Electrical Resistivity of Iron-Carbon Alloys

Abstract

The electrical resistivity of alpha iron-carbon solid solutions prepared from iron sources of two different general impurity levels has been studied as a function of applied longitudinal magnetic field up to 60 kOe at 4.2°K. It is demonstrated that the presence of interstitial carbon increases the resistivity of iron and drastically alters the shape of the magnetoresistivity curves, particularly at low fields. The residual resistivity contribution per at.% carbon in solution in high-purity iron is about 4.9 μΩ·cm. At 78°K the value is approximately 6.0 μΩ·cm/at.% carbon, indicating a positive deviation from the Matthiessen rule. In comparison, the residual resistivity of a lower-purity iron is about 6.5 μΩ·cm/at.% carbon at both 4.2° and 78°K. The magnetoresistivity data for the two iron materials containing carbon in interstitial solid solution are shown to obey the Kohler rule to a moderate approximation. In addition, some data are presented which demonstrate that the magnetoresistivity is dependent on the dispersion of the carbon in the iron.