Sintering of Cold Spray Additively Manufactured Aluminum 6061

Cold spray additive manufacturing (CSAM) is an innovative method for producing freeform and near-net-shape components with high deposition rates and low thermal gradients. The CSAM fabrication technology used here targets low cost using air as a carrier gas, aiming to compete with casting for small production runs. However, incomplete interparticle bonding and intense plastic deformation during supersonic impact of deposition results in cold worked, non-ductile materials. This exploratory study investigates heat treatments of CSAM aluminum 6061 for interparticle boundary healing and compares the CSAM results to cast aluminum 356.0 T6. CSAM tensile specimens in four heat treatment groups were compared to a non-heat-treated control. Three-stage (sintering, solutionizing and aging) heat treatments were performed in air and a further group in a carbon monoxide atmosphere. Microstructural evolution and mechanical performance were measured. Heat treatment resulted in increased UTS, YS and reduced porosity and comparable mechanical properties (up to 280MPa and 8% strain to failure) to cast aluminum 356.0 T6. Although the heat-treated CSAM microstructures exhibited clear signs of sintering including densification and particle and pore coalescence, the solutionizing and aging processes appeared incomplete. Further tailoring heat treatments for CSAM aluminum 6061 could add strength while maintaining its custom manufacturing ability.