Abstract
The effects of high-temperature annealing on cold-worked microduplex austenite/ferrite stainless steels have been studied by following the hardness variations with time and investigating the resulting microstructural changes using transmission electron microscopy. It has been found that the resulting microstructures are affected by the relative volume fractions of austenite and ferrite present initially, by the deformation level, and by the temperature and time of the anneal. A well-defined subgrain structure was found to form in the ferrite phase during the earliest stages of annealing in all the cases investigated. By contrast, the austenitic phase volumes exhibited only a limited tendency to develop observable recovered dislocation substructures. Where the austenite was found to recrystallize, the process could be seen to have occurred discontinuously by movement of a high-angle interface. However, the mechanisms for recrystallization of the ferrite depended on phase volume fractions. In specimens which contained approximately equal volume fractions of ferrite and austenite a continuous recrystallization process was found, whereas a discontinuous mechanism was observed in specimens which comprised about 75 vol.-% ferrite.
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