Research On Production Process And Welding Property Of Al-5.4Si-0.5Mg Aluminum Welding Wire

A1-12.7Si-0.7Mg alloy was a newly developed heat-treatable wrought aluminum-silicon alloy with high strength and excellent plasticity, while the composition design and manufacturing processes of its special welding wire was just beginning. In this paper, Al-5.4Si-0.5Mg alloy welding wire was prepared through semi-continuous casting, hot extrusion and cold drawing processes as the special filler wire to weld A1-12.7Si-0.7Mg alloy by TIG welding. Then the as-welded joints were treated in different solid solution and artificial aging treatment conditions. Microstructures of these joints with and without heat treatments were subsequently observed by OM, SEM and TEM and mechanical properties of these joints were tested by the microhardness tester and the tensile testing machine to evaluate the weld quality. A comprehensive analysis was carried out on the welding performance and heat-treatment effect of A1-5.4Si-0.5Mg alloy welding wire, and the results were actually meaningful for promoting application of A1-12.7Si-0.7Mg alloy.The results showed that:1. The self-made O1.2mm Al-5.4Si-0.5Mg welding wire which was produced through semi-continuous casting, hot extrusion and cold drawing processes had a smooth finish and homogeneous microstructure. Welded joints using the as-produced filler wire had a fine appearance of weld.2. After solid-solution and aging treatment, the eutectic silicon phase transformed from a short rod-like structure to a fine granular morphology and diffused in Al matrix, the Al matrix phase transformed from columnar dendrites to fine equiaxed grains in the weld zone. Meanwhile, the columnar grains disappeared in the fusion zone and some black ultra-fine Mg2Si phase, grey AlFeSi phase and eutectic Si phase dissolved into the matrix in the heat affected zone. The silicon particle size and Al grain size increased gradually as the solid-solution temperature increased and there were more precipitate of the Mg2Si phase when the aging time increased.3. After solid-solution and aging heat-treatment, the microhadness in different zones of the joints increased significantly and tended to be uniform finally. The maximum microhardness could be obtained when the joints were solution treated at 540 ? and artificially aged for 3 hours.4. The ultimate tensile strength of the untreated joints was 195 MPa which reached nearly 100% of the base material and the elongation of the joints was 8%. Tensile strength of the treated joints increased significantly after solid solution and artificial aging treatment, while the elongation decreased progressively. After solid-solution at 540 ? for 1.5 hours and aging at 180? for 3 hours, the ultimate tensile strength and the elongation of the joints was 381 MPa and 4%, respectively. The increase of the treated joints in tensile strength was nearly 96 percent of the untreated ones, and the heat treatment had a remarkable effect on strengthening of the welded joints.5. The novel Al-5.4Si-0.5Mg welding wire showed an excellent weldability and the as-welded joints proved to be heat-treatable.