Microstructure evolution and dynamic recrystallisation behaviour in hot deformation of Haynes 214 superalloy

The microstructure evolution and dynamic recrystallisation (DRX) behaviour of Haynes 214 superalloy were investigated in the deformation temperature range of 900 ~ 1180 ℃ and strain rate range of 0.1 ~ 10 s−1 during isothermal compression tests. According to the true stress-strain curves that were obtained from the tests, it was found that temperature and strain rate significantly influence the hot deformation behaviour of Haynes 214 alloy. The fraction and grain size of the dynamic recrystallisation both increase as deformation temperature increases. Fine and uniform DRX grains are obtained at low and high strain rates, whereas at 1 s−1, DRX grain size and fraction decrease. In addition, both continuous dynamic recrystallisation (CDRX) and discontinuous dynamic recrystallisation (DDRX) occur during hot deformation, both being affected by strain rate and deformation temperature. At the same time, the fraction of ∑3 n (n = 1, 2, 3) twin boundary increases as temperature increases and is higher at a lower strain rate (0.1 s−1) and higher strain rate (5, 10 s−1), but lower at the intermediate strain rate of 1 s−1.