Kinetics of $\alpha $ to $\omega $ structural transition in zirconium

Zirconium (Zr), along with the other group IV-B transition metals titanium (Ti) and hafnium (Hf), has been widely investigated at high P-T conditions. Initial interest in Zr may have been driven in part by need to understand structural stability at conditions that these materials could experience in a wide range of commercial applications. Multiple studies demonstrate that, at elevated pressure, these metals and their alloys undergo a structural transition from hexagonal close-packed ($\alpha )$ phase to another hexagonal ($\omega )$ phase. Subsequently, $\alpha $-$\omega $ transition has been investigated in detail -- results indicate that the $\alpha $-$\omega $ boundary is significantly influenced by sample purity, experimental conditions (e.g. hydrostatic vs. uniaxial compression), loading conditions (e.g. shock vs. slower ``static'' loading), etc. Early measurements also indicate that kinetics at the onset of $\alpha $-$\omega $ transition may play a significant role in establishing the phase boundary and thus must be fully investigated to gain a more comprehensive understanding of behavior of Zr at high P-T. Ongoing advances in large scale x-ray sources and detector and instrumentation technologies have made investigations of transition kinetics over broader P-T and compression/strain rate conditions possible. Using DAC coupled with piezoelectric and/or gas membrane loading, $\alpha $-$\omega $ transition in Zr was investigated as a function of compression (P-jump) rate. Relevant results, as well as broader impacts regarding $\alpha $-$\omega $ transition mechanism, will be presented.