ABSTRACT

Zero-macroscopic-strain deformation twinning (ZMS-DT) is widely observed in many face-centred-cubic (FCC) metals and alloys. However, the driving force of ZMS-DT is a controversial issue and has not been fully clarified for a long time. Based on molecular dynamics simulations to various FCC metals, we found that ZMS-DT, i.e. Σ₃{112} incoherent twin boundary migration can be driven by simultaneously applying both normal and shear strains/stresses to the twin boundary (TB), and changing the sign of the normal or the shear strain/stress can change the direction of the incoherent TB migration. With analysing the results of atomistic strain energy calculation and anisotropic elasticity theory, we revealed the strain energy imbalance, which originates from elastic anisotropic response of materials, between the two sides of the twin boundary under normal–shear strain (or stress) coupling condition essentially drives the TB migration and twin growth. Eventually, we deduce that the elastic anisotropy ratio can be one of the key material constants which affect the twinnability of FCC metals.

摘要

零宏观应变变形孪生 (ZMS-DT) 在许多面心立方 (FCC) 金属和合金中被广泛观察到。然而，ZMS-DT 的驱动力是一个有争议的问题，长期以来一直没有完全阐明。基于对各种 FCC 金属的分子动力学模拟，我们发现 ZMS-DT，即 Σ ₃{112} 非相干孪晶边界迁移可以通过同时向孪晶边界 (TB) 施加法向和剪切应变/应力来驱动，并且改变法向或剪切应变/应力的符号可以改变非相干 TB 迁移的方向. 通过对原子应变能计算结果和各向异性弹性理论的分析，我们从本质上揭示了正切应变（或应力）耦合条件下孪晶边界两侧之间由材料弹性各向异性响应引起的应变能不平衡。推动结核病迁移和孪生增长。最终，我们推断弹性各向异性比可能是影响 FCC 金属孪晶性的关键材料常数之一。