Effects of laser shock processing on stress corrosion cracking susceptibility of AZ31B magnesium alloy

Laser shock processing (LSP) is a new technique for strengthening metals. The effects of LSP on the stress corrosion cracking (SCC) susceptibility of AZ31B magnesium (Mg) alloy were investigated. Water-immersed specimens of AZ31B magnesium alloy were shocked by Q-switched Nd: glass laser with a wavelength of 1064 nm. A fine-grained structure with an average sub-grain size of 5.8 μm was obtained after four laser impacts. Residual stress distribution as a function of depth was assessed by using X-ray diffraction technology. It was observed that with increasing the number of laser impacts, the compressive residual stress near the surface increased. The depth of the compressive residual stress induced by LSP exceeded 0.8 mm from the surface. SCC test in 1 wt.% NaOH solution showed that LSP retarded the SCC initiation and growth in AZ31B Mg alloy.