Cyclic Deformation in Metallic Glasses

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• 作者：Z. D. Sha ; S. X. Qu ; Z. S. Liu ; T. J. Wang ; H. Gao
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：October 14, 2015
• 年：2015
• 卷：15
• 期：10
• 页码：7010-7015
• 全文大小：492K
• ISSN：1530-6992

文摘

Despite the utmost importance and decades of experimental studies on fatigue in metallic glasses (MGs), there has been so far little or no atomic-level understanding of the mechanisms involved. Here we perform molecular dynamics simulations of tension鈥揷ompression fatigue in Cu₅₀Zr₅₀ MGs under strain-controlled cyclic loading. It is shown that the shear band (SB) initiation under cyclic loading is distinctly different from that under monotonic loading. Under cyclic loading, SB initiation takes place when aggregates of shear transformation zones (STZs) accumulating at the MG surface reach a critical size comparable to the SB width, and the accumulation of STZs follows a power law with rate depending on the applied strain. It is further shown that almost the entire fatigue life of nanoscale MGs under low cycle fatigue is spent in the SB-initiation stage, similar to that of crystalline materials. Furthermore, a qualitative investigation of the effect of cycling frequency on the fatigue behavior of MGs suggests that higher cycling frequency leads to more cycles to failure. The present study sheds light on the fundamental fatigue mechanisms of MGs that could be useful in developing strategies for their engineering applications.