A Study of Thermal Expansion Properties of Fe-Ni-Co Super-invar Alloys by Michelson Interferometer

Michelson interferometer was designed for measuring the thermal expansion coefficients of the ternary Fe-NiCo alloys and the binary Fe-Ni alloys with different chemical compositions at the temperature range from 25 ℃ to 65 ℃.The experiment results show that the thermal expansion coefficients of the ternary Fe64Ni36-xCoxalloys are strongly dependence on its chemical composition; the thermal expansion coefficient of the Fe64Ni31Co5 alloy reaches a minimum value of 0. 79 × 10- 6/℃,deviation from the composition of the Fe64Ni31Co5 alloy,the thermal expansion coefficients increase. The thermal expansion coefficients of the binary Fe-Ni alloys are also strongly dependence on its chemical composition; the thermal expansion coefficient of the Fe65Ni35 alloy reaches a minimum value of 1. 58 × 10- 6/℃,deviation from the composition of the Fe65Ni35 alloy,the thermal expansion coefficients increase. The thermal expansion coefficient of the Fe64Ni31Co5super-invar alloy is lower than that of the Fe65Ni35 invar alloy. The variation of the thermal expansion coefficient of the binary Fe-Ni alloy with Ni content is relatively large,while the variation of the thermal expansion coefficient of the ternary Fe64Ni36- xCoxalloy with Co content is relatively small.