Unusual grain coarsening behavior of bismuth under high pressure

It is well known the atomic diffusion caused by high temperature leads to conspicuous grain coarsening, which is of crucial importance to the properties of materials. High pressure usually slows down the diffusion rate of atoms and refines the grain size. In this study, using synchrotron angle dispersive x-ray diffraction (ADXRD) techniques, we observed an abnormal grain coarsening behavior of bismuth (Bi) stemming from the high pressure phase transition at room temperature, demonstrating that the grain coarsening can also be triggered by pressure. Two factors mainly give raise to this unusual coarsening behavior of Bi: (1) the nucleation rate of new phase is very slow during transformation according to the kinetics study of the phase transition in Bi, which inhibits the grain refinement; (2) the liquid interphase in the phase transition process enables the recrystallization of Bi under high pressure. Our experiment results are consistent with the previous theoretical calculations, which is crucial for describing the nucleation and growth process and clarifying the phase transition mechanisms in Bi.