Abstract: To explore the effect of preheating temperature on the bonding quality between arc additive magnesium alloy and substrate, AZ91 magnesium alloy samples are prepared using arc additive technology under the conditions of maintaining the substrate at room and preheating temperature（25 ℃） and preheating（100 ℃, 200 ℃, 300 ℃, 400 ℃）. The macroscopic forming of the samples and the microstructure and mechanical properties of the substrate bonding position and the bottom region are analyzed in depth. The study found that the surface of the obtained sample components is smooth, but with the increase of preheating temperature, slight collapse occurred at both ends of the components, and the microstructure showed equiaxed crystal characteristics, mainly composed of α-Mg, β-Mg₁₇Al₁₂, and η-Al₈ Mn₅. At room temperature（25 ℃）, the fusion between the deposited layer and the substrate is poor, with cracks and porosity defects, and the shear strength of both is only 53.4 MPa; After preheating, the bonding between the deposited layer and the substrate is significantly improved, and the shear strength increased to 144.7 MPa at 400 ℃. The average hardness decreases from 76.9 HV to 60.9 HV as the preheating temperature increases. Meanwhile, the mechanical properties of the magnesium alloy bottom area samples obtained by arc additive manufacturing are superior to those of traditional die cast magnesium alloys. With the increase of preheating temperature, the tensile strength first increases and then decreases, and the elongation at break linearly increases.

Key words: preheating temperature, wire arc additive manufacturing, AZ91 magnesium alloy, microstructure, mechanical properties