Effects of process parameters on microstructure and properties of aluminum alloy fabricated by friction extrusion additive manufacturing

Abstract

The friction extrusion additive manufacturing (FEAM) process of aluminum 6061-T651 cylindrical bar was successfully achieved by using independently developed solid-state friction extrusion additive equipment. The forming characteristics, microstructure features and mechanical properties of the final specimen obtained under different rotational speeds were comparatively analysed and discussed. The results show that for a given transverse movement speed of 300 mm/min, a fully dense single-channel double-layer specimen with thickness of 2 mm and 4 mm without any internal defects can be obtained by using the rotational speed of 600 r/min and 800 r/min respectively. The final specimen achieved under the higher rotational speed presents a flat interface, a narrower deposition layer, and a rougher surface because the effects of friction and extrusion experienced by the rotational shoulder are weakened during the deposition process. The plastic deformation and thermal cycle experienced by the bonding interface under 600 r/min are more significant than those under 800 r/min, and the grains are refined to 6.0 μm. The softening degree of the interface obtained under 600 r/min is more serious, and the hardness in this region is only 52.7%-56.2% of the value of the as-received feed rod, while this value can reach 56.0%-61.3% of the hardness of the base material. The final specimen attains a good comprehensive mechanical property. The ultimate tensile strength of the final specimen obtained under rotational speeds of 600 and 800 r/min can reach 66% and 70% of the value of the as-received feed rod respectively, while the percentage elongation after the break can reach 212% and 169% of the value of the base material respectively. The tensile properties of 6061 aluminum alloy prepared in this paper have obvious advantages compared with those of other Al-Mg-Si alloys fabricated by other well-developed additive manufacturing processes.

Keywords

• friction extrusion additive manufacturing
• 6061-t651 aluminium alloy
• bonding interface
• microstructure
• mechanical property