Deformation twins are three-dimensional domains, traditionally viewed as ellipsoids because of their two-dimensional lenticular sections. In this work, we performed statistical analysis of twin shapes viewing along three orthogonal directions: the ‘dark side’ (DS) view along the twin shear direction (>η>1), the twinning plane normal (TPN) view (>k1) and the ‘bright side’ (BS) view along the direction >λ(=>k1 × >η1). Our electron back-scatter diffraction results show that twins in the DS and BS views normally exhibit a lenticular shape, whereas they show an irregular shape in the TPN view. Moreover, the findings in the TPN view revealed that twins grow faster along >λ the lateral direction than along >η1 the forward propagation direction at the initial stages of twin growth. These twin sections are irregular, indicating that growth is locally controlled and the overall shape is not perfectly ellipsoidal. We explain these findings using atomistic models, and ascribe them to differences in the mobility of the edge and screw components of the twinning dislocations.
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机译：变形双胞胎是三维域，由于其二维透镜状截面，传统上被视为椭圆体。在这项工作中，我们对沿三个正交方向的孪生形状视图进行了统计分析：沿孪生剪切方向（>η > 1 ）的“暗侧”（DS）视图，孪生平面法线（TPN）视图（> k 1）和“光面”（BS）视图沿>λ（= > k 1×>η 1）。我们的电子背散射衍射结果表明，DS和BS视图中的孪晶通常显示为透镜状，而TPN视图中则显示为不规则形状。此外，TPN视图中的发现表明，在双胞胎生长的初始阶段，双胞胎沿>λ的横向生长比沿>η 1的正向传播方向快。这些孪生部分是不规则的，表明生长受到局部控制，整体形状不是完美的椭圆形。我们使用原子模型解释这些发现，并将它们归因于孪生位错的边缘和螺钉组件的活动性差异。
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