Strong grain neighbour effects in polycrystals
High value hexagonal alloys Ti and Zr have safety critical applications in the aerospace and nuclear industries. Understanding and improving their performance requires untangling the complex patterning of stress and strain at the microstructural level. The MicroMechanics Group has used 3D-X-ray Diffraction, coupled with crystal plasticity FEM simulations, to study stress evolution across thousands of contiguous grains in polycrystals loaded in situ at the ESRF ID11. Large anisotropy in elastic stiffness, thermal expansion and plastic flow stress in these materials ensure that the local grain neighbourhood has a profound effect on stress development in any particular grain. Indeed the neighbourhood effect is so strong that for many grains the stress level can actually drop despite the global stress state increasing during tensile plastic flow.
The work is available in Nature Communications.