Study on the effect of Ar-He shielding gas on the weld formation, microstructure and mechanical properties of 5083 aluminum alloy weld

In this paper, the ER5356 aluminum alloy wire was used for cold metal transfer (CMT) welding of the 5083-H111 base metal with 20 mm thickness. The effects of four shielding gases, which were 100%Ar, 75%Ar+25%He, 50% Ar+50%He and 100%He on the weld formation, microstructure and mechanical properties were investigated using optical microscope, scanning electron microscope (SEM), x-ray diffraction (XRD) and mechanical testing. The results showed that with the increase of He in the shielding gas, the weld penetration and width increased, and the porosity in the weld zone decreased significantly; the microstructure changed from coarse dendrites to fine equiaxed crystals, and the microstructure was gradually refined; the tensile strength of deposited metal increased from 220 MPa to 270 MPa, with an increase of 22.7%, the tensile fracture was quintessential ductile fracture, and the hardness increased from 64.2 HV to 68.4 HV. The addition of He in the shielding gas can effectively inhibit the generation of pores and promote the beta-Al3Mg2 phase in the weld microstructure, thus improving the mechanical properties of the deposited metal.