Nanoindentation size effect on stochastic behavior of incipient plasticity in a LiTaO3 single crystal
Nanoindentation size effect on stochastic behavior of incipient plasticity in a LiTaO3 single crystal
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DOI：
10.1016/j.engfracmech.2020.106877
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发表时间：
2020-03-01
影响因子：
5.4
通讯作者：
Zhang, Taihua
中科院分区：
文献类型：
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作者：
Ma, Yi;Huang, Xianwei;Zhang, Taihua
我们研究了在典型取向（0 1 (1)/ bar 2），即LiTaO3单晶的Y-42度平面上，球形纳米压痕下首次弹出事件的特征。采用3个不同半径的球尖探测屈服应力及其初始塑性发生时的随机行为。屈服应力值分别为10.75 +/- 0.78、6.3 +/- 0.44和5.36 +/- 0.4 GPa，分别相当于半径为0.76、2.95和9.8 μ m的球形尖端条件下的E/14、E/30和E/36。初期塑性的发生在大范围内呈均匀和散射分布。根据屈服应力的统计分布计算塑性单元的活化体积，0.76、2.95和9.8 μ m针尖的活化体积分别为6、12和12埃(3)。压痕尺寸对启动塑性的阈值应力和塑性单元激活的临界体积有很强的影响。此外，LiTaO3单晶的初始塑性与加载历史无关。在加载速率0.125 ~ 2 mN/s范围内，得到的屈服应力及其统计分布基本一致。
We investigated the characteristic of first pop-in event under spherical nanoindentation in the typical orientation (0 1 (1) over bar 2), i.e., Y-42 degrees plane of a LiTaO3 single crystal. Three spherical tips with different radii were adopted to probe yield stress and its stochastic behavior as the incipient plasticity occurred. The values of yield stress were 10.75 +/- 0.78, 6.3 +/- 0.44 and 5.36 +/- 0.4 GPa, which were equivalent to E/14, E/30 and E/36 under spherical tips with radii of 0.76, 2.95 and 9.8 mu m, respectively. The occurrence of incipient plasticity exhibited a uniform and scattering distribution in a wide range under all the tips. The activation volumes of plastic unit were computed based on the statistical distribution of yield stress, which were 6, 12 and 12 angstrom(3) for 0.76, 2.95 and 9.8 mu m tips. A strong indentation size effect was revealed on the threshold stress for evoking incipient plasticity and the critical volume for plastic unit activation. Furthermore, incipient plasticity of LiTaO3 single crystal was confirmed to be loading history-independent. The obtained yield stress and its statistic distribution were similar within the range of loading rate from 0.125 to 2 mN/s.