The Effect of Laser Shock Peening on the Microstructure and High-Temperature Mechanical Properties of AZ31 Alloy

Laser shock peening (LSP) is a promising surface technique to improve mechanical properties. The effect of LSP on the microstructure, high-temperature mechanical properties and residual stress of the AZ31 alloy was investigated by 3D profilometer, transmission electron microscopy, x-ray diffraction, Vickers tester, respectively. The results reveal that both nano-grain layer and compressive residual stress layer were formed in the surface of AZ31 alloy after LSP treatment. The strength of AZ31 alloy is remarkably improved by LSP as the tensile temperature is below 200 °C. While LSP has no obvious effect on the mechanical properties as the tensile temperature is above 300 °C. Fractographs of as-rolled and LSPed AZ31 alloys indicate that quasi-cleavage fracture is the dominant fracture model as the tensile temperature is below 200 °C, while ductile fracture is dominant fracture model as the tensile temperature is above 300 °C. Additionally, the strengthening mechanism of the mechanical properties of the AZ31 alloy by LSP treatment was analyzed in detail.