Effect of Laser Surface Melting Parameters on Surface Integrity, Microstructure, Phase Particles Distribution and Corrosion Resistance of WA-DED AZ31 Magnesium Alloy

Abstract The feasibility of laser surface melting (SLM) as a surface modification of WA-DED deposited AZ31 Magnesium alloy was experimentally investigated. Emphasis was placed on identifying the effects of independent critical LSM process parameters, such as laser power, scan speed, and hatch distance, and their corresponding laser energy densities on surface integrity, including roughness, wettability, microstructure, phase formation, microhardness, and electrochemical corrosion of WA-DED deposited AZ31 Mg alloy. The optimized LSM process parameters were a laser power of 50 W with a scan speed of 700 mm/min, and a hatch distance of 33 %, and a calculated laser energy density (LED) of 7.14 J.mm−2. The surface roughness of the WA-DED specimen increased to 5.5 μm after SLM at an LED of 7.14 JJmm−2; however, this poor surface roughness exhibited increased surface wettability. Moreover, at the same LED, the microstructure of the surface is refined to 4 μm, up to a depth of 297 μm from the surface, and HAGB dominates the grains, with an orientation towards the 0001 basal plane. Therefore, the surface hardness increased to 142 HV. The intermetallic phases of Al12Mg17 and Al8Mn5 were refined up to 50 nm with uniform distribution in the α-Mg matrix. The refined phases reduced the area ratio of the cathode (Al12Mg17) and anode (α-Mg), which slowed down the initiation of corrosion pits, resulting in increased corrosion resistance to 0.435 mm.y−1.