Effect of laser shock times on electrochemical performance of AZ31 magnesium alloy

In order to study effect of laser shock times on corrosion resistance of AZ31 magnesium alloy, AZ31 magnesium alloy was processed at different laser shock process (LSP)times by Nd:glass laser with pulse width of 23ns. Microstructures were observed by transmission electron microscopy. Polarization curves and electrochemical impedance spectroscopy were obtained in NaCl solution with 0.035 mass fraction by means of electrochemical measurement technique. The results show that plastic deformation with ultrahigh strain rate happens because of laser shock wave at the surface layer of AZ31 magnesium alloy. High density dislocations with intersect and entanglement of twin crystal exist in the crystal grains and the dislocations led to grain refinement. Polarization curves and electrochemical impedance spectroscopy shows that corrosion potential of AZ31 increases up to 267mV after the first laser shock. Corrosion current increases slightly, reaction resistance increases and corrosion resistance is improved significantly. With the increase of impact times from LSP, corrosion resistance of alloy is not improved significantly. The corresponding impedance spectroscopy has the same conclusion with polarization curves. The study is helpful for improving the corrosion resistance of magnesium alloy during laser shocking processing.