Study on laser surface melting of AZ31B magnesium alloy with different ultrasonic vibration amplitude

The laser surface melted layers were fabricated on AZ31B magnesium alloy by ultrasonic vibration-assisted using with different vibration amplitude. Microstructural evolution and corrosion resistance were studied systematically. The uniformity and compactness of the microstructure can be get further improved with the increase of vibration amplitude, while the coarse microstructure is observed at an even higher vibration amplitude. The melted layer with a reasonable vibration amplitude at the maximum outputs of 80% possess the highest microhardness, and the lowest corrosion current density as well as the minimal corrosion rate than the substrate. The results of electrochemical impedance spectra (EIS) and corrosion morphology are in agreement with potentiodynamic polarisation measurements, the charge transfer resistance (Rct) and corrosion area of the sample at 80% vibration amplitude are highest and smallest, respectively. Experimental results revealed that the melted layer fabricated at 80% of the maximum vibration amplitude output value exhibit the best anti-corrosion performance.