Achieving exceptional strength-ductility synergy in additively manufactured Hastelloy X superalloys by stabilizing cellular structures via Ta addition

Additive manufacturing of Hastelloy X superalloys remains challenges for practical aerospace applications due to the inadequate mechanical property at both ambient and high temperatures. To this end, this work proposes a novel Ta-modified strategy manipulating elemental segregation to stabilize cellular structures, thereby obtaining an outstanding combination between strength and ductility across a wide temperature regime. In particular, the tensile strength and elongation of Ta-modified superalloys can reach up to 1 214 MPa and 28.4%, respectively, highly increased by 47% and 10% compared to original Hastelloy X superalloys at 25 °C. Meanwhile, the tensile strength and elongation at 650 °C significantly increase to 843 MPa and 26.8% respectively, 38% and 150% stronger than their counterparts of the original Ta-free Hastelloy X superalloys at identical conditions. Microstructural observations reveal that prominent local segregation of Ta/Mo elements and in situ MC precipitates along cellular boundaries synergistically enhanced the stability of cellular structures. The stabilized cellular structures serve as continuous and skeleton-like networks during deformation, synergistically contributing to outstanding ductility and enhanced mechanical strength, as well as sustained strain-hardening ability. The present work provides new insights into an efficient alloy design method for additively manufactured nickel-based superalloys with outstanding mechanical property within a wide temperature regime.