Regulation of the Concentration Heterogeneity and Thermal Expansion Coefficient in the Metastable Invar FeNi Alloy.

Mössbauer spectroscopy and electron microscopy study of the active redistribution of Ni atoms during the process of polymorphous transformation α→γ in the metastable FeNi alloy revealed that slow heating (at the rate of 0.2 K/min) results in the depletion of the initial α-phase with a beneficiation of developing disperse γ-phase plates according to the equilibrium diagram. A regulation possibility of the concentration heterogeneity and austenite thermal expansion coefficient resulted from the polymorphous transformation α→γ was shown. Comparison with data of FeNi alloy irradiation by high-energy electrons responsible for the variation of atomic distribution and thermal expansion coefficient (owing to the spinodal decomposition) was performed.