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 plastic deformation on the magnetostriction constant of nickel

The magnetostriction constant of nickel was measured as a function of plastic deformation up to an elongation of 30%. The values of the magnetostriction constant in deformed samples deviate considerably, a fact which cannot be explained by errors of measurement. The absolute value of the magnetostriction constant decreases with increasing plastic deformation (by around 5%).

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30% . , . ( 5%).

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In conclusion the authors thank J. Kaczér, C. Sc. and B. esták, C. Sc. for carefully reading the paper and for their remarks, J. Míová for help in the measurements and workers of the chemical department of our Institute for careful preparation of the samples.     

The magnetostriction of Invar alloys

The principles of the theory of a phase transition into a magnetically ordered state are formulated for Invar alloys and other similar inhomogeneous ferromagnets, for which the concept of a local Curie temperature distribution corresponding to the experimentally observed broadened temperature interval of the transition into the ferromagnetic state has existed for 10 years. A method is proposed for obtaining information about the local temperature distribution from experimental data on the change in the properties of magnets in response to a change in temperature. For iron-nickel-chromium alloys it is shown how to obtain the temperature dependence of the magnetostrictional susceptibility of the paraprocess from data on the magnetic contribution to the thermal expansion coefficient. This confirms the important role of the local Curie temperature distribution, and it also indicates a need for new analysis of experimental data on temperature-broadened magnetic ordering phase transitions. Zh. éksp. Teor. Fiz. 113, 213–227 (January 1998)     

Effect of deformation on Barkhausen jumps of fine wires of iron,nickel and iron-nickel alloy

The induction technique was used to measure the potential difference of Barkhausen jumps (V_B) for fine wires of technical iron, nickel and iron-nickel alloy. The effect of deformation and mechanical stresses on the dispersal band and on the behaviour of the measured values was studied. The theory of the measurement process is described in terms of magnetic domain theory. The behaviour of V_B reflects the magnetude of the applied stress.     

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 effect of aluminum overlayers on the magnetization of iron and iron-nickel alloys

Iron and iron-nickel films 2 to 10 nm thick were prepared in a high vacuum magnetometer. The magnetic moment of each iron or iron nickel film was measured in situ, then an aluminum overlayer (2–30 nm thick) was deposited on the ferromagnetic film, and the magnetic moment was again measured in situ. The aluminum overlayer decreases the magnetic moment as if the iron film or iron-nickel film thickness decreases by about 0.3 to 0.5 nm.     

Electron irradiation effects on iron-nickel invar alloys

Electron irradiation was used as a means of accelerating the diffusion in Fe-Ni alloys. Mössbauer effect, X-ray and electron microscopy experiments on samples with 28 to 50% Ni show that the Invar character disappears after irradiation up to 250°C, in particular the variation of the lattice parameter versus temperature becomes linear around room temperature. At the same time, two phases appear in the alloy, one rich in nickel and ordered with FeNi (AuCu) superstructure, the other rich in iron and probably ordered (Fe₃Ni). The Invar state is therefore shown to be a metastable state. A diagram of the Fe-Ni alloy is proposed.     

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.     

Mössbauer study of the polymorphism in iron and iron-nickel alloys under deformation and high pressure

Structural and phase transitions in iron and binary iron-nickel alloys containing 6–32 at % nickel have been investigated by Mössbauer spectroscopy in situ under quasi-hydrostatic compression and compression shear. It is shown that the deformation decreases the onset pressure of the α-phase transition to the high-pressure ∈ and γ phases. Shear changes the transformation mechanism due to the formation of a large number of structural defects; it is an independent parameter of the phase transition kinetics. Compression shear leads to an irregular change in the hyperfine parameters of the initial and newly formed phases, which is due to the stress relaxation as in the trip effect.     

Neutron irradiation effects on martensitic iron-nickel alloys

Summary Iron-nickel alloys in the range from 29 to 32 wt.% Ni have been irradiated with an integral flux of 3·10¹⁸ n cm⁻² and then subjected to martensitic transformation. the resistivity, magnetoresistivity and Hall-effect measurements performed on the irradiated samples allow us to support the formation of iron-rich or nichel-rich ordered microstructures and additional α-phase from the supersaturated γ-matrix. The nickel content of the above-ordered region, is evaluated from the behaviour of the anomalous Hall effect in the irradiated specimens with different composition.

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Riassunto Leghe di ferro-nichel, con contenuto in Ni variabile dal 29% al 32%, sono state irradiate con un fascio di neutroni avente flusso integrale di 3·10¹⁸ n cm⁻² a 80°C e sono state successivamente sottoposte a trasformazione martensitica mediante raffreddamento. Le misure di resistività, di magnetoresistenza e di effetto Hall compiute sui campioni irradiati consentono di fare l'ipotesi della presenza nella fase supersatura γ di microstrutture ordinate, ricche di Fe o di Ni, oltre ad una fase α addizionale. Dal comportamento dell'effetto Hall anomalo nei campioni irradiati si è valutato il contenuto di Ni presente nelle regioni ordinate.

     

Magnetic properties of electrodeposited iron-nickel alloys

The basic magnetic properties, viz., magnetic saturation and coercive force, have been established by measurement of about 150 specimens for electrodeposited iron-nickel alloys over the entire range of chemical compositions. The magnetization data were related ot the physicochemical aspects of the electrodeposition process.     

Effect of elastic stress on the magnetostriction of ferromagnets

An experimental study has been made of the effect of elastic tensile stresses on the magnetostriction curves of polycrystalline nickel, transformer steel, an equiatomic cobalt-platinum alloy, and an Invar iron alloy with 30–40 wt. % nickel. The sign of the magnetostriction changes during the rotation process under the effect of sufficiently high stress. The effect is explained on the basis of the concept of a magnetic rotation texture, developed earlier by one of the authors. A change in the magnetostrictive susceptibility for the paraprocess of the Invar alloy is found to be caused by the stress; the signs of the magnetostrictive constants are determined for the hardened cobalt-platinum alloy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 2, pp. 89–94, February, 1969.     

On the dissymmetry of mossbauer spectra in iron-nickel alloys

Valuable information about the disappearance of magnetism in the invar region (concentration of 30–45 pct of nickel) may be obtained by the examination of Mössbauer spectra.^I–5 However, it appears that some characteristics of these spectra are already present in non invar spectra have not been taken in account up to now: even in a 50 pct alloy, the six lines have anomalous widths and heights, and it is the aim of this note to put a quantitative interpretation of this fact, letting for the future the extension to invar spectra.     

Inhomogeneous elastic deformation of nanofilms and nanowires of NiAl and FeAl alloys

The molecular dynamics study of the uniaxial tension of nanofilms and nanowires of NiAl and FeAl intermetallide alloys has been performed. It has been shown that such samples are elastically deformed until failure at a strain of ? _xx ≈ 0.35. There is an ? _xx interval where the homogeneous deformation is thermodynamically unstable, leading to the formation of domains with different strains. The strain-stress dependence in the thermodynamically unstable region is almost linear, but has different slopes for a nanofilm and a nanowire because of the difference in the dynamics of domain walls.     

Thermally activated deformation in some neutron ibradiated binary nickel alloys

Low temperature deformation behaviour of some neutron irradiated, binary nickel alloye, Ni-1%Ti, Ni-5%Ti and Ni-8%Fe has been investigated in 77–300 X temperature range. The studies have confirmed the irradiation induced defects responsible for both the changes in thermally activated deformation parameters and radiation hardening