Surface microstructure and property modifications in a Mg-8Gd-3Y-0.5Zr magnesium alloy treated by high current pulsed electron beam

Abstract

In the present study, the effect of high current pulsed electron beam (HCPEB) surface treatments on the microstructure, composition, stress states and properties of a Mg-8Gd-3Y-0.5Zr alloy has been investigated. The surface layers showed different features in microstructure and residual stress states under different number of pulses. Such a variation is essentially due to the different level of the dissolution of β-Mg5(Gd,Y) particles in remelted layers and the impact from thermal stresses generated by HCPEB treatments. The results have shown that, after 5 pulses of HCPEB treatment, maximum hardness in the surface layer of the sample was increased by 35% and the corrosion rate in 3.5 wt% NaCl water solution was reduced by 30% as compared with those of the untreated sample. The formation of nano structured cells of Mg-RE solid solution and β-Mg5(Gd,Y) nano precipitates, together with the residual compressive stress in the surface layer of the 5 pulsed sample account for the increased microhardness and improved corrosion resistance of the HCPEB treated Mg-8Gd-3Y-0.5Zr Mg alloy.