Research on Dynamic Recrystallization Behavior of 23Cr-2.2Ni-6.3Mn-0.26N Low Nickel Type Duplex Stainless Steel

The difference of crystal structure and stacking fault energy (SFE) of two phases in duplex stainless steels (DSS) make different softening mechanism during hot deformation. Due to different austenite stability of Mn and Ni, the substitution of Mn for Ni will significantly affect dynamic recrystallization (DRX) behavior of compression deformation. The DRX behaviors of 23Cr-2.2Ni-6.3Mn-0.26N low nickel type DSS were studied in the deformation temperatures of 1073 similar to 1423 K and strain rates of 0.01 similar to 10 s(-1) by using a thermal simulator. The results showed that the deformation procedure of samples are mainly softened by dynamic recovery (DRV) of two phases at low temperature and high deformation strain rate, and mainly softened by austenite DRX at high temperature and low deformation strain rate. At the low strain rates of 0.01 and 0.1 s(-1), the grain size of austenite DRX increased with the increase of deformation temperature. The softening mechanism of samples are related to the Z parameter, and the deformation softening is mainly caused by austenite DRX under the condition of low Z value. Based on the thermal deformation equation, the apparent stress index of samples were calculated as 5.18, and the apparent activation energy of thermal deformation was calculated as 391.16 kJ/mol. The constitutive equation of the relationship between the peak flow stress and the Z parameter was established by hyperbolic sinusoidal model proposed by Sellars. The critical stress of DRX increases with increasing strain rate and decreasing deformation temperature, while the critical strain of DRX increases with the decrease of deformation temperature, and increases at first and then decreases with increasing strain rate (0.1 similar to 10 s(-1)) at low deformation temperature. The relationship between the DRX critical stress (strain) and peak stress (strain), as well as DRX characteristic parameters and Z parameter correlation models, and the austenite phase DRX volume fraction models were determined. Moreover, the DRX volume fraction models predict that the increase of strain rate and the decrease of deformation temperature can delay occurrence of DRX.