Effect of CuO addition on microstructure and mechanical properties of 4043 aluminum alloy prepared by LWAM

Laser and wire additive manufacturing (LWAM) is a potential method to prepare high-performance aluminum (Al) alloys, while the microstructural optimization and property improvement of LWAM Al alloys are still far from clear. In this paper, CuO addition as powder spread between base layers on the microstructure evolution and mechanical properties of LWAM 4043 aluminum alloy was systematically studied. Experimental results obviously showed that epitaxial growth of α-Al and Si-rich eutectic grids appeared within the CuO interlayers. The microstructural modification led to comprehensive increases in the tensile mechanical properties. Quantitatively, the alloy with CuO addition displayed a yield strength of 85.1 MPa, ultimate strength of 206.4MPa, and tensile elongation of 23.8%, which is increased by 19.5%, 11.6% and 27.3%, respectively, as compared with its CuO-free counterpart. The strength-ductility synergy is mainly related to the formation of multi-scaled heterogeneous microstructures, where interaction between Cu and Al atoms precipitate nanosized second phase particles to offer additional strengthening effect, while the heterogeneous microstructures block the microcrack growth to improve the ductility. This study provides a new idea for printing high-performance Al alloys that could evade the strength-ductility off-trade dilemma.