Toko Tokunaga

Corrosion Resistance and Tensile Property of Al-Coated Mg-Li Alloy Produced by Hot Extrusion

Al-coated Mg-Li alloy rods and plates having a homogeneous coating layer of 180μm in thickness have been produced by hot extrusion of Mg-Li alloy billets together with Al disks. The Al-coated Mg-Li alloy exhibits an excellent corrosion resistance in a weight-loss test with a 0.5 mass% HCl aqueous solution, and it has been revealed by a potentiometric corrosion test with a 3 mass% NaCl aqueous solution that the Al-coated Mg-Li alloy has the same electric potential as that of pure Al. Al-coated Mg-Li alloy sheets produced by hot forging of the extruded plates exhibits good elongation of 22 %, 40 % and 130 % at room temperature, 200 °C and 300 °C, respectively.

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 alloy billet and an extrusion die having an inversely angled face was successfully extruded together with the magnesium alloy billet and, as a result, the aluminum coated the extruded magnesium 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°C plastic deformation without fracture occurred. Notably, the intermetallic layer formed on the boundary between the magnesium alloy substrate and the aluminum coating layer plastically deformed without cracking at 300°C. A tensile test at room temperature resulted in a UTS of about 320 MPa and a plastic elongation of 18%.