Friction Stir Processed High Purity Mg Coating on MgZnYNd Alloy with Improved Corrosion Resistance

In this study, a series of high purity Mg coating on Mg-2Zn-0.46Y-0.5Nd alloys were successfully prepared by friction stir processing technique at different tool travelling speeds. For all the samples, the high purity Mg coating were strongly bonded with the Mg-2Zn-0.46Y-0.5Nd alloy substrate, and no intermetallic compounds were found at the interface. Along the interface, a mixed structure consisting of coarse pure Mg and fine Mg-2Zn-0.46Y-0.5Nd grain structure were formed due to the upward flowing of the materials from the substrate. The corrosion current density of the high purity Mg coated Mg-2Zn-0.46Y-0.5Nd alloy in 3.5% NaCl solution reached 4.8063 x 10(-6) A/cm(2), which was much lower than that of the friction stir processed Mg-2Zn-0.46Y-0.5Nd alloy without coating (2.0139 x 10(-5) A/cm(2)). In the high purity Mg coating, galvanic corrosion was not easy to form, which greatly improved the corrosion resistance of the substrate.