Ultrafast Dynamic Compression Technique to Study the Kinetics of Phase Transformations in Bismuth

Preheated Bi (296--532 K) was ramp compressed with 15--35 ns rise times to a peak stress of ~11 GPa to explore structural phase-transformation kinetics under dynamic loading conditions. At high strain rates, ̇ ε>5×10⁶ s^-1, deviation from equilibrium phase boundaries suggests that compression time scales are comparable to the new phase incubation period. The dependence of ΔP/kT on ̇ ε is consistent with a thermally activated transformation.