Investigation of critical processing parameters for laser surface processing of AZ31B-H24

The abundance of electrochemically noble secondary phases present in the heterogeneous microstructure of Mg alloys leads to accelerated corrosion of the surrounding Mg matrix by micro-galvanic coupling. The extent of disintegration of the large Al-Mn intermetallic particles (IMPs) present in the Mg alloy AZ31B was investigated with respect to laser processing parameters of a nanosecond pulsed Excimer laser. The parameters investigated were overall pulse per area, laser fluence (J/cm2), and background pressure of Ar gas. Observation of resulting IMP dissolution, morphology, and subsequent reduction in cathodic corrosion kinetics are reported. Laser fluence and pulse per area were observed to have the largest impact on the corrosion kinetics and overall dissolution of IMPs, with the highest fluence (1.5J/cm2) and 100 or above pulse per area exhibiting an order of magnitude reduction in cathodic kinetics. •Investigation of processing parameters for optimized secondary phase dissolution•Laser fluence above the ablation threshold crucial to lowering cathodic kinetics•Progressively slower cathodic kinetics was observed with more pulses per area.•The absolute lowest cathodic kinetics was for specimens processed at 10Torr.