A. I. Ul’yanov

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.

Effect of the magnetic properties of cementite on the coercive force of high-carbon steels after quenching and tempering

From an analysis of temperature dependences of the coercive force, contributions of different mechanisms to the formation of the coercive force of steel U9A samples after quenching and tempering have been determined. It is shown that the main contribution to the formation of the coercive force upon tempering at intermediate and high temperatures Ttemp comes from the magnetic hardness of cementite. The coercive force of cementite is determined by its structural state and in the range of tempering temperatures equal to 300–700°C changes along a curve with a maximum, thereby forming a maximum in the Hc(Ttemp) dependence of this steel as well.

Magnetic properties of cementite and the coercive force of carbon steels after plastic deformation and annealing

Magnetic hysteresis properties of cementite obtained by the method of mechanical alloying have been studied. It is shown that the strongly deformed cementite is in a low-coercivity state, and the cementite annealed at 500°C is in a high-coercivity state. The need to allow for the contribution of the coercivity of cementite to the coercive force of high-carbon steel is shown. Taking into account this point of view, the behavior of the coercive force depending on the degree of cold plastic deformation by drawing is explained for a number of carbon steels with a structure of fine platelike and globular cementite.

The role of cementite in the formation of magnetic hysteresis properties of plastically deformed high-carbon steels: III. Magnetic properties of patented wire made of steel 25

Temperature dependences of the coercive force of mechanically alloyed cementite and wires made of patented steel 25 that were subjected to plastic deformation and subsequent annealing are presented. As is shown, cementite can be in both low-and high-coercivity states, for which the coercive force measured at room temperature is 80 and 240 A/cm, respectively; the coercive force measured at liquid-nitrogen temperature (−196°C) is 190 and 530 A/cm, respectively. Based on an analysis of the temperature dependences of the coercive force of deformed wires made of patented steel 25, the role of cementite in the formation of the coercive force of low-carbon steels was determined. It is shown that, in spite of a relatively small amount of pearlite, the contribution due to the magnetic hardness of cementite to the coercive force should be taken into account. In this case, the contribution due to the interaction of ferrite domain walls with weakly magnetic cementite inclusions is substantially lower.

Regularities of the change in the coercive force under biaxial asymmetric deformation of steel 3

The change in the coercive force under biaxial asymmetric (tension and compression in mutually perpendicular directions) cyclic deformation of cross-shaped steel 3 specimens in the elastic region of deformations was studied. Specimens were deformed beforehand under biaxial asymmetric loading to various degrees of plastic deformation. It was demonstrated that the elastic-deformation dependences of the coercive force measured along the tension and compression directions are qualitatively similar to those under uniaxial tension or compression. It was also shown that, under cyclic elastic loading, these dependences are reversible for well-annealed steel and have a hysteresis that expands with increasing degree of plastic deformation for plastically deformed steel. The possible causes of the hysteresis in the dependence of the coercive force on the elastic cyclic deformations under biaxial loading are discussed. It was supposed that the hysteresis of the coercive force was caused by the appearance of free (not bound in carbide phases) carbon atoms playing the role of interstitial impurity atoms for the α-iron lattice in plastically deformed carbon steels. The possibility of estimating the stressed-strained state of steel under biaxial loading using a magnetic method was discussed.

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.

Coercive Force of Ferromagnetic Steels under the Biaxial Symmetrical Tension of a Material

Patterns of coercive force variations of Ct.3 and X70 ferromagnetic steels under biaxial symmetrical tension within both elastic and plastic ranges of deformation were studied using X-shaped specimens. It was shown that the coercive force of isotropic polycrystalline materials increased during plastic deformation under biaxial symmetrical tension and was proportional to applied stresses (loads). Plastic deformation of materials with high initial coercive-force anisotropy along the principal directions (X70 steel) leads to an abrupt decrease in anisotropy and subsequent alternation of its sign. The patterns of a material’s coercive force behavior allow the coercive force to be used for estimating the stress-strain state (from both an increase in the coercive force and its variations during loading as compared to that of the initial material) of articles made from the studied steels under biaxial symmetrical tensile deformation.

The influence of biaxial elastic deformation on the coercive force and local remanent magnetization of construction steels

The influence of biaxial elastic tension-compression and tension-tension deformation on the coercive force and remanent magnetization of Cτ3 steel and 09Γ2C pipe steel cross-shaped specimens is studied. It is shown that coercive force grows monotonically with increasing load in the direction of compression under elastic tension-compression deformation and almost does not change under elastic tension-tension deformation. The local remanent magnetization decreases for all the considered types of biaxial elastic deformation. The possibility of using these methods for the evaluation of the stressed state of complexly deformed carbon steel products is discussed.

Coercive-force hysteresis of carbon steels during elastic cyclic tensile deformation

Dependences of the coercive force and mechanical stresses on cyclic tensile in the region of elastic deformation of steel samples with various carbon contents (Armco iron, 3, 8) are investigated. It is shown that the dependence of the coercive force on cyclic elastic tensile deformation is reversible for well-annealed samples. The dependence for plastically deformed steels has a hysteresis loop that is significantly determined by the carbon content and increases with an increasing degree of plastic deformation. It is assumed that the hysteresis of the coercive force as a function of elastic cyclic tensile deformations in plastically deformed carbon steels is caused generally by the appearance “free” carbon atoms, i.e., those not bound in carbide phases, which act as interstitial impurity atoms in the lattice of α-iron.