Investigation of crossed-twin structure formation in magnesium and magnesium alloys
Investigation of crossed-twin structure formation in magnesium and magnesium alloys
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DOI：
10.1016/j.jallcom.2022.168094
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发表时间：
2023-02
影响因子：
6.2
通讯作者：
Jiaxiang Wang;Mariyappan Arul Kumar;I. Beyerlein
中科院分区：
文献类型：
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作者：
Jiaxiang Wang;Mariyappan Arul Kumar;I. Beyerlein
在这项工作中，合金化添加的倾向上的孪生孪晶相互作用转变为交叉孪晶结构的镁合金的影响进行了研究。一个全场弹粘塑性快速傅里叶变换（EVP-FFT）框架结合离散孪晶模型和位错密度为基础的硬化定律的滑移强度被用来计算周围的相互作用的孪晶晶体基质中的细观力学场。沿着纯镁，选用AZ 31和MgLi合金，研究合金元素对塑性各向异性的影响。选择这些合金是因为它们的塑性各向异性测量值（定义为锥体和基底滑移模式的临界分辨剪切应力之间的比率）跨越了很宽的范围。为了量化孪晶厚度的作用，我们探测了一系列的撞击孪晶厚度，同时固定受体孪晶厚度。分析表明：（i）在低塑性各向异性材料（如MgLi合金）中，由两个孪晶的相互作用产生的交叉孪晶结构形成的局部驱动应力低于高塑性各向异性材料（如纯Mg），以及（ii）在纯Mg、AZ 31和MgLi合金中形成交叉孪晶结构所需的临界撞击孪晶厚度是受体孪晶厚度的1.5、1.75和1.5倍。我们提出了交叉孪晶结构形成的趋势和实验观察到的更高的延展性MgLi合金相比，纯镁之间的关系。研究结果的一个关键含义是，交叉孪晶结构的形成可以被阻碍，从而提高镁合金的延展性，通过适当地选择合金元素，降低锥体c+ a滑移的滑移强度。
In this work, the effect of alloying addition on the propensity for twin-twin interactions to transform into crossed-twin structures in magnesium alloys is investigated. A full-field elasto-viscoplastic fast Fourier transform (EVP-FFT) framework combined with a discrete twin model and dislocation density-based hardening law for slip strengths is used to calculate the micromechanical fields in the crystalline matrix around the interacting twins. AZ31 and MgLi alloys are selected along with pure Mg to study the influence of plastic anisotropy in connection with alloying elements. These alloys were selected since their plastic anisotropy measure, which is defined as the ratio between the critical resolved shear stress for pyramidal and basal slip modes, spanned a wide range. To quantify the role of twin thicknesses, we probe a range of impinging twin thicknesses while fixing the recipient twin thickness. The analysis reveals that:(i) the local driving stress for crossed twin structure formation generated from the interaction of the two twins is lower in a low plastically anisotropic material, like a MgLi alloy, than a high plastically anisotropic material like pure Mg and (ii) the critical impinging twin thickness needed to form the crossed twin structure in pure Mg, AZ31 and MgLi alloys is∼ 0.5,∼ 0.75 and∼ 1.5 times the recipient twin thickness. We propose a relationship between the tendency for crossed twin structure formation and the experimentally observed higher ductility in MgLi alloys compared to pure Mg. One key implication of the findings is that crossed-twin structure formation can be hindered and the ductility of magnesium alloy thereby improved by properly choosing alloying elements that lower the slip strength for pyramidal c+ a slip.