The relationship between hardness and solute carbon concentration estimated via electrical resistivity measurement was investigated in as-quenched and tempered martensitic steels containing carbon of ...0.3–0.6 mass%. As a result of corelating the amount of hardening due to carbon in solid solution with the solute carbon concentration, by the calculation to subtract precipitation strengthening, grain refinement strengthening, dislocation strengthening, and softening due to retained austenite from the total strengthening, we derived an equation of solid solution strengthening, where the hardening increases proportionally to the 1/2 or 2/3 power of the solute carbon concentration. It was confirmed that the effects of the factors other than solid solution strengthening due to carbon on hardness are relatively small in tempered specimens when the tempering temperature is less than 673 K; therefore, the change in hardness in tempered martensitic steels can be mostly explained by solute carbon concentration regardless of carbon content.
The electrical resistivity of low-carbon martensitic steels was measured to estimate the carbon concentration in the solid solution. Since electrical resistivity is influenced not only by solute ...carbon but also by substitutional elements, lattice defects, and second phase, the effects of these factors need to be subtracted from the total electrical resistivity to obtain an accurate solute carbon concentration via this method. Consequently, the effects of dislocations and grain boundaries were much smaller than those of solute elements, representing approximately 1–2% of the total electrical resistivity in martensitic steel. However, substitutional elements and retained austenite were found to be significantly effective. By subtracting these effects from the measured value, the change in electrical resistivity owing to solute carbon (Δρsol.C) could be formulated as a function of the carbon concentration in the solid solution of martensite (Csol) as follows:Δρsol.CmΩmm = 0.25 × Csolmass%The estimated solute carbon concentration was confirmed to correspond to the directly measured value by atom probe tomography.
The relationship of solid solution carbon and electrical resistivity in retained austenite was investigated by using as-quenched martensitic specimens of Fe-10mass%Ni alloys with added carbon up to ...0.9 mass%. With increasing carbon content, the volume fraction of retained austenite increased, and simultaneously, the electrical resistivity of the bulk specimen also increased. Four-types of multi-phase models were applied to evaluate the electrical resistivity of each phase. As a result, the electrical resistivity of retained austenite was found to be increased with the increment of solute carbon concentration monotonously. The dependence of the solute carbon concentration (Csol) on the electrical resistivity of retained austenite (Δργ) could be formulated as Δργ mΩ•mm = 0.26 × Csol mass%.
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The relationship between hardness and solute carbon concentration estimated via electrical resistivity measurement was investigated in as-quenched and tempered martensitic steels containing carbon of ...0.3-0.6 mass%. As a result of corelating the amount of hardening due to carbon in solid solution with the solute carbon concentration, by the calculation to subtract precipitation strengthening, grain refinement strengthening, dislocation strengthening, and softening due to retained austenite from the total strengthening, we derived an equation of solid solution strengthening, where the hardening increases proportionally to the 1 / 2 or 2 / 3 power of the solute carbon concentration. It was confirmed that the effects of the factors other than solid solution strengthening due to carbon on hardness are relatively small in tempered specimens when the tempering temperature is less than 673 K; therefore, the change in hardness in tempered martensitic steels can be mostly explained by solute carbon concentration regardless of carbon content.
Electrical resistivity of low-carbon martensitic steels was measured to estimate the carbon concentration in solid solution. Since electrical resistivity is influenced not only by solute carbon but ...also by substitutional elements, lattice defects and second phase, the effects of these factors need to be subtracted from total electrical resistivity, in order to obtain the accurate solute carbon concentration by this method. As a result, the effects of dislocations and grain boundaries were much smaller than that of solute elements, being only 1 - 2% of the measured electrical resistivity, in martensitic steel. On the other hand, substitutional elements and retained austenite were found to be significantly effective. By subtracting these effects from the measured value, the change in electrical resistivity due to solute carbon, Δρsol.C, could be formulated as a function of the carbon concentration in solid solution of martensite, Csol, as follows:Δρsol.C mΩmm = 0.25 × Csol mass%The estimated solute carbon concentration was confirmed to correspond to the directly measured value by atom probe tomography.
Electrical resistivity of low-carbon martensitic steels was measured to estimate the carbon concentration in solid solution. Since electrical resistivity is influenced not only by solute carbon but ...also by substitutional elements, lattice defects and second phase, the effects of these factors need to be subtracted from total electrical resistivity, in order to obtain the accurate solute carbon concentration by this method. As a result, the effects of dislocations and grain boundaries were much smaller than that of solute elements, being only 1 - 2% of the measured electrical resistivity, in martensitic steel. On the other hand, substitutional elements and retained austenite were found to be significantly effective. By subtracting these effects from the measured value, the change in electrical resistivity due to solute carbon, Δρsol.C, could be formulated as a function of the carbon concentration in solid solution of martensite, Csol, as follows:Δρsol.C mΩmm = 0.25 × Csol mass%The estimated solute carbon concentration was confirmed to correspond to the directly measured value by atom probe tomography.
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