Effect of alloying on thermal expansion of Superinvar alloy

Conclusions

• 1. We investigated the effect of Cu, Mo, Nb, Cr, Ti, Mn, and Re on the expansion coefficient of Superinvar in the range of 20–80°C. It was found that with up to 0.6% Cu, up to 0.6% Mo, up to 0.6% Nb, up to 0.2% Cr, up to 0.9% Mn, and up to 0.6% Re the stability of the γ phase increases, raising the expansion coefficient.

• 2. Small amounts of silicon substantially increase the expansion coefficient and lower the stability of γ phase. With an increase of the silicon content from 0.06 to 0.1% the expansion coefficient rises from −2·10⁻⁷ deg⁻¹ to 21·10⁻⁷ deg⁻¹ at 20–80%C and M_s rises from −40 to 0°C. The silicon content of Superinvar must be held to a minimum.