Additive friction stir deposition of an Al-Cu-Mg alloy: Microstructure evolution and mechanical properties

Abstract

Additive Friction Stir Deposition (AFSD), an emerging solid-based additive manufacturing technology, has demonstrated significant potential in the fabrication of high-strength aluminum alloys. In this study, a 22 mm thick 2024 aluminum alloy deposit having ten layers was for the first time successfully fabricated using the AFSD technique. The correlation between the microstructure evolution and mechanical properties within the deposit was revealed. The results indicated that the deposit exhibited very fine recrystallized microstructure and excellent mechanical properties. Dynamic recrystallization occurred with the average grain sizes at the top, center, and bottom of the deposit being 3.0 μm, 4.7 μm, and 4.8 μm, respectively. The Al₂CuMg (S phase) at grain boundaries of the deposit was observed to fracture due to the plastic deformation of the feedstock during the deposition process. The Vickers hardness of the deposit cross-section along the build direction (BD) changed from 125 HV of the top to 85 HV of the bottom. Better tensile properties in the TD compared to the BD were observed with the excellent tensile strength of 532 MPa and 473 MPa, and the elongation of 31.2 % and 15.2 %, respectively. The synergistically improvement of the tensile strength and elongation in the TD was attributed to the uniform microstructure and mechanical properties exhibited by each deposit layer.