Abstract It is well known that twinning likely nucleates and forms pairs at grain boundaries (GBs) during the deformation of Mg alloys. Therefore, the crystallography of GBs plays an important role in selecting twin variants. In this regard, the Schmid factor (SF) cannot predict from which GBs twinning prefers to nucleate. To solve this problem, a composite Schmid factor (CSF) is proposed in this paper that incorporates both the SF and a geometric compatibility factor (m'). First, the link of the CSF with the SF and m' is defined and discussed based on theoretical derivations, which is further verified in terms of crystal plasticity finite element simulations. Then, experiments were carried out to investigate the effects of this parameter in predicting {10–12} extension twins in AZ31 Mg alloys. A CSF threshold for the activation of common-boundary twins was noticed and it decreases with the applied strain. By contrast, the SF threshold and its dependence with strain is not obvious. Moreover, the CSF is more effective in predicting the variants of common-boundary twins especially for small strain.

中文翻译：

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通过复合施密德因子了解镁合金中常见的晶界孪晶

摘要 众所周知，在镁合金变形过程中，孪晶可能在晶界（GBs）处成核并形成对。因此，GB 的晶体学在选择孪生变体方面起着重要作用。在这方面，施密德因子 (SF) 无法预测孪晶倾向于从哪个 GB 中成核。为了解决这个问题，本文提出了一种复合施密德因子 (CSF)，它结合了 SF 和几何兼容性因子 (m')。首先，基于理论推导定义和讨论了 CSF 与 SF 和 m' 的联系，并在晶体塑性有限元模拟方面进一步验证。然后，进行了实验以研究该参数在预测 AZ31 镁合金中的 {10-12} 拉伸孪晶中的影响。注意到激活共同边界双胞胎的脑脊液阈值，它随着施加的应变而降低。相比之下，SF 阈值及其与应变的依赖性并不明显。此外，CSF 在预测共同边界双胞胎的变异方面更有效，尤其是对于小应变。