Dynamic dislocation response in aluminum single crystals under multiple laser peening: A physics-based crystal plasticity study

Abstract

Understanding dislocation dynamics at high strain rates is critical for analyzing the deformation behavior of metals under laser peening (LP). However, power law crystal plasticity models cannot capture the dislocation motion and evolution during high-dynamic laser shock loading. This study simulates the dislocation response of aluminum single crystals under laser peening based on a crystal plasticity finite element (CPFE) model incorporating thermal activation and phonon drag. After calibrating the unknown parameters with the experimental data from the split Hopkinson pressure bar (SHPB) and plate impact tests, we simulate the dynamic deformation behaviors in aluminum single crystals subjected to single and multiple laser shocks. The results indicate that dislocation patterns are axisymmetric during laser irradiation, as the dislocation velocities are close to limits, decreasing the differences among slip systems. The dislocation patterns become anisotropic during pressure relaxation as dislocations slip along the most susceptible direction. Moreover, phonon drag introduces additional slip resistance during the first laser shock, while peak resolved shear stress decreases in multiple laser shocks. The primary reason is that a higher mobile dislocation density can reduce the average dislocation velocity. Furthermore, the increment in dislocation density increases in the triple laser shocks because dislocation evolution is dominated by multiplication, the rate of which is proportional to the initial dislocation density. Additionally, the low-symmetry structure can cause a higher multiplication rate, introducing a higher dislocation density in 〈111〉-oriented single crystals than in 〈001〉 and 〈011〉. This investigation implies that the initial dislocation density and lattice orientation play crucial roles in the high dynamic deformation and microstructure evolution under LP.