Papers by Author: A. Dehghan-Manshadi

Abstract: The effect of initial grain size on the recrystallization behaviour of a type 304 austenitic stainless steel was investigated using hot torsion. Refinement of the initial grain size to 8 μm had a considerable effect on the flow curve shapes, peak and critical strains and also on DRX kinetics, compared with an initial grain size of 35 μm. Microstructural investigations using EBSD suggest a transition from conventional (discontinuous) to continuous dynamic recrystallization with decreasing initial grain size. Also, there was a moderate effect of initial grain size on the DRX grain size.

Abstract: A 304 austenitic stainless steel was deformed using hot torsion to study the evolution of dynamic recrystallization (DRX). The initial nucleation of dynamically recrystallization occurred by the bulging of pre-existing high angle grain boundaries at a strain much lower than the peak strain. At the peak stress, only a low fraction of the prior grain boundaries were covered with new DRX grains. Beyond the peak stress, new DRX grains formed layers near the initial DRX and a necklace structure was developed. Several different mechanisms appeared to be operative in the formation of new high angle boundaries and grains. The recrystallization behaviour after deformation showed a classic transition from strain dependent to strain independent softening. This occurred at a strain beyond the peak, where the fraction of dynamic recrystallization was only 50%.