Innovative Additive Manufacturing of Ultrahigh-Strength and Heat-Resistant Aluminum Alloy

Additive manufacturing (AM) advances the use of complex-geometry aluminum (Al) alloys for lightweight aerospace components. However, AM of high-strength Al alloys is challenging due to their inherent high susceptibility to cracking. Inoculating with scandium or zirconium effectively suppresses cracking in AM Al alloys but is costly. This work designs a low-cost AA7075 Al wire with TiC and Ti duplex inoculants, followed by an innovative annular laser beam AM process that produces a smoother melt-pool temperature gradient, reducing susceptibility to cracking. Crack-free, equiaxed, fine-grained microstructures are achieved throughout the printed sample and, together with multi-type precipitates at multiple scales, yield good homogeneity in mechanical properties and excellent strength-ductility synergies at both room and high temperatures. The tensile yield strength (YS) reaches 501-511 MPa with ductility of 7.3%-8.1%, comparable to wrought AA7075 alloy and superior to almost all laser-deposited Al alloys. Additionally, the YS at 250°C reaches 275 MPa, which is higher than that of almost all AM-printed Al alloys reported to date. This material-process co-innovation strategy solves multiple challenges in AM Al alloys (i.e., material printability, microstructural homogeneity, mechanical anisotropy, strength-ductility trade-off, high-temperature strength, and cost efficiency), and could be generally applied to other hot-cracking-susceptible and poorly printable materials.