The role of cementite in the formation of magnetic hysteresis properties of plastically deformed high-carbon steels: II. Magnetic properties of patented wire made of steel 70

It is shown that, during discussion of the mechanism reliable for formation of the coercive force in high-carbon steel, in addition to the interaction between the domain walls and weakly magnetic cementite inclusions, the contribution from the cementite’s magnetic hardness should be considered. With the use of the temperature dependence of the coercive force in deformed and annealed specimens, the contribution of each of the considered mechanisms to the specimens’ coercive force is estimated.     

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.     

The effect of cementite on the formation of the magnetic hysteresis properties of thermally treated carbon steels

The role of cementite in the mechanisms of formation of the coercive force of high-purity 60 and 13 model steels and 9A and 12A industrial steels after quenching and subsequent medium- and high-temperature tempering is determined from the analysis of the temperature dependences of the coercive force. It is shown that cementite as a hard-magnetic phase plays an important part in the formation of the dependence H _c (T _temp) measured at room temperature. The maximum contribution caused by the coercivity of cementite to H _c of the model steels is proportional to the volume content of cementite. In the industrial steels, an effect on the coercivity of cementite is produced by carbideforming unavoidable impurities.     

The possibility of testing the structural state of highly-deformed high-carbon steels by the magnetic method

The influence of cold plastic deformation on phase transformations and on the magnetic properties of powder specimens of the Fe-5-at. % C alloy modeling U12 high-carbon steel has been investigated in the context of nondestructive testing. It has been shown that under high plastic deformation dissolution of cementite Fe3C occurs by the scheme -Fe + Fe₃C -Fe + (Fe₃C)_d + -Fe + Am(Fe-C). An increase in the rate of plastic deformation of powders decreases the coercive force from 50 to 13 A/cm due to the low coercivity of the #x03B1;-Fe and Am(Fe-C) phases. The structural state of high-carbon steels following a strong cold plastic deformation can be determined by measuring two magnetic parameters: the coercive force, and the temperature dependence of differential magnetic permeability.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 42–52.Original Russian Text Copyright © 2004 by A.I. Ulyanov, Arsenteva, Zagainov, A.L. Ulyanov, Elsukov, Dorofeev.     

The effect of tempering temperature on the coercive force of high-carbon steels measured at room temperature and a temperature above the curie point of cementite

The role of cementite in the formation of the H _c of carbon steels after quenching and tempering is determined based on analysis of dependences of the coercive force of У9A steel in the measurement temperature range from the temperature of liquid nitrogen to the cementite Curie point. It is shown that the key contribution to the formation of the maximum in the H _c (T _temp) dependence measured at room temperature is due to the magnetic hardness of cementite, whose maximum lies at T _temp = 500°C. The coercive force measured at 250°C is mainly related to the interaction of the domain walls of the ferrite matrix with nonferromagnetic inclusions of cementite, the maximum of which is at T _temp = 400°C, thus causing a shift of the maximum in the H _c (T _temp) dependence measured at the temperature above the cementite Curie point toward lower tempering temperatures.     

Influence of structural features of welded joints of low-alloy steels on magnetic and micromagnetic properties

Variations of magnetic (coercive force H _c , residual induction B _r , maximum magnetic permeability μ_max, maximum magnetic-permeability field H _μmax, saturation magnetization J _max) and micromagnetic (number of pulses N and RMS Barkhausen-noise amplitude U) characteristics along the parent metal-welded joint direction were studied for welds of steels 10XCHД, 15XCHД, 09Γ2C, and X70.     

Comparative analysis of the magnetic characteristics of plastically deformed metal in different zones of a welded pipe under elastic deformation

Comparative analysis of the effect that the pre-history of plastic deformation by uniaxial tension has on the regularities in the behavior of some magnetic parameters of metal in different zones of a welded large-diameter pipe made of strength grade X70 steel has been carried out under the conditions of subsequent elastic uniaxial tension (compression).     

Role of the structural state in the formation of deformation,strength, tribological,and technology properties of structural materials

Improving the strength and reliability of machine parts and structures requires the development and validation of refined calculation methods for durability and survivability at the design stage and at the stage of operation of products under extreme loading conditions (large variable loads, high temperatures, vibration feedback). The establishment of such methods requires research in behavior of structural materials and coatings based on experimental studies in conditions close to operational loadings.     

Effect of anneal on magnetic properties and structural state of iron powders ground in carbon-rich medium

Intense milling of iron powders in a carbon-rich liquid leads to carbonization of powder particles to concentrations of up to several weight percents, alongside the notable reduction in the dimensions of mosaic blocks and formation of a nanocrystalline structure, which results in a lower coercive force of the powder. X-ray and Mössbauer data indicate that Fe?C disordered solid solutions are formed in the regions of mosaic-block boundaries in the process of the powder milling. The anneal forms the Fe₃C ordered carbide phase from the disordered solid solution, which raises the coercive force in the powders beyond 100 A/cm.     

The role of a stressed state in the formation of stress-corrosion flaws in pipelines

In recent years, as a result of performance of intensive in-tube flaw detection, the integrity and reliable operation of trunk pipelines have been achieved. However, because of an unpredictable development of such tube flaws as stress corrosion, the probability of occurrence of emergencies in pipelines substantially increases. An analysis of the stressed state in pipelines exposed to their main load—the operating pressure—and various types of additional forces is presented. As a result, it is shown that the obtained direction, value, and location of the effective maximum stresses in the tube wall fully correspond to the pattern of statistical formation of stress-corrosion flaws in pipelines. It can be concluded from the data of this study that the standardized tube-strength margin is insufficient; during tube operation, this circumstance may lead to the formation of stresses at the level of the metal yield stress and initiation and growth of stress-corrosion cracks.     

Magnetic properties of cementite and the coercive force of a Fe-5 at % C alloy after hardening and tempering

The role of cementite in the mechanisms of formation of H _c for specimens of a model high-carbon Fe-5 at % C alloy after hardening and tempering is determined from the analysis of the temperature dependences of the coercive force measured in the range from the temperature of liquid nitrogen to the Curie point for cementite. This analysis is based on the different characters of the temperature dependences of the contributions to H _c due to cementite as weakly magnetic inclusions at which the matrix’s domain walls are decelerated and cementite as a hard magnetic phase. It is shown that the magnetic hardness of cementite makes the main contribution to the formation of the coercive force in the region of medium and high tempering temperatures.     

Modeling relations between physical properties and chemical composition of steels in quenched state

Linear statistical models with multiple parameters have been developed for predicting the magnitudes of the coercive force, saturation magnetization, electric conductivity, and hardness of highcarbon and alloyed steels of various chemical compositions quenched in the normal regimes.     

Multiparameter methods in magnetic structuroscopy and nondestructive testing of mechanical properties of steels

Methods of nondestructive testing of the quality of metal in hot-rolled, thermally treated, and other states are considered for the cases when structural changes are diversified, one of such structural transformations having an opposite effect on the sensitivity of a particular characteristic to the accompanying transformation, and when one-parameter inspection according to the coercive force is either inefficient or impossible. The natures of the structural and phase sensitivity of the coercive force, the saturation magnetization, and the magnetic permeability are analyzed. Examples of the practical application of multiparameter magnetic structuroscopy are considered.     

The role of substrates on the structural,optical, and morphological properties of zno nanotubes prepared by spray pyrolysis

ZnO films were deposited onto glass, ITO coated glass, and sapphire substrate by spray pyrolysis, and subsequently annealed at the same temperature of 400°C for 3 h. The role of substrate on the properties of ZnO films was investigated. The structural and optical properties of the films were investigated by X‐ray diffractometer (XRD) and photoluminescence (PL) spectrophotometer, respectively. The surface morphology of the nanostructured ZnO film was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Crystallographic properties revealed that the ZnO films deposited on sapphire and ITO substrates exhibit a strong c‐axis orientation of grains with hexagonal wurtzite structure. Extremely high UV emission intensity was determined in the film on ITO. The different luminescence behaviors was discussed, which would be caused by least value of strain in the film. Films grown on different substrates revealed differences in the morphology. ZnO films on ITO and sapphire substrates revealed better morphology than that of the film on glass. AFM images of the films prepared on ITO show uniform distribution of grains with large surface roughness, suitable for application in dye sensitized solar cells. Microsc. Res. Tech. 77:211–215, 2014. © 2013 Wiley Periodicals, Inc.     

Momentum transmission of a diaphragmed magnetic spectrometer: I. Analysis and definitions

An experimental device consisting of a plane source of charged particles and of a magnetic spectrometer equipped with horizontal and vertical diaphragms is considered. An analysis intended to achieve an exact analytical expression to connect the observed particle flux to the source emission and spectrometer transmission characteristics is developed. An analytical expression for the average value of the source brightness that is actually obtained from corpuscular flux measurements is also given. The effectiveness of the diaphragms in defining the domains of the initial conditions of the particles is also emphasized and general definitions of these domains are introduced. These definitions are stated for exact optical transformations, i.e., accounting for geometric and chromatic aberrations, and for general positions of the diaphragms along the optical axis as well as for symmetrical or asymmetrical apertures of the same. The results obtained and the introduced definitions will be used in Part II of this work. The important case of a thick source is considered in Appendix A.     

The structure and assembly of collagen fibrils*: I. Native-collagen fibrils and their formation from tropocollagen

Hypotheses to explain the formation of native-collagen fibrils from tropocollagen macromolecules have been considered and their inconsistencies examined. A new model for the tropocollagen macromolecule is suggested and a new mechanism for its assembly into native-collagen fibrils is offered. It is postulated that the tropocollagen macromolecule is divided into 5 main bonding zones separated by 4 main non-bonding zones. The macromolecules are assembled into native fibrils by allowing a main bonding zone on a particular macromolecule an initial random choice in combining, in a structurally complementary manner, with a main bonding zone on another macromolecule. The evidence for the proposals arises from the use of negative-staining techniques and high-resolution electron microscopy. The work described includes a more detailed discussion of some preliminary findings reported earlier (Grant, Home, & Cox, 1965b).     

Methods for the measurement of polarization optical properties: I. Birefringence

A simple birefringence detection system has been developed that can be used with any standard polarizing microscope. A Foster prism is utilized in separating the orthogonal components of the resultant linearly polarized light coming from a properly oriented λ/4 plate. The light intensities of the orthogonal components are measured simultaneously and a mathematical manipulation yields a direct read-out of phase retardation (nm). The theory and practical use of this technique is discussed, as well as the present and future applications.     

The possibility of separate measurements of the amounts of ferrite and deformation martensite in three-phase austenitic-class steels using the magnetic method

Corrosion-resistant austenitic steels of the chromium-nickel class, which initially include ferrite and deformation martensite (????-phase) were the objects of study. These studies were aimed at the development of a method for magnetic nondestructive testing of the percentages of ferrite and deformation martensite in a three-phase austenitic material.