Study of dynamic polymorphic phase transition in tin and its kinetics

Previous studies of tin (Sn) dynamic phase diagram were focused on either shock or shockless loading of tin from its β-phase towards γ phase. Due to multiple techniques involved the  β- γ phase boundary has been established based on substantially scattered points on pressure-temperature plane and is characterized by substantial uncertainty while the kinetics of the transition is not thoroughly understood yet. The goal of the present study was to accurately locate the dynamic β- γ boundary and to analyze the effect of initial sample state on kinetics of β- γ transition. This was done in several series of planar impact experiments with VISAR monitoring of the velocity of the rear surface of the samples of different thickness preheated up to temperatures varied from 300 K to Sn melting point.

Analysis of the evolution of the three-wave (elastic-plastic-transformation) structure with propagation distance showed that the dynamic tensile (spall) strength of β- Sn decreases linearly with temperature while temperature variation of the yield strength is much weaker. The initial and the maximum rates β- γ transformation at different temperatures were determined based on, respectively, the plastic wave decay with propagation distance and the slope of the transformation wave.