Abstract This work adapts a recently developed multi-level constitutive model for polycrystalline metals that deform by a combination of elasticity, crystallographic slip, and deformation twinning to interpret the deformation behavior of alloy WE43 as a function of strain rate. The model involves a two-level homogenization scheme. First, to relate the grain level to the level of a polycrystalline aggregate, a Taylor-type model is used. Second, to relate the aggregate level response at each finite element (FE) integration point to the macro-level, an implicit FE approach is employed. The model features a dislocation-based hardening law governing the activation stress at the slip and twin system level, taking into account the effects of temperature and strain rate through thermally-activated recovery, dislocation debris formation, and slip-twin interactions. The twinning model employs a composite grain approach for multiple twin variants and considers double twinning. The alloy is tested in simple compression and tension at a quasi-static deformation rate and in compression under high strain rates at room temperature. Microstructure evolution of the alloy is characterized using electron backscattered diffraction and neutron diffraction. Taking the measured initial texture as inputs, it is shown that the model successfully captures mechanical responses, twinning, and texture evolution using a single set of hardening parameters, which are associated with the thermally activated rate law for dislocation density across strain rates. The model internally adjusts relative amounts of active deformation modes based on evolution of slip and twin resistances during the imposed loadings to predict the deformation characteristics. We observe that WE43 exhibits much higher strain-hardening rates under high strain rate deformation than under quasi-static deformation. The observation is rationalized as primarily originating from the pronounced activation of twins and especially contraction and double twins during high strain rate deformation. These twins are effective in strain hardening of the alloy through the texture and barrier hardening effects.

中文翻译：

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作为应变率函数的 WE43 镁稀土合金的机械响应、孪晶和织构演变：实验和多级晶体塑性建模

摘要 这项工作采用最近开发的多晶金属多级本构模型，该模型通过弹性、晶体滑移和变形孪晶的组合变形，以将 WE43 合金的变形行为解释为应变速率的函数。该模型涉及两级同质化方案。首先，为了将晶粒水平与多晶骨料的水平联系起来，使用了泰勒型模型。其次，为了将每个有限元 (FE) 积分点的聚合级别响应与宏观级别相关联，采用了隐式 FE 方法。该模型具有基于位错的硬化规律，控制滑移和孪生系统水平的激活应力，通过热激活恢复、位错碎片形成、和滑动孪生相互作用。孪晶模型对多个孪晶变体采用复合晶粒方法并考虑双重孪晶。该合金在准静态变形率下的简单压缩和拉伸以及室温下高应变率下的压缩下进行测试。使用电子背散射衍射和中子衍射表征合金的显微组织演变。将测量的初始纹理作为输入，表明该模型使用一组硬化参数成功捕获了机械响应、孪晶和纹理演化，这些硬化参数与跨应变速率的位错密度的热激活速率定律相关。该模型根据施加载荷期间滑移和孪生阻力的演变在内部调整主动变形模式的相对量，以预测变形特征。我们观察到 WE43 在高应变率变形下比在准静态变形下表现出更高的应变硬化率。该观察结果被合理化为主要源于双胞胎的显着激活，尤其是在高应变率变形期间的收缩和双胞胎。这些孪晶通过织构和阻挡硬化效应对合金的应变硬化有效。该观察结果被合理化为主要源于双胞胎的显着激活，尤其是在高应变率变形期间的收缩和双胞胎。这些孪晶通过织构和阻挡硬化效应对合金的应变硬化有效。该观察结果被合理化为主要源于双胞胎的显着激活，尤其是在高应变率变形期间的收缩和双胞胎。这些孪晶通过织构和阻挡硬化效应对合金的应变硬化有效。