Overcoming the challenges of fusion-based brass additive manufacturing through solid-state additive friction-stir deposition

Processing Cu-Zn alloys (brass) using fusion-based additive manufacturing (AM) techniques presents significant challenges due to volatile elements and the inherently high thermal conductivity of these alloys. Addressing these issues often demands increased energy input, modifications to laser systems, and compositional adjustments to mitigate zinc loss. However, such solutions are complex and remain in the early stages of development. In contrast, Additive friction stir deposition (AFSD), a solid-state AM technique, offers a promising alternative to overcome these limitations. This study represents a pioneering effort to deposit dual-phase brass (Cu-40Zn) using a closed-loop temperature-controlled AFSD. The influence of processing temperature (ranging from 0.38 to 0.61 T_p/T_m) on microstructural evolution and mechanical performance was systematically investigated along the build and longitudinal direction. The resulting microstructure was predominantly governed by dynamic recrystallization and post-dynamic recrystallization (P-DRX) due to repeated thermal cycles. The as-deposited brass exhibited a balanced strength-ductility combination, with yield strength ranging from 215 to 437 MPa and elongation from 34 % to 67 %. Tensile properties in longitudinal and build directions revealed that grain boundary strengthening was the primary mechanism for improving the mechanical performance. The as-deposited properties were comparable to those of wrought counterparts, thus highlighting the potential of AFSD for fabricating high-performance brass components.