It is known that the mechanical behavior of many hexagonal close-packed (HCP) materials is sensitive to textural variations. In the technologically important magnesium (Mg) alloys, the anisotropic plastic behaviors and their dependence on different processing-induced textures have been reasonably well studied under relatively simple stress states. However, a detailed assessment of the rate-dependent microstructure–property linkages under triaxial stress states is relatively less explored. In this work, we present a computational investigation of the role played by strain rate, texture, and stress state in the macro–micro mechanical characteristics of Mg alloys. Three-dimensional boundary value problems using smooth and notched round bar geometries subjected to tensile deformation are modeled using a crystal plasticity framework that includes slip and twinning deformation mechanisms. We examine the responses over six orders of magnitudes of strain rates, for three different initial textures that span a broad spectrum of textural strengths, and three specimen geometries that induce varying levels of stress triaxiality. The simulations reveal a remarkable transition of the tensile response from a conventional power-law type to a sigmoidal type for certain combinations of textures, stress triaxiality levels, and strain rates. While the stress response is strongly rate-dependent, the macroscopic deformation anisotropy has a negligible effect from strain rate compared to the role of the stress state and texture. We discuss the potential implications of these observations on the rate-dependent failure of Mg alloys.

众所周知，许多六角密堆积 (HCP) 材料的机械行为对质地变化很敏感。在技​​术上重要的镁 (Mg) 合金中，在相对简单的应力状态下，各向异性塑性行为及其对不同加工诱导织构的依赖性已经得到了很好的研究。然而，在三轴应力状态下对速率相关的微观结构-性能联系的详细评估相对较少。在这项工作中，我们对应变率、织构和应力状态在镁合金宏观-微观机械特性中所起的作用进行了计算研究。使用经受拉伸变形的光滑和缺口圆棒几何形状的三维边界值问题使用晶体塑性框架进行建模，该框架包括滑移和孪生变形机制。我们检查了六个数量级的应变率的响应，对于跨越广泛的纹理强度的三种不同的初始纹理，以及引起不同水平应力三轴性的三种试样几何形状。模拟显示，对于某些纹理、应力三轴度水平和应变率的组合，拉伸响应从传统的幂律类型显着转变为 sigmoidal 类型。虽然压力反应强烈依赖于速率，与应力状态和织构的作用相比，宏观变形各向异性对应变速率的影响可以忽略不计。我们讨论了这些观察结果对镁合金速率相关失效的潜在影响。