Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation
Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation
复制标题
纳米压痕法研究 LiTaO3 单晶的室温蠕变行为和位错成核激活体积
DOI：
10.3390/ma12101683
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发表时间：
2019-05-02
期刊：
影响因子：
3.4
通讯作者：
Zhang, Taihua
中科院分区：
文献类型：
--
作者：
Ma, Yi;Huang, Xianwei;Zhang, Taihua
晶体取向对LiTaO 3单晶的机械不均匀性的影响是众所周知的，而与时间相关的塑性行为，即，蠕变仍然缺乏理解。基于纳米压痕技术，系统地研究了X-112°、Y-36°和Y-42°三种典型取向下不同保持深度（100 nm ~ 1100 nm）下的室温蠕变流动。在X-112°平面内的抗蠕变能力比其它平面强得多。同时，在Y-36°和Y-42°平面上，蠕变特征相似。取向对蠕变变形的影响与取向对硬度的影响一致。纳米压痕长度尺度对蠕变变形起着重要的作用，即蠕变应变在所有平面内都随着压痕深度的增加而逐渐减小。基于应变速率敏感性和屈服应力，计算了不同压痕深度下位错形核的激活体积。Y-36°和Y-42°平面的激活体积范围为5 × 10 - 3至23 × 10 - 3，表明点状缺陷可能是塑性起始的来源。在X-112°平面内，活化体积在6 × 10 - 3和83 × 10 - 3之间。多个原子的协同迁移也可能是深压痕位错激活的机制。
The crystal orientation effect on mechanical heterogeneity of LiTaO3 single crystals is well known, whilst the time-dependent plastic behavior, i.e., creep is still short of understanding. Relying on nanoindentation technology, we systematically studied room-temperature creep flows at various holding depths (100 nm to 1100 nm) in three typical orientations namely the X-112°, Y-36° and Y-42° planes. Creep resistance was much stronger in the X-112° plane than the others. In the meanwhile, creep features were similar in the Y-36° and Y-42° planes. The orientation effect on creep deformation was consistent with that on hardness. The nanoindentation length scale played an important role in creep deformation that creep strains were gradually decreased with the holding depth in all the planes. Based on strain rate sensitivity and yield stress, the activation volumes of dislocation nucleation were computed at various nanoindentation depths. The activation volumes ranged from 5 Å3 to 23 Å3 for the Y-36° and Y-42° planes, indicating that a point-like defect could be the source of plastic initiation. In the X-112° plane, the activation volume was between 6 Å3 and 83 Å3. Cooperative migration of several atoms could also be the mechanism of dislocation activation at deep nanoindentation.