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C N Tome - One of the best experts on this subject based on the ideXlab platform.

  • rolling induced face centered cubic titanium in Hexagonal Close packed titanium at room temperature
    Scientific Reports, 2016
    Co-Authors: Anil Kumar, C N Tome, Jun Wang, Z Zhang, Scott X Mao
    Abstract:

    Combining transmission electron microscopes and density functional theory calculations, we report the nucleation and growth mechanisms of room temperature rolling induced face-centered cubic titanium (fcc-Ti) in polycrystalline Hexagonal Close packed titanium (hcp-Ti). Fcc-Ti and hcp-Ti take the orientation relation: 〈0001〉hcp||〈001〉fcc and , different from the conventional one. The nucleation of fcc-Ti is accomplished via pure-shuffle mechanism with a minimum stable thickness of three atomic layers, and the growth via shear-shuffle mechanisms through gliding two-layer disconnections or pure-shuffle mechanisms through gliding four-layer disconnections. Such phase transformation offers an additional plastic deformation mode comparable to twinning.

  • pure shuffle nucleation of deformation twins in Hexagonal Close packed metals
    Materials research letters, 2013
    Co-Authors: Jun Wang, C N Tome, S K Yadav, J P Hirth, Irene J. Beyerlein
    Abstract:

    The propagation of deformation twins in Hexagonal-Close-packed metals is commonly described by a conventional glide-shuffle mechanism. The widely accepted convention is that this process is also responsible for twin nucleation, but lacks direct confirmation. Using atomistic simulations, we identify an unconventional pure-shuffle mechanism for the nucleation of (1¯012) twins, which then grow through the conventional glide-shuffle mechanism entailing the glide of twinning disconnections. The pure-shuffle nucleation of twins at grain boundaries can be ascribed to a high-stress concentration and pre-existing grain boundary dislocations.

  • a constitutive model of twinning and detwinning for Hexagonal Close packed polycrystals
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012
    Co-Authors: Huamiao Wang, C N Tome, Jian Wang
    Abstract:

    Abstract A new constitutive model to describe twinning and detwinning for polycrystalline materials with the Hexagonal Close packed (HCP) crystallographic structure is developed and implemented in the recently developed elastic viscoplastic self-consistent (EVPSC) polycrystal model. The new model is then applied to magnesium alloy Mg–3 Al–1 Zn (AZ31B) sheet under cyclic loadings and strain path changes. It is demonstrated that the new twinning model is able to capture key features associated with twinning and detwinning observed experimentally.

  • 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.

  • slip assisted twin growth in Hexagonal Close packed metals
    Scripta Materialia, 2009
    Co-Authors: Laurent Capolungo, Irene J. Beyerlein, C N Tome
    Abstract:

    We study two possible twin growth mechanisms in Hexagonal Close-packed (hcp) metals: a slip-assisted one, based on dislocation reactions at twin interfaces, and a slip-independent one, based on the direct activation of twin dislocations. A twin thickening rate law is developed to estimate the contribution of slip dislocations to twin growth in hcp crystals. Application of the model to Mg single crystals, and comparison with experimental data, suggests that { 1 0 1 ¯ 2 } twin thickening proceeds independently of slip.

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

  • a constitutive model of twinning and detwinning for Hexagonal Close packed polycrystals
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012
    Co-Authors: Huamiao Wang, C N Tome, Jian Wang
    Abstract:

    Abstract A new constitutive model to describe twinning and detwinning for polycrystalline materials with the Hexagonal Close packed (HCP) crystallographic structure is developed and implemented in the recently developed elastic viscoplastic self-consistent (EVPSC) polycrystal model. The new model is then applied to magnesium alloy Mg–3 Al–1 Zn (AZ31B) sheet under cyclic loadings and strain path changes. It is demonstrated that the new twinning model is able to capture key features associated with twinning and detwinning observed experimentally.

  • 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.

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

  • Grain neighbour effects on twin transmission in Hexagonal Close-packed materials
    Nature communications, 2016
    Co-Authors: M. Arul Kumar, Irene J. Beyerlein, Rodney J. Mccabe, Carlos N. Tomé
    Abstract:

    Materials with a Hexagonal Close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

  • (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.

Irene J. Beyerlein - One of the best experts on this subject based on the ideXlab platform.

  • Grain neighbour effects on twin transmission in Hexagonal Close-packed materials
    Nature communications, 2016
    Co-Authors: M. Arul Kumar, Irene J. Beyerlein, Rodney J. Mccabe, Carlos N. Tomé
    Abstract:

    Materials with a Hexagonal Close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

  • Twinning-Associated Boundaries in Hexagonal Close-Packed Metals
    JOM, 2014
    Co-Authors: Jiquan Wang, Yanyao Jiang, Qin Yu, Irene J. Beyerlein
    Abstract:

    In this article, we highlighted twinning-associated boundaries that play crucial roles in nucleation, growth, and interactions of deformation twins. According to microscopic characterizations and atomistic simulations in Mg, three types of boundaries are reviewed, including (I) prismatic-basal boundaries associated with twin nucleation via pure-shuffle mechanism, (II) serrated coherent twin boundaries associated with twin growth and shrinkage via glide and climb of twinning dislocations, and (III) tilt prismatic–prismatic and basal–basal boundaries associated with co-zone twin–twin interactions. More importantly, these boundaries affect twinning and detwinning processes that may correspond to twinning-induced hardening and seem universally associated with twins in Hexagonal Close-packed metals.

  • pure shuffle nucleation of deformation twins in Hexagonal Close packed metals
    Materials research letters, 2013
    Co-Authors: Jun Wang, C N Tome, S K Yadav, J P Hirth, Irene J. Beyerlein
    Abstract:

    The propagation of deformation twins in Hexagonal-Close-packed metals is commonly described by a conventional glide-shuffle mechanism. The widely accepted convention is that this process is also responsible for twin nucleation, but lacks direct confirmation. Using atomistic simulations, we identify an unconventional pure-shuffle mechanism for the nucleation of (1¯012) twins, which then grow through the conventional glide-shuffle mechanism entailing the glide of twinning disconnections. The pure-shuffle nucleation of twins at grain boundaries can be ascribed to a high-stress concentration and pre-existing grain boundary dislocations.

  • slip assisted twin growth in Hexagonal Close packed metals
    Scripta Materialia, 2009
    Co-Authors: Laurent Capolungo, Irene J. Beyerlein, C N Tome
    Abstract:

    We study two possible twin growth mechanisms in Hexagonal Close-packed (hcp) metals: a slip-assisted one, based on dislocation reactions at twin interfaces, and a slip-independent one, based on the direct activation of twin dislocations. A twin thickening rate law is developed to estimate the contribution of slip dislocations to twin growth in hcp crystals. Application of the model to Mg single crystals, and comparison with experimental data, suggests that { 1 0 1 ¯ 2 } twin thickening proceeds independently of slip.

Dhananjai Pandey - One of the best experts on this subject based on the ideXlab platform.