Papers by Keyword: Nanocrystalline Alloy

Abstract: A technique for creating multilayer composites has been developed. Mechanical properties of two-layer composites without carbon nanotubes and with carbon nanotubes were carried out by the method of local loading. The dependences of microhardness on the magnitude of the load and the depth of indentation were determined. An equation for determining the coefficient of microdestruction viscosity for two-layer composite material has been developed.

Abstract: Temperature dependences of the kinematic viscosity, density, and electrical resistivity of Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ and Fe_84.5Cu_0.6Nb_0.5Si_1.5B_8.6P₄C_0.3 multicomponent melts have been studied. We found different behavior of the temperature dependences of viscosity near the critical point T_k = 1760 K during heating, which is associated with different chemical compositions of the clusters in the melt. In the cooling stage, the activation energy of the viscous flow for these two melts is the same and equal to 43 kJ·mol^-1. At a temperature of 1720 K, the relative free volume is 5.1 and 7.5 % of the total melt volume for Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ and Fe_84.5Cu_0.6Nb_0.5Si_1.5B_8.6P₄C_0.3 respectively. In the cooling stage, the electrical resistance of melt is higher than at the heating stage.

Abstract: The size of the nanoparticles participating in the viscous flow and the diffusion coefficient were calculated using statistical mechanical theory of absolute reaction rates and the Arrhenius equation. As experimental data, temperature dependence of the kinematic viscosity and density of Fe_73.5Cu₁Mo₃Si_13.5B₉ melt was used. At a temperature of 1600 K, after the melt is overheated above the critical temperature T_k = 1770 K, the nanoparticles size decreases from 0.92 to 0.47 nm, and the diffusion coefficient increases from 2.4·10^-10 to 4.5·10^-10 m²·s^-1.

Abstract: In this work, we investigated the dynamics of nanocrystallization from the amorphous state of the Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ alloy together with magnetic phase transformations. The thermomagnetic analysis was performed with the simultaneous recording of the temperature inside the core by a thermocouple and the inductance of the winding wound over the core. It was found that the permeability of the core after the crystallization peak first increases rapidly, and then decreases and stabilizes at some level. Permeability growth begins at a temperature that coincides with the Curie point of the Fe₈₀Si₂₀ solid solution. A decrease in permeability was associated with stabilization of the structure of the amorphous and crystalline phases upon cooling. With decreasing temperature, the active redistribution of chemical elements is suppressed, and silicon atoms occupy a stable position in the crystal lattice of iron. Nanocrystalline cores have different Curie temperatures in the state after the peak of crystallization and 300 seconds after the peak. This indicates the continuation of the diffusion of silicon from the amorphous matrix into Fe-Si nanocrystals for some time after the crystallization peak.

Abstract: In this work, the effect of different inhibitors on the thermal stability of the magnetic properties in Fe_73.5Cu₁M₃Si_13.5B₉ nanocrystalline alloys, where M = Nb, W, Mo, was investigated. Nanocrystalline alloy with tungsten has the greatest thermal stability. The change in the magnetic properties in the ageing process was associated with vacancies and vacancy clusters, the formation of which is facilitated by large atoms of inhibitory elements occupying free positions in the substitution solid solution.

Abstract: An amoprphous and nanocrystalline ribbon is produced applying the technology of rapid molten metal quenching. The chemical composition of the alloy is required to contain elements ensuring the amorphous structure formation in the course of quenching. A great number of various chemical elements in amorphous and nanocrystalline alloys contribute to the complex process of the structure formation in the course of heat treatment of the amorphous precursor. After heat treatment, the structure of the soft magnetic material can remain amorphous or partially crystallized or nanocrystalline. The results of an investigation into the melts’ property of iron-based amorphous and nanocrystalline alloys are presented in the paper. The structure has been shown to influence mechanical properties of the material in preparing the melt before casting.

Abstract: To describe the thermal stability of the nanocrystalline solid solution with weak segregation such as Cu-Zn system, we developed a hybrid model combining the first principles calculation and thermodynamic evaluation. The dependence of the solute segregation behavior on the solute concentration, grain size and temperature were demonstrated. We found that the segregation energy does not change with the solute concentration monotonically. At a constant solute concentration and a given temperature, a nanograin structure can remain stable if the initial grain size is kept in a critical range. The model predictions were confirmed by the experimental measurements that a state of steady nanograin growth can be achieved by designing a certain solute concentration and a proper initial grain size.

Abstract: Structural and chemical attributes of amorphous and nanocrystalline metals, which affect their corrosion behaviour are outlined. Effects of the fraction of intercrystalline regions, diffusivity, chemical homogeneity / heterogeneity and local ordering are indicated. These features can lead to higher or lower corrosion resistance as compared to coarse-grained counterparts, depending on the nature of tested metal and corrosive environment. Contributions of these factors are represented by two examples of passive behavior of nanocrystalline metals and amorphous Ni-P alloys.

Abstract: Magnetic properties of nanocrystalline Fe_73.5Cu₁Nb₃Si_15.5B₇ ribbons with anisotropy induced by stress-annealing at different temperatures have been investigated.The results show that the magnetic properties were improved with the increase of temperature and excellent DC bias property was obtained after annealing above 580°C due to the transverse strip domain structure.

Abstract: A novel measuring method based on Fe-based nanocrystalline alloy was studied to achieve accurate measurement of the lubrication oil pressure of auto engines. A magnetoelastic inductance pressure sensor was designed. Its operating principle, structure, output characteristics, and major parameters were discussed. The static characteristics of the sensor as well as its temperature, excitation circuit intensity, and influence on output frequency were analyzed through an experiment. Results show that the sensor is stable and reliable at high temperatures, and it has a simple structure. It can efficiently measure the lubrication oil pressure of auto engines.