Microstructural evolution and properties analysis of laser surface melted and Al/SiC cladded magnesium-rare earth alloys

The influence of laser surface melting and Al–SiC cladding on the microstructure, mechanical, and electrochemical properties of Mg-Gd-Y-Zn-Zr alloys was studied. The presence of α-Mg, Mg₅(Gd,Y,Zn) and Mg₁₀(Y,Gd)Zn phases in the melted layer and Al₄C₃, SiC, Si, Mg₂Si and Mg₁₇Al₁₂ phases in cladded layer were confirmed from XRD results. Microstructures and chemical composition results also indicated a refined microstructure and re-distribution of the second phase. The finite element model (FEM) temperature profiles confirmed the variation in cooling rates of melted and cladded zones which supported the achieved microstructures. The microhardness values across the melted and cladded layers were significantly increased as a result of grain refinement, re-distribution of the second phases of the melted layer and the presence of hard-ceramic phases in the cladded layers. Potentiodynamic polarization studies revealed a decrease in corrosion current density (i_corr) value and enhanced corrosion resistance of the laser melted alloy. The Al/SiC cladded layer showed a nobler shift in corrosion potential (E_corr) and a significant decrease in i_corr value due to the thick ceramic layer which acts as a barrier to the corrosive attack.