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 LiTaO₃ 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.

中文翻译：

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通过纳米压痕揭示了LiTaO3单晶的时间依赖性变形的塑性模式。

近年来，仪器纳米压痕已被广泛应用于检测多种材料（尤其是薄膜和非均质材料）中随时间变化的塑性变形或蠕变行为。但是，迄今为止，纳米压痕保持阶段的变形机理尚未被很好地揭示。在当前的工作中，对脆性的LiTaO ₃进行了高载荷的纳米压痕保持测试单晶。研究了具有不同保持时间的残留印痕的表面形态。结果表明，次生裂纹的产生以及主裂纹和次生裂纹的扩展是初始保温阶段随时间变化的塑性变形的主要机制，而裂纹的密度和长度在稳态保温阶段是不变的。建议压头下方发生非局部塑性变形。可以得出结论，在纳米压痕作用下，脆性陶瓷的时变塑性变形是由瞬时开裂，连续的加载序列和在室温下高剪切压缩应力引起的均匀蠕变流组成的。