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arXiv 1303.6483cond-mat.mtrl-scinlin.CD
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金属玻璃锯齿状流动中的隐藏秩序

Hidden order in serrated flow of metallic glasses

Ritupan Sarmah, G. Ananthakrishna, B. A. Sun, W. H. Wang

摘要:

我们报告的统计和动态分析结果的锯齿形的应力-时间曲线从压缩恒定应变率测试两个金属玻璃样品具有不同的延展性水平,努力提取隐藏的信息,在看似不规则的锯齿。在这两种合金样品中检测到两种不同类型的动力学。对应于韧性较低的$Zr_{65}Cu_{15}Ni_{10}Al_{10}$合金的应力-应变曲线显示出有限的关联维数和正的李雅普诺夫指数,这表明潜在的动力学是混沌的。相比之下,对于更具延展性的$Cu_{47.5}Zr_{47.5}Al_{5}$合金,应力降幅度及其持续时间的分布服从幂律缩放,这让人想起自组织临界状态。指数也满足与自组织临界性相容的标度关系。可能的物理机制,有助于两个不同的动态制度进行了讨论,通过借鉴与锯齿状屈服的结晶样品的类比。分析表明,塑性较小的试样的塑性变形主要是由于单个剪切带的粘滑,而塑性较大的试样的塑性变形主要是由于大量剪切带的同时形核及其相互作用。

英文摘要:

We report results of statistical and dynamic analysis of the serrated stress-time curves obtained from compressive constant strain-rate tests on two metallic glass samples with different ductility levels in an effort to extract hidden information in the seemingly irregular serrations. Two distinct types of dynamics are detected in these two alloy samples. The stress-strain curve corresponding to the less ductile $Zr_{65}Cu_{15}Ni_{10}Al_{10}$ alloy is shown to exhibit finite correlation dimension and a positive Lyapunov exponent, suggesting that the underlying dynamics is chaotic. In contrast, for the more ductile $Cu_{47.5}Zr_{47.5}Al_{5}$ alloy, the distributions of stress drop magnitudes and their time durations obey a power law scaling reminiscent of a self-organized critical state. The exponents also satisfy the scaling relation compatible with self-organized criticality. Possible physical mechanisms contributing to the two distinct dynamic regimes are discussed by drawing on the analogy with the serrated yielding of crystalline samples. The analysis, together with some physical reasoning, suggests that plasticity in the less ductile sample can be attributed to stick-slip of single shear band, while that of the more ductile sample could be attributed to the simultaneous nucleation of large number of shear bands and their mutual interactions.

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