Metallographic structure evolution of 6061-T651 aluminum alloy processed by laser shock peening: Effect of tempering at the elevated temperatures

► LSP is the principal element inducing the “metallographic variation” (MV) at elevated temperature. ► The affected layer has a higher magnitude of residual compressive stress between 25 °C and 300 °C. ► The main mechanism of stress relaxation between 200 °C and 300 °C is the dislocation slip and climb. ► Recovery creep is the main relaxation mechanism between 400 °C and 500 °C.