Hot Deformation Behavior and Microstructure Evolution of the Maraging Stainless Steel

Hot deformation behavior of the maraging stainless steel is studied in temperature range from 900 to 1150 degrees C and strain rate from 0.1 to 10 s-1. When the deformation temperature is 900-950 degrees C, the abnormal stress increase is observed at the end of the flow curves. Transmission electron micrographs reveal that the Laves phase at the interface between prior austenitic (gamma) and high-temperature ferrite (delta) impedes hot deformation. The microstructure analysis shows that the dynamic recrystallization (DRX) mechanism of gamma and delta is discontinuous DRX and continuous DRX, respectively. When the specimens are deformed at 950 degrees C, the extent of DRX at a strain rate of 5 s-1 is higher than at 0.1 s-1. This anomaly is due to adiabatic heating causing the actual deformation temperature at high strain rate (epsilon.$\overset{.}{\epsilon}$) to be higher than at low epsilon.$\overset{.}{\epsilon}$, indicating that DRX is more influenced by temperature compared to epsilon.$\overset{.}{\epsilon}$. The influences of adiabatic heating and friction are corrected. Strain-dependent constitutive equation is developed based on the revised flow curves, yielding an average absolute relative error of 4.69% and a correlation coefficient of 0.99; the prediction accuracy exceeds 90% when the relative error is within 10%.