where ρi is the elemental resistivity of solute i in the matrix [32]. For
transition metals (e.g. Fe), electron-electron scattering makes a signifi-
cant contribution to ρ0(T) at low temperature. It is found that ρ0(T)
should be represented by 1/(1/ρ0(T)+ 1/ρsat) for steels, where ρsat is
the saturation resistivity [32]. ρ0(T) and ρsat take the same values for
all carbides and phases in steels. According to Matthiessen's theory,
the electrical resistivity of κ-carbide is higher than that of α phase due
to higher C, Al and Mn compositions in κ than in α. In microstructure
configurations illustrated in Fig. 4, the system electrical resistivity of lamellar
structure in Fig. 4(a) is closely to that for κ-carbide, but that in
Fig. 4(b) is closely to that of α phase [30,33]. The experimental measured
values are consented to the theoretical analysis.