Galina S. Kraynova

Structure Evolution of Fe- and Co-Based Amorphous Alloys Studied by the Electrical Resistivity Measurements

The subject of this study is the change of the electrical resistivity of Fe-based metallic glasses during heat treatment. Electrical resistivity is a structure-sensitive characteristic of materials. In metallic glasses, the scattering of conduction electrons on the disordered structure is the main mechanism responsible for the electrical resistivity. Hence amorphous metallic alloys have a much higher residual resistivity as compared to their crystalline analogs. It is typical for metallic glasses that the temperature coefficient of resistivity (TRC) is smaller than for the corresponding crystalline materials, and it can be either positive or negative.

SEM identification of the amorphous state of Fe−B ribbons

Based on X-ray diffraction and electron microscopy data on morphological inhomogeneities at the interfaces in Fe−B ribbons, the boundary boron concentration separating the crystal and amorphous states upon spinning (~10 at %) is established. A modulated isotropic stochastic wave structure is detected, the relaxation of which can be presented as spinodal decomposition.

Effect of composition on the structural relaxation of amorphous iron-based alloys

The structural relaxation of iron-based amorphous alloys upon changes in their relative electrical resistance and magnetic moments upon a rise in temperature is investigated. The presence of Nb in Fe(Cu, Nb)–Si,B alloys stabilizes amorphous states, lowering the Curie temperature TCam and raising the temperature of the paramagnetic–ferromagnetic magnetic phase transition.

Surface irregularities and magnetism in amorphous metal foils on Fe basis

This paper presents the study results of morphology contact and free surface at amorphous metal foils (Fe7Co71Ni12(SiB)10, Fe70Ni10(SiB)10, Fe60Co30(SiB)10) and their analysis of the elemental composition. Using spectral methods of research was allowed to make a comparative analysis size and anisotropy of distribution topological inhomogeneities. A parallel study of spinning foils by Mossbauer spectroscopy and Vibrating sample magnetometer (VSM) possible to determine the magnetic state of the samples.

Influence of Fe-Co ratio and Ni,Cr dopants on structural evolution of metallic amorphous alloys

In this paper the analysis of structure changes in series of amorphous alloys with different Fe/Ni and Fe/Co ratio and Cr addition is made. It has been shown that within temperature range 230С <T< 4500С the structure of alloys keeps its amorphous character and only a slight changes in heat flow occur. At temperatures above 450°C the structure evolution depends of the Fe/Ni and Fe/Co ratio and some dopants.

Analysis Methods of Images Surface of Fast Tempered Alloys

This work proposed a method for processing of microscopic images of complex structural non-crystalline objects. The declared approach assumes procedure of system parametrization of images without procedure of allocation of components. It is based on concept of fields of anisotropy inhomogeneities on microscopic images. On an example of images of a microrelief spinning tapes effectiveness of the given procedure for reception of quantitative characteristics about objects is shown. The entered factor of anisotropy has allowed to allocate multiscale character of morfo-inhomogeneities interfaces of tapes and has allowed to describe process of spining depending on technological modes of reception. It is shown, that the further progress of the given approach can be carried out by methods of informo-dynamics.

Complex Analysis of Electrical Resistivity Dynamics of Co82Fe4Cr3Si8B3 Amorphous Alloy under Heat Treatment

In this paper the detailed analysis of thermal behavior of electrical resistivity of Co82Fe4Cr3Si8B3 amorphous alloy is made. It has been shown that within temperature range 230С <T< 5600С the structure of the alloy keeps its amorphous character and only a slight changes occurred. A high temperature (above room temperature) resistivity minimum was found at 160°C. This feature was related with Curie temperature of the alloy. It has been shown that change of electrical resistivity behavior at 350°C can be explained by reaching the Debye temperature of the alloy.

Changes of Structure and Magnetic Properties of Fe66Co24Si3B7 Amorphous Alloy under Heat Treatment

In this paper features of structure at the atomic level, magnetic properties, and mechanisms of structural relaxation during thermal annealing of melt-spun ribbon Fe66Co24Si3B7 (ribbon thickness is 28 microns) will be discussed. By means of differential scanning calorimetry and X-ray diffraction analysis of melt-spun alloy it has been shown that structural relaxation processes have complex multi-step nature, primarily related with instability of alloy. Using this data it has been shown that magnetic structure-sensitive properties, such as coercivity and magnetic moment, can be considered as structural relaxation indicators in amorphous alloys. The original amorphous material when heated to crystallization temperature partially passes to the crystalline state, causing the increase in residual magnetic moment and coercivity.

Magnetic Properties of Amorphous Nanocrystalline Alloys Based on Iron with Different Contents of Nobium in Structural Relaxation Processes

Magnetic properties of amorphous nanocrystalline alloy Fe–(Cu, Nb)–(Si, B) during stepwise annealing are investigated by means of X-ray diffraction analysis, vibration magnetometry, and Mössbauer spectroscopy. It is shown that an increase of the Nb content reduces the amount of the nanocrystalline component in the alloy, stabilizing the amorphous state and magnetic softness during structural relaxation.

Kinetics of the Fractal Mesodefect Structure of Melt-Spun Fe70Cr15B15(Sn) Alloys during Annealing

We have studied the effect of tin microalloying on the kinetics of the fractal mesodefect structure of melt-spun Fe70Cr15B15(Sn) alloys during thermal loading. It is established that the morphology evolution of ribbon interfaces correlates with the kinetics of physical properties. Symmetry character of melt-spun alloys is identified by the form of fractal dimensionality spectrum. Reduction of the fractal dimension is observed at stages of both vitrification and nanocrystallization. Residual alloying by tin of the contact interface of ribbon changes a topology of the localized states that lowers the temperature of vitrification.