Multiphase Strength Coupled with Phase Change Kinetics in RMI Experiments on Tin Across the Beta-Gamma Boundary

A series of impact-driven Richtmyer-Meshkov Instability (RMI) experiments were used to study multiphase strength, in the presence of phase change kinetics, in tin across the ambient beta phase and higher-pressure gamma phase. Two experiments at shock stresses of 4 and 6 GPa did not change phase, and the measured velocities were used to calibrate a strength model for the beta phase. As with all the experiments in this study, representative strain rates ranged from about 10⁶ to 10⁷ /second. An experiment shocked to 14 GPa overdrove the phase transition, was sensitive to strength in both phases, and was used to calibrate strength in the gamma phase, assuming independence from kinetics. Finally, the data from an experiment shocked to 11 GPa showed simultaneous indications of strength and slow kinetics of the beta-gamma phase change and was used solely for validation. Two sets of parameters for phase change kinetics, combined with the calibrated strength models, were checked against that 11 GPa data. The kinetics parameters came from two independent Bayesian calibrations that simultaneously fit various combinations of the multiphase strength, forward and reverse transition kinetics, anelasticity, and phase boundaries. Data used simultaneously in the fits included flyer plate data and ramp-release data from pulsed-power machines. The comparisons with the 11 GPa RMI data show that the multiphase strength was highly coupled with phase change kinetics and the equation of state. Combined experimental and modeling strategies for handling the complex, coupled problem will be discussed.