Microstructural evolution and mechanical behaviour in the hot deformation of GH3128 alloy

In this study, the microstructural evolution and mechanical behaviour of the GH3128 alloy during hot deformation were investigated, which is crucial for optimising hot processing. The investigation was performed by hot tensile deformation at 750-950 °C and analysis by electron backscatter diffraction (EBSD), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that two types of second-phase M23C6 and MC carbide particles existed during hot deformation, with content percentages and distributions relating to the temperature. The increase in temperature gradually promoted the precipitation of the second phase in the grain boundary. Dynamic recrystallisation occurred during hot deformation via coexisting mechanisms of twin-induced nucleation and particle-stimulated nucleation. The dynamic recrystallisation fraction gradually increased with an increase in temperature. In addition, the variation law of mechanical behaviour with temperature was revealed and explained from the perspective of microstructural evolution. In particular, the elongation decreased with an increase in temperature from 800 °C to 950 °C, mainly due to the precipitation of the second phase in the grain boundary at high temperatures, coarsening of grains and decreasing of grain uniformity. Concomitantly, the fracture mechanism changed from ductile fracture to ductile brittle fracture with an increase in temperature. These results provide a theoretical basis and guidance for the hot-working process of GH3128.