An investigation of the mechanical behaviors of micro-sized tungsten whiskers using nanoindentation
An investigation of the mechanical behaviors of micro-sized tungsten whiskers using nanoindentation
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利用纳米压痕技术研究微米级钨晶须的机械行为
DOI：
10.1016/j.msea.2013.11.084
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发表时间：
2014-01
期刊：
影响因子：
6.4
通讯作者：
Liu, Yong
中科院分区：
文献类型：
--
作者：
Ni, Song;Wang, Shiliang;He, Yuehui;Liu, Yong
采用纳米压痕法对单晶微米钨晶须的力学行为进行了实验研究。在加载阶段，位错的形核和增殖表现为位移突跃或弹入现象。采用赫兹接触理论和Kick定律描述材料的弹性变形，而理想钨晶须的理论强度可由临界弹入载荷导出。弹入后的弹塑性变形符合Taylor关系。在实验中观察到要么只有一个主要的弹出或一系列的不连续性，归因于不同的临界载荷在第一弹出发生。在恒载600 s条件下考察了晶须的蠕变行为。用位移-时间曲线计算了应力指数n，与传统的拉伸蠕变试验结果吻合较好。蠕变行为由位错控制（幂律）机制控制，annof ~5。在试验参数范围内，应力指数随保载载荷的增加而增加，随加载速率的增加而保持稳定。
The mechanical behaviors of single crystalline micro-sized tungsten whiskers were experimentally characterized using nanoindentation. Nucleation and multiplication of dislocations were seen as displacement burst or pop-in events in the load–displacement curves during loading segment. The Hertzian contact theory and Kick's law were used to describe the elastic deformation of the material, whereas the theoretical strength of the perfect tungsten whiskers can be derived from the critical pop-in load. The elastic–plastic deformation after the pop-in agrees well with the Taylor relation. Either only one major pop-in or a series of discontinuities was observed in the experiments, attributed to the different critical loads at which the first pop-in occurs. Creep behaviors of the whiskers were also investigated under a constant load for 600 s. The stress exponentnwas calculated using the displacement–time curve and agrees well with the value obtained using the traditional tensile creep testing method. The creep behavior is dominated by the dislocation-controlled (power-law) mechanism with annof ~5. Additionally, the stress exponentnis proved to increase with increasing the holding load, and remains stable with increasing the loading rate in the range of testing parameters selected in the experiments.
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