Microstructural development during warm rolling of an IF steel

Wedge-shaped slab rolling was employed to investigate the microstructural evolution of an interstitial-free (IF) steel during warm working in the temperature range 500-800 degrees C. Mean flow stress-strain curves calculated from load-time data of rolling tests reasonably correspond to work hardening and dynamic recovery behaviour. The development of substructures in the deformed material was investigated using optical and electron microscopy. A close correlation was observed between mechanical behaviour and microstructural development during deformation. Microbands in directions of +/-35 degrees with respect to the rolling direction, independent of strain, temperature and initial grain orientations are the most noticeable features in the microstructural observations. The sequences of substructural changes from the appearance of early microbands at very low strains, their development with strain, to the formation of equiaxed subgrains at higher strains and temperatures were followed by TEM. (C) 1997 Acta Metallurgica Inc.