ABSTRACT The deformation process of titanium with an initial crack was simulated under uniaxial tension by the molecular dynamics method. The effect of [0001], and orientations on the microstructure deformation mechanisms at the crack tip was investigated using embedded atom method potentials. In the simulation, various deformation evidence were clearly observed, such as dislocation nucleation and movement, stacking faults formation, deformation twinning and phase transformation. The stress–strain curves showed that orientations had a greater influence on the plastic stage and less on the elastic stage. By applying uniaxial tension with a constant strain rate along different orientations, microstructure deformation at the crack tip was analysed. When loading along [0001] orientation, twinning was the main deformation mechanism and stacking fault occurred and expanded along slip system with the increase in strain. Applying uniaxial tension along orientation, an abnormal ‘secondary increase’ phenomenon was observed in the stress–strain curve. At the same time, dislocation loops appeared at the crack tip and they expanded, merged with the increase in strain. The massive phase transformation from HCP to BCC was observed in the model when loading along orientation, which was caused by multiple Shockley incomplete dislocations under the size limitation.

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不同方向拉伸钛裂纹尖端显微组织变形机制研究

摘要 采用分子动力学方法模拟了单轴拉伸下钛初始裂纹的变形过程。使用嵌入原子法电位研究了[0001]和取向对裂纹尖端微观结构变形机制的影响。在模拟中，可以清楚地观察到各种变形证据，如位错成核和运动、堆垛层错的形成、变形孪晶和相变。应力-应变曲线表明，取向对塑性阶段的影响较大，而对弹性阶段的影响较小。通过沿不同方向施加恒定应变率的单轴拉伸，分析裂纹尖端的微观结构变形。当沿[0001]方向加载时，孪晶是主要的变形机制，随着应变的增加，层错沿滑移系统发生和扩展。沿取向施加单轴张力，在应力-应变曲线中观察到异常的“二次增加”现象。同时，位错环出现在裂纹尖端并随着应变的增加而扩大并合并。当沿取向加载时，模型中观察到从 HCP 到 BCC 的大量相变，这是由尺寸限制下的多个 Shockley 不完全位错引起的。与应变的增加相结合。当沿取向加载时，模型中观察到从 HCP 到 BCC 的大量相变，这是由尺寸限制下的多个 Shockley 不完全位错引起的。与应变的增加相结合。当沿取向加载时，模型中观察到从 HCP 到 BCC 的大量相变，这是由尺寸限制下的多个 Shockley 不完全位错引起的。