Abdolvand Hamidreza, Wright Jonathan, Wilkinson Angus J
Department of Mechanical and Materials Engineering, Western University, Spencer Engineering Building, London, ON, N6A 5B9, Canada.
Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
Nat Commun. 2018 Jan 12;9(1):171. doi: 10.1038/s41467-017-02213-9.
Anisotropy in single-crystal properties of polycrystals controls both the overall response of the aggregates and patterning of local stress/strain distributions, the extremes of which govern failure processes. Improving the understanding of grain-grain interactions has important consequences for in-service performance limits. Three-dimensional synchrotron X-ray diffraction was used to study the evolution of grain-resolved stresses over many contiguous grains in Zr and Ti polycrystals deformed in situ. In a significant fraction of grains, the stress along the loading axis was found to decrease during tensile plastic flow just beyond the macroscopic yield point; this is in the absence of deformation twinning and is a surprising behaviour. It is shown that this phenomenon is controlled by the crystallographic orientation of the grain and its immediate neighbours, particularly those adjacent along the loading axis.
多晶体单晶特性中的各向异性既控制着聚集体的整体响应，也控制着局部应力/应变分布的图案化，其极端情况决定了失效过程。增进对晶粒间相互作用的理解对于服役性能极限具有重要意义。利用三维同步加速器X射线衍射研究了原位变形的Zr和Ti多晶体中许多相邻晶粒上晶粒分辨应力的演变。在相当一部分晶粒中，发现在宏观屈服点之后的拉伸塑性流动过程中，沿加载轴的应力会降低；这是在没有变形孪晶的情况下出现的，是一种令人惊讶的行为。结果表明，这种现象受晶粒及其紧邻晶粒的晶体取向控制，尤其是沿加载轴相邻的那些晶粒。
