Strong grain neighbour effects in polycrystals

• Published in: Nature communications Vol. 9; no. 1; pp. 171 - 11
• Main Authors: Abdolvand, Hamidreza, Wright, Jonathan, Wilkinson, Angus J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12-01-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 639/166/988; 639/301/1023/1026; 639/301/1023/303; Crystallography; Crystals; Deformation; Grains; Humanities and Social Sciences; multidisciplinary; Physics; Plastic flow; Polycrystals; Science; Science (multidisciplinary); Single crystals; Twinning; X-ray diffraction; Yield point; Zirconium; FINITE-ELEMENT MODEL; UNIAXIAL DEFORMATION; STRESS-FIELDS; X-RAY-DIFFRACTION; TEXTURED ZIRCALOY-2; PURE TI; REORIENTATION; IN-SITU; TWIN; PLASTICITY
• ISSN: 2041-1723; 2041-1723
• 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.
Understanding how individual crystals share load inside a polycrystal is crucial to improve component lifetime, but remains difficult to measure. Here, the authors show that the crystal orientation of a grain and that of its neighbours can surprisingly cause stress relaxation in zirconium and titanium under load.