Mechanisms of dynamic recrystallization in austenitic steel alloy 800H

Nucleation mechanisms and microstructure evolution during dynamic recrystallization (DRX) of an austenitic steel Alloy 800H were studied at temperatures of 0.73-0.85 Tm and true strain rates of 10-3-10-1 s-1. Investigations were carried out by evaluation of EBSD/SEM and Kikuchi patterns/TEM. At high temperatures and low strains bulging of prior grain boundaries could frequently be observed. Nucleation due to instabilities of the substructure only very locally occurred. A high twin frequency indicated that twinning is an active nucleation mechanism that promotes the expansion of the recrystallization front. At medium high temperatures DRX started in the region of grain boundaries due to an orientation gradient in a highly inhomogeneous microstructure. (orig.)