Crystal plasticity study of monocrystalline stochastic honeycombs under in-plane compression
Crystal plasticity study of monocrystalline stochastic honeycombs under in-plane compression
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DOI：
10.1016/j.actamat.2015.11.016
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发表时间：
2016-01
期刊：
影响因子：
9.4
通讯作者：
D. Ma;P. Eisenlohr;E. Epler;C. Volkert;P. Shanthraj;M. Diehl;F. Roters;D. Raabe
中科院分区：
文献类型：
--
作者：
D. Ma;P. Eisenlohr;E. Epler;C. Volkert;P. Shanthraj;M. Diehl;F. Roters;D. Raabe
我们使用面心立方（fcc）材料的晶体塑性本构描述对单晶随机蜂窝在面内压缩下的塑性变形进行了研究，重点关注塑性变形的早期阶段，并确定了塑性变形过程中晶体取向和细胞结构之间的相互作用。我们观察到，尽管具有随机结构，但令人惊讶的是，蜂窝中的滑移系统激活在塑性变形的早期阶段几乎与相应的块状单晶相同。然而，另一方面，蜂窝体的屈服应力几乎与其晶体取向无关。在以各种晶体取向排列的纳米多孔金微柱的压缩测试中发现了类似的机械响应。蜂窝体的宏观应力张量表现出与其各自的块体单晶相同的各向异性。然而，局部应力存在明显的波动，甚至比多晶的波动还要大。这解释了为什么与晶体取向相关的泰勒/施密德因子对于估计蜂窝体的屈服应力不如大块单晶和多晶有用，以及为什么蜂窝体中的塑性变形发生在比其相应的大块单晶更小的应变下。除了这些发现之外，晶体学重新取向的观察表明，传统的取向分析工具，例如反极图和相关工具，通常无法研究单晶多孔材料的塑性变形机制。
We present a study on the plastic deformation of single crystalline stochastic honeycombs under in-plane compression using a crystal plasticity constitutive description for face-centered cubic (fcc) materials, focusing on the very early stage of plastic deformation, and identifying the interplay between the crystallographic orientation and the cellular structure during plastic deformation. We observe that despite the stochastic structure, surprisingly, the slip system activations in the honeycombs are almost identical to their corresponding bulk single crystals at the early stage of the plastic deformation. On the other hand, however, the yield stresses of the honeycombs are nearly independent of their crystallographic orientations. Similar mechanical response is found in compression testing of nanoporous gold micro-pillars aligned with various crystallographic orientations. The macroscopic stress tensors of the honeycombs show the same anisotropy as their respective bulk single crystals. Locally, however, there is an appreciable fluctuation in the local stresses, which are even larger than for polycrystals. This explains why the Taylor/Schmid factor associated with the crystallographic orientation is less useful to estimate the yield stresses of the honeycombs than the bulk single crystals and polycrystals, and why the plastic deformation occurs at smaller strains in the honeycombs than their corresponding bulk single crystals. Besides these findings, the observations of the crystallographic reorientation suggest that conventional orientation analysis tools, such as inverse pole figure and related tools, would in general fail to study the plastic deformation mechanism of monocrystalline cellular materials.