Effect of initial feedstock conditions on microstructure and mechanical properties of additive friction stir deposited Al–Cu–Mg–Ag alloy

Additive Friction Stir Deposition (AFSD), a solid-state additive process, builds parts without melting and promotes dynamic recrystallization. In present work, as-cast (AC), cast-solutionized (AC-ST), and as-extruded (EXT) Al–Cu–Mg–Ag alloys were used as feedstock to produce three AFSD samples. How the initial feedstock conditions control microstructural evolution, texture development, and mechanical behaviors of the Al–Cu–Mg–Ag alloy during AFSD was systematically investigated. The results show that AFSD markedly refines the grains: the average grain sizes in AC-AFSD, AC-ST-AFSD, and EXT-AFSD decrease to 4.2 μm, 2.6 μm, and 2.9 μm, respectively, mainly due to dynamic recrystallization (DRX). The tensile strength and elongation of the AFSD samples are as follow: 358 MPa and 8.7 % for AC-AFSD sample, 412 MPa and 12.1 % for AC-ST-AFSD sample, and 316 MPa and 16.6 % for EXT-AFSD sample, respectively. These results suggest that the AFSD sample with the initial AC-ST condition exhibits the best comprehensive performance, even outperforming the conventional hot-extruded and T6-treated sample (tensile strength of 400 MPa and elongation of 12.3%). The difference in the mechanical properties of the AFSD samples is mainly associated with the residual second phase, grain size as well as the texture, and the former one plays the dominant role. This work elucidates the regulatory mechanism of initial feedstock conditions on microstructure and mechanical properties of the AFSD Al–Cu–Mg–Ag alloy, and provides practical guidance and process optimization strategies for microstructure-based design of high-performance heat-treatable Al alloy solid-state additive manufacturing (AM) components without post heat treatment.