Incompatibility stresses at grain boundaries in Ni bicrystalline micropillars analyzed by an anisotropic model and slip activity
Incompatibility stresses at grain boundaries in Ni bicrystalline micropillars analyzed by an anisotropic model and slip activity
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DOI：
10.1016/j.actamat.2014.09.033
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发表时间：
2015-01
期刊：
影响因子：
9.4
通讯作者：
I. Tiba;T. Richeton;C. Motz;H. Vehoff;S. Berbenni
中科院分区：
文献类型：
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作者：
I. Tiba;T. Richeton;C. Motz;H. Vehoff;S. Berbenni
由于材料的弹性和塑性各向异性，双晶体中会产生不相容应力。本文通过对直径为10 μm的镍双晶微柱的实验和理论研究，研究了这些应力。在整个逐步压缩试验中，通过扫描电子显微镜分析滑移痕迹，以确定两种晶体中的活动滑移面和方向。本文提出了一个考虑非均匀弹性和非均匀塑性耦合作用对内部力学场影响的分析模型。考虑到实验观察到的不相等的晶体体积分数和倾斜的晶界，该模型提供了明确的表达式在两个晶体中的应力。它是用来预测解析的剪切应力在每个晶体中可能的滑移系。由本模型在纯弹性的预测塑性的发病相比，由经典的施密德定律。与施密德定律相反，分析模型的预测是在最高应力的晶体和主动滑移系统的实验观察完全一致。除了整个模型中的弹性影响之外，还考虑了塑性不相容性的影响。分析表明，弹塑性耦合不相容性以及不同的晶体体积分数对滑移系激活过程有显着的影响。
Incompatibility stresses can develop in bicrystals due to material elastic and plastic anisotropies owing to different crystal orientations separated by grain boundaries. Here, these stresses are investigated by combining experimental and theoretical studies on 10 μm diameter Ni bicrystalline micropillars. Throughout stepwise compression tests, slip traces are analyzed by scanning electron microscopy to identify the active slip planes and directions in both crystals. An analytical model is presented accounting for the effects of heterogeneous elasticity coupled to heterogeneous plasticity on the internal mechanical fields. This model provides explicit expressions of stresses in both crystals considering experimentally observed non-equal crystal volume fractions and inclined grain boundaries. It is used to predict the resolved shear stresses on the possible slip systems in each crystal. The predictions of the onset of plasticity as given by the present model in pure elasticity are compared with those given by the classical Schmid’s law. In contrast with Schmid’s law, the predictions of the analytical model are in full agreement with the experimental observations regarding the most highly stressed crystal and active slip systems. The effects of plastic incompatibilities are also considered in addition to the elastic ones throughout the model. The analysis shows that elastic/plastic coupling incompatibilities together with different crystal volume fractions have significant effects on the slip system activation process.