Abstract
The resistivity of Fe-Ni-Cr solid solutions increases and the temperature coefficient decreases with rise in nickel content. This explains the peculiarity observed in γ′-forming stainless steels of a resistance increase on ageing that is greater when measured at the ageing temperature than at a low temperature. A range of steels with varying Ni content and Ti/Al ratio has been examined and the anomalous resistivity increase calculated. This is shown to be independent of temperature within the accuracy of the experiments and to decrease slowly with increase in γ′ size, but some effect remains at particle sizes of 25–30 nm dia. Cold work lowers the resistivity of Fe-Ni-Cr alloys with high Ni content and a rapid increase occurs on annealing at 500°C (773 K). A similar effect is observed in the high-nickel γ′ - forming alloys and is thought to be due to short-range order in the matrix.
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