Papers by Keyword: Amorphous Alloy

Abstract: The amorphous-forming ability (AFA) and the magnetic properties of the amorphous Fe-B-C-Si soft magnetic alloys have been investigated. Though the ternary Fe-B-C alloys exhibit high magnetization, their AFA is poor, which has prevented their practical application. It was confirmed that the addition of Si to the Fe-B-C alloys significantly improves AFA. Furthermore, it has been found that the composition range of the Fe-B-C-Si alloys with sufficient AFA can be identified by focusing on the enthalpy of mixing (ΔH_mix) and δ, which is related to the ratio of atomic radius between the constituent elements, of the alloys. The Fe-B-C-Si amorphous alloys that combine the high saturation magnetization of 175−177 A m²/kg with sufficient AFA to produce thick sheets whose thickness of 70 μm or more have been successfully developed by using the relationship between ΔH_mix, δ and AFA as a guideline. The Fe-B-C-Si amorphous alloys are expected to be applied to core materials for various magnetic components.

Abstract: Ni-based metallic amorphous alloys in ribbons shape are used in the manufacture of electrical resistances due to their high electrical resistivity, a value that does not change with temperature. The production of such resistances involves joining processes of amorphous ribbons. The amorphous alloys are difficult to weld by conventional melting processes, even in the presence of inert gas. Consequently, this paper presents the research carried out regarding the capacitor energy storage welding technique of Ni₆₃Cr₁₂Fe₄Si₈B₁₃ amorphous ribbons. The structural analysis was done by microscopy, X-ray diffraction, and differential scanning calorimetry, and the mechanical behavior was determined by nanoindentation. The joints obtained showed that the proposed welding technology is appropriate for this type of joint.

Abstract: This paper presents a model of a thin film formation process of an amorphous alloy as a sequential procedure when a conditional unit of substance is randomly thrown onto a substrate at each next step. The islands of a precipitant are generated on the substrate with an increase of number of steps (density defects of substance). We determine the probability distribution of an island area, which shows the maximum informational entropy. An algorithm for computing estimates of parameters of this distribution is obtained. The results of processing experimental data are presented. We demonstrate that the proposed distribution is more consistent with the experimental data than the Pareto distribution.

Abstract: In the paper, the atomic structure of amorphous and nanocrystalline alloys of the electrolytically obtained CoP, NiP, CoNiP, CoW, and CoNiW systems has been studied. The structure was investigated by electron microscopy and diffraction using a Libra 200 HR FE transmission electron microscope at an accelerating voltage of 200 kV within a temperature range of 50-35 °C. The obtained radial atom distribution function and the coordination sphere radii are in good agreement with the data for the cobalt structure in the cubic and hexagonal modifications. The high coordination numbers of the third and fourth coordination spheres allow suggesting a predominantly cubic structure of the local atom environment in CoP samples but somewhat lower, which is explained by the presence of free volume and phosphorus atoms distorting the local structure. When heating, the near atomic order also corresponds to the cubic phase of cobalt, and the ordering occurs in the second, third, and fourth coordination spheres. The data obtained for CoNiP alloys indicate that by configuration, the local atomic environment is closer to the hexagonal structure of nickel. In general, the structure of the CoP-CoNiP system alloy films obtained by electrolytic deposition is already in one of the local minima of the total system energy, which is confirmed by the near atomic order similar to the cubic phase of cobalt or hexagonal phase of nickel. This determines the good stability of the structure and properties during thermal exposure.

Abstract: The thermal and magnetic properties of the ternary Fe-B-C and quaternary Fe-B-C-Si amorphous alloys have been investigated. It has been discovered that the ternary Fe-B-C amorphous alloys with compositions close to Fe_79.3B_14.3C_6.4 exhibit a glass transition prior to crystallization on heating. The alloys also have high mass magnetization of 176–178 A m²/kg at room temperature. In addition, the glass-forming ability (GFA) of the alloys is significantly enhanced by the addition of 4 at% Si while maintaining high magnetization of approximately 170 A m²/kg at room temperature. In was found that the Fe₂₃(B, C)₆ phase (Cr₂₃C₆-type) is formed during crystallization of the quaternary Fe-B-C-Si alloys with the large GFA. It was also confirmed that the amorphous powders of Fe-Cr-B-C-Si alloys could be produced by a conventional water atomization method and exhibit the low core losses of 305–362 kW/m³ at 100 kHz and 100 mT. The quaternary Fe-B-C-Si amorphous alloys with high GFA, high magnetization and low core losses are suitable for a core material of various magnetic components.

Abstract: Titanium nickelide (nitinol) is of great applied interest in various industries due to unique combination of its physical and mechanical characteristics. In the present work, we consider the possibility of obtaining nitinol with mesoporous structure by rapidly cooling the molten sample to room temperature. Based on molecular dynamics simulation data, it was shown that the rapid cooling of the nitinol melt leads to formation of a porous structure. It was shown that the inner pore wall is formed mainly by titanium atoms, which provide biocompatibility of nitinol. It was found that the porosity of nitinol weakly depends on the cooling rate, while the porosity increases linearly with decreasing melt density.

Abstract: Scaling of minor hysteresis loops in the amorphous alloy Co₆₆Fe₃Cr₃Si₁₅B₁₃ with a very high initial permeability (more than 150000) and low coercivity (about 0.1 А/m) has been studied. In weak magnetic fields and in the region of maximal growth of permeability a similarity of minor loops was detected. Analytical expressions for hysteresis losses are derived which provide a good accordance of calculations with the results of measurements.

Abstract: Ti-based amorphous alloys containing no harmful elements are desired. However, many Ti-based amorphous alloys contain toxic elements such as Al, Ni, V and Be. The presence of toxic elements within amorphous alloys is a concern when they are intended for use as a biomaterial. This problem has steered many researchers toward the development of Ti-based amorphous alloys without toxic elements. Our novel amorphous alloys were developed based on this principle. A series of Ti44Zr10Pd10Cu6+xCo23-xTa7 (x = 0, 4, 8) amorphous alloys were developed for biomedical application. A series of protocol tests were performed to check for biocompatibility and potential use of the novel alloys in humans. First, alloy ingots were alloyed by induction melting and then cast into copper molds. The cast rod was then used as the plasma cathode in a filtered cathodic vacuum arc deposition chamber to coat the 25-nm amorphous alloy thin film on the cover glass slides. These coated cover glass slides were then examined for biocompatibility. Cell proliferation and cell differentiation were investigated using Methylthiazol Tetrazolium assay test and by alkaline phosphatase assay on osteoblast like cells (SaOS-2), respectively. Field emission scanning electron microscopy was performed to evaluate the thin film surface characteristics. The thickness of thin film was analyzed using a Stylus profilometer. An adhesion scratch test was administered to evaluate the thin film adhesive strength and indirect hardness comparison. Electron Dispersive X-ray Spectrometry was performed to study the elemental composition. Lastly, a medical grade Ti-6Al-4V alloy was studied in parallel as a control material. Results indicated that all investigated Ti-based amorphous alloys were non-cytotoxic and were comparable to the Ti-6AL-4V. They also demonstrated an ability to support differentiation of osteoblast like cells. The adhesion and the hardness of the thin films on the substrates were superior to that of Ti-6Al-4V. The results suggested that the novel alloys in this study could be potentially utilized in biomedical applications.

Abstract: The alloys Al₈₈Co₄Y₈, Al₈₈Ni₄Y₈, Al₈₇Ni₁₀Ce₃ and Al₈₅Ni₁₀Ce₅ were heated and mixed by using intermediate frequency furnace. By controlling different melt superheat tempratures, a series of thin strip alloy samples were prepared by single roller spinning quenching method. The X-ray diffraction (XRD) results show that melt temperatures have different effects on the amorphous structure formation of Al-(Co,Ni)-(Y,Ce) alloy. In addition The glass forming ability of Al-based amorphous alloy prepared by thermal analysis was analyzed. Experiments results indicate that the higher the melt temperature of Al₈₈Co₄Y₈ alloy, the easier the formation of the crystallization phase.

Abstract: It is clearly seen that the magnetic induction of the amorphous ribbon produced by conventional technology implying heating up to 1490 °С increases as the thickness of specimens increases, with this growth being especially intensive at the 100 А/m magnetic field strength. At the same time, the melt preparation supplemented by overheating contributes to the magnetic induction stabilization, i.e. magnetic induction is essentially independent of the ribbon’s thickness. It is only at high values of h that a slight increase in magnetic induction becomes evident. The fracture diameter of the free side surface is linearly increasing as the annealing temperature increases. The structure has been shown to influence magnetic and mechanical properties of the material in preparing the melt before casting.