Zhou Shengyun, Huang Xianwei, Lu Congda, Liu Yunfeng, Zhang Taihua, Ma Yi
College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China.
Key Laboratory E&M, Zhejiang University of Technology, Ministry of Education & Zhejiang Province, Hangzhou 310014, China.
Micromachines (Basel). 2020 Sep 21;11(9):878. doi: 10.3390/mi11090878.
Recently, instrumental nanoindentation has been widely applied to detect time-dependent plastic deformation or creep behavior in numerous materials, particularly thin films and heterogeneous materials. However, deformation mechanism at nanoindentation holding stage has not been well revealed hitherto. In the current work, nanoindentation holding tests with high loads were performed on a brittle LiTaO single crystal. The surface morphologies of residual impressions with various holding times were investigated. It was indicated that generation of secondary cracks and propagation of both main and secondary cracks were the dominating mechanism for time-dependent plastic deformation at the initial holding stage, and the density and length of cracks were invariable at the steady-state holding stage, which suggested a nonlocalized plastic deformation beneath the indenter. It could be concluded that time-dependent plastic deformation of brittle ceramic under nanoindentation is composed of instant cracking as the continuation of loading sequence and homogeneous creep flow by high shear-compression stress at room temperature.
最近，仪器化纳米压痕已被广泛应用于检测多种材料，特别是薄膜和异质材料中的时间依赖性塑性变形或蠕变行为。然而，迄今为止，纳米压痕保持阶段的变形机制尚未得到很好的揭示。在当前的工作中，对脆性钽酸锂单晶进行了高载荷纳米压痕保持试验。研究了不同保持时间下残余压痕的表面形貌。结果表明，二次裂纹的产生以及主裂纹和二次裂纹的扩展是初始保持阶段时间依赖性塑性变形的主导机制，并且在稳态保持阶段裂纹的密度和长度不变，这表明压头下方存在非局部塑性变形。可以得出结论，纳米压痕下脆性陶瓷的时间依赖性塑性变形由作为加载序列延续的即时开裂和室温下高剪切压缩应力引起的均匀蠕变流动组成。
