铁冲击相变的分子动力学研究

Shock-induced phase transformations of iron studied with molecular dynamics

用分子动力学方法模拟了单晶铁(Fe)在一定初始温度下冲击相变(α相→ε相)的微观过程,结果显示温度会导致冲击相变压力阈值降低.基于此微观过程,对加卸载波系的传播规律进行了相应计算和分析,结果表明在卸载过程中逆相变波(ε相→α相)相对于波前以当地纵波声速传播,而相对波后以亚声速传播,这可由卸载压力-密度曲线给出相应解释;计算了不同初态的卸载压力-密度状态曲线,并给出了逆相变带的分布,其分布规律显示了卸载过程逆相变的滞后现象.

Molecular dynamics simulations are used to investigate the shock-induced phase transformation of iron at a certain initial temperature, which shows that the temperature lowers the threshold pressure of shock-induced phase transformation. Also, the evolution of the loading and unloading waves is calculated and analyzed, and it is found that the velocity of the inverse phase transformation wave（during ε phase →α phase）equals the longitudinal sound speed of the wave front and is less than that of the wave rear. The pressure and density of unloading traces is also calculated, which affords a good explanation to the evolution of the unloading waves, and the phase transformation band of unloading is obtained, which shows the hysteresis in the reverse transformation.