Moessbauer study of amorphous invar structure and two-level model of expansion anomaly

Methods of Moessbauer spectroscopy and dilatometry are used to study local atomic structure and thermal expansion of amorphous invar Fe83B17 alloy. Availability of the regions which local order corresponds to metastable orthorhombic and tetragonal Fe3B phases is anticipated. Quantitative ratio of these regions is calculated from Moessbauer spectra and constituted 1:3. A quantitative two-level volumetric striction model, in which under heating reversible relaxation of orthorhombic Fe3B type configurations to tetragonal ones takes place, which causes decrease of iron interatomic distances, is suggested