THE DEVIATION FROM MATTHIESSENS-RULE DURI NG QUENCH-AGING OF COPPER ADDED LOW-CARBON STEELS

The interaction between copper atom and carbon atom in 0.03mass% carbo n steels, containing from 0 to 0.55mass% copper, has been studied by t he measurement of electrical resistivity and its deviation from Matthi essen's rule (DMR). The electrical resistivity measured at 77K and 273 K decreases during isothermal aging at 523K for all steels which were quenched from 973K in the ferrite single phase region. Its DMR increas es during. aging for steels except copper-free -steel. The increments of the DMR increases with the increase of copper content of steels. Th ese phenomena can be explained in terms of Cu-C pairs in the solid sol ution 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 decompose d with the precipitation of cementite during aging. According to the c oncept, the amount of carbon atoms as Cu-C pairs increases. whereas th e amount of carbon atoms as single atom in the solid solution decrease s 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 bin ding energy of a Cu-C pair is calculated to be approximately -5.1x10(- 20)].