Study On The TIG Welding Of Dissimilar Magnesium Alloy And Copper

The joining of dissimilar magnesium alloys to copper is of great industrial significance as it allows design engineers to take advantages of the excellent property sets of both materials. To date, no reports have been published on the welding of the two dissimilar metals.AC TIG welding and TIG welding with pulse were adopted to join AZ31 plates. The electric arc was studied with high speed camera and the infrared thermal imaging system. It was found that TIG welding with pulse had a more quick cooling rate. The crystal grains in the heat affected zone were relatively fine and the heat affected zone was smaller when welding with pulse. The joint with pulse had an improved intensity.The dissimilar materials are difficult to weld on account of the formation of brittle intermetallic phase and wide difference in physical and mechanical properties. The melting point of magnesium alloy is 649℃ and the melting point of copper is 1084℃, so it is difficult for the two metals to melt at the same time and to form a joint. In this paper, dissimilar magnesium alloy and copper were lap welded by TIG welding, Intermetallic compounds were observed in the interfacial region. It was shown that the intermetallic compounds were the cause of embrittleness of the weld. The strength is about 23 MPa. The strength of joints is not badly influenced only when the thickness of intermetallic compound is very thin, so it is difficult to improve the strength by controlling the thickness in the melting welding, because the heat input is concentrated in the melting welding.With iron plate as interlayer, the embrittleness of joint was obviously decreased, the tensile strength of the joint are high compared with those without iron plate. The strength is about 75 MPa. It was found that iron plate joined copper with solid solution and iron plate joined magnesium alloy together with interatomic force, The weld fractured at the interfacial region between iron plate and magnesium alloy. Metallic oxides were observed in the interfacial region between iron plate and magnesium alloy. It was the main reason influenced the strength of weld.