The influence of phase and substructural evolution during dynamic loading on subsequent mechanical properties of zirconium

Abstract

At high pressures zirconium undergoes a phase transformation from the hexagonal closed packed (hcp) α-phase to the simple hexagonal ω-phase. In high purity Zr and under shock loading conditions the phase transformation has been observed to begin at approximately 7GPa [1]. Evolution of the plastic response and phase transformation during dynamic loading is not well understood and therefore the contributions of this evolution to strength and damage are not well predicted. Here, through a combination of post-mortem and in situ techniques, different dynamic drive conditions are utilized to create a set of specimens with various volume fractions of retained high pressure ω-phase and stored plastic work. The mechanical properties of these well-characterized microstructures are subsequently examined. The results indicate that while both plastic deformation and the volume fraction of the high pressure phase play important roles in determining subsequent material properties, the effect of texture evolution due to plastic work may be of critical importance in determining these properties. This finding sheds an insight into strength under pressure.