Abstract
The interaction between copper atom and carbon atom in 0.03mass% carbon steels, containing from 0 to 0.55mass% copper, has been studied by the measurement of electrical resistivity and its deviation from Matthiessen's rule (DMR). The electrical resistivity measured at 77K and 273K decreases during isothermal aging at 523K for all steels which were quenched from 973K in the ferrite single phase region. Its DMR increases during aging for steels except copper-freesteel. The increments of the DMR increases with the increase of copper content of steels. These phenomena can be explained in terms of Cu-C pairs in the solid solution of the present steels, analogous to Mn-N pairs in Fe-Mn-N alloys. The Cu-C pairs may be formed in as-quenched ferrite and be decomposed with the precipitation of cementite during aging. According to the concept, the amount of carbon atoms as Cu-C pairs increases, whereas the amount of carbon atoms as single atom in the solid solution decreases at the solution treatment temperature of 973K as the copper content of steels increases. The formation of Cu-C pairs in the alpha irons is also suggested from the hardness comparison between the present Fe-Cu-C steels and the decarburized Fe-Cu ones just after quenched. The binding energy of a Cu-C pair is calculated to be approximately -5.1 × 10-20J.
