Topological model of type II deformation twinning in 10M Ni-Mn-Ga
Topological model of type II deformation twinning in 10M Ni-Mn-Ga
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DOI：
10.1016/j.actamat.2020.10.020
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发表时间：
2020-12-01
期刊：
影响因子：
9.4
通讯作者：
Pond, Robert
中科院分区：
文献类型：
--
作者：
Karki, Bibek;Mullner, Peter;Pond, Robert
用拓扑方法模拟了10 M Ni-Mn-Ga中的Ⅱ型孪晶结构。该方法预测的孪生参数与Bevis和Crocker的运动学模型相同。此外，拓扑建模提供了机制洞察边界迁移率，孪生应力和它们的温度依赖性。设想II型孪晶由其I型缀合物的前体形成。前体k（1）平面上的断开排列成倾斜壁，在旋转畸变松弛之后，倾斜壁形成平均平行于k（2）平面的II型边界。组件缺陷可能会排列成尖锐的壁或通过扭结松弛成不太有序的结构。这两个界面都可以容纳额外的滑移断开，其运动沿着边界产生组合迁移和剪切。这些缺陷的运动的容易性随着它们的核心宽度而增加，并且这又随着边界的尖锐度的增加而减小。在其他材料中的一些实验证据表明，II型孪晶可以通过采用低折射率刻面的配置来降低它们的界面能，这降低了孪晶边界的流动性。拓扑模型表明，这样的连贯刻面结构是不可能在10 M镍锰镓，在协议的高流动性II型孪晶界。(C)2020 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The structure of type II twins in 10M Ni-Mn-Ga is modeled using the topological method. This method predicts the same twinning parameters as the kinematic model of Bevis and Crocker. Furthermore, topological modeling provides mechanistic insight into boundary migration rates, the twinning stresses and their temperature dependence. A type II twin is envisaged to form from a precursor, which is its type I conjugate. Disconnections on the precursor k(1) plane align into a tilt wall, which, after the relaxation of the rotational distortions, forms the type II boundary parallel on average to the k(2) plane. The component defects may align into a sharp wall or relax by kinking into a less orderly configuration. Both interfaces can host additional glissile disconnections whose motion along a boundary produces combined migration and shear. The ease of motion of these defects increases with their core width, and this, in turn, decreases with increasing sharpness of the boundary. Some experimental evidence in other materials suggests that type II twins can reduce their interfacial energy by adopting a configuration of low-index facets, which reduces twin boundary mobility. Topological modeling suggests that such a coherently faceted structure is unlikely in 10M Ni-Mn-Ga, in agreement with the high mobility of type II twin boundaries. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.