中文摘要：

激光冲击强化利用离子体力学效应在金属表面形成较深的残余压应力层,细化表层晶粒,大幅度提高金属抗疲劳、抗磨损和抗腐蚀等机械性能。目前现有实验手段很难获取超高应变速率下塑性变形过程中微观结构演变的动态过程。本文采用LAMMPS软件对在2×10^7s^-1应变率,15 ns的加载时间,300 K温度下的多晶铜塑性变形行为进行分子动力学模拟,获得超高应变速率力学效应下多晶铜塑性变形微观结构的演变过程。超高应变率下力学效应作用下,形变孪晶是中层错能金属亚微米晶粒细化的主要变形方式。

英文摘要：

Laser shock processing utilizes mechanical effect with ultrahigh strain rate to generate deeper residual compressive stress and grain refinement layer, which improves mechanical properties, such as fatigue resistance,wear resistance and corrosion resistance. To date, it is very difficult to present dynamic microstructure evolution at ultra- short time（several ten nanoseconds） during the plastic deformation at ultrahigh strain rate using experimental method. At temperature of 300 K, a molecular dynamics of polycrystalline Cu with a loading duration of 15 ns at a strain rate of 2×10^7s^-1 is conducted to describe the microstructure evolution process with the LAMMPS soft. Under the mechanical effect of laser shock wave with a ultra-high strain rate, deformation twinning is the important microstructure of grain refinement of the alloys with medium stacking fault energy.