Effect of Flow Localization on the Microstructure Evolution during Close-Die Forging Inconel 718 Alloy

Forging of high strength materials is a very demanding process. This is particularly true in the case of Ni base alloys. Forging at elevated temperatures involves large strains at relatively low stresses, and involves heavy modifications on the microstructure. The final grain size usually depends on dynamic recovery and recrystallization phenomena. In this work, an impression forging process of Inconel 718 alloy was simulated at 1000°C and strain rate of 0.072s^-1. For the numerical analysis of the grain size evolution, a recrystallization model was implemented into a commercial code Deform 2D^TM. During the forging process, the grain size near to the dies change base on the material flow path developed as observed experimentally. The as-heated grain size which increase during heating and decrease during deformation and cooling stage was observed in the four stages of the process. It was conclude that forging operations affect the flowing behavior, changing the microstructure during deformation and their post grain size evolution during cooling .This study points out the influence of flow pattern, forging temperature and velocity in the grain size evolution of impression forging operations.