Dislocation density-based modeling of subsurface grain refinement with laser-induced shock compression

Laser shock peening (LSP) is an innovative surface treatment technique applied to improve the mechanical properties and surface microstructures of metallic components. This paper is concerned with prediction of the microstructural evolution of metallic components subjected to single or multiple LSP impacts. A numerical framework is developed to model the evolution of dislocation density and dislocation cell size using a dislocation density-based material model. It is shown that the developed model captures the essential features of the material mechanical behaviors and predicts that the total dislocation density reaches the order of 1014 m−2 and a minimum dislocation cell size is below 250 nm for LSP of monocrystalline coppers using the laser energy density on the order of 500 GW/cm2. It is further shown that the model is cable of predicting the material strengthening mechanism in terms of residual stress and microhardness of the LY2 aluminum alloy due to grain refinement in a LSP process with less laser energy densities on the order of several GW/cm2.