Effect of laser cavitation peening on surface integrity and electrochemical corrosion behavior of magnesium alloy

A novel method of laser cavitation peening (LCP) was employed to process the AZ31B magnesium (Mg) alloy. The processes of bubble evolution and LCP impact were investigated. The influences of LCP on the surface integrity (surface morphology and roughness, microhardness, residual stress, phase) and electrochemical corrosion behavior of AZ31B Mg alloy under various processing parameters (laser energy and defocusing amount) were systemically investigated. The results show that the laser breakdown extent, bubble radius, pulsation period, and bubble energy increase with the increase of laser energy. The maximum radius of the cavitation bubble decreases significantly as the defocusing amount increases from 0 mm to 2 mm. LCP enhances the microhardness and introduces the compressive residual stress into the surface layer of the AZ31B, but it also increases the surface roughness. The surface morphology of LCP processed AZ31B has significant differences under various processing parameters, and the microhardness and residual stress increase as increasing the laser energy. LCP improves the anti-corrosion of AZ31B effectively except for the condition of 200 mJ laser energy. The best defocusing amount for enhancing the surface integrity and electrochemical performance of AZ31B by LCP processing is 1 mm, and the higher laser energy has the better corrosion resistance.