Lattice transformation in grain boundary migration via shear coupling and transition to sliding in face-centered-cubic copper
Lattice transformation in grain boundary migration via shear coupling and transition to sliding in face-centered-cubic copper
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DOI：
10.1016/j.actamat.2021.117127
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发表时间：
2021-08
期刊：
影响因子：
9.4
通讯作者：
Bin Li;Janel Leung
中科院分区：
文献类型：
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作者：
Bin Li;Janel Leung
对称倾斜晶界通过剪切耦合的迁移已经在实验和模拟中得到了广泛的研究。已有文献报道高温下剪切耦合向GB滑动转变，但低温下如何转变尚未研究。剪切耦合过程中原子尺度上的晶格转变尚未完全理解。在原子模拟中，通过跟踪面心立方铜中[001]倾斜轴对称倾斜晶界在100 K剪切应变作用下的运动模式，观察到晶界运动的新特征.结果表明，两个低指数面（110）和（100）与边界面之间的角度可以用来定义剪切的标称大小。近似地，如果这两个平面中的一个具有s < 0.5的值，则发生剪切耦合，该平面是主动不变平面;如果0.5 <s< 0.6，则GB以剪切耦合+滑动的方式移动，即剪切耦合过渡到滑动的混合模式;如果两个平面都具有s> 0.6的值，则仅发生GB滑动。仔细的结构分析表明，对于所有的GB进行剪切耦合，一些GB原子平面保持不变，非常相似的变形孪晶的第一个不变的平面，而其他GB原子平面交换他们的位置在GB正常方向通过高度协调和复杂的原子洗牌。这种行为允许识别朝向相邻晶粒重新取向的转变单元。确定了晶格转变的限速因素，并可用于推断剪切耦合的动力学模型。
Migration of symmetric tilt grain boundaries (GBs) via shear coupling has been studied extensively in experiments and simulations. It was reported that shear coupling transitioned to GB sliding at high temperatures, but how such transition occurs at low temperatures has not been investigated. Lattice transformation on the atomic scale during shear coupling has not been fully understood. In this work, mode of motion of symmetric tilt GBs with [001] tilting axis in face centered cubic copper under a shear strain parallel to the boundary plane at 100Kwas carefully characterized by tracking the positions of the corresponding planes in atomistic simulations and new features of GB motion were observed. The results show that the angles between the two low-index planes, (110) and (100), and the boundary plane can be used to define a nominal magnitude of shears. Approximately, if one of these two planes has a value ofs< 0.5, shear coupling occurs with this plane being the active invariant plane; if 0.5 <s< 0.6, GB moves by shear coupling + sliding, i.e. a hybrid mode by which shear coupling transitions to sliding; if both planes have a value ofs> 0.6, only GB sliding occurs. Careful structural analyses show that, for all the GBs that undergo shear coupling, some GB atomic planes remain invariant, very similar to the first invariant plane in deformation twinning, whereas the other GB atomic planes swap their positions in the GB normal direction through highly coordinated and complex atomic shuffles. This behavior allows identification of transformation units that are reoriented toward the neighboring grain. Rate-limiting factors are identified for lattice transformation and can be used to infer a kinetics model for shear coupling.