Critical Shape for the Growth of Grain Boundary Twin Embryos in Mg and Mg Alloys: Crystal Plasticity Modeling
Critical Shape for the Growth of Grain Boundary Twin Embryos in Mg and Mg Alloys: Crystal Plasticity Modeling
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DOI：
10.3390/alloys1020013
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
Yanqing Su;M. Arul Kumar;I. Beyerlein
中科院分区：
文献类型：
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作者：
Yanqing Su;M. Arul Kumar;I. Beyerlein
多晶六角形关闭填充（HCP）金属在工程设计中的应用受到了由于孪晶和有限的可塑性而引起的各向异性响应。在变形中，双胞胎通常在晶界（GB）上启动，并在整个谷物上繁殖并繁殖。在这项工作中，研究了MG和MG合金中的GB双胚胎，以及影响其传播的条件。使用微力机械晶体可塑性模型，研究了胚形形状在可以支持其膨胀的胚胎边界处占上风的驱动力中的作用。模型的胚胎要么是平面，在剪切方向上延伸的延伸比正常平面的延伸更多，要么是e。结果表明，胚胎越细，增厚和正向传播的驱动力越大。具有低棱柱性临界分解剪应力（CRS）比的合金可促进胚胎增厚和大型CRS值的滑动模式，这主要适应双剪切型剪切。相邻的谷物具有方向，可以通过锥体滑动来局部适应胚胎双剪切，促进向前传播，但对增厚几乎没有影响。当两个类似胚胎沿着同一GB时，它们的配对相互作用会促进前进的传播，但会阻碍增厚。
Application of polycrystalline hexagonal close packed (HCP) metals in engineering designs has been constrained by their anisotropic responses due to twinning and limited plasticity. In deformation, twins most often initiate at grain boundaries (GBs), and thicken and propagate across the grain. In this work, the GB twin embryos in Mg and Mg alloys, and the conditions that influence their propagation are investigated. Using a micromechanical crystal plasticity model, the role of embryo shape on the driving forces prevailing at the embryo boundaries that could support its expansion is studied. The modeled embryos are either planar, extending more in the shear direction than normal to the twin plane, or equiaxed. Results show that the thinner the embryo, the greater the driving forces for both thickening and forward propagation. Alloys with low prismatic-to-basal critical resolved shear stress (CRSS) ratios promote embryo thickening and large CRSS values for the slip mode that primarily accommodates the twin shear encourage propagation. The neighboring grains with orientations that enable local accommodation of the embryo twin shear by pyramidal slip promote forward propagation but have little effect on thickening. When two like embryos lie along the same GB, their paired interaction promotes forward propagation but hinders thickening.