铁的冲击相变机制的分子动力学研究

 用分子动力学方法模拟计算了在冲击波加载条件下，单晶铁中的结构相变（由体心立方结构α相到六角密排结构ε相），相互作用势采用铁的嵌入式原子势（EAM），单晶铁样品的尺寸为28.7 nm×22.9 nm×22.9 nm，总原子数为1.28×10⁶个。通过推动一个运动活塞对静止靶的作用来产生冲击压缩，加载方向沿单晶铁的[100]晶向。通过对原子位置的追踪，揭示了铁的冲击相变机制，计算结果表明相变机制包括两步：首先是在{011}面上的原子受到沿〈100〉晶向的压缩，使{011}面转化成正六角形密排面；然后是在{011}面上原子沿〈0-11〉晶向的滑移，完成由bcc结构到hcp结构的相变。同时发现滑移面只出现在与冲击波加载方向平行的(011)和(0-11)面上。

Phase Transformation Mechanism of Single Crystal Iron from MD Simulation

Shock-induced phase transformation (body-centered cubic α phase to hexagonal close-packed ε phase) in single crystal iron has been investigated by means of molecular dynamics (MD) simulations using an embedded atom method (EAM) potential. The simulated dimension is 28.7 nm×22.9 nm×22.9 nm in size with 1.28×10⁶ atoms. The shock wave is generated by using a piston impact on the sample along the [100] direction. By analyzing the motion history of atoms under shock compression, the phase transformation mechanism has been outlined. The simulation results show that the phase transformation mechanism contains two steps: the atoms on the {011} planes are compressed along the 〈100〉 direction to form a hexagon in the first step, and then the atoms on {011} planes in the 〈0-11〉 direction are slipped to create the hcp structure in the second step. The results also show that the slip planes are only the (011) and (0-11) planes which are parallel with the shock wave propagation.