The influence of plastic deformation on the magnetostriction constant of iron-nickel alloys

The magnetostriction constant of three iron-nickel alloys and one Fe-Ni-Co alloy was measured as a function of the plastic elongation up to about 25%. The magnetostriction constant decreases with deformation in all materials. In Fe-Ni-Co alloy the volume magnetostriction also decreases. The influence of crystallographic texture is discussed and it is shown that it is not a decisive factor. The observed decrease is explained by assuming the influence of lattice deformation on spin-orbital interaction.

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- Fe-Ni-Co 25%. . Fe-Ni-Co . , . .

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In conclusion the authors thank Z. Málek and S. Libovický for carefully reading this paper and for remarks, J. Míová for help in the measurements, J. Cáslavský for X-ray determination of the texture and members of the chemical department of the Institute of Physics for thermal treatment and analysis of the samples.     

The influence of elastic deformation on the magnetostriction constant of nickel and iron-nickel alloys

The dependence of the magnetostriction constant of different materials in the form of a wire on the elastic elongation was measured. With pure nickel the magnetostriction constant is independent of the elastic deformation. All three alloys of iron and nickel and the triple alloy Fe-Ni-Co exhibit a linear dependence on the deformation, which differs for different crystallographic texture. In two iron-nickel alloys the dependence of the magnetostriction constants of the single crystal on the elastic deformation was calculated from measurements on polycrystals having different crystallographic textures. In the triple alloy Fe-Ni -Co a considerable linear decrease in the volume magnetostriction with the elastic elongation was also found. The observed changes can be explained by assuming the influence of the lattice deformation on the spinorbital interaction in alloys.

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. . - Fe-Ni-Co , . - . , Fe-Ni-Co . - .

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A preliminary report on some of the results of this paper was given at the conference on magnetism in Kyoto (Japan) in September 1961.

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In conclusion the authors thank Z. Frait C. Sc. and S. Libovický for remarks, J. Míová for help in the measurements, members of the chemical department of our institute for annealing and analyzing the samples and members of the Metal Research Institute in Panenské Beany for their exceptional helpfulness in preparing the wires.     

The magnetostriction of aluminum substituted nickel ferrites

The room temperature magnetostriction constant λ₁₁₁ of the system NiFe_2?xAl_x0₄ is determined for 0<x<0.3. An unconventional system is used for the magnetostriction measurements. The growth, composition and saturation magnetization of the crystals are discussed. The values of x = 0 are in good agreement with those given in the literature. The saturation magnetostriction decreases with increasing aluminum content.     

The forced magnetostriction of nickel at 4.2 K

The forced volume magnetostriction of polycrystalline nickel at 4.2 K has been determined with a relative accuracy of 2 × 10^?2. Combining our result with previous data on the forced magnetostriction, we derive for the forced magnetostriction constants: h'₀ = (40 ± 1) × 10^?8T^?1, h'₁ = (-95 ± 2) × 10^?8T^?1, h'₂ = (-19 ± 2) × 10 ^?8T^?1.     

Effect of plastic deformation and quenching on the absolute thermal emf of nickel

The effect of the degree and rate of plastic deformation of nickel on the change of its absolute thermal emf was studied. The dynamic effect of the change of thermal emf was established, the dynamic coefficient being 1.22–1.25. Plastic deformation of quenched nickel reduced its absolute thermal emf, on the basis of which conclusions are drawn about the contributions, different in sign, of holes and dislocations to the change of the absolute thermal emf of nickel. The kinetics were studied of the recovery of the thermal emf induced in nickel by plastic deformation, and the existence was established of two stages of recovery, differing in nature and with different activation energies, 0.1 and 0.3 eV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 77–81, June, 1971.     

The influence of plastic deformation on the magnetoelastic properties of the CSN12021 grade steel

Magnetoelastic properties of materials are strongly influenced by changes of the dislocation structure that take place during the process of plastic deformation. Such changes can be used as a basis for a method of nondestructive evaluation (NDE) of the deformation level. So far, various methods, based on magnetic hysteresis loop properties as well as on the Barkhausen effect (BE), have been proposed. In the paper, the results obtained with the help of the abovementioned methods are compared with the results of the magnetoacoustic emission (MAE) signal measurements. The MAE signal is relatively easy to implement as a nondestructive method and unlike the BE effect signal gives information about the whole magnetized volume.     

The inhomogeneity of plastic deformation

Considerable local strain differences occur in single crystals as a consequence of slip bands. A significant contribution to this phenomenon is the effect of the deformation rate on the inhomogeneity of its distribution. In polycrystalline materials the plastic deformation is affected by grain boundaries and their vicinity as well as by various orientations of single grains in onephase metals and alloys, and by various component properties in multiphase materials. In some cases it has been possible to describe these phenomena by means of micromechanics. Valuable information has also been acquired by means of three-dimensional stereology.     

Classical magnetostriction of nickel in high magnetic field

A simple model is proposed as a possible explanation for the checkerboard pattern of modulations in the hole density observed in recent tunneling experiments on underdoped cuprates. Two assumptions are made; first, an enhanced hole density near the acceptor dopants and secondly short range correlations in the positions of these dopants caused by their electrostatic and anisotropic elastic interactions. Together these can lead to a structure factor in qualitative agreement with experiment.     

The influence of the shape of load stress pulses on the course of plastic deformation of crystalline materials

The present paper deals with the derivation of the relationship between the course of macroscopic deformation and the dynamic properties of dislocation in loading material with stress pulses of general shape, and duration in tens of microseconds. On the basis of the obtained relationships, the correctness of the definition of the yield point under these conditions of loading, suggested previously (Czech. J. Phys.B 20 (1970), 776) on the basis of the analysis of the phenomenon of delayed deformation at elevated loading rates, is demonstrated.In the calculation we proceed, on the one hand, from the relation for the dislocation rate proposed by J. J. Gilman= exp(-D/) and, on the other hand, the damping mechanism of a viscous type, where=b/B.In both cases the correctness of the suggested definition is shown. The results of the theoretical analysis agree with the hitherto known experimental results.     

The influence of quantum-mechanical athermal phenomena on the thermal instability of plastic deformation in crystals at low temperatures

The way in which athermal (quantum) mechanisms that allow dislocations to overcome local barriers affect the thermal instability of plastic deformation of crystals is discussed theoretically for the case of low and ultralow (<1 K) temperatures. Calculations show that increasing the athermal component of the dislocation activation leads to a considerable narrowing of the temperature/strain-rate region where discontinuous strains appear, and that further increases in the quantum component of the process by which dislocations surmount local barriers leads to the complete disappearance of these discontinuous strains. Experimental situations in which the effects of thermal instability and athermal effects are observed at the same time in a number of crystals under conditions of low-temperature strain are discussed in light of these results. Fiz. Tverd. Tela (St. Petersburg) 39, 1392–1398 (August 1996)     

The effect of grain size on the deformation resistance of nickel

The effect of the grain sizel of commerical nickel on the lower yield point, _y, and flow stress, _f , has been investigated. From the relationship between _y andl ^–1/2 and between _f andl ^–1/2, and also by extrapolation, the parameters ₁( _i ^f ) and k_y(kf), which occur in Petch's well-known expression, were determined. It was found that the values of these parameters depend on the previous history of the samples. It is suggested that the more marked dependence of the deformation resistance of nickel on grain size arising from certain thermal treatments is due to the segregation of impurities to the grain boundaries. It is shown that this is in accord with the presence of grain-boundary hardening and with its dependence on quenching temperature.     

The effect of plastic deformation on the transverse magnetoresistivity of potassium

A number of pure potassium samples have been plastically deformed under tension at low temperatures and the effect of this on the transverse magnetoresistivity at fields up to 6 T has been investigated. Although the influence of the dislocations so introduced is readily visible in the change of the zero field resistivity ?₀, there is no appreciable effect on the magnetoresistivity other than a shift by an amount equivalent to the change in ?₀.     

Dynamics of plastic deformation: Waves of localized plastic deformation in solids

Conclusions It has been shown here that a localized plastic deformation in structurally inhomogeneous media can be of a wave nature and can propagate in the form of nonlinear plastic waves, not only at the microscopic level but also at the mesoscopic level. It has been established that there is an interrelationship between this new effect and grain-boundary slippage (an effect which has been under study for a long time) and also with certain types of quasiviscous fracture in plastically deformable materials.We have discussed certain specific practical problems in the mechanics of plastic deformation, and for certain types of fracture. In the future, these problems will be discussed at a more profound level and in greater detail, because of experimental studies which are presently being carried out on the dynamics of deformation for various types of loading and fracture [17, 18, 31]. We hope that the approach proposed here for a theoretical study of the localization of deformation and fracture can be taken to study such effects as splitting off [31], the influence of defect fluxes on grain-boundary slippage [22], superplasticity [23], the behavior of tectonic faults and boundaries of various types [32], electroplastic and magnetoplastic effects, and high-temperature localization of deformation [25].The general nature of the approach proposed here results from the circumstance that a localization of deformation is present explicitly or implicitly during plastic deformation, and the behavior of this deformation plays a role of fundamental importance in the propagation of plastic deformation through a material.The author wishes to thank V. E. Panin for a constant discussion of this problem and I. O. Nedavnii for carrying out the numerical calculations.V. V. Kuibyshev Tomsk State University. Institute of Strength Physics and Materials Science. Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 19–41, April, 1992.     

Features of the change in the hall constant during the plastic deformation of alloys with a low stacking-fault energy

The effect of short-range order and stacking faults on the Hall constant of a number of binary copper-base alloys have been investigated experimentally.     

Variation of apparent creep activation energy in plastic deformation of molybdenum in diffusion contact with nickel

The variation of the apparent creep activation energy as a function of the state of grain boundaries is investigated in the deformation of molybdenum in the presence of diffusion fluxes of nickel at the grain boundaries. It is shown that this energy varies in the same way as in the plastic deformation of classical superplastic materials.Physics Institute of Strength and Materials Science, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 110–113, May, 1993.     

Effect of plastic straining on magnetostriction of ferromagnetic polycrystals—experiments and multiscale modeling

The influence of plastic deformations on magnetostriction of NO–3% Si–Fe alloy is studied. Experimental measurements are presented. The magnetostriction is strongly anisotropic before deformation and plastic strain tends to homogenize this behavior. The modeling consists in the calculation of a specific residual stresses field and its introduction in the magnetic model. Experiments and modeling are in good agreement.