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首页> 外文期刊>International Journal of Plasticity >A study of microstructure-driven strain localizations in two-phase polycrystalline HCP/BCC composites using a multi-scale model
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A study of microstructure-driven strain localizations in two-phase polycrystalline HCP/BCC composites using a multi-scale model

机译：多尺度模型研究两相多晶HCP / BCC复合材料的微观结构驱动应变局部化

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In this work, we present a 3D microstructure-based, full-field crystal plasticity finite element (CPFE) model using a thermally activated dislocation-density based constitutive description and apply it to study the deformation of a two-phase hexagonal close packed (HCP)-body center cubic (BCC) Zr/Nb composite. The microstructure models were created using a synthetic grain structure builder (DREAM.3D) and a meshing toolset for the 3D network of grains, grain boundaries, and bimetal interfaces. The crystal orientations, grain shapes, and grain sizes for each phase were initialized based on the measured data. With this novel technique, we aspire to couple the evolution of microstructural heterogeneities with the evolution of spatially resolved mechanical fields during the deformation of complex composites. Here, we apply it to understand the role that microstructure plays in the development of the local concentrations in strain and strain rate that can trigger plastic instabilities, such as shear banding. Our chief findings are that 1) local areas of relatively high (and relatively very low) strain concentration occur at triple junctions or quadruple points and then connect via straining to create a banded configuration that extends across the polycrystalline layer, 2) this event starts in the Zr phase and not in the Nb phase, and 3) the triggering hot spots in strain occur at junctions that join grains with very dissimilar reorientation propensities and vice versa for cold spots. In order to determine how such influential localizations can be prevented during processing via application of intermediate annealing treatments, we used the model to also explore the effects of annealing-induced changes in accumulated dislocation density, crystallographic texture and grain shape on the development of strain localizations during subsequent deformation. We found that while it is difficult to avoid strain localizations at grain junctions, when provided a microstructure containing a few large grains spanning the thickness, elongated grain shapes, and reduced dislocation density, the linkage of hot spots in the form of a band can be postponed. At the end we show that when an additional softening mechanism is introduced, these localized strain concentration areas can lead to shear bands. (C) 2015 Elsevier Ltd. All rights reserved.
机译：在这项工作中，我们使用基于热活化位错密度的本构描述提出了一个基于3D微结构的全场晶体可塑性有限元（CPFE）模型，并将其用于研究两相六方密堆积（HCP）的变形-体心立方（BCC）Zr / Nb复合材料。使用合成晶粒结构构建器（DREAM.3D）和网格工具集创建了微观结构模型，该工具集用于晶粒，晶粒边界和双金属界面的3D网络。基于测量的数据初始化每个相的晶体取向，晶粒形状和晶粒尺寸。通过这种新颖的技术，我们希望在复杂复合材料的变形过程中将微观结构异质性的演化与空间分辨机械场的演化耦合起来。在这里，我们应用它来理解微观结构在应变和应变率局部浓度的发展中所起的作用，这些局部和浓度会触发塑性不稳定性，例如剪切带。我们的主要发现是：1）应变浓度相对较高（且相对非常​​低）的局部区域出现在三重结或四重点处，然后通过应变进行连接，以形成在多晶层上延伸的带状结构; 2）此事件始于Zr相而不是Nb相; 3）应变的触发热点发生在连接晶粒的连接处，这些晶粒具有非常不同的重新取向倾向，反之亦然。为了确定在加工过程中如何通过应用中间退火处理来防止这种有影响的局部化，我们使用该模型还探索了退火诱导的累积位错密度，晶体织构和晶粒形状变化对应变局部化发展的影响。在随后的变形中。我们发现，虽然很难避免应变在晶粒连接处的局限性，但是当提供的微观结构中包含一些跨越厚度的大晶粒，细长的晶粒形状和降低的位错密度时，带状热点的联系可以推迟了。最后，我们表明，当引入其他软化机制时，这些局部应变集中区域会导致剪切带。 （C）2015 Elsevier Ltd.保留所有权利。

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