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 gamma'' and delta phase in Inconel 718 alloy. The results show the precipitation behaviors are tailored by the deformation temperatures that gamma'' phase precipitation is accelerated at 800 degrees C in place of d phase as for 900 degrees C. Deformation at 800 degrees C and 900 degrees C makes the precipitation peaks for gamma'' phase shift towards lower temperatures to be 742 degrees C and 735 degrees C, while the precipitation peaks for d phase moving towards higher temperatures to be 941 degrees C and 943 degrees C, respectively. When subjected to the deformation& isothermal treatment at 800 degrees C, the thus formed structure is composed of ellipsoidal, disc and irregular-shaped gamma'' precipitates with sizes varying from 80 nm to 440 nm in the interior of broadened GBs, as well as dispersively ultrafine intragranular gamma'' particles. As for the specimen deformed at 900 degrees C, the delta-phase precipitation is promoted under the effect of static recrystallization occurring at the initial aging stage, that granular, disc and needle-shaped delta precipitates with 7.5 vol % are generated in the limited duration of 1 h. (C) 2017 Elsevier B.V. All rights reserved.