Influence of Friction Stir Processing Post-Treatment on the Microstructure and Mechanical Properties of 205A Aluminum Alloy Produced by Wire Arc-Directed Energy Deposition

Although wire arc-directed energy deposition (WA-DED) technology demonstrates advancements in the rapid manufacturing of high-strength Al-Cu aluminum alloy components, coarse microstructures and pore defects inhibit its further development and application. In this study, friction stir processing (FSP) post-treatment was employed to improve the microstructure and mechanical properties of the 205A aluminum alloy component produced by WA-DED, and the effects of rotational rate on the microstructure and properties were also investigated. Key findings showed that the average grain size of the as-deposited sample was significantly refined from 22.8 μm to less than 5 μm after FSP post-treatment, and most of the pore defects were eliminated. Most of the α-Al + θ-Al2Cu eutectic structures distributed on the grain boundaries were dissolved into the α-Al matrix after FSP post-treatment, and the element segregation phenomenon was effectively improved. The microhardness of the stirred zone significantly increased due to the microstructure refinement and pore elimination. The excellent elongation of the component was obtained after FSP post-treatment using a relatively low rotational rate of 800 min−1. Comparatively, after improving the rotational rate to 1200 min−1, the strength of the component slightly increased with the reduction in elongation. Compared to the as-deposited sample, the average yield strength, ultimate tensile strength, and elongation increased by 32.7%, 20.6% and 56.7%, respectively.