On the role of anomalous twinning in the plasticity of magnesium
On the role of anomalous twinning in the plasticity of magnesium
复制标题
DOI：
10.1016/j.actamat.2015.10.043
复制
发表时间：
2016-01
期刊：
影响因子：
9.4
通讯作者：
K. Molodov;T. Al-Samman;D. Molodov;G. Gottstein
中科院分区：
文献类型：
--
作者：
K. Molodov;T. Al-Samman;D. Molodov;G. Gottstein
特殊取向的镁单晶在环境温度和高温下在通道模具压缩中变形，c 轴与压缩方向成 45° 倾斜，并且< 10 1 ´ 0 > 平行于横向约束方向。样本因基底滑移而变形，导致 c 轴朝压缩方向旋转。在室温下，从变形的早期阶段开始，宏观带包括平行于约束方向形成的反常{10 1´ 2}延伸孪晶网格。这些双胞胎的特征是负施密特因子，并产生与施加的变形相反的应变。在最终的真实应变为− 1 时，基质的很大一部分被孪晶消耗，导致 c 轴重新定向，远离压缩方向，从而延迟了硬基础织构成分的形成。对六种可能的延伸孪生变体的位移梯度张量的分析表明，组成能带的选定孪生变体涉及与基底滑移引起的晶格旋转相反的晶格旋转。在高温下观察到较少的孪晶，宏观带在 370°C 时消失。讨论了变形不均匀性和反常孪晶对镁变形行为的作用。
Specially oriented Mg single crystals were deformed at ambient and elevated temperatures in channel-die compression with the c-axis inclined at 45° to the compression direction and< 10 1¯ 0> parallel to the lateral constraint direction. The specimens deformed by basal slip, entailing a rotation of the c-axis towards the compression direction. At room temperature, starting already during early stages of deformation, macroscopic bands comprising a mesh of anomalous {10 1¯ 2} extension twins formed parallel to the constraint direction. These twins were characterized by a negative Schmid factor and produced a strain opposite to the imposed deformation. At the final true strain of− 1, a significant volume fraction of the matrix was consumed by twins, causing a reorientation of the c-axis farther away from the compression direction, and hence delaying the formation of a hard basal texture component. An analysis of the displacement gradient tensors for the six possible extension twin variants showed that the selected twin variants, of which the bands were composed, involved a lattice rotation opposite to the one caused by basal slip. Less twinning was observed at elevated temperatures with the macroscopic bands disappearing at 370° C. The obtained results are discussed with respect to deformation heterogeneity and the role of anomalous twinning for the deformation behavior of magnesium.