized processing with a very tight hatch distance. Extensive martensite decomposition providing a uniform, fine lamellar alpha + beta microstructure is obtained along the building direction. Moreover, structural evidence of the formation of the intermetallic alpha(2)-Ti3Al phase is provided. Variations in the lattice parameter of beta serve as an indicator of the microstructural degree of stabilization. Interconnected 3D networks of beta are generated in regions highly affected by the intensified intrinsic heat treatment applied. The results obtained reflect a contribution towards simultaneous selective laser melting-manufacturing and heat treatment for fabrication of Ti-6Al-4V parts