Extension of the classical theory for types I and II twinning
Extension of the classical theory for types I and II twinning
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DOI：
10.1557/s43578-020-00003-6
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发表时间：
2021-01-05
影响因子：
2.7
通讯作者：
Wang, J.
中科院分区：
文献类型：
--
作者：
Hirth, J. P.;Wang, J.
一个平面位移图显示了四个孪生元素，平面和方向，是孪生的经典理论的基础。一个方面的经典理论的I型和II型孪生被证明是不适用时，孪生旋转是大的。我们采用具有一定非线性特征的拓扑模型推导出一组修正的孪生元。对于与一个小的旋转，无论是经典的理论和拓扑模型的I型和II型孪生，它给出了相同的一组孪生元素。然而，只有拓扑模型适用于大旋转的情况。在经典模型中，第二类孪晶的孪晶面是无理面，除非它是无理面，而第一类孪晶是复合面。通常，对于给定的取向关系，这个无理平面接近于低指数取向。然后，它可以有利于界面分解成低指数，合理的方面，分离的断开。这在不改变方向关系的情况下发生。我们应用拓扑模型来描述NiTi中的不合理的II型孪晶和刻面。结果与TEM观测结果一致。
A plane-displacement diagram showing the four twinning elements, planes and directions, is fundamental to the classical theory of twinning. One aspect of the classical theory of type I and II twinning is shown to be inapplicable when the twin rotation is large. We employ the topological model with certain nonlinear characteristics to deduce a modified set of twinning elements. For twinning associated with a small rotation, both the classical theory and the topological model for type I and II twinning are shown, which give the same set of twinning elements. However, only the topological model is applicable for the large rotation case. As for the classical model, the twin plane in the type II twinning case is irrational unless it, and the type I twin is compound. Often, this irrational plane is close to a low-index orientation for a given orientation relationship. Then it can be favorable for the interface to break up into low-index, rational facets, separated by disconnections. This occurs without changing the orientation relationship. We apply the topological model to describe both the irrational type II twins and faceting in NiTi. The results agree with TEM observations.