Wire arc additive manufacturing of a heat-resistant Al-Cu-Ag-Sc alloy: microstructures and high-temperature mechanical properties

With a high energy efficiency, low geometric limitation, and low cracking susceptivity to cracks, wire arc additive manufacturing (WAAM) has become an ideal substitute for casting in the manufacturing of load-bearing high strength aluminum components in aerospace industry. Recently, in scientific researches, the room temperature mechanical performance of additive manufactured high strength aluminum alloys has been continuously broken through, and proves these alloys can achieve comparable or even higher properties than the forged counterpart. Since the aluminum components for aerospace usage experience high-low temperature cycling due to the absence of atmosphere protection, the high temperature performances of additive manufactured high strength aluminum alloys are also important. However, few research focuses on that. A special 2319AgSc with 0.4 wt.% Ag and 0.2 wt.% Sc addition designed for high temperature application is deposited successfully via cold metal transfer (CMT) based on WAAM. The microstructures and high temperature tensile properties are investigated. The results show that the as-deposited 2319AgSc alloy presents an alternate distribution of columnar grains and equiaxed grains with no significant textures. Main second phases are Al₂Cu and Al₃Sc, while co-growth of Al₂Cu and bulk Al₃Sc is found on the grain boundary. During manufacturing, nanoscale Al₂Cu can precipitate out from the matrix. Ag and Mg form nano-scale Ω phase on the Al₂Cu precipitates. At 260 ℃, average yield strengths in the horizontal direction and vertical direction are 87 MPa±2 MPa, 87 MPa±4 MPa, while average ultimate tensile strengths are 140 MPa±7 MPa, 141 MPa±11 MPa, and average elongations are 11.0%±2.5%, 13.5%±3.0%. Anisotropy in different directions is weak.