Abstract:An optimized microcrystalline wax-based feedstock was used to fabricate 3D 7075 Al alloy through metal fused deposition modeling (Metal-FDM). The affinity between the wax-based binders and powders was evaluated by a hot-press experiment. The phases, morphology evolution, tensile strength and friction performance of the sintered Al alloy were studied. The feedstock displayed shear-thinning behavior for a smooth extrusion process, resulting in a satisfactory surface quality and minimal stacking pores in the 3D structure. The morphology evolution of Al alloy sintered in nitrogen could be divided into four stages, including the precipitation of fine Mg₂Si and Si at 500 °C, appearance of Mg₂Si phase over 560 °C, nitridation of the oxide layers on alloy powders and enhanced grain growth via the diffusion process over 620 °C. The 3D 7075 Al alloys achieved a high relative density of 95%, exhibiting a tensile strength ranging from 120 to 141 MPa and a tensile strain of 1.0%-2.5%.

Key words: 7075 aluminum alloy; metal fused deposition modeling; metal injection molding; microstructure evolution; mechanical property