Multipass forging of Inconel 718 in the delta-Supersolvus domain: assessing and modeling microstructure evolution

¹ Manoir Aerospace-Forges de Bologne SAS, 52905 Chaumont, France
² MINES ParisTech, CEMEF – Centre de mise en forme des matériaux, CNRS UMR 7635, CS 10207 rue Claude Daunesse, 06904 Sophia Antipolis Cedex, France
³ Thermomechanical Metallurgy Laboratory – PX Group Chair, Ecole Polytechnique Fédérale de Lausanne (EPFL), Rue de la Maladière 71B – CP 526, 2002 Neuchâtel, Switzerland

^a Corresponding author: meriem.zouari@mines-paristech.fr

Abstract

This work is focused on the evolution of the microstructure of Inconel 718 during multi-pass forging processes. During the forming process, the material is subjected to several physical phenomena such as work-hardening, recovery, recrystallization and grain growth. In this work, transformation kinetics are modeled in the δ-Supersolvus domain (T>Tsolvus) where the alloy is single-phase, all the alloying elements being dissolved into the FCC matrix. Torsion tests were used to simulate the forging process and recrystallization kinetics was modeled using a discontinuous dynamic recrystallization (DDRX) two-site mean field model. The microstructure evolution under hot forging conditions is predicted in both dynamic and post-dynamic regimes based on the initial distribution of grain size and the evolution of dislocation density distribution during each step of the process. The model predicts recrystallization kinetics, recrystallized grain size distribution and stress–strain curve for different thermo-mechanical conditions and makes the connection between dynamic and post-dynamic regimes.