Effect of different wire composition on microstructure and properties of welded joint of 6XXX extruded alloys

Er/Zr and Sc/Zr were added into 5xxx series alloy to prepare welding wires, and the welding wires with the different compositions were used to weld 6xxx extruded alloy. The effects of different alloying additions on the microstructure and properties of welded joints were investigated. The results show that Al3(Sc1-x, Zrx) particles in the Al-Mg-Sc-Zr alloy welding wire can be used as heterogeneous nucleation site, which can effectively refine the grain structure and reduce the flow of low melting point elements to the PMZ of the joint. Compared with Al-Mg and Al-Mg-Er-Zr welding wire, the grain refinement in WZ is improved by 20.5 % and 13.8 %, and that in FZ is improved by 35.0 % and 8.1 %. At the same time, the refined grain structure can effectively eliminate the stress concentration of the joint and reduce the probability of liquation cracks. The joint welded by Al-Mg-Sc-Zr wire possesses the highest ultimate tensile strength of 249 MPa, while the joints welded by Al-Mg-Sc-Zr wire and Al-Mg wire possess ultimate tensile strength of 159 MPa and 128 MPa, respectively.