The Microstructure Evolution and Dynamic Softening Mechanism of a 00Cr27Ni7Mo5N Hyper Duplex Stainless Steel

Abstract

The microstructure evolution and dynamic softening mechanism of a 00Cr27Ni7Mo5N hyper duplex stainless steel during uniaxial hot compression are investigated based on the electron backscattered diffraction and transmission electron microscopy. The (sub)grains of ferrite are significantly refined at the temperature of 1050 °C using the strain rate of 0.01 to 1 s−1. The softening mechanism within ferrite are classified as continuous dynamic recrystallization (CDRX). However, the dynamic softening within ferrite is diminished at a strain rate of 10 s−1. A softening mechanism analogous to discontinuous dynamic recrystallization (DDRX) is observed in the ferrite/austenite interphase mantle regions. The dynamic softening within austenite is remarkably limited at the temperature of 1050 °C, which appears to be complex‐shaped deformation bands. There are a small number of recrystallized grains within austenite. The dynamic softening of hyper duplex stainless steel is dominated by ferrite. The formation of DRX nuclei and growth of austenite by strain‐induced boundary migration mechanism is observed at the temperature of 1250 °C with different strain rates, indicating its softening mechanism is akin to DDRX. In addition, the increase in temperature and the decrease in strain rate is favorable to the dynamic softening of austenite.