Magneto-acoustic and Barkhausen emission: Their dependence on dislocations in iron
TL;DR: Magneto-acoustic emission (MAE) and Barkhausen emission (BE) have been measured from polycrystals of pure iron which were then heat-treated at successively higher temperatures as mentioned in this paper.
Abstract: Magneto-acoustic emission (MAE) and Barkhausen emission (BE) have been measured from polycrystals of pure iron which had been strained by 4.9%. The specimens were then heat-treated at successively higher temperatures. The heat treatments resulted in stress recovery and, at higher temperatures, a reduction in the dislocation density. BE activity and MAE activity profiles were measured after each anneal as a function of the magnetizing field, and the number of Barkhausen events was counted as a function of their peak amplitude. At low fields the intensity of the BE and MAE activities shows a strong trend as a function of the annealing temperature, which is in agreement with the temperature dependence of the dislocation density. At higher fields there are additional fluctuations in the BE and MAE activities as a function of the annealing temperature which occur at temperatures below those of dislocation recovery. These results show that both MAE and BE are sensitive to the dislocation density, and t...
Citations
More filters
TL;DR: A review of the current understanding of the subject, giving were possible examples of the approach and techniques used to obtain this, can be found in this paper, where the authors also highlight areas of current research activity and indicate the type of work still required to provide information on aspects that currently lack a full understanding.
213 citations
TL;DR: In this article, a review of magnetic NDT technologies is presented, which includes magnetic flux leakage (MFL), magnetic Barkhausen noise (MBN), and recently developed metal magnetic memory (MMM).
181 citations
30 Aug 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the characteristics of the Barkhausen noise phenomenon for various crystalline microstructures of plain steels are investigated using the same magnetisation rate for different materials, specially developed to provide fully reproducible experimental conditions.
Abstract: The characteristics of the Barkhausen noise phenomenon are investigated for various crystalline microstructures of plain steels. The measurements of the magnetic Barkhausen noise (MBN) and of the acoustic Barkhausen noise (ABN) are performed using the same magnetisation rate for different materials, specially developed to provide fully reproducible experimental conditions. The MBN fingerprints of single constituent steels (ferrite, pearlite and martensite) are first studied. Then, examples of MBN characteristics for more complex microstructures are presented. The results concerning single constituent steels are discussed in terms of shape, amplitude and position of the MBN and ABN fingerprints, taking into account two main aspects: the elementary Barkhausen events (sources), linked to the interaction of the magnetic domain microstructure with the crystalline microstructure, and the propagation of the electromagnetic waves in the material as well as its detection at the pick-up coil, both strongly influencing the frequency spectrum of the detected signal. This approach enables us to get a better understanding of the dependency of Barkhausen noise on the crystalline microstructure, which is then used to explain the characteristics of MBN observed for more complex microstructures.
101 citations
TL;DR: In this paper, the authors discuss the progress made in the application of non-destructive testing (NDT) techniques in evaluating various microstructural features and mechanical properties with emphasis on recent studies.
Abstract: Non-destructive evaluation (NDE) of materials for characterising various key microstructural features, mechanical properties (tension, creep, fatigue crack growth, hardness and fracture toughness), deformation and damage mechanisms has attracted considerable attention in the past 20 years as a primary step towards ensuring structural integrity of components. However, until recently, the correlations between the various NDE parameters and material properties have been only empirical and based on physical principles. The interaction between the NDE probing medium and the mechanical behaviour is not yet fully understood. The purpose of this review is to discuss the progress made in the application of non-destructive testing (NDT) techniques in evaluating various microstructural features and mechanical properties with emphasis on recent studies. Reinterpretation of older data, in the light of present understanding of the interaction of the NDE probing medium with material parameters, is carried out selectively. The NDT techniques evaluated include acoustic emission, ultrasonic attenuation and velocity, magnetic hysteresis parameters, magnetic Barkhausen emission, acoustic Barkhausen emission, laser interferometry, positron annihilation, X-ray diffraction and small angle neutron scattering. Critical assessments of the applicability of the various NDE techniques for the material parameters are provided.
78 citations
TL;DR: In this paper, a two stage process of irreversible domain wall movement during magnetization is proposed considering the grain boundaries and second phase precipitates as the two major obstacles to domain wall movements.
77 citations
References
More filters
Book•
[...]
01 Jan 1964
TL;DR: Paleomagnetism is the study of the magnetic properties of rocks as discussed by the authors, and it is one of the most broadly applicable disciplines in geophysics, having uses in diverse fields such as geomagnetic, tectonics, paleoceanography, volcanology, paleontology, and sedimentology.
Abstract: Paleomagnetism is the study of the magnetic properties of rocks. It is one of the most broadly applicable disciplines in geophysics, having uses in diverse fields such as geomagnetism, tectonics, paleoceanography, volcanology, paleontology, and sedimentology. Although the potential applications are varied, the fundamental techniques are remarkably uniform. Thus, a grounding in the basic tools of paleomagnetic data analysis can open doors to many of these applications. One of the underpinnings of paleomagnetic endeavors is the relationship between the magnetic properties of rocks and the Earth’s magnetic field. In this chapter, we will review the basic physical principles behind magnetism: what are magnetic fields, how are they produced, and how are they measured? Although many find a discussion of scientific units boring, much confusion arose when paleomagnetists switched from “cgs” to the Système International (SI) units, and mistakes abound in the literature. Therefore, we will explain both unit systems and look at how to convert successfully between them. There is a review of essential mathematical tricks in Appendix A, to which the reader is referred for help.
2,365 citations
TL;DR: Granular inclusions, grain boundaries, lamellar precipitates, and the crystalline surface have been examined as possible nucleation centers for domains of reverse magnetization in ferromagnetic materials as discussed by the authors.
Abstract: Granular inclusions, grain boundaries, lamellar precipitates, and the crystalline surface have been examined as possible nucleation centers for domains of reverse magnetization in ferromagnetic materials. It is concluded that the surface density of magnetic poles at the grain boundaries ${\ensuremath{\omega}}^{*}$ is the most common source of nucleation energy in polycrystalline materials.
243 citations
143 citations
TL;DR: In this article, a theoretical treatment of the action of internal stresses on domain walls and on uniformly magnetized Weiss domains is presented, based on micromagnetics, dislocation theory, and probability theory.
Abstract: This paper presents a theoretical treatment of the action of internal stresses on domain walls and on uniformly magnetized Weiss domains. The theory is based on micromagnetics, dislocation theory, and probability theory. Experimental results on the domain structure, the temperature dependence of the reversible susceptibility, and the coercive field of plastically deformed nickel, cobalt, and silicon‐iron single crystals and neutron‐irradiated nickel single crystals are discussed on the basis of the theory. The experiments are interpreted in terms of the magneto‐elastic interaction between dislocations and magnetization and agree satisfactorily with the theoretical predictions. The observed variations of the domain structure during the magnetization process can be accounted for in terms of the theory of phases (Neel, Lawton, and Stewart) and the mobility of the domain walls.
132 citations
TL;DR: In this paper, the effect of stress on the magnitude of acoustic emission during magnetization of mild steel and nickel has been investigated, and it has been shown that the acoustic emission shows a strong dependence on stress.
Abstract: The effect of stress on the magnitude of acoustic emission during magnetization of mild steel and nickel has been investigated. It has become clear that the magnitude of acoustic emission during magnetization shows a strong dependence on stress. This effect should have nondestructive testing applications suited for field inspection.
49 citations