Spatial and temporal heterogeneity of Kohlrausch-Williams-Watts stress relaxations in metallic glasses
Spatial and temporal heterogeneity of Kohlrausch-Williams-Watts stress relaxations in metallic glasses
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DOI：
10.1016/j.commatsci.2021.110673
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发表时间：
2021-07-02
影响因子：
3.3
通讯作者：
Ishii, Akio
中科院分区：
文献类型：
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作者：
Ishii, Akio
采用分子动力学（MD）方法对Zr 50 Cu 40 Al 10金属玻璃的应力松弛过程进行模拟，证实应力松弛的时间依赖性符合Kohlrausch-Williams-Watts（KWW）方程，并推导出Kohlrausch指数β（KWW）的温度依赖性。我们还计算了基于原子应变的局部塑性变形，然后讨论了松弛的形态，并计算了应力松弛的概率密度相对于由变形的原子数的特征时间的松弛。之后，我们推导出应力松弛的时间依赖性作为模式平均衰减函数，它表示空间和时间的异质性。模拟和计算的结果都再现了KWW弛豫形式，并且一致性良好，证实了KWW弛豫的空间和时间非均匀性。金属玻璃应力松弛的不均匀性是由微观局部塑性变形引起的局部应力变化决定的。
We perform a molecular dynamics (MD) stress relaxation simulation for Zr50Cu40Al10 metallic glass to confirm that the time dependency of stress relaxation conforms with the Kohlrausch-Williams-Watts (KWW) equation, and to derive the temperature dependency of the Kohlrausch exponent beta(Kww). We also calculate local plastic deformation based on atomic strain, then discuss the morphology of relaxation and calculate the probability density of stress relaxation with respect to the characteristic time of relaxation from the number of deformed atoms. Afterward, we derive the time dependency of stress relaxation as a mode-averaged decay function, which expresses spatial and temporal heterogeneity. Both the results of simulation and calculation reproduce the KWW relaxation form and are in good agreement, confirming the spatially and temporally heterogeneous nature of KWW relaxation. The heterogeneity of the stress relaxation of metallic glass is determined by local stress changes caused by microscopic local plastic deformation.