EBSD investigation of the effect of strain path changes on the microstructure and texture of duplex stainless steel during hot deformation

The effect of strain path changes on the microstructure/crystallographic texture characteristics was studied in a 22Cr-6Ni-3Mo duplex stainless steel subjected to several deformation regimes comprising forward and reverse torsion, performed at a temperature of 1000 deg. C using a strain rate of 1 s-1. A high-resolution EBSD technique, utilising an FEI Sirion FEG SEM in conjunction with a HKL Technology EBSD attachment, was successfully implemented for precise phase and substructural characterisation of the above steel. The austenite/ferrite ratio as well as the crystallographic texture, subgrain size and misorientation angles corresponding to each phase were determined over large sample areas. The results indicated that the austenite and ferrite phases, present in approximately equal volume fractions, softened via dynamic recovery and extended dynamic recovery, respectively. The phase ratio appeared to remain stable during straining. There seemed to be generally more strain partitioned to the ferrite compared to the austenite. Twin relationships in the austenite appeared partly restored after the full strain reversal. The austenite crystallographic texture displayed a tendency to revert back to the original texture after the strain reversal whereas the ferrite texture evolution appeared more complex. The obtained subgrain characteristics indicated that the reversed torsion might have caused some dissolution (and possible re-formation) of subboundaries in both phases. Nevertheless, the effect of strain path changes on the substructure characteristics generally appeared relatively moderate