Phase transitions in Zr at sub-nanosecond time scales

Solid-solid phase transitions are investigated in Zr thin films using shock compression induced by a short laser pulse (< 1 ns). Shock wave profiles are measured at free surfaces for films of different thicknesses (a few micrometers) using chirped-pulse line velocimetry with 10 ps time resolution. Experiments are performed at pressures up to & SIM;50 GPa, which is sufficient to reach the omega and beta phases under equilibrium conditions. The shock wave structures are analyzed using a general Lagrangian analysis method, which allows for the calculation of stress-strain paths and assessments of phase transition behavior. In agreement with recent short laser pulse experiments using ultra-fast x-ray diffraction, we do not find any clear evidence of the alpha-omega transition, though this would be expected from the phase diagram. Instead, we infer a direct transformation to a metastable beta-phase at lower shock pressures (< 20 GPa) and equilibrium beta at higher pressures. Through the velocimetry analysis, we find alpha-beta transformation onset times of less than & SIM;100 ps and completion times of less than & SIM;200 ps.

Automated summary

This study investigates solid-solid phase transitions in Zr thin films using shock compression induced by a short laser pulse. The results show a direct transformation to a metastable beta-phase at lower shock pressures, and equilibrium beta at higher pressures. The onset times of the alpha-beta transformation are found to be less than 100 ps, with completion times less than 200 ps.