Grain boundary (GB) motions, such as migration, sliding and rotation, have been shown to play a vital role in the mechanical performance of polycrystalline metals. Despite extensive efforts have been made on the pure polycrystalline metals, few attentions have been paid to those in alloys. In this work, taking conventional nanoscale Cu–Al binary alloy system as an example, we intend to shed some light on understanding its GB motions under shear loading by means of molecular dynamics (MD) simulations. It is found that either shear-coupled GB migration or sliding motion can be observed, depending on GB tilt angles, temperatures and Al solute concentrations. By systematical MD simulations, the Al concentration required for transition between shear-coupled migration and sliding is found to decrease with increasing tilt angles (θ ≤ 50°) at fixed temperature, whereas it switches to the opposite trend for larger tilt angles. Furthermore, the GBs migrate much slower comparing with those in pure Cu, which shows the drag effects of the Al solutes in the alloy form. Moreover, the critical stress during shear loading shows a linear dependence on 2/3 power of the temperature.

中文翻译：

---

从原子模拟中提取 Cu-Al 合金中的晶界运动

晶界 (GB) 运动，如迁移、滑动和旋转，已被证明在多晶金属的机械性能中起着至关重要的作用。尽管已经对纯多晶金属进行了广泛的努力，但很少有人关注合金中的那些。在这项工作中，以传统的纳米级 Cu-Al 二元合金系统为例，我们打算通过分子动力学（MD）模拟来理解其在剪切载荷下的 GB 运动。发现根据 GB 倾斜角、温度和铝溶质浓度，可以观察到剪切耦合的 GB 迁移或滑动运动。通过系统的 MD 模拟，发现剪切耦合迁移和滑动之间过渡所需的 Al 浓度在固定温度下随着倾斜角 (θ≤50°) 的增加而降低，而对于较大的倾斜角，它会转变为相反的趋势。此外，与纯铜相比，GB 的迁移速度要慢得多，这表明合金形式的 Al 溶质的拖曳效应。此外，剪切载荷期间的临界应力显示出对温度的 2/3 次幂的线性依赖性。