Laser cladding of a Mg based Mg–Gd–Y–Zr alloy with Al–Si powders

Abstract

In the present work, a Mg based Mg–Gd–Y–Zr alloy was subjected to laser cladding with Al–Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5wt.%) aqueous solution. The corrosion potential was increased from −1.77V for the untreated alloy to −1.13V for the laser clad alloy with scanning rate of 2mm/s, while the corrosion current density was reduced from 2.10×10−5Acm−2 to 1.64×10−6Acm−2. The results show that laser cladding is an efficient method to improve surface properties of Mg–Rare earth alloys.