Study On Fusion Welding Technique To Dissimilar Alloys Of Magnesium Alloy And Aluminum Alloy

With the wider use of magnesium alloys, the problem of joining magnesium to aluminum was unavoidable to meet, especially in aviation, spaceflight, motorcar manufacture and chemical industry, and so on. The joining of dissimilar metal magnesium and aluminum can bring their own good characters into play together, which was very expected. The technique development of joining magnesium to the other metals restricts the range of magnesium use and accelerates the use of magnesium. The progress in joining dissimilar will make more design program feasible and give the designer more choices. What's more, the study on the joining dissimilar metal magnesium and aluminum alloys will make the flow in welding pool and element diffusion more obvious. As the most used welding method, fusion welding of magnesium and aluminum alloys with successfully was meaningful definitely.In this article, fusion welding method was adopted to joining dissimilar metal magnesium and aluminum alloys. All kinds of joining form was attempted, including materials (pure magnesium or magnesium alloy, pure aluminum or aluminum alloy), welding wire (magnesium welding wire, aluminum welding wire), welding method ( shielded metal arc welding, tungsten insert gas welding), current polarity (direct current straight positive DCSP, direct current reversed polarity DCRP, Alternative Current AC), joining form (lap joining, butting joining).According to the discussion about the binary diagram of magnesium and aluminum and the fracture analysis, it was proved that the major problem for fusion welding dissimilar metal magnesium and aluminum alloys was the intermetallic compounds of magnesium and aluminum which was very brittle. Two solutions were proposed in this article. For the first, interlay was added to avoid the contact of magnesium and aluminum and the produce of the intermetallic compounds; for the second, laser- TIG hybrid welding method was adopted to reduce the contact period of magnesium and aluminum and the mount of intermetallic compounds produced.The joining of magnesium and aluminum was made successfully by fusion- brazing welding method with interlay plating. It was found that tin can be plated on the magnesium plate through scratching and dipping into used as interlay. Tin interlay increased the wetability of magnesium and aluminum under the condition of arc, reduced the mount of intermetallic compounds produced, but not prevented the formation of intermetallic compounds completely. Therefore, the joint strength can only satisfy certain request.At the foundation of this, laser- TIG hybrid welding method was adopted to realize the joint with higher strength. The hybrid welding technique to join magnesium and aluminum was studied. The relationships between the microstructure, micro hardness and strength separately were analyzed. The reason for the strength improvement by the laser- TIG hybrid welding method was explained.