Hot deformation behavior of a precipitate free Ni-based superalloy

K.PRADEEP; FRANCO LIZZI; GERALD SCHADEN; ALEKSANDAR STANOJEVIC; MARTIN STOCKINGER; SILVANA SOMMADOSSI; CECILIA POLETTI

Ghent

Conferencia; 7th International Conference on Recrystallization and Grain Growth; 2019

UGent, Belgium

Hot deformation behavior of a precipitate free Ni-based superalloyK.Pradeep1, Franco Lizzi2, Gerald Schaden3, Aleksandar Stanojevic3, Martin Stockinger3, Silvana Sommadossi2 Cecilia Poletti1.1Institute of Materials Science, Joining and Forming, Graz University of Technology, Graz Austria.2Comahue National University, Neuquén, Argentina.3Voestalpine Böhler Aerospace GmbH & Co KG, 8605 Kapfenberg, Austria.The thermomechanical processing of Inconel 718 involves microstructural changes, including complex interactions with large amounts of different precipitates. In this work, we characterize a material free of gamma prime, double prime and delta produced by powder metallurgy. The mechanisms responsible for the evolution of the microstructure of this Inconel 718 precipitate free during hot deformation are studied using hot compression testing on Gleeble ® 3800 and microscopy in the strain rate range of 0.01-10s-1 and between 900 and1025°C. Flow curves, grain size and recrystallization percentage are correlated with the temperatures and strain rates. Flow curves shows stress values up to1.5% lower than conventional Inconel 718 and some common features related to twinning at high strain rates. Different techniques like light optical microscopy and electron backscatter diffraction are used to analyse the developed microstructure. Recrystallized and non-recrystallized grains are distinguished, and annealing twins formed during dynamic recrystallization were reconstructed. Additionally, we show the influence of the adiabatic heating on the flow stress and the microstructure.Based upon the experimental work, a new model which takes precipitate data such as size and number density is proposed to describe the behaviour of this nickel alloy at elevated temperatures and different strain rates. The microstructure model can describe the flow softening as well as the dependency of the flow with respect to the temperature and the strain rate. The results such as dislocation density evolution, recrystallization fraction and grain size which are mainly related to discontinuous dynamic recrystallization can be obtained as outputs from the developed model .Keywords : Inconel 718, precipitate free, hot deformation, Gleeble®, flow curves, dynamic recrystallization.