Recovery of Lattice Defects in Cementite in Cold-Rolled Carbon Steels(Metallurgy)

Transmission electron microscopic observations were made on the recovery process of lattice defects in cementite in high carbon steels annealed after 92%cold rolling. Thermomagnetic and X-ray analyses were also performed as additional examinations. No observable change in the defect structure of cementite occurs at temperatures below about 400°C.Annealing at higher temperatures results in the disappearance of the moirc pattern, a considerable decrease of dislocation density and the formation of well-developed subboundaries. Above about 600°C, these defects disappear gradually with the progress of spheroidization. These results suggest that the recovery of lattice defects in cementite is caused by polygonization accompanied by climbing or cross slipping of dislocations.