Outstanding strength-ductility synergy in Inconel 718 superalloy via laser powder bed fusion and thermomechanical treatment

Addressing the strength-ductility dilemma in Inconel 718 superalloy using traditional strengthening strategies is a challenging. Here, based on the unique initial microstructure resulting from laser powder bed fusion (LPBF), we proposed a novel strategy that combines the LPBF with a subsequent thermomechanical treatment to simultaneously improve the strength and ductility of Inconel 718, having an architecture of abundant annealing twins at a finer grain size and coherent nano-precipitates (γ", γ'). The CR-A5-DA specimen exhibits mechanical properties with a yield strength of 1563.1 ± 10.5 MPa, tensile strength of 1759.7 ± 11.6 MPa, and maintained a favourable tensile elongation of 17.3 ± 0.8%. The outstanding strength-ductility synergy is mainly attributed to the amplification of effects, such as finer grains, intricate interactions between microstructures (twins + disperse nano-precipitates) and dislocations, driven by LPBF and thermomechanical treat. Meanwhile, the dynamic Hall-Petch effect and additionally strengthened microstructures induced by tensile loading, including nanotwins, stacking faults and Lomer-Cottrell locks, further improve the work hardening ability. This study presents a novel idea for the production of metal structural materials with a high strength-ductility synergy and broadens the scope of applications for additive manufacturing.