Development of High Corrosion- and Wear-Resistant Al-Si Alloy Coating on AZ80 Mg Alloy by Hot Extrusion

Mg alloys have been known as the lightest metal materials. However, their practical use is strictly limited due to their poor corrosion and wear resistances. To improve those resistances simultaneously, the present authors have fabricated an Al-Si alloy coating on a Mg alloy substrate by hot extrusion. The Al-Si alloy for coating material was prepared by powder metallurgy and casting processes. An AZ80 Mg alloy billet, a compacted Al-Si alloy plate or a cast Al-Si alloy plate, a die and rams were put in bottom of an extrusion container, and the Mg alloy and the Al-Si alloy were indirectly extruded together. By the hot extrusion, the Mg alloy was successfully coated with the Al-Si alloys prepared in both the powder metallurgy and the casting. The Al-Si alloy-coated Mg alloys showed a high corrosion resistance in a 1.0 mol/L HCl aqueous solution. Also, the wear resistance of the Mg alloy was significantly improved by the Al-Si alloy coating layers. The highest wear resistance was obtained with a cast Al-20 vol.%Si alloy coating layer. The coating improved the wear resistance by 50% compared with the AZ80 Mg alloy.