Molecular dynamics simulation of the effect of shock velocity on microstructure and mechanical properties of laser shock peening of polycrystalline <i>γ</i>-TiAl

Abstract The molecular dynamics method and piston impact method are employed to study laser shock peening (LSP) of polycrystalline γ -TiAl alloys at various shock velocities. The purpose of this paper is to reveal the dynamic evolution mechanism of shock wave propagation characteristics and microstructure of γ -TiAl alloy during LSP, and to elucidate the effect laws of different shock velocities on dislocation motion, phase transformation and defect evolution. Results show that, during the loading stage, atomic velocity is affected by elastoplastic segregation, and the shear stress is influenced by grain boundaries and dislocations, with plastic deformation primarily expanding inward from grain boundaries. During the holding stage, phase transformation from γ to α 2 occurred at 0.5 km s −1 and 0.8 km s −1 , both exhibiting deformation twins. At 0.8 km s −1 , dislocations concentrated at grain boundaries; in other modes, they were more distributed in stacking faults. During the unloading stage, dislocations stabilized after elastic recovery. Post-LSP, polycrystalline γ -TiAl displayed small equiaxed grains, twins, and γ / α 2 lamellar structures with improved tensile properties and hardness—indicating significant potential for enhancing γ -TiAl alloy properties through this technology. This study provides an atomic-scale basis for the dynamic evolution mechanism of the microstructure of γ -TiAl alloys strengthened by LSP, which breaks through the limitations of the experimental methods for the characterization of dynamic processes.