Subdivision of Dynamic Recrystallization Mechanism in the Transition Zone and Microstructure Evolution of Incoloy825 Alloy

The hot deformation behavior of Incoloy825 alloy is investigated by isothermal compression test at the temperature range of 950-1150 degrees C with strain rates of 0.001-10 s(-1). The dynamic recrystallization (DRX) mechanism in the transition zone is subdivided and clearly revealed. The results show that the instability domain is mainly located in the low temperature with high strain rate region (950-1050 degrees C, 1-10 s(-1)). The feasible domain can be divided into two parts: the first is located in the temperature range of 1000-1150 degrees C with a strain rate of 0.001 s(-1), the second is located in strain rate of 0.01-1 s(-1) at 1150 degrees C, and the optimum processing parameters is the temperature of 1150 degrees C with a strain rate of 1 s(-1). A transition zone of the DRX mechanism appears during hot deformation, in which three DRX mechanisms occur, discontinuous dynamic recrystallization (DDRX) mechanism, continuous dynamic recrystallization mechanism (CDRX), and twin dynamic recrystallization (TDRX) mechanism. The formation of a DRX grain is the comprehensive effect of multiple mechanisms, which can promote and transform each other. Each mechanism contributes a different role.