Elastic Anisotropy and Its Temperature Dependence of Single Crystals of 63% Fe-32% Ni-5% Co Alloy (Super-Invar)

Temperature dependences of thermal expansion and Young’s modulus in single crystals of 63% Fe-32% Ni-5% Co alloy were measured over a temperature range −30° to 600°C. The single crystal rods with several crystal directions were prepared to have a length of about 12 cm and a diameter of about 3 mm. The principal elastic parameters and Young’s moduli for the three principal directions calculated from the measured values of thermal expansion and Young’s modulus for the single crystals. The results showed that the temperature dependences of Young’s moduli for the three principal directions were similar to each other, and that the Young’s moduli at 20°C in the 〈100〉, 〈110〉 and 〈111〉 directions were 5.8×105, 12.53×105 and 20.42×105 kg/cm2, respectively.The crystal anisotropy of Young’s modulus, E〈111〉⁄E〈100〉 of the alloy was estimated to be 3.52 at 20°C.