Aluminum Coating on Magnesium-Based Alloy by Hot Extrusion and Its Characteristics

Although magnesium-based alloys have excellent mechanical properties, their very poor corrosion resistance limits their application. It has been considered that aluminum coating would solve this problem because aluminum has an excellent corrosion resistance. This study proposes a superior coating method based on the hot extrusion process. An aluminum plate set between the magnesium-based alloy billet and an extrusion die having an inversely angled face was successfully extruded together with the magnesium-based alloy billet and, as a result, the aluminum coated the extruded magnesium-based alloy with a uniform thickness. Corrosion tests based on dipping in HCl aqueous solution and potential measurement in NaCl aqueous solution showed that the extruded sample exhibited the same corrosion resistance as the aluminum. A three point bending test at room temperature resulted in fracture after plastic deformation, while at high temperatures between 100 and 300 degrees C plastic deformation without fracture occurred. Notably, the intermetallic compound layer formed on the boundary between the magnesium-based alloy substrate and the aluminum coating layer plastically deformed without cracking at 300 degrees C. A tensile test at room temperature resulted in a UTS of about 320 MPa and a plastic elongation of 18%. [doi:10.2320/matertrans.M2012026]