Microstructure refinement and mechanical properties enhancement of wire and arc additively manufactured 6061 aluminum alloy using friction stir processing post-treatment

Microstructure refinement and mechanical properties enhancement were achieved by utilizing friction stir processing (FSP) as post-treatment to 6061 aluminum alloy fabricated by wire and arc additive manufacturing (WAAM). FSP led to a significant microstructure refinement and porosity reduction. The average grain size decreased from approximately 128 mu m to about 5 mu m. Because of the refined microstructure and the reduced porosity, the average microhardness, yield strength, and ultimate tensile strength increased by 31.5 %, 23.3 % and 6.0 %, respectively. The elongation difference between the horizontal and vertical direction was reduced from 4.5 % to 1.4 %. The properties anisotropy caused by delamination was weakened by the FSP. This work provides a valid option for the quality assurance of the WAAM process of aluminum alloys.