TRANSMISSION ELECTRON MICROSCOPE STUDY ON DEFORMATION AND FRACTURE OF CEMENTITE IN COLD-ROLLED STEELS.

Abstract

Plastic deformation of cementite due to dislocation gliding was demonstrated to occur in carbon steels during cold rolling. Many straight dislocations were observed on slip planes, and the density of such dislocations was greatly increased in proportion to the increase in the deformation of steels. Slip planes of cementite crystals at room temperature were determined. Most of the dislocations on the slip planes were screw dislocations. The fracture of lamellar cementite proceeded as follows: Heterogeneous gliding results in division of the original cementite crystal into several undeformed blocks. The mutual gliding displacement betwen two adjacent blocks (height of slip steps) increases with successive deformation of the cementite. Finally, the cementite is completely broken away along the boundaries of the blocks probably due to the stress concentration at the slip steps. This paper was first published in Japanese in J Jap Inst Met v 17 1973, p 875.