Microstructure and mechanical properties of high Mg content Al-Mg alloys by double wires gas tungsten arc additive manufacturing process

As the properties of the high strength Al-Mg alloy component is difficult to be improved, a new gas tungsten arc additive manufacturing process was proposed to increase the Mg content in Al-Mg alloy component. Two heterogeneous wires were synchronously fed into the same molten pool, using ER5356 as the main melting wire, and a small amount of AZ31 as the auxiliary melting wire. Five groups of thin wall components with high Mg content were deposited by adjusting the ratio of the feed speed of the two wires. The microstructural characteristics, evolution and mechanical properties of the components were investigated. The results show that with the wire feed speed ratio between AZ31 and ER5356 increasing from 1:10 to 1:3, the α(Al) phase transforms from equiaxed grains to dendrites, and the β-Al3Mg2 phase transforms into divorced eutectics. The average grain size increases from 17.26 μm to 21.35 μm and then decreases to 14.69 μm, meanwhile, the content of the β phase and the eutectic structure increases. Compared with the Al-Mg alloy component deposited by traditional single wire feed gas tungsten arc additive manufacturing process, the micro Vickers hardness of the high Mg content components reaches 114.93 HV on an average, increased by 64.2% and the ultimate tensile strength reaches 342 MPa, increased by 24.8%. © 2022, China Science Publishing & Media Ltd. All right reserved.