Unique universal scaling in nanoindentation pop-ins
Unique universal scaling in nanoindentation pop-ins
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DOI：
10.1038/s41467-020-17918-7
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发表时间：
2020-08-21
影响因子：
16.6
通讯作者：
Ogata, Shigenobu
中科院分区：
文献类型：
--
作者：
Sato, Yuji;Shinzato, Shuhei;Ogata, Shigenobu
幂律在许多科学领域都是普遍存在的，并在许多科学领域中得到了积极的研究，包括材料的塑性。在这里，我们报告的幂律统计在第二次和随后的弹出的幅度在负载控制的纳米压痕测试，而第一弹出的特点是高斯样统计与一个定义良好的平均值。从类高斯到幂律的转变是由于在锐压头引起的应力和位错密度场的突然衰减中，变形机制从位错形核到位错网络演化的变化。基于体心立方（BCC）铁的（100）和（111）表面以及面心立方（FCC）铜的（100）表面上的纳米压痕测试，确定幂律的标度指数分别为5.6、3.9和6.4。这些幂律指数远高于那些通常观察到的微柱塑性（1.0-1.8），这表明纳米压痕塑性属于不同的普适性类比微柱塑性。虽然在纳米压痕过程中观察到幂律，并且对于面心立方金属，幂律指数估计为约1.5-1.6，但是指数的起源仍然不清楚。在本文中，我们展示了幂律统计量的弹出幅度和揭示的性质的指数。
Power laws are omnipresent and actively studied in many scientific fields, including plasticity of materials. Here, we report the power-law statistics in the second and subsequent pop-in magnitudes during load-controlled nanoindentation testing, whereas the first pop-in is characterized by Gaussian-like statistics with a well-defined average value. The transition from Gaussian-like to power-law is due to the change in the deformation mechanism from dislocation nucleation to dislocation network evolution in the sharp-indenter induced abruptly decaying stress and dislocation density fields. Based on nanoindentation testing on the (100) and (111) surfaces of body-centered cubic (BCC) iron and the (100) surface of face-centered cubic (FCC) copper, the scaling exponents of the power laws were determined to be 5.6, 3.9, and 6.4, respectively. These power-law exponents are much higher than those typically observed in micro-pillar plasticity (1.0-1.8), suggesting that the nanoindentation plasticity belongs to a different universality class than the micro-pillar plasticity. Although power laws are observed during nanoindentation and the power-law exponents are estimated to be approximately 1.5-1.6 for face-centered cubic metals, the origin of the exponent remains unclear. In this paper, we show the power-law statistics in pop-in magnitudes and unveil the nature of the exponent.