Effect of dislocation and grain boundary on deformation mechanism in ultrafine-grained interstitial-free steel

Ultrafine-grained interstitial-free steel fabricated by the accumulative roll-bonding method was subjected to tensile tests and analyses of AFM, TEM and XRD to identify the effects of interaction between dislocations and grain boundaries (GB) on the deformation mechanism. The AFM analyses indicated that the main deformation mechanism of this material changed from dislocation motion to grain boundary sliding (GBS) with decreasing strain rate. TEM observations and XRD analysis revealed showed that dislocations piled up at GB and the dislocation density decreased with increasing strain. Those suggest the dislocations are absorbed into GB during deformation, activating slip-induced GBS.