Effect of Sc Content on the Microstructure and Properties of Al–Mg–Sc Alloys Deposited by Wire Arc Additive Manufacturing

Despite showing considerable potential, wire arc additive manufacturing (WAAM) has been limited to producing Al–Mg alloys. As the addition of Sc can improve the mechanical properties of Al–Mg alloys, in this study, Al–Mg–Sc alloy deposits with different Sc contents were prepared by a WAAM process. The porosity, microstructure, and mechanical properties of the deposits were studied. At Sc contents less than 0.15%, Sc was completely dissolved in the Al matrix without grain refinement, and the mechanical properties were slightly improved. At a Sc content of 0.3%, the primary Al3Sc phase precipitated out of the as-deposited body, resulting in an abrupt change in the microstructure, significant grain refinement, significantly increased tensile strength and yield strength, with a tensile strength, yield strength, and elongation of 372 MPa, 270 MPa, and 22.5%, respectively. Following heat treatment at 350 °C for 1 h, the grain boundaries were refined and the secondary Al3Sc phase was precipitated. Furthermore, the tensile strength and yield strength were significantly increased to 415 MPa and 279 MPa, respectively, and elongation decreased to 18.5%. At a Sc content of 0.45%, due to the aggregated precipitated phase, the coarsened grain boundaries and the limited solid solution amount of Sc in the α(Al) matrix (~ 0.25%), the mechanical properties were not further improved compared with the deposit with Sc content of 0.3%. Thus, based on economic considerations, the optimal Sc content was 0.3%. Owing to their enhanced mechanical properties, WAAM-produced Al–Mg–Sc alloys are expected to have a wide range of applications in aviation, aerospace.