A. study of microstructures responsible for the emergence of the invar and permalloy effects in Fe-Ni alloys

摘要

The paper presents experimental results obtained by transmission electron microscopy and X-ray photo-electron spectroscopy on the Fe_(68)Ni_(32) and Fe_(23)Ni_(77) alloys, which indicate that in these alloys, the phase transition ordering-phase separation occurs in the temperature range near 600 °C. Above the transition temperature, the sign of the ordering energy is positive; clusters enriched in atoms of one of the components are observed in the structure of the alloys. A modulated microstructure is formed after heat treatment at temperatures, at which the invar effect in the Fe_(68)Ni_(32) alloy is the maximum. Below the transition temperature, the sign of the ordering energy is negative, which determines a tendency to form chemical compounds. After aging at these temperatures, when the Fe_(23)Ni_(77) alloy has high permalloy properties, highly-dispersed fully coherent particles of the L1_2 (γ') phase are found to precipitate in the solid solution.