Strain heterogeneity, recovery and recrystallization of nanostructured ODS alloys during cold deformation

Abstract

Nanostructured ferritic oxide dispersion strengthened (ODS) alloys are promising materials for high-temperature applications as they contain uniform nano-oxide dispersoids, which exert a Zener pinning force to inhibit dislocation movement and retard the recrystallization process. Recrystallization behaviour of iron-based ODS alloys is complicated and strongly depends on the deformed state of severely strained materials. In the present work, the effect of cold rolling followed by annealing on the development of recrystallized grain structures was investigated. A different level of cold deformation introduces the heterogeneous distribution of stored energy in the material. Inhomogeneous microstructure stimulates nucleation of recrystallization. This paper investigates variations of stored energy and dislocation density with varying levels of strain using DSC and TEM. The results indicate that heavy deformation alters the amount of stored energy and the number of effective nuclei and therefore it affects the rate of recrystallization. In addition, the change in stored energy is related to the number and configuration of the dislocations in the material. © 2012 The Japan Institute of Metals.