I${}_1$ stacking faults (SFs) in Mg alloys are regarded as the nucleation sites of $〈$c+a$〉$ dislocations that are critical for these alloys to achieve high ductility. Previously it was proposed that the formation of I${}_1$ SFs requires the accumulations of a large number of vacancies, which are difficult to achieve at low temperatures. In this study, molecular dynamics (MD) and molecular statics (MS) simulations based on empirical interatomic potentials were applied to investigate the deformation defect evolutions from the symmetric tilt grain boundaries (GBs) in Mg and Mg-Y alloys under external loading along $〈c〉$-axis. The results show the planar faults (PFs) on Pyramidal I planes first appear due to the nucleation and glide of $〈\frac{1}{2}c+p〉$ partial dislocations from GBs, where $〈p〉=\frac{1}{3}〈10\overline{1}0〉$. These partial dislocations with pyramidal PFs interact with other defects, including pyramidal PFs themselves, GBs, and $〈p〉$ partial dislocations, generating a large amount of I${}_1$ SFs. Detailed analyses show the nucleation and growth of I${}_1$ SFs are achieved by atomic shuffle events and deformation defect reactions without the requirements of vacancy diffusion. Our simulations also suggest the Y clusters at GBs can reduce the critical stress for the formation of pyramidal PFs and I${}_1$ SFs, which provide a possible reason for the experimental observations that Y promotes the $〈$c+a$〉$ dislocation activities.

我${}_1$镁合金中的堆垛层错（SFs）被认为是$〈$c+a$〉$位错对于这些合金实现高延展性至关重要。以前有人提出，我的形成${}_1$SFs需要大量空位的积累，这在低温下很难实现。在这项研究中，应用基于经验原子间势的分子动力学 (MD) 和分子静力学 (MS) 模拟来研究 Mg 和 Mg-Y 合金在外部载荷下沿对称倾斜晶界 (GBs) 的变形缺陷演变。$〈C〉$-轴。结果表明，Pyramidal I 平面上的平面断层（PFs）首先出现是由于$〈\frac{1}{2}C+p〉$GB的部分位错，其中$〈p〉=\frac{1}{3}〈10\overline{1}0〉$. 这些带有锥体 PF 的部分位错与其他缺陷相互作用，包括锥体 PF 本身、GB 和$〈p〉$部分位错，产生大量的 I${}_1$科幻小说。详细分析显示 I 的成核和生长${}_1$SFs 是通过原子混洗事件和变形缺陷反应实现的，不需要空位扩散。我们的模拟还表明，GB 处的 Y 簇可以降低形成锥体 PF 和 I 的临界应力。${}_1$SFs，这为 Y 促进$〈$c+a$〉$错位活动。