Microstructural evolution and mechanical properties of Inconel 718 alloy manufactured by selective laser melting after solution and double aging treatments

In this study, Inconel 718 (IN718) alloy was manufactured by selective laser melting (SLM), and the effects of solution and double aging treatments (SDA) on the microstructure and mechanical properties of the IN718 alloy were investigated. Results revealed that the increase of the solution temperature promotes the increase of the number of recrystallized grains of the IN718 alloy. When the solution temperature is 940 ℃, a large amount of needle-like γ″ are formed. With the increase of the solution temperature (980 ℃–1140 ℃), the needle-like γ″ phase in the alloy begins to decrease and gradually disappear, accompanying the precipitation of the nanoscale granular γ'/γ" composite phase. When the solution temperature is 1140 ℃, an enhanced ultimate tensile strength (UTS) of 1451 MPa and a slight sacrifice of fracture elongation (23.7%) are achieved for the IN718 alloy. The formed nanoscale granular γ'/γ" composite phase and annealing twins were responsible for the enhanced mechanical properties of the IN718 alloys.