Dual-phase stainless steels in comparison with ferritic or austenitic steels are more widely used in various industries due to good combination of mechanical properties and corrosion resistance. However, due to the existence of austenite and ferrite phases in microstructure of these steels, as well as the difference in strength and formability of these phases, there is a challenge in the hot deformation process of these steels. In this research, in order to investigate the hot deformation behavior as well as microstructural evolutions of Ti bearing 2304 dual-phase stainless steel, hot compression tests were performed in the temperature range of 900-1150 °C and strain rates of 0.001-1 s−1 under a constant strain of 0.5. The hyperbolic sine (sinh) equation was used to model relationship among process parameters of temperature, strain rate and stress with an activation energy of 515 kJ/K mol. The reduction of the volume fraction of the austenite phase with increasing temperature, as well as the change in the geometric shape of austenite phase from the continuous state to the globular state were observed with increasing process temperature and decreasing strain rate. The processing map and microstructure results introduced domains located at strain rates of 0.001 and 1 s−1 and in the temperature range of 1050-1150 °C as appropriate regions for deformation, while dynamic recovery, partial dynamic recrystallization and phase transformation were softening mechanisms. Flow instability was observed at 1150 °C and 0.001 s−1 which were related to non-uniform distribution of austenite phase and presence of coarse precipitates.

Keywords