The electrical characteristics of a nickel-chromium-aluminium-copper resistance wire

The changes in electrical resistance and temperature coefficient of resistance during the heat treatment of a nickel-chromium-aluminium-copper alloy, known commercially as Evanohm, are presented. From the nature of the resistance/temperature curve and X-ray diffraction data, it is proposed that the electrical changes be attributed to short-range order. Data are presented to show that both the mean temperature coefficient of resistance and the minor deviations in linearity in the resistance/temperature curve vary in a systematic manner during heat treatment and that the changes are independent of prior thermal history. Resistance changes after heat treatment, caused by either surface tarnishing, oxidation, or the application of strain during fabrication, are discussed.