College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
Research Center for Structural Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
Phys Rev E. 2019 Oct;100(4-1):043002. doi: 10.1103/PhysRevE.100.043002.
Avalanche behaviors, characterized by power-law statistics and structural relaxation that induces shear localization in amorphous plasticity, play an essential role in deciding the mechanical properties of amorphous metallic solids (i.e., metallic glasses). However, their interdependence is still not fully understood. To investigate the influence of structural relaxation on elementary avalanche behavior, we perform molecular-dynamics simulations for the shear deformation test of metallic glasses using two typical metallic-glass models comprising a less-relaxed (as-quenched) glass and a well-relaxed (well-aged) glass exhibiting a relatively homogeneous deformation and a shear-band-like heterogeneous deformation, respectively. The data on elementary avalanches obtained from both glass models follow the same power-law statistics with different maximum event sizes, and the well-relaxed glass shows shear localization. Evaluating the spatial correlation functions of the nonaffine squared displacements of atoms during each elementary avalanche event, we observe that the shapes of the elementary avalanche regions in the well-relaxed glasses tend to be anisotropic, whereas those in the less-relaxed glasses are relatively isotropic. Furthermore, we demonstrate that a temporal clustering in the direction of the avalanche propagation emerges, and a considerable correlation between the anisotropy and avalanche size exists in the well-relaxed glass model.
雪崩行为以幂律统计和结构弛豫为特征，这会导致非晶态塑性中的剪切局部化，在决定非晶态金属固体（即金属玻璃）的力学性能方面起着至关重要的作用。然而，它们之间的相互依赖性尚未完全理解。为了研究结构弛豫对基本雪崩行为的影响，我们使用两种典型的金属玻璃模型对金属玻璃的剪切变形测试进行了分子动力学模拟，这两种模型包括弛豫程度较低（淬火）的玻璃和弛豫程度较高（老化）的玻璃，后者表现出相对均匀的变形和剪切带样的不均匀变形。从这两种玻璃模型中获得的基本雪崩数据都遵循相同的幂律统计规律，只是最大事件大小不同，而且弛豫程度较高的玻璃会发生剪切局部化。在每个基本雪崩事件中评估原子非仿射平方位移的空间相关函数时，我们观察到弛豫程度较高的玻璃中基本雪崩区域的形状往往具有各向异性，而弛豫程度较低的玻璃中的基本雪崩区域则相对各向同性。此外，我们还证明了在雪崩传播方向上出现了时间上的聚集现象，并且在弛豫程度较高的玻璃模型中，各向异性与雪崩大小之间存在着很大的相关性。
