Study On CMT Technique To Dissimilar Metal Between Magnesium Alloy And Aluminum Alloy

In this paper, weldability of dissimilar metal between AZ31B magnesium alloy and 6061 aluminum alloy was researched through CMT&MIG. Several different joint types were tried with ER4043 and HS201 as weld filler metals. Well welding joints were got respectively through the analysis and adjustment of welding parameters. The relation of main parameter and weld appearance was got. Welding mechanism of Mg-Al dissimilar metals with aluminum and copper wire was revealed respectively through analyzing weldability.Mechanical property test show that the biggest joint tensile strength of aluminum and copper wire were 3.24MPa and 34.7MPa. The crack occured in the Mg-side fusion zone, hardness test showed that the hardness was high here. The feature of the fracture which was analyzed by macrography, SEM and EDAX was brittle fracture. There were many intermetallic compounds in the fracture. These compounds were rigid, distributing continuously in the fusion zone,was the main influence factor of joint strength.Joint analysis were carried out by using metallographical, SEM and EDAX. The results showed that experiment with aluminum welding wire under the optimum parameters had low heat input, but a layer of intermetallic compounds of Mg₂Al₃ and Mg₁₇Al₁₂was still found in Mg-side fusion zone with 35μm wide at least. Quantity of intermetallic compounds was reduced with the decreasing of welding variables. Welding joints with copper wire can stop the direct contact of Mg and Al, eliminated the Mg-Al intermetallics. Because of the contrast in density of Mg, Al and Cu, the fusion area on either side had the irregular shape, some parts render interlaced and mixed whirlpool-like. Al-side fusion area produced a variety of Al-Cu intermetallic compounds, organization of welding area was Cu-based solidsolution, Mg-side fusion area had Cu2Mg and CuMg₂ intermetallic compounds. For non-homogeneous distribution of welding temperature field, the thickness of the compounds was different. The content of Mg,Al,Cu was changed with gradient. The group element type, content and distribution in welding area were also changed with the distribution of elements.