A. V. Zagainov

Structure and magnetic properties of Fe100-xSnx (3.2 < × < 62) alloys obtained by mechanical milling

Abstract The structure and magnetic properties of mechanically ground Fe-Sn alloys have been studied by X-ray diffraction, magnetic measurements, and 57Fe and 119Sn Mossbauer spectroscopy. It has been shown that the alloys are nanocrystalline and have the disordered bcc structure with Sn concentrations x 32.7. The concentration dependences of the magnetic ordering temperature, average magnetic moment per Fe atom, average hyperfine magnetic field and isomer shift, as well as those of the bcc lattice parameter and grain size are nonlinear and reveal a number of peculiarities at 12–15, 25 and 50 at% Sn. The ferromagnetic state is shown to form in alloys with x

Hysteresis magnetic properties of the Fe(100−x)C(x); x=5–25 at% nanocomposites as-mechanically alloyed and after annealing

Abstract The paper presents the results on coercive force and specific saturation magnetization depending on the phase composition and grain size of the Fe–C powders after mechanical alloying and subsequent annealing.

The role of cementite in the formation of magnetic hysteresis properties of plastically deformed high-carbon steels: I. Magnetic properties and structural state of cementite

Magnetic properties of cementite after strong plastic deformations and subsequent annealing in a broad range of temperatures are studied. The plastically deformed cementite is shown to exist in a soft (Hc ≈ 80 A/cm) state; the annealed cementite, in a hard (Hc ≈ 240 A/cm) state. The nature of the cementite’s soft and hard states is discussed. The field dependence of the cementite’s magnetostriction is measured. The longitudinal magnetostriction of the polycrystalline cementite’s saturated state is shown to be negative and approximately four times smaller than iron’s magnetostriction in the saturated state.

Magnetic properties of amorphous Fe78P22 alloy obtained by mechanical grinding

Abstract The amorphous Fe 78 P 22 alloy obtained by mechanical grinding was studied by X-ray analysis, Mossbauer spectroscopy and magnetic measurements. The measured values of the average hyperfine magnetic field H , mean magnetic moment per Fe atom m Fe and Curie temperature T c agree with those obtained earlier for electrodeposited and then ground samples and are in good qualitative agreement with the model describing macroscopic characteristics through the parameters of local environment but essentially disagree with the literature data for the samples obtained by rapidly quenching and only by electrochemical deposition.

Structural state and magnetic properties of cementite alloyed with manganese

Using X-ray diffraction analysis, Mössbauer spectroscopy, and magnetic measurements, the structure, parameters of hyperfine interactions, localization of Mn atoms in the lattice, coercive force, and specific saturation magnetization have been investigated in the mechanically alloyed and annealed cementite (alloyed with manganese) of compositions (Fe1 − xMnx)3C (x = 0–0.12). It has been shown that strongly deformed cementite resides in the low-coercivity state and, after annealing in the vicinity of 500°C, in the high-coercivity state. Alloying with manganese reduces the coercive force, the specific saturation magnetization, and the Curie temperature of cementite. Inhomogeneities of the distribution of manganese atoms indicate the temperature dependence of the coercive force of mechanically alloyed and annealed cementite samples.

Using magnetic testing to optimize the technology of manufacturing stain-proof austenitic steels

Some results are presented that are concerned with the use of magnetic methods and tools for nondestructive testing of articles made of OAO Izhstal’ austenitic chrome-nickel steels. It is shown that modern magnetic-testing techniques help significantly in optimizing the industrial process while improving the technical specs of the produce.

Phase composition, structural state, and magnetic properties of nanocomposites of composition (Fe,Cr)75C25: Mechanosynthesis and isochronous annealings

The effect of the alloying element Cr on the structure, parameters of hyperfine interactions, and magnetic properties of the nanocomposites of compositions (Fe1 − xCrx)75C25, where x = 0.01–0.10, which was obtained by mechanical synthesis with subsequent annealing, has been investigated. It has been established that alloying with chromium reduces the coercive force, saturation magnetization, and Curie temperature of cementite. At the same time, alloying with chromium increases the thermal stability of cementite.

Formation of chromium-alloyed cementite in the process of mechanosynthesis and subsequent annealings

Mössbauer spectroscopy and magnetic measurements have been used to investigate the formation of phases in the process of mechanosynthesis of a nanocomposite of composition (Fe0.93Cr0.07)75C25 in a planetary ball mill with the subsequent annealings at various temperatures. It has been shown that, at the initial stage of the mechanosynthesis, an amorphous Fe-C phase is formed. Later, an amorphous Fe-Cr-C phase is formed and, in the process of the subsequent mechanosynthesis, an alloyed cementite is formed from it. It has been found that, due to the products of the pickup from the milling balls made of ShKh15 steel, the changes in the initial composition (Fe0.93Cr0.07)75C25 of the powders that reach 5 wt % have almost no effect on the phase composition, specific saturation magnetization, and the coercive force of samples annealed at 800°C for 1 h.

On the causes of the formation of a maximum in the dependences of the coercive force of simple carbon steels on the tempering temperature

The dependences of the coercive force Hc of quenched specimens made of simple carbon steels on the tempering temperature Tt were measured at room and liquid-nitrogen temperatures. These studies showed that the formation of the character of Hc(Tt) dependences for the mentioned steels within the region of medium and high tempering temperatures is caused by the content of cementite and its magnetic hysteresis properties.

Structural and phase transformations during heat treatment of the Fe(71.4)Si(14.3)C(14.3) amorphous alloy prepared by mechanical alloying

Differential scanning calorimetry, X-ray diffraction, Mössbauer spectroscopy of 57Fe nuclei, magnetic measurements, and different heat treatments have been used to study the sequence and mechanisms of solid-state reactions in the Fe-Si-C amorphous alloy in the course of the structure transition to equilibrium. Three stages of structural and phase transformations have been found; these are the structural relaxation, formation of an Fe5SiC silicocarbide, and its decomposition. It has been shown that the second and third stages occur during isochronous annealing within sufficiently narrow temperature ranges of 380–405 and 530–555°C, respectively. The kinetics of the decomposition of the metastable Fe5SiC silicocarbide and the formation of the ordered Fe-Si alloy during isothermal annealing has been studied.