Static recrystallization behaviors and mechanisms of 7Mo super-austenitic stainless steel with undissolved sigma precipitates during double-stage hot deformation

Static recrystallization (SRX) behaviors and corresponding recrystallization mechanisms of 7Mo super-austenitic stainless steel were studied under different deformation conditions. The order of influence of deformation parameters on static recrystallization behaviors, from high to low, is followed by temperature, first-stage strain and strain rate. Meanwhile, the effect of holding time on static recrystallization behaviors is significantly controlled by temperature. In addition, with the increase in temperature from 1000 to 1200 °C, the static recrystallization mechanism evolves from discontinuous static recrystallization and continuous static recrystallization (cSRX) to metadynamic recrystallization and cSRX, and finally to cSRX. The cSRX exists at all temperatures. This is because high stacking fault energy (56 mJ m −2 ) promotes the movement of dislocations, making the deformation mechanism of this steel is dominated by planar slip of dislocation. Large undissolved sigma precipitates promote static recrystallization through particle-stimulated nucleation. However, small strain-induced precipitates at grain boundaries hinder the nucleation of conventional SRX and the growth of recrystallized grains, while the hindering effect decreases with the increase in temperature.