Hot Deformation Behavior of 17-7 PH Stainless Steel

To investigate the hot deformation behavior of 17-7 PH stainless steel, hot compression tests were carried out at the temperatures of 950, 1050 and 1150 oC and strain rates of 0.001 s-1 to 0.1 s-1. Accordingly, the hot working behavior was studied by the analyses of flow stress curves, work hardening rate versus stress curves, exponent- type constitutive equations and deformed microstructures. Meanwhile, the average normalized critical stress for initiation of dynamic recrystallization (DRX) was determined using a 3rd order polynomial curve fitting. The results show that the flow stress depends strongly on the deformation temperature and the strain rate, and it increases with the deformation temperature decreasing and the strain rate increasing. Furthermore, it was found out that the co- existence of δ- ferrite lowers the softening rate at high Z (Zener- Holloman parameter) conditions. The experimental results were then used to determine the constants of constitutive equations. There is a good agreement between the measured and predicted results indicating a high accuracy of exponent- type constitutive equations.