Microstructure evolution of Haynes230 superalloy during hot deformation

Hot compression tests of Haynes230 superalloy were conducted using a Thermecmastor-Z simulator in the temperature range of 950~1250°C and strain rates of 0.001~10 s^-1. Optical microscope (OM) and transmission electron microscope (TEM) techniques were employed to investigate the microstructure evolution and nucleation mechanisms of dynamic recrystallization (DRX). Results show that both the size and volume fraction of DRX grains increase with the increasing of deformation temperature but decrease with the increasing of strain rate. The dominant nucleation mechanism of DRX is bulging of the original grain boundaries. The necklace structure of recrystallized grains along original grain boundaries plays an important role for nucleation and growth of DRX grains. The relationship between DRX steady state grain size and Zener-Holloman parameter can be well established by a power law function.