Effect of 60∘ dislocation on transformation stresses, nucleation, and growth for phase transformations between silicon I and silicon II under triaxial loading: Phase-field study
Effect of 60∘ dislocation on transformation stresses, nucleation, and growth for phase transformations between silicon I and silicon II under triaxial loading: Phase-field study
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DOI：
10.1016/j.actamat.2019.07.021
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发表时间：
2019-09
期刊：
影响因子：
9.4
通讯作者：
Hamed Babaei;V. Levitas
中科院分区：
文献类型：
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作者：
Hamed Babaei;V. Levitas
采用先进的相场方法（PFA）模拟了单晶硅中60 °位错处的应力诱发马氏体相变（PT），该方法考虑了一般应力张量的原子模拟得到的晶格不稳定性条件.有限的弹性，转换和塑性应变被认为是。有限元法（FEM）模拟阐明了两种不同的成核机制和纳米结构演变为两种不同的应力滞后情况。对于传统的有限应力滞后区，PT开始于无势垒的结晶平衡不完全胚的成核，其失去稳定性并生长形成具有不同界面的传播马氏体带。然而，在独特的零应力滞后区，其中PT无缺陷晶体均匀地发生通过中间相没有成核，界面和生长，PT开始于位错，但传播准均匀，没有界面，类似于无缺陷的情况下，宏观应力-应变曲线是水平的，没有滞后过程中的直接反向PT。尽管位错产生了±（6− 12）GPa范围内的大的正应力，宏观PT应力相对较小的减少1.6 GPa可以通过应力对晶格不稳定性判据的相互补偿贡献来定量解释。
Stress-induced martensitic phase transformations (PTs) at a stationary 60∘ dislocation in single-crystalline Si are modeled by an advanced phase-field approach (PFA), which takes into account the lattice instability conditions obtained by atomistic simulations for the general stress tensor. Finite elastic, transformation, and plastic strains are considered. Finite element method (FEM) simulations elucidate two different mechanisms of nucleation and nanostructure evolution for two different stress-hysteresis cases. For a traditional finite-stress-hysteresis region, the PT starts with the barrierless nucleation of a thermodynamically-equilibrium-incomplete embryo, which loses its stability and grows forming a propagating martensitic band with distinct interfaces. However, in the unique zero-stress-hysteresis region, where PT for defect-free crystal occurs homogeneously through intermediate phases without nucleation, interfaces, and growth, the PT starts at a dislocation but spreads quasi-homogeneously, without interfaces, similar to the defect-free case; the macroscopic stress-strain curve is horizontal and without hysteresis during direct-reverse PTs. Despite large normal stresses produced by dislocation in the range of±(6− 12) GPa, a relatively small reduction in macroscopic PT stress by 1.6 GPa is quantitatively explained by mutually compensating contributions of stresses into lattice instability criterion.