Relationship Between Magnetic Properties and Hardness and Its Effect on Recovery and Recrystallization in Cold-Rolled Steel

The investigation of the correlation between coercive force, hardness, and internal microtexture is important to improving the precision of nondestructive evaluation techniques based on magnetic measurements. In this paper, low-carbon steels were cold-rolled and heat treated at 773 and 873 K to induce recovery and recrystallization, and their coercive force and Vickers hardness were evaluated after different heat treatment times. Changes in microstructures were observed using electron backscattered diffraction and transmission electron microscopy. It was found that the sensitivity of the coercive force decreases as recovery progresses, whereas the hardness is insensitive to the recovery process. Dislocations are mainly rearranged during recovery, but also mobile dislocations disappear to reduce internal stresses, thereby reducing the number of effective pinning sites for domain-wall motions. Fixed dislocations disappear in the recrystallization process, which is attributed to the decrease in hardness.