Cementite dissolution in heavily cold drawn pearlitic steel wires

The influence of cold wire drawing on the structure of a pearlitic steel containing 0.7 wt% of carbon and subjected to a strain of approximately 3.5 has been studied. The as-deformed microstructure is very fine, with an interlamellar spacing close to 20 nm, and contains high internal elastic strains. The main result concerns the cementite phase which undergoes a dissolution, at least partial, during wire drawing. The proposed interpretation of the cementite dissolution is based on the destabilization of this phase due to the increase of its free energy arising from thinning of cementite lamellae and creation of slip steps during wire drawing. Post-deformation annealings lead to restoration of the phase equilibrium by precipitation of the cementite, and also to recovery of the defects, mainly interfaces, stored in the microstructure during deformation. Copyright (C) 1997 Acta Metallurgica Inc.