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

The aim of the study was to investigate the influences of laser shock processing (LSP) on residual stress relaxation and metallographic structure evolution of 6061-T651 aluminum alloy at elevated temperature (up to 500 °C). Residual stress was determined by XRD with sin2ψ method, optical microscopy and TEM observations of the grain, and precipitated phase evolutionary process after LSP were carried out. The results showed that the effects of temperature on residual stress relaxation could be described, and the residual stress relaxation was analyzed precisely using the Zener–Wert–Avrami function. The main mechanism of stress relaxation between 200 °C to 300 °C was the dislocation slip and dislocation climb, and dynamic recovery was the main mechanism during the stress relaxation deformation between 400 °C to 500 °C. The evolution mechanism of grain and precipitated phase of 6061-T651 aluminum alloy between 25 °C and 500 °C was proposed. LSP still had a beneficial effect on residual stress at the elevated temperature 300 °C. Laser shock processing was the principal element for inducing the “metallographic variation” (MV) effect of 6061-T651 aluminum alloy at the elevated temperature.