Microstructural evolution of rhenium Part I: Compression

A comprehensive study of the microstructural evolution of pure rhenium during compression has been conducted using TEM and EBSD analysis. Under compression, slip and dislocation plasticity was predominantly active in the low strain regime, with {112̅1}〈112̅6〉 twinning occurring at all strain amounts and dominating after yield. This is contrary to deformation twins typically being active during the initial low strain regime of twinning dominated metals. It was observed that twins could bypass grain boundaries, as previously reported. In addition, a mechanism of twins “jogging” along the c-axis past twin boundaries was observed using TEM. This mechanism allowed for multiple twin variants to be active within individual grains. Twin “jogging” helps to explain the excellent ductility in rhenium accommodating the lack of dislocation plasticity. Postmortem TEM imaging showed dislocation density steadily increased around the twins, a result of twin boundaries impeding dislocation slip, confirming observations seen in highly work-hardened tension samples. Additionally, dislocation populated twin boundaries have shown {112̅1}〈112̅6〉 type twins resist growing in size when surrounded by dislocations, tending instead to form new twins as strain increases.