Twinning

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Jian Wang - One of the best experts on this subject based on the ideXlab platform.

  • Experimentally quantifying critical stresses associated with basal slip and Twinning in magnesium using micropillars
    Acta Materialia, 2017
    Co-Authors: Yue Liu, Jian Wang, Nathan A. Mara, M. Arul Kumar, Siddhartha Pathak, Rodney J. Mccabe, Carlos N. Tomé
    Abstract:

    Abstract Basal slip and { 01 1 ¯ 2 } Twinning are two major plastic deformation mechanisms in hexagonal closed-packed magnesium. Here we quantify the critical stresses associated with basal slip and Twinning in single-crystal and bi-crystal magnesium samples by performing in situ compression of micropillars with different diameters in a scanning electron microscope. The micropillars are designed to favor either slip or Twinning under uniaxial compression. Compression tests imply a negligible size effect related to basal slip and Twinning as pillar diameter is greater than 10 μm. The critical resolved shear stresses are deduced to be 29 MPa for Twinning and 6 MPa for basal slip from a series of micropillar compression tests. Employing full-field elasto-visco-plastic simulations, we further interpret the experimental observations in terms of the local stress distribution associated with multiple Twinning, twin nucleation, and twin growth. Our simulation results suggest that the Twinning features being studied should not be close to the top surface of the micropillar because of local stress perturbations induced by the hard indenter.

  • Twinning-like lattice reorientation without a crystallographic Twinning plane
    Nature communications, 2014
    Co-Authors: Bo-yu Liu, Jian Wang, Xiyan Zhang, Zhi-wei Shan, Chun-lin Jia, Jun Sun
    Abstract:

    Twinning on the plane is a common mode of plastic deformation for hexagonal-close-packed metals. Here we report, by monitoring the deformation of submicron-sized single-crystal magnesium compressed normal to its prismatic plane with transmission electron microscopy, the reorientation of the parent lattice to a 'twin' lattice, producing an orientational relationship akin to that of the conventional Twinning, but without a crystallographic mirror plane, and giving plastic strain that is not simple shear. Aberration-corrected transmission electron microscopy observations reveal that the boundary between the parent lattice and the 'twin' lattice is composed predominantly of semicoherent basal/prismatic interfaces instead of the Twinning plane. The migration of this boundary is dominated by the movement of these interfaces undergoing basal/prismatic transformation via local rearrangements of atoms. This newly discovered deformation mode by boundary motion mimics conventional deformation Twinning but is distinct from the latter and, as such, broadens the known mechanisms of plasticity.

  • a crystal plasticity model for hexagonal close packed hcp crystals including Twinning and de Twinning mechanisms
    International Journal of Plasticity, 2013
    Co-Authors: Huamiao Wang, Jian Wang, C N Tome
    Abstract:

    Together with slip, deformation Twinning and de-Twinning are the plastic deformation mechanisms in hexagonal close packed (HCP) crystals, which strongly affect texture evolution and anisotropic response. As a consequence, several Twinning models have been proposed and implemented in the existing polycrystalline plasticity models. De-Twinning is an inverse process with respect to Twinning, which is relevant to cycling, fatigue and complex loads but is rarely incorporated into polycrystalline plastic models. In this paper, we propose a physics-based Twinning and de-Twinning (TDT) model that has the capability of dealing with both mechanisms during plastic deformation. The TDT model is characterized by four deformation mechanisms corresponding to twin nucleation, twin growth, twin shrinkage and re-Twinning. Twin nucleation and twin growth are associated with deformation Twinning, and twin shrinkage and re-Twinning are associated with de-Twinning. The proposed TDT model is implemented in the Elasto-Visco-Plastic Self-Consistent (EVPSC) model. We demonstrate the validity and the capability of the TDT model by simulating cyclic loading of magnesium alloys AZ31B plate and AZ31 bar. Comparison with the measurements indicates that the TDT model is able to capture the key features observed in experiments, implying that the mechanical response in the simulated materials is mainly associated with Twinning and de-Twinning.

  • 1 012 Twinning nucleation mechanisms in hexagonal close packed crystals
    Acta Materialia, 2009
    Co-Authors: Jian Wang, J. P. Hirth, C N Tome
    Abstract:

    Abstract Mechanisms for ( 1 ¯ 0 1 2 ) Twinning in hexagonal-close-packed crystals at an atomic scale were studied using topological analysis and atomistic simulations. Two Twinning mechanisms were found: a normal-Twinning mechanism in which a stable twin nucleus is created by simultaneous nucleation of multiple Twinning dislocations; and a zonal-Twinning mechanism in which a stable twin nucleus is created by simultaneous nucleation of a partial dislocation and multiple Twinning dislocations. The Twinning direction, dependent on the ratio of lattice parameters c/a, is along [ 1 0 1 ¯ 1 ] when c / a 3 , but along the opposite direction when c / a > 3 . Atomistic simulations, using density function theory for Mg, Zr and Zn and an empirical potential for Mg, were performed to study the kinetics and energetics associated with the two Twinning mechanisms. The results show that the zonal-Twinning mechanism is energetically favorable relative to the normal-Twinning mechanism, because the zonal dislocation has a smaller Burgers vector.

  • (1¯012) Twinning nucleation mechanisms in hexagonal-close-packed crystals
    Acta Materialia, 2009
    Co-Authors: Jian Wang, John P. Hirth, Carlos N. Tomé
    Abstract:

    Abstract Mechanisms for ( 1 ¯ 0 1 2 ) Twinning in hexagonal-close-packed crystals at an atomic scale were studied using topological analysis and atomistic simulations. Two Twinning mechanisms were found: a normal-Twinning mechanism in which a stable twin nucleus is created by simultaneous nucleation of multiple Twinning dislocations; and a zonal-Twinning mechanism in which a stable twin nucleus is created by simultaneous nucleation of a partial dislocation and multiple Twinning dislocations. The Twinning direction, dependent on the ratio of lattice parameters c/a, is along [ 1 0 1 ¯ 1 ] when c / a 3 , but along the opposite direction when c / a > 3 . Atomistic simulations, using density function theory for Mg, Zr and Zn and an empirical potential for Mg, were performed to study the kinetics and energetics associated with the two Twinning mechanisms. The results show that the zonal-Twinning mechanism is energetically favorable relative to the normal-Twinning mechanism, because the zonal dislocation has a smaller Burgers vector.

Kaneaki Tsuzaki - One of the best experts on this subject based on the ideXlab platform.

  • effect of strain rate on hydrogen embrittlement susceptibility of Twinning induced plasticity steel pre charged with high pressure hydrogen gas
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Motomichi Koyama, Gregory Gerstein, H J Maier, Kaneaki Tsuzaki
    Abstract:

    Abstract The effects of tensile strain rate on the hydrogen-induced mechanical and microstructural features of a Twinning-induced plasticity (TWIP) steel were investigated using a Fe-23Mn-0.5C steel with a saturated amount of hydrogen. To obtain a homogeneous hydrogen distribution, high-pressure hydrogen gas pre-charging was performed at 423 K. Similar to previous studies on hydrogen embrittlement, the deterioration in the tensile properties became distinct when the strain rate was decreased from 0.6 × 10−3 to 0.6 × 10−4 s−1. In terms of microstructural features, hydrogen-precharging decreased the thickness of deformation twin plates, and it localized dislocation slip. Moreover, facets of the hydrogen-induced quasi-cleavage feature on the fracture surface became smoother with decreasing strain rate. In this study, we proposed that a combined effect of hydrogen segregation, slip localization, and thinning of twin plates causes the hydrogen embrittlement of TWIP steels, particularly at a low strain rate.

  • hydrogen assisted failure in a Twinning induced plasticity steel studied under in situ hydrogen charging by electron channeling contrast imaging
    Acta Materialia, 2013
    Co-Authors: Eiji Akiyama, Motomichi Koyama, Kaneaki Tsuzaki, Dierk Raabe
    Abstract:

    We investigated the hydrogen embrittlement of a Fe–18Mn–1.2%C (wt.%) Twinning-induced plasticity steel, focusing on the influence of deformation twins on hydrogen-assisted cracking. A tensile test under ongoing hydrogen charging was performed at low strain rate (1.7 � 10 � 6 s � 1 ) to observe hydrogen-assisted cracking and crack propagation. Hydrogen-stimulated cracks and deformation twins were observed by electron channeling contrast imaging. We made the surprising observation that hydrogen-assisted cracking was initiated both at grain boundaries and also at deformation twins. Also, crack propagation occurred along both types of interfaces. Deformation twins were shown to assist intergranular cracking and crack propagation. The stress concentration at the tip of the deformation twins is suggested to play an important role in the hydrogen embrittlement of the Fe–Mn–C twining-induced plasticity steel.

Motomichi Koyama - One of the best experts on this subject based on the ideXlab platform.

  • effect of strain rate on hydrogen embrittlement susceptibility of Twinning induced plasticity steel pre charged with high pressure hydrogen gas
    International Journal of Hydrogen Energy, 2016
    Co-Authors: Motomichi Koyama, Gregory Gerstein, H J Maier, Kaneaki Tsuzaki
    Abstract:

    Abstract The effects of tensile strain rate on the hydrogen-induced mechanical and microstructural features of a Twinning-induced plasticity (TWIP) steel were investigated using a Fe-23Mn-0.5C steel with a saturated amount of hydrogen. To obtain a homogeneous hydrogen distribution, high-pressure hydrogen gas pre-charging was performed at 423 K. Similar to previous studies on hydrogen embrittlement, the deterioration in the tensile properties became distinct when the strain rate was decreased from 0.6 × 10−3 to 0.6 × 10−4 s−1. In terms of microstructural features, hydrogen-precharging decreased the thickness of deformation twin plates, and it localized dislocation slip. Moreover, facets of the hydrogen-induced quasi-cleavage feature on the fracture surface became smoother with decreasing strain rate. In this study, we proposed that a combined effect of hydrogen segregation, slip localization, and thinning of twin plates causes the hydrogen embrittlement of TWIP steels, particularly at a low strain rate.

  • hydrogen assisted failure in a Twinning induced plasticity steel studied under in situ hydrogen charging by electron channeling contrast imaging
    Acta Materialia, 2013
    Co-Authors: Eiji Akiyama, Motomichi Koyama, Kaneaki Tsuzaki, Dierk Raabe
    Abstract:

    We investigated the hydrogen embrittlement of a Fe–18Mn–1.2%C (wt.%) Twinning-induced plasticity steel, focusing on the influence of deformation twins on hydrogen-assisted cracking. A tensile test under ongoing hydrogen charging was performed at low strain rate (1.7 � 10 � 6 s � 1 ) to observe hydrogen-assisted cracking and crack propagation. Hydrogen-stimulated cracks and deformation twins were observed by electron channeling contrast imaging. We made the surprising observation that hydrogen-assisted cracking was initiated both at grain boundaries and also at deformation twins. Also, crack propagation occurred along both types of interfaces. Deformation twins were shown to assist intergranular cracking and crack propagation. The stress concentration at the tip of the deformation twins is suggested to play an important role in the hydrogen embrittlement of the Fe–Mn–C twining-induced plasticity steel.

Dierk Raabe - One of the best experts on this subject based on the ideXlab platform.

  • hydrogen assisted failure in a Twinning induced plasticity steel studied under in situ hydrogen charging by electron channeling contrast imaging
    Acta Materialia, 2013
    Co-Authors: Eiji Akiyama, Motomichi Koyama, Kaneaki Tsuzaki, Dierk Raabe
    Abstract:

    We investigated the hydrogen embrittlement of a Fe–18Mn–1.2%C (wt.%) Twinning-induced plasticity steel, focusing on the influence of deformation twins on hydrogen-assisted cracking. A tensile test under ongoing hydrogen charging was performed at low strain rate (1.7 � 10 � 6 s � 1 ) to observe hydrogen-assisted cracking and crack propagation. Hydrogen-stimulated cracks and deformation twins were observed by electron channeling contrast imaging. We made the surprising observation that hydrogen-assisted cracking was initiated both at grain boundaries and also at deformation twins. Also, crack propagation occurred along both types of interfaces. Deformation twins were shown to assist intergranular cracking and crack propagation. The stress concentration at the tip of the deformation twins is suggested to play an important role in the hydrogen embrittlement of the Fe–Mn–C twining-induced plasticity steel.

  • the effect of grain size and grain orientation on deformation Twinning in a fe 22 wt mn 0 6 wt c twip steel
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010
    Co-Authors: I Gutierrezurrutia, Stefan Zaefferer, Dierk Raabe
    Abstract:

    Abstract We investigate the effect of grain size and grain orientation on deformation Twinning in a Fe–22 wt.% Mn–0.6 wt.% C TWIP steel using microstructure observations by electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD). Samples with average grain sizes of 3 μm and 50 μm were deformed in tension at room temperature to different strains. The onset of Twinning concurs in both materials with yielding which leads us to propose a Hall–Petch-type relation for the Twinning stress using the same Hall–Petch constant for Twinning as that for glide. The influence of grain orientation on the Twinning stress is more complicated. At low strain, a strong influence of grain orientation on deformation Twinning is observed which fully complies with Schmid's law under the assumption that slip and Twinning have equal critical resolved shear stresses. Deformation Twinning occurs in grains oriented close to 〈1 1 1〉//tensile axis directions where the Twinning stress is larger than the slip stress. At high strains (0.3 logarithmic strain), a strong deviation from Schmid's law is observed. Deformation twins are now also observed in grains unfavourably oriented for Twinning according to Schmid's law. We explain this deviation in terms of local grain-scale stress variations. The local stress state controlling deformation Twinning is modified by local stress concentrations at grain boundaries originating, for instance, from incoming bundles of deformation twins in neighboring grains.

Carlos N. Tomé - One of the best experts on this subject based on the ideXlab platform.

  • Experimentally quantifying critical stresses associated with basal slip and Twinning in magnesium using micropillars
    Acta Materialia, 2017
    Co-Authors: Yue Liu, Jian Wang, Nathan A. Mara, M. Arul Kumar, Siddhartha Pathak, Rodney J. Mccabe, Carlos N. Tomé
    Abstract:

    Abstract Basal slip and { 01 1 ¯ 2 } Twinning are two major plastic deformation mechanisms in hexagonal closed-packed magnesium. Here we quantify the critical stresses associated with basal slip and Twinning in single-crystal and bi-crystal magnesium samples by performing in situ compression of micropillars with different diameters in a scanning electron microscope. The micropillars are designed to favor either slip or Twinning under uniaxial compression. Compression tests imply a negligible size effect related to basal slip and Twinning as pillar diameter is greater than 10 μm. The critical resolved shear stresses are deduced to be 29 MPa for Twinning and 6 MPa for basal slip from a series of micropillar compression tests. Employing full-field elasto-visco-plastic simulations, we further interpret the experimental observations in terms of the local stress distribution associated with multiple Twinning, twin nucleation, and twin growth. Our simulation results suggest that the Twinning features being studied should not be close to the top surface of the micropillar because of local stress perturbations induced by the hard indenter.

  • effect of dislocation transmutation on modeling hardening mechanisms by Twinning in magnesium
    International Journal of Plasticity, 2012
    Co-Authors: Andrew L. Oppedal, El H Kadiri, J C Baird, G.c. Kaschner, Carlos N. Tomé, Sven C Vogel, Mark F. Horstemeyer
    Abstract:

    Abstract Textured hexagonal close packed double-lattice structures show stronger anisotropy than textured cubic structures. The reason lies behind the necessity to activate deformation Twinning and hard slip dislocation modes. Although the mechanisms behind activation of dislocations with non-basal Burgers vectors are still not fundamentally understood, the effect of Twinning on hardening presents the most substantial challenge to polycrystal plasticity modelers. The origin of the increasing strain hardening rate regime (Regime II) upon profuse Twinning is still not fundamentally clear. Previous successful attempts to fit the stress–strain behaviors based on a Hall–Petch effect by twin segmentation had systemically led to discrepancies in predicting intermediate textures and/or twin volume fraction evolutions. A recent dislocation-based hardening rule incorporated into the Visco-Plastic Self-Consistent (VPSC) model allows slip and Twinning to be physically coupled in the simulations. In this paper, we investigate hardening mechanisms in pure magnesium and apply a dislocation based formalism to model anisotropy. In contrast to magnesium alloys, we show that pure magnesium under large strains develops substantial multivariant Twinning and multifold Twinning. These Twinning phenomena are accompanied by a marked grain refinement and blunting of former twin boundaries. This blunting suggests severe accommodation effects in the soft matrix that caused the twin boundary to lose coherency. Thus, multivariant and multifold Twinning take place to accommodate further deformation, but the subsequent twin–twin interactions arise to contribute in material hardening. The strain path anisotropy related to the saturation stresses revealed major missing links for comprehending hardening by Twinning and substantiated dislocation transmutation effect by Twinning shear.

  • (1¯012) Twinning nucleation mechanisms in hexagonal-close-packed crystals
    Acta Materialia, 2009
    Co-Authors: Jian Wang, John P. Hirth, Carlos N. Tomé
    Abstract:

    Abstract Mechanisms for ( 1 ¯ 0 1 2 ) Twinning in hexagonal-close-packed crystals at an atomic scale were studied using topological analysis and atomistic simulations. Two Twinning mechanisms were found: a normal-Twinning mechanism in which a stable twin nucleus is created by simultaneous nucleation of multiple Twinning dislocations; and a zonal-Twinning mechanism in which a stable twin nucleus is created by simultaneous nucleation of a partial dislocation and multiple Twinning dislocations. The Twinning direction, dependent on the ratio of lattice parameters c/a, is along [ 1 0 1 ¯ 1 ] when c / a 3 , but along the opposite direction when c / a > 3 . Atomistic simulations, using density function theory for Mg, Zr and Zn and an empirical potential for Mg, were performed to study the kinetics and energetics associated with the two Twinning mechanisms. The results show that the zonal-Twinning mechanism is energetically favorable relative to the normal-Twinning mechanism, because the zonal dislocation has a smaller Burgers vector.