| Abstract: | The normalized and normalized plus cold-rolled structures and their effects on the formation of austenite in 0.08C-1.5Mn steel were examined by TEM. It was shown that during intercritical annealing, the austenite formation was accompanied by spheroidization of cementite in the initially normalized structure, a result attributed to the existence of more dislocation in ferrite and degenerated pearlite containing many changes in spacing and interruption in lamellar morphology in the normalized condition. The austenite nucleated not only at the cementite particles located at the triple points and faces of ferrite grain boundaries, but also at the interfaces of ferrite and cementite which was within ferrite matrix. Due to the effect of cold rolling, the lamellar cementite in the cold-rolled structure was distorted severely and even fragmented. Also, a great amount of dislocations were introduced into the ferrite matrix. These effects of the cold rolling accelerated the spheroidization of cementire and enhanced the possibility that the austenite formed within ferrite grains during intercritical annealing. The relationship between austenite formation and cementite spheroidization and the possible sites of austenite nucleation were discussed. |
