Microstructural and defect evolution during WAAM resulting in mechanical property differences for AA5356 component

The development of wire arc additive manufacturing (WAAM) provides a new solution for manufacturing aluminum alloy (AA) components used in lightweight mobile heat storage equipment. AA5356 component is deposited at a wire feed speed of 7.3 m/min and a welding speed of 1000 mm/min with the cold metal transfer-advanced mode. Adjusting the deposition angle to 90° between layers can enhance the microstructure and mechanical properties of the WAAM AA5356 component. The quasi in situ idea is proposed to investigate the microstructures, defects evolution, and mechanical property differences during the successive deposited. The results showed that the average grain size increases with increasing deposition height. The microstructures are uniform, except for the interlayer with refined equiaxed grains. The porosity increases gradually from 1.23% to 1.75% as the deposition height increases, and the average diameter of the micropores increases from 16.54 μm to 21.91 μm. In contrast, the microhardness of WAAM AA5356 component gradually decreases, and the microhardness of the interlayer area is higher than that of the innerlayer. The ultimate tensile strength, yield strength, and elongation are 286 MPa, 142 MPa, and 23%, respectively. Compared with casting AA5356, the ultimate tensile and yield strengths are 32.2% and 40.5% greater, respectively, while the elongation is almost equal. As the grain sizes increase with the heat accumulation effect, the microhardness decreases and the elongation increases while the tensile strength decreases, mainly due to the high proportion of large micropores in the top area.