Effect of welding wire composition on microstucture and properties on Al/Cu laser welding-brazing joints

The laser welding-brazing connection of 2A16 aluminum alloy and T2 copper was successfully realized by adding Zn-Al welding wire. The microstructure of the joints was characterized by the scanning electron microscope and energy dispersive spectrometer. Meanwhile, the effects of three kinds of welding wire of Zn-2%Al, Zn-5%Al and Zn-10%Al on the joint formation, microstructure and machanical properties were investigated. Results indicated that the Al/Cu laser welding-brazing joints was mainly composed of CuZn phase, Al₂Cu phase, Al₄Cu₉ phase, CuZn₅ phase, α-Al solid solution, β-Zn solid solution, and α-Al+β-Zn eutectic structure. The wettability of the molten metal was increased with the decrese of Zn content in the welding wire. When the Zn-10% Al wire was used as filler metal, the diffusion reaction at the interface was gradually sufficient, and the thickness of the interface layer gradually increased to 7.02 μm. The “mechanical occlusion” is formed between the welding zone and the interface layer, which improves the machanical properties of the joint. The maxmuim tensile strength is up to 204 MPa when Zn-10% Al welding wire is used. The microhardness from Cu side to Al alloy side of the Al/Cu joints is increased first and then decreased. The highest microhardness is occurred at interface layer, reaching 330.1 HV.