Enhanced strength-ductility synergy in a selective laser melted Inconel 718 superalloy by refining γ″ precipitates

An optimized heat treatment procedure containing homogenization and single aging at temperature of 700°C (HA700) was proposed for selective laser melted Inconel 718 superalloy. The results showed that many ultrafine γ′ and γ″ phases with size of 10–35 nm precipitated from the HA700 sample due to reduced aging temperature and time. Especially, the morphology of γ″ phase changed to be near spherical shape with aspect ratio of 1–3 rather than typical disc-like shape in the traditional homogenized plus double aged sample (HA). With the aid of well-dispersed ultrafine γ″ precipitates, the HA700 sample achieved a simultaneous improvement in strength of ∼10% and ductility of ∼13% compared to HA sample. This single aging strategy could provide new insights into optimizing the mechanical properties of Inconel 718 alloy.