Finite-element analysis of microstructure evolution in the cogging of an Alloy 718 ingot

Microstructural changes during the cogging of an Alloy 718 ignot processed by (vacuum induction melting)/(vacuum arc re-melting) were predicted using the combined approach of three-dimensional finite element simulation and modeling for the recrystallization and grain growth. In order to establish recrystallization and grain growth models for Alloy 718 ingot, hot compression and isothermal heat treatment tests were carried out at different temperatures and strain rates. The constitutive equations for metadynamic and static-recrystallization behavior were generated using the experimental data collected from various references. From the experimental results, it was found that the dissolution temperature of delta-phase (Ni3Nb) played an important role in the microstructural refinement of Alloy 718 ingot. The predicted grain size and its distribution were compared with the microstructures of the cogged billet, and the reliability of the prediction was discussed. (c) 2006 Elsevier B.V. All rights reserved.