Temperature dependences of thermal expansion and saturation magnetization in Fe(67.0%)-Ni(32.5%)-Co(0.5%) Invar alloy with nanocrystalline structure

The effect of the nanocrystalline structure of Fe(67.0%)-Ni(32.5%)-Co(0.5%) Invar alloy on its thermal expansion is considered. It is found that the structure with grain mean sizes of about 100 nm increases its temperature coefficient of thermal expansion in the range of “invarness,” i.e., in the temperature range where the alloy offers the Invar properties. Reasons for this behavior are analyzed by taking the temperature dependence of the saturation magnetization.