Three-dimensional investigation of grain boundary-twin interactions in a Mg AZ31 alloy by electron backscatter diffraction and continuum modeling
Three-dimensional investigation of grain boundary-twin interactions in a Mg AZ31 alloy by electron backscatter diffraction and continuum modeling
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DOI：
10.1016/j.actamat.2013.09.005
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发表时间：
2013-12-01
期刊：
影响因子：
9.4
通讯作者：
Perez-Prado, M. T.
中科院分区：
文献类型：
--
作者：
Fernandez, A.;Jerusalem, A.;Perez-Prado, M. T.
采用三维电子背散射衍射方法研究了晶界取向差θ对镁AZ 31合金中孪晶的影响。该方法在由取向有利于孪晶的中心晶粒和三个晶界组成的体积中进行，θ为15 ° ~ 64 °。这项研究证实了以前的观察，孪晶成核和传播的青睐在低θ。此外，它揭示了非施密德效应，如低施密德因子（SF）的变体或双拉伸孪晶的激活，是不存在的低取向差边界附近，他们变得更加丰富，θ增加。个别双胞胎变体的3-D形态被发现与它们的SF有关。高SF变体具有良好的板形态，而低SF变体采用不规则形状。本文将作者最近提出的晶体塑性连续体模型应用于实验试件的一个很高的晶内分辨率和大尺度有限元多晶集合体模型。该模型成功地捕捉到了θ对双胞胎传播和变异选择的影响。它最终预测：（i）随着θ的增加，局部非基底滑移增加，（ii）低θ GB有利于通过非施密德应力集中的孪晶成核，但传播立即被宏观应力容纳，以及（iii）高θ GB不是有利的孪晶成核位点，尽管具有高冯米塞斯应力集中。(C)2013 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The effect of grain boundary (GB) misorientation (theta) on twinning in a Mg AZ31 alloy is investigated using a three-dimensional (3-D) experimental and modeling approach, in which 3-D electron backscattered diffraction is performed in a volume consisting of a central grain, favorably oriented for twinning, and surrounded by three boundaries, with theta ranging from 15 degrees to 64 degrees. This study corroborates previous observations that twin nucleation and propagation are favored at low theta. Furthermore, it reveals that non-Schmid effects, such as the activation of low Schmid factor (SF) variants or of double tensile twins, are absent in the vicinity of low misorientation boundaries and that they become more abundant as theta increases. The 3-D morphology of individual twin variants is found to be related to their SF. High SF variants have well-established plate morphology, while low SF variants adopt irregular shapes. A crystal plasticity continuum model recently proposed by the authors is used in a very high intragrain resolution and large-scale finite element polycrystalline aggregate model of the experimental specimen. This model is shown to successfully capture the influence of theta on twin propagation and variant selection. It ultimately predicts (i) a rise in local non-basal slip with increasing theta, (ii) that low theta GB favor twin nucleation by non-Schmid stress concentrations, but that propagation is immediately accommodated by the macroscopic stress, and (iii) that high theta GB are not favorable twin nucleation sites, despite having high von Mises stress concentrations. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.