Origin of serrated flow in bulk metallic glasses
Origin of serrated flow in bulk metallic glasses
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DOI：
10.1016/j.jmps.2018.11.015
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发表时间：
2019-03
影响因子：
5.3
通讯作者：
Xie Xie-Xie;Y. Lo;Y. Tong;J. Qiao;Gongyao Y. Wang;S. Ogata;H. Qi;K. Dahmen;Yanfei Gao;P. Liaw
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文献类型：
--
作者：
Xie Xie-Xie;Y. Lo;Y. Tong;J. Qiao;Gongyao Y. Wang;S. Ogata;H. Qi;K. Dahmen;Yanfei Gao;P. Liaw
块体金属玻璃（BMG）具有非晶态结构，并表现出独特的力学性能，例如极高的强度和优异的损伤容限，使其成为潜在的结构材料。迄今为止，人们对非晶合金的宏观力学性能和相应的微观变形缺陷进行了大量的研究。然而，由于缺乏适当的实验技术来直接探测适当空间和时间尺度上的不均匀变形过程，人们对室温下宏观不均匀变形与微观变形载体之间的联系仍然知之甚少。在这里，我们提出了变形的细节，通过在现场热成像与连续锯齿行为相关的热带的演变。我们的实验工作第一次阐明了锯齿流与剪切带活动的耦合，特别是剪切带成核或传播的早期阶段引起的经常被忽略的细锯齿。同时，采用动力学蒙特卡罗（kMC）方法，结合局部加热（热软化和β弛豫）效应，模拟了BMG的锯齿行为，与实验结果吻合较好。这些发现将使我们对剪切带运作的基本理解深入到微观水平，这可能为BMG应用中剪切带的控制提供指导。
Bulk metallic glasses (BMGs) possess amorphous structure and show unique mechanical properties, such as extremely high strength and excellent damage tolerance, entitling them as potential structural materials. So far a great amount of work has been conducted to study BMGs’ macroscopic mechanical properties and examine corresponding microscopic deformation defects. However, the connection between macroscopic inhomogeneous deformation at room temperature and microscopic deformation carriers is still poorly understood, due to the lack of an appropriate experimental technique to directly probe the inhomogeneous deformation process on the proper spatial and temporal scales. Here we present the deformation details via in situ thermal imaging about the evolution of heat bands associated with successive serration behavior. For the first time, our experimental work clarifies the coupling of serrated flows with shear band activities, especially the often omitted fine serrations induced by shear band nucleation or the early stage of propagation. Meanwhile, serration behavior of BMGs is simulated through the kinetic Monte Carlo (kMC) method by integrating local heating (thermal softening and β-relaxation) effects, which exhibits good agreement with experimental results. These findings will advance our fundamental understanding of the shear band operation down to microscopic level, which may shed light on the control of shear banding for the application of BMGs.