强激光辐照下孔洞尺寸对铁相变过程的影响

 利用分子动力学模拟研究了完美单晶铁以及含不同尺寸孔洞的单晶铁相变过程，分析了孔洞尺寸对相变过程的影响。模拟结果表明：孔洞的存在降低了相变的阈值应力，加速了相变区域成核速率和相变传播速率;随着孔洞直径的增大，相变的阈值应力逐渐降低；孔洞也改变了相变的初始成核区域，使相变区域呈现出一个蝴蝶状的形貌；孔洞反射的稀疏波对相变成核区域的影响随孔洞体积增大而增大，导致孔洞周围出现大量的无序结构原子；孔洞体积对相变的影响也体现在了粒子速度空间分布上，压缩过程中孔洞周围出现的大量“热点”导致了更低的粒子速度空间分布。

Effect of void volume on phase transformation of iron under laser shock loading

The laser shock-induced phase transformation of iron with different volume voids has been investigated by means of molecular dynamics(MD)simulations.By comparing the perfect single crystal iron and the iron with different volume voids,the effects of the void volume have been presented.Simulation results show that the void decreases the phase transformation pressure,and the bigger void induces lower pressure;the increase of void volume speed up the nucleation and the expansion of transformation;the void also changes the initial nucleation district,and makes a butterfly shaped nucleation pattern.The influence of rarefaction wave in bigger void is stronger,which affects phase transformation nucleation sites,and brings on a lot of atoms with amorphous structures.The effect of void volume is also shown in the particle velocity profile by the production of a lot of "hot spots",which lower the particle velocity in the defective iron.