晶界对纳米多晶铝中冲击波阵面结构影响的分子动力学研究

Molecular dynamics investigation of shock front in nanocrystalline aluminum: grain boundary effects

用分子动力学方法研究了纳米多晶铝在冲击加载下的冲击波阵面结构及塑性变形机理.模拟研究结果表明:在弹性先驱波之后,是晶界间滑移和变形主导了前期的塑性变形机理;然后是不全位错在界面上成核和向晶粒内传播,然后在晶粒内形成堆垛层错、孪晶和全位错的过程主导了后期的塑性变形机理.冲击波阵面扫过之后留下的结构特征是堆垛层错和孪晶留在晶粒内,大部分全位错则湮灭于对面晶界.这个由两阶段塑性变形过程导致的时序性塑性波阵面结构是过去未见报道过的.

The shock front structure and the plastic deformation of nanocrystalline aluminum under shock loading are investigated by using molecular dynamics simulations. The simulation results show that： after the elastic wave was generated,the grain boundary sliding and deformation dominated the early plastic deformation mechanisms,then the partial dislocations were nucleated at the deformed grain boundaries and spread within the grains,finally the process of stacking faults,deformation twins and full dislocation formation in the grain dominated the latter stage of the plastic deformation. The structural characteristics after the shock front swept over is that the stacking faults and the deformation twins are left in grains,and the majority of the full dislocations are annihilated at the opposite grain boundaries. It is reported for the first time that the shock front structure reflects the time sequence of two different plastic deformation mechanisms in nanocrystalline aluminum.