Microstructure and mechanical properties of aluminum alloy prepared by laser-arc hybrid additive manufacturing

The aluminum alloy with low density, high specific strength and excellent fracture toughness could meet the demand of lightweight large-scale manufacturing, and it has been extensively used in the field of aerospace, rail transit, and automotive. Laser-arc additive manufacturing has the advantage of stable forming process and fewer defects due to the addition of a laser, so it has the great potential advantage in additive manufacturing of aluminum alloy. In this paper, the aluminum alloy thin-wall was prepared by arc and laser-arc hybrid additive manufacturing, and the microstructure, the phase structure, microhardness, and tensile property were analyzed. The results show that the microstructure exhibited the periodic distribution characteristics in both additive manufacturing processes, and in the bottom, the middle, and the top area, it presents the coarse columnar, fine columnar, and fine equiaxed dendritic, respectively. In hybrid additive manufacturing, a laser affected zone with refinement grains appeared, and the size of the heat affected zone was obviously reduced. In both additive manufacturing processes, α-Al phase, Al-Si phase, and small amount of the Al-Si-Sr phase all were found, but the Al-Si-Sr phase was reduced in hybrid additive manufacturing. Although the element segregation was found in both additive manufacturing processes, the Sr became more uniform in hybrid additive manufacturing. The microhardness was increased from 52.0 ± 2.7 HV0.05 in arc additive manufacturing to 56.2 ± 2.9 HV0.05 in hybrid additive manufacturing. The tensile strength was increased from 143.6 ± 2.9 MPa in arc additive manufacturing to 164.4 ± 4.8 MPa in hybrid additive manufacturing, and the elongation is 20.8 ± 0.8% in the arc additive manufacturing and 19.6 ± 1.1% in additive manufacturing, respectively.