Frictional angular rolling extrusion of interstitial-free steel sheets

Interstitial-free steel sheets were processed using a novel severe plastic deformation technique – frictional angular rolling extrusion (FARE), in order to produce ultrafine grained structures. The deformation was carried out at room temperature and individual sheet specimens were repeatedly processed to various passes. An overall grain size of 200 nm was achieved after eight passes (or an equivalent total strain of 5.3). The present paper reports the evolution of microstructures during deformation, which were examined and characterized using electron backscatter imaging and high resolution EBSD in a field emission gun SEM. The mechanisms of grain refinement are discussed.