Effect of hot deformation on γ″ and δ phase precipitation of Inconel 718 alloy during deformation&isothermal treatment

A deformation&isothermal treatment is applied to investigate the effect of hot deformation on precipitation of γ″ and δ phase in Inconel 718 alloy. The results show the precipitation behaviors are tailored by the deformation temperatures that γ″ phase precipitation is accelerated at 800 °C in place of δ phase as for 900 °C. Deformation at 800 °C and 900 °C makes the precipitation peaks for γ″ phase shift towards lower temperatures to be 742 °C and 735 °C, while the precipitation peaks for δ phase moving towards higher temperatures to be 941 °C and 943 °C, respectively. When subjected to the deformation&isothermal treatment at 800 °C, the thus formed structure is composed of ellipsoidal, disc and irregular-shaped γ″ precipitates with sizes varying from 80 nm to 440 nm in the interior of broadened GBs, as well as dispersively ultrafine intragranular γ″ particles. As for the specimen deformed at 900 °C, the δ-phase precipitation is promoted under the effect of static recrystallization occurring at the initial aging stage, that granular, disc and needle-shaped δ precipitates with 7.5 vol % are generated in the limited duration of 1 h.