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The new method of time-averaged speckle images and the well-known method of speckle-field interference studied the development of plastic deformations occurring during multicycle fatigue of structural steel. The correctness of strain determination by the new method is evaluated by comparing the data obtained by the two methods. Two optical systems including laser modules with different wavelengths were investigated. The proposed optical system allows to determine the components Δuy, Δuz of the relative displacement vector of two surface points located at a distance (measurement base) Δs = 66 μm. The known scheme makes it possible to describe deformations by the traditional method on the base of 470 μm. The object of study was a flat specimen made of 09Г2С steel with two side notches. Fatigue tests were carried out on a resonance-type machine at different cycle amplitudes. It is shown that at all cycle amplitudes the development of plastic deformations occurs by the mechanism of cyclic creep. There is a good correlation between the data obtained by two different speckle methods. At the same time, the strain estimated by the new method is in some cases an order of magnitude higher than the strain calculated by the known method. Obviously, this is due to the existence of local smallsized (of the order of 101 μm) strain areas which cannot be measured by conventional methods. The ultimate tensile strain Δuy/Δs calculated by the new method is of the order of 10–1, which coincides with the similar strain occurring in tensile testing of standard specimens. The results obtained by the new method justify the need of developing sensors and nondestructive testing devices of a new generation, allowing to estimate the time to fatigue crack initiation by the rate of change of physical quantities and by their limit values.

Direct measurements of the magnetocaloric effect were performed in a Heusler Ni44.4Mn36.2Sn14.9Cu4.5 alloy at cryogenic temperatures in magnetic fields up to 10 T. The maximum value of the inverse magnetocaloric effect in a 10 T field was ∆Tad = –2.7 K in the vicinity of the first-order magnetostructural phase transition at T0 = 117 K. Ab initio and Monte Carlo calculations were performed to discuss the effect of Cu doping into a Ni-Mn-Sn compound on the ground-state structural and magnetic properties. It is shown that with increasing Cu content the martensitic transition temperature decreases and the Curie temperature of austenite slightly increases. In general, the calculated transition temperatures and magnetization values correlated well with the experimental ones.

The effect of a high magnetic field up to 12 T and a high hydrostatic pressure up to 12 kbar on the stability of the metamagnetic isostructural phase transition and the multicaloric effect of Fe49Rh51 alloy has been studied. The phase transition temperature shifts under the magnetic field and the hydrostatic pressure on with the rates of dTm/μ0dH = −9.2 K/T and dTm/dP = 3.4 K/kbar, respectively. The magnetocaloric and multicaloric (under two external fields) effects were studied via indirect method using Maxwell relations. The maximum of the entropy change is increasing toward the high temperature region from ∆S~2.5 J/(kg K) at 305 K to ∆S~2.7 J/(kg K) at 344 K under simultaneously applied magnetic field of 0.97 T and hydrostatic pressure of 12 kbar. The obtained results were explained using the first-principle calculations of Gibbs energies and the phonon spectra of the ferromagnetic and the antiferromagnetic phases. Taking into account the low concentration of antisite defects in the calculation cells allows us to reproduce the experimental dTm/dP coefficient.

The bi- and tri- layered magnetoelectric composites were fabricated from magnetic Fe49Rh51 and piezoelectric PbZr0.53Ti0.47O3 materials. It was shown the electric field-induced stresses reduce the magnetization around magnetic phase transition temperature of Fe49Rh51: by 5.4% for tri-layer PZT/FeRh/PZT composite and by 3.6% for bi-layer FeRh/PZT composite. The magnetoelectric properties were studied at 320 K, the magnetization rate was estimated for the magnetic field of 0.5 T. The heterogeneous distributions of stresses and magnetization in volume of magnetic layer under applied magnetic and electric fields were demonstrated using COMSOL Multiphysics software. The obtained results demonstrate the tri-layered composite is more effective for tuning the magnetization

In this work, Pr2-xNdxFe17 (x = 0 - 2) ribbons with thickness of about 15 μm were prepared by melt-spinning method. The alloy ribbons were then annealed at different temperatures (900 - 1100°C) for various time (0.25 - 2 h). The formation of the (Pr,Nd)2Fe17 (2:17) crystalline phase in the alloys strongly depends on the Pr/Nd ratio and annealing conditions. Annealing time for the completed formation of the 2:17 phase in the rapidly quenched ribbons is greatly reduced in comparison with that of bulk alloys. Curie temperature, TC, of the alloys can be controlled in room temperature region by changing Pr/Nd ratio. Maximum magnetic entropy change (|ΔSm|max) and full width at haft the maximum peak (FWHM) of the magnetic entropy change of the alloys were respectively found to be larger than 1.5 J.kg−1K−1 and 40 K in room temperature region with magetic field change ΔH = 12 kOe.

Magnetic phase transition, magnetocaloric effect and critical parameters of Ni50-xCoxMn50-yAly (x = 5 and 10; y = 17, 18 and 19) rapidly quenched ribbons have been studied. X-ray diffraction patterns exhibit a coexistence of the L21 and 10M crystalline phases of the ribbons. Magnetization measurements show that all the samples behave as soft magnetic materials with a low coercive force less than 60 Oe. The shape of thermomagnetization curves considerably depends on Co and Al concentrations. The Curie temperature (TC) of the alloy ribbons strongly increases with increasing the Co concentration and slightly decreases with increasing the Al concentration. The Ni45Co5Mn31Al19 and Ni40Co10Mn33Al17 ribbons reveal both the positive and negative magnetocaloric effects. Under magnetic field change (ΔGH) of 13.5 kOe, the maximum magnetic entropy change (|ΔSm|max) of the Ni45Co5Mn31Al19 ribbon is about 2 and -1 J·kg−1·K−1 for negative and positive magnetocaloric effects, respectively. Basing on Arrott - Noakes and Kouvel - Fisher methods, critical parameters of the Ni45Co5Mn31Al19 ribbon were determined to be TC ≈ 290 K, β ≈ 0.58, γ ≈ 0.92 and δ ≈ 2.59. The obtained values of the critical exponents indicate that the magnetic order of the alloy ribbon is close to the mean-field model.

In this paper, we investigated the influence of additional compounds of Dy-Nb-Al, Nd-Cu-Al… on the coercivity of the sintered Nd16.5Fe77B6.5 magnets. The additional compounds were first prepared by arc-melting method and then ground into particles with size in the range of 40 - 80 nm using a high energy ball milling method. After that, the additional powder were mixed with micrometer Nd-Fe-B powder before magnetic anisotropic pressing, vacuum sintering and annealing. The structure of the magnets was thoroughly analyzed using X-ray diffraction and electron microscopy techniques. The magnetic properties of the magnets were investigated on a pulsed field magnetometer. The results show that the coercivity of the sintered Nd-Fe-B magnets can be improved by introducing additional nanoparticles to their grain boundaries. The improvement of the coercivity of the magnets is clearly dependent on composition and fraction of the additional compounds. The coercivity has been enhanced 40% for the magnets by adding 3 wt% of the Dy-free compound of Nd40Cu30Al30.

High cooling power of magnetocaloric refrigeration can be achieved only at large amounts of heat, which can be transferred in one cycle from cold end hot end at quasi-isothermal conditions. The simple and robust experimental method of direct measuring of the transferred heat of materials with magnetocaloric effect (MCE) in thermal contact with massive copper block with definite heat capacity in quasi-isothermal regime was proposed. The vacuum calorimeter for the specific transferred heat ΔQ and adiabatic temperature change ΔT measurements of MCE materials in the fields of Bitter coil magnet up to H = 140 kOe was designed and tested on samples of Ni43Mn37.9In12.1Co7 Heusler alloy with inverse MCE in the vicinity of meta-magnetostructural phase transition (PT). It was found, that the magnetic field H = 80 kOe produces complete PT from martensite to austenite with ΔQ = - 1600 J/kg at initial temperature 273 K.