Microstructure evolution in an interstitial-free steel during cold rolling at low strain levels

Microstructure development in an interstitial-free steel during cold rolling at low strain levels (ε 9.8%) has been investigated by using transmission electron microscopy. At a strain of 2.2%, {112} slip systems operate in addition to {110} slip planes. Dislocation reactions occur at this stage to produce immobile 100 seg-ments in the scissors configuration and these segments are also found at higher strain in the dislocation walls of microbands. The formation of microbands starts at small reductions (ε ∼ 6.7%), and microbands are of lenticular shapes and have habit planes running approximately parallel to {110} planes. Two sets of dislocations comprise the microband walls; one is predominant and has its Burgers vector lying on the microband’s habit plane. The secondary set is much less dense, and its slip plane is not coplanar with the microband habit plane. A considerable misorientation exists between the inner region of a microband and either of its two neighbouring matri-ces, rather than between the two matrices, which is consistent with Jackson’s double cross-slip model. However, the growing end of a microband indicates the splitting of a dense dislocation sheet. In the specimen that was rolled to ε = 9.8%, some grain