Hot deformation and recrystallization behavior of a new nickel-base superalloy for ultra-supercritical applications

Abstract

The hot deformation behavior of nickel-base superalloy at different temperatures (950–1150 °C) and strain rates (0.01–10 s−1) was investigated by using Gleeble-3800 thermal simulation machine. And the strain compensation Arrhenius model was established according to the obtained stress and strain with the calculated values of the correlation coefficient and the average absolute relative error of 0.986 and 7.17953%, respectively. Meanwhile, the recrystallization fraction model was also established. EBSD was utilized to characterize the microstructure of the experimental materials, and it is found that with the increase of deformation temperature, the recrystallization fraction shows a gradual increasing trend, and the grain grows gradually, while with the increase of strain rate, the recrystallization fraction first decreases and then increases. In addition, the recrystallization mechanism of the test materials is dominated by discontinuous dynamic recrystallization and supplemented by continuous dynamic recrystallization. Recrystallization is initially formed at the original grain boundary, and then gradually develop from the grain boundary to the interior of the grain. The twins inside the grain hinder the dislocation movement, which is conducive to DRX nucleation at the twin boundary. As the recrystallization fraction increases, Σ3 twin boundary fraction increases first and then decreases, and the reason for this change is further discussed.

Keywords

• Nickel-base superalloy
• Hot deformation behaviour
• Microstructural evolution
• Recrystallization
• Twin