Experimental study and numerical simulation of dynamic recrystallization for a FGH96 superalloy during isothermal compression

Abstract

Hot compression tests of a FGH96 superalloy under the conditions of temperatures from 1020 to 1110 °C and strain rates from 10−3 to 1 s−1 were carried out on a Gleeble-3180D thermo simulator. The microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX) for the superalloy were analyzed by electron backscatter diffraction (EBSD) technique and transmission electron microscope (TEM). A DEFORM-3D Finite Element (FE) software was used to simulate the distributions of deformation and microstructures of the compressed specimens. The results show that the flow stress curves of FGH96 superalloy exhibit typical features of dynamic recrystallization (DRX). The constitutive equation is established based on the friction-corrected flow stress data. Increasing temperature or decreasing strain rate is found to result in the increases of both the DRX fraction and the grain size. The nucleation mechanisms of DRX for the superalloy mainly include dominant discontinuous dynamic recrystallization (DDRX) and assisting nucleation by twins. The prediction models of DRX, which are expressed as a function of Z parameter, are obtained on the basis of the compression data and quantitatively microstructural characterization. By comparing the simulated results with that of the experiment, the accuracy of the developed DRX models is validated.

Keywords

• Nickel-base superalloy
• Dynamic recrystallization
• Hot compression
• Nucleation
• Finite element (FE) simulation