マグネシウム合金の超音波接合性およびろう付性に及ぼすハロゲン表面処理の影響

摘要

In this study, we applied a halogen surface treatment to the AZ31B magnesium alloy in order to reduce the surface film thickness, and investigated the effect of the treatment on the ultrasonic weldability and brazeability of the magnesium alloy. The following results were obtained. A halogen surface treatment by pickling the magnesium alloy into hydrofluoric acid successfully produced a thin and protective film of MgF_2 on the surface. The thickness of the surface film was less about one tenth and one third that of the specimen surfaces treated by wet polishing and dry polishing using emery paper, respectively. The ultrasonic weldability of the magnesium alloy was improved by the halogen surface treatment and the cross tensile strength of the weld increased. The weld strength showed about three times and two times that with the specimens treated by wet polishing and dry polishing using emery paper, respectively. Furthermore, ductile fracture mode was observed on the fracture surface of the weld with the halogen-treated specimen. Brazing filler metal hardly wet on the surface treated by wet polishing and dry polishing using emery paper, however, the brazing filler metal easily wet on the surface processed by the halogen treatment. The contact angle between the solidified brazing filler metal and the base metal was about 60 degree, and the halogen surface treatment improved the brazeability of the magnesium alloy.