中文摘要：

采用离散元方法，结合基于无扩散相变的两相模型、热力学相容的自由能函数与有限速率相变动力学方程，模拟了α铁的冲击相变过程。计算得到了铁的相边界及冲击Hugoniot关系，并对多晶铁的冲击相变过程进行了模拟。研究结果表明：冲击波的波面不规则程度随传播距离的增加而增加，大晶粒模型内冲击波前沿的不规则程度更高；多晶金属内的相变为非均匀相变，相变首先发生在晶粒边界处，以指状向晶粒内部生长；对于多晶冲击相变过程进行了统计，得到了冲击相变的局部压力-相变质量份额曲线。

英文摘要：

Numerical simulations on α-iron and polycrystalline iron are conducted using discrete element method （DEM） combined with undiffused two-phase transition model, thermodynamic consistent free energy function, and phase transition kinetics of relaxation equation. The phase boundary and Hugoniot relation are obtained through numerical simulation. The simulation result of polycrystalline iron shows that the shock-front irregularities rise when the propagation distance of shock wave increases; and the shock- front is more irregular in the coarse grain model than in the fine grain model; the phase transitions in the polycrystalline are heterogeneous, and the transitions are observed first along grain boundaries. The curve of local average pressure and transformed mass fraction is obtained.