Molecular statics and molecular dynamics simulations of the critical stress for motion of a /3 〈112¯0〉 screw dislocations in α-Ti at low temperatures using a modified embedded atom method potential
Molecular statics and molecular dynamics simulations of the critical stress for motion of a /3 〈112¯0〉 screw dislocations in α-Ti at low temperatures using a modified embedded atom method potential
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DOI：
10.1016/j.actamat.2012.12.011
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发表时间：
2013-04
期刊：
影响因子：
9.4
通讯作者：
S. Rao;A. Venkateswaran;M. Letherwood
中科院分区：
文献类型：
--
作者：
S. Rao;A. Venkateswaran;M. Letherwood
采用改进的嵌入原子法（MEAM）势，通过分子静力学、分子动力学和恒温定容（NVT）模拟，确定了0 ~ 50 K温度范围内α-Ti中α/3 <$112 <$0 <$螺位错的核心结构和运动临界应力.α-Ti中的α/3 <$112 <$$> 0 <$螺旋位错有五种不同的芯结构，一种完全在棱柱面上扩展，三种部分在棱柱面上扩展，部分在棱锥面和基面上扩展，一种在基面上主要是Shockley部分分裂。在棱镜平面上完全展开的芯被认为是能量最低的结构。在0 K温度下，最小能量结构完全分布在棱柱平面上的Peierls应力是一个很高的值，为6.875×10−3μ，其中μ是剪切模量，与所施加应力的方向无关。结果表明，这种高Peierls应力在0 K的MEAM势的角相互作用的后果。在零外加应力下的扭结对形成能很低，等于0.16eV。NVT分子动力学模拟结果表明，在5 ~ 50 K温度范围内，通过形成扭折对来移动螺位错所需的最小应力明显低于0 K Peierls应力值。一个经典的现象学扭结对模型拟合的分子动力学数据，并用于校正显着较低的应变率的变形实验中存在的分子动力学模拟相比。修正后的模拟数据与α-Ti单晶中α/3 <$112 <$0取向棱柱滑移屈服应力的低温实验观测值符合较好。所建立的α-Ti棱柱体滑移的扭折对模型将有助于更高尺度的α-Ti变形行为的晶体塑性模型的建立。
Molecular statics and molecular dynamics, and constant temperature, constant volume (NVT) simulations, were performed to determine the core structure and critical stress for motion of a/3〈112¯0〉 screw dislocations in α-Ti at temperatures ranging from 0 to 50K using a modified embedded atom method (MEAM) potential. Five different core structures were obtained for the a/3〈112¯0〉 screw dislocations in α-Ti, one completely spread on the prism plane, three others partially spread on the prism plane and partially spread on the pyramidal and basal planes, and one with predominantly Shockley partial splitting on the basal plane. The core completely spread on the prism plane is found to be the lowest energy structure. The Peierls stress for the minimum energy structure completely spread on the prism plane at 0K is found to be a high value of 6.875×10−3μ, where μ is the shear modulus and is independent of the orientation of the applied stress. It is shown that this high Peierls stress at 0K is a consequence of the angular interactions in the MEAM potential. The kink-pair formation energy at zero applied stress is found to be low and equal to 0.16eV. NVT molecular dynamics simulations show that the minimum stress required to move the screw dislocations by kink-pair formation at temperatures ranging from 5 to 50K is significantly lower than the 0K Peierls stress value. A classical phenomenological kink-pair model is fitted to the molecular dynamics data and used to correct for the significantly lower strain rate of deformation present in experiments as compared to molecular dynamics simulations. The corrected simulation data are in reasonable agreement with low-temperature experimental observations of yield stress in single-crystal α-Ti oriented for a/3〈112¯0〉 prism slip. The developed kink-pair model for prism slip in α-Ti will be useful in higher length scale crystal plasticity models for the deformation behavior of α-Ti.