Effect of Pre-Deformation on Fracture Behavior Transition due to Strain-Rate Change in Fe-5%Si Alloy

dislocations were successfully introduced within the grains (cid:15) All rolled alloys were fractured with local elongation (cid:9) necking (cid:10)(cid:1) at slower strain rate (cid:15) When strain rate was faster (cid:13) the local elongation disappeared and the fracture manner was turned to brittle (cid:15) The strain rate at which fracture behavior changed increased with increasing of the reduction (cid:15) On the other hand (cid:13) the almost fully recrystallized Si steel was fractured in the brittle manner at any strain rate and the transition strain rate was not found (cid:15) The fractured tensile specimen with no local elongations contains deformation twins ; however (cid:13) these deformation twins were not observed in the fractured specimen with local elongations (cid:15) This result indicates that the dislocation structure evolved during rolling suppressed the twinning and that the dislocation structure is effective for the enhancement of both ductility and toughness in Fe-5%Si alloy (cid:15)