Microstructure and tensile fracture behavior of three-stage heat treated inconel 718 alloy produced via laser powder bed fusion process

Abstract In this study, Laser Powder Bed Fusion (LPBF) Inconel 718 is subjected to various heat treatments, namely double aging, solid solution + double aging, and homogenization + solid-solution + double aging, to investigate the effect of heat treatment on room- and high-temperature tensile properties. The results show that all three heat treatments increase hardness and room-temperature tensile strength, but greatly reduce ductility. With an increase in tensile test temperature, the stress-induced Portevin-Le Chatelier (PLC) effect can effectively prevent the occurrence of oxidation at grain boundaries and maintain a certain ductility in the range of room temperature to 600 °C. However, when the temperature is 650 °C, the PLC effect disappears, resulting in a high-temperature embrittlement effect.