Mechanism of Microband Formation in Cold Rolled Interstitial-Free Steel

The mechanism of the shear band formation in the high cold rolled BCC metal is analyzed. Based on the plastic deformation theory, the shear distribution in the deformed grain is calculated by using the Taylor constraint model and the Bishop & Hill maximum work principle. Results show that when the rolling direction (RD) is parallel to a certain direction of a grain, the large localized shear occurs on one slip plane, thus generating microbands in the grain because of the high localized shear strain. The angle between the RD and the shear band is about 30°. The plate-like structure of the microband is formed because of the dislocation double cross slip. The transmission electron microscope (TEM) observation of the microband in the cold rolled BCC metal confirms the formation mechanism of the microband.