Formation of shear band in cold rolled boby-centered cubic metal

The mechanism of shear band formation in the high cold rolled boby-centered cubic(BCC) metal is investigated.Based on the plastic deformation theory,the shear distribution in the deformed grain is calculated by using the Taylor relaxed constraint model and the Bishop Hill maximum work principle.It is shown that when the rolling direction is parallel to(〈1 1 2〉) and the normal direction is parallel to 〈1 1 1〉,almost all the shear can concentrate on one slip plane,such highly localized shear make the shear band form the grain.The angle between the rolling direction and the shear band is about 35°.Since the shear is uniformly distributed in active slip system for the other orientation of the grain,the deformation is homogenous,therefore,the shear band cannot occur in such case.The TEM observation of the shear band in cold rolled BCC metal confirms the formation mechanism of the shear band.