Microstructural evolution and mechanical properties of 7050 aluminum alloy modified via laser shock peening at different heat-treated states

Abstract

In this study, a combination of laser shock peening (LSP) and solid solution treatment (ST) was employed to modulate the microstructures of 7050 aluminum alloy, aiming to optimize mechanical properties and fatigue life. Microstructure observations showed that after LSP, the material experienced significant plastic deformation, introducing numerous dislocations, thereby enhancing the mechanical and fatigue properties of 7050Al. In comparison to a single LSP process, the process of ST prior to LSP is more advantageous for promoting the accumulation of dislocations and the transmission of shock waves, leading to the successful introduction of a deeper hardened layer exceeding 1 mm in depth. The migration and movement of dislocations result in the formation of subgrains, consequently initiating a mechanism for fine-grain strengthening. The surface hardness demonstrates a 30% increase, accompanied by a rise in residual compressive stress by 167 MPa. The yield strength and ultimate tensile strength exhibit notable increments of 23% and 17%, respectively, which attributed to the synergistic interplay of grain boundary strengthening, precipitation strengthening, and dislocation strengthening. Moreover, the fatigue life shows a substantial enhancement of 5.3 times.