V. M. Nadutov

Hyperfine Magnetic Structure and Magnetic Properties of Invar Fe-Ni-C Alloys

Fee Fe-Ni-C alloys in comparison with binary Fe-Ni alloys were studied by the Mossbauer spectroscopy and magnetic methods. The saturation magnetization and the magnetic susceptibility were measured for the alloys within a temperature range of 77 — 450 K. The martens tic points and Curie temperatures were obtained. A supplement to the Window method for the fitting of asymmetrical Mossbauer spectra of invar alloys is proposed. The probability distribution P(H) was determined and isomer shifts were estimated.

Small-Angle Neutron Scattering in F.C.C. Fe-Ni and Fe-Ni-C Alloys

Small-angle neutron scattering was studied in Invar Fe-Ni-C alloys in comparison with the Fe-Ni alloy. Mössbauer measurement was carried out to indicate magnetic structure. The non-linear SANS curves were analysed using a power law function and the Porod approximation and interpreted in terms of aggregates characterized by smooth surfaces or fractal properties. The size and shape of the inhomogeneities were estimated by using the Indirect Fourier Transformation analysis.

Allotropic forms of carbon in the Invar Fe–Ni–C alloy before and after plastic deformation by upsetting

Abstract The effect of cold plastic deformation by upsetting (e = 1.13) on structure and hybridised bonds of carbon in the fcc Invar Fe-30.9%Ni-1.23% C alloy was studied by means of X-ray phase analysis and X-ray photoelectron spectroscopy. Carbon precipitates along grain boundaries and inside of grains in the alloy after annealing and plastic deformation were revealed. The presence of mainly sp2- and sp3-hybridised C–C bonds attributing to graphite and amorphous carbon as well as the carbon bonds with impurity atoms and metallic Fe and Ni atoms in austenitic phase were revealed in the annealed and deformed alloy. It was shown for the first time that plastic deformation of the alloy results in partial destruction of the graphite crystal structure, increasing the relative part of amorphous carbon, and redistribution of carbon between structural elements as well as in a solid solution of austenitic phase.

Mössbauer and SANS Studies of Anti‐Invar Fe‐Ni‐C Alloy under Magnetic Field

Anti‐Invar effect in the f.c.c.‐Fe‐25.3%Ni‐C alloy was revealed, i.e., enhanced thermal expansion coefficient (TEC) (∼20×10−6 K−1) which was accompanied by almost temperature‐insensitive behavior in a temperature range of 122–525 K that was considerably expanded to the low temperature range due to alloying with carbon. The Mossbauer and small‐angle neutron scattering (SANS) experiments with the varying temperature and in an external magnetic field of 1.5–5 T have revealed an existence of inhomogeneous magnetic order in anti‐Invar alloy below and above the magnetic transition point. The anti‐Invar behavior correlates with the thermally induced change in the magnetic order and interspin interaction.

Mössbauer and Structural Studies of f.c.c. Fe‐Ni‐C‐based PVD CAE Coatings

The physical vapor deposition by cathode arc evaporation (PVD CAE) technique in microdrops mode was applied for deposition of austenitic nanocrystalline coatings of the Fe−31.2%Ni−2%Co−0.002%Y and Fe−31.4%Ni−2%Co−0.72%C−0.001%Y alloys on Cu substrate. The Mossbauer spectroscopy, X‐ray diffraction analysis, transmission electron microscopy and dilatometry have been used to study the structure, magnetic order and thermal expansion of coatings. The estimated coherently diffracting domains values (CDD) and the TEM data testify that austenitic structure in coatings is dispersed and the presence of carbon intensifies the dispersion process of structural elements. Mossbauer analysis has shown that PVD CAE process results in the decomposition of an austenitic solid solution on microareas enriched both in Ni and Co and in Fe, which leads to the formation of a specific magnetic order characterized by existence of the ferromagnetic low‐moment (FM LM) and antiferomagnetic high‐moment (AM HM) phases and provides stabl...