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In this paper, we report on the synthesis of terbium sesquioxide (Tb2 O3 ) nanopowder by laser ablation of a solid target material in Ar gas flow using an ytterbium fiber laser with an average power of 300 W. The as-synthesized nanoparticles featured spherical morphology, an average size of 13 nm and a substantially monoclinic crystal structure, whose symmetry was converted into cubic by heat treatment at 850°C under vacuum. Pressureless densification of powder compact at 1450°C yields 95.6 % of the relative density indicating excellent sinterability of the produced nanoparticles. XPS analysis was used to estimate the ratio between O and Tb concentrations as [O] / [Tb] =1.51, which is close to the Tb2 O3 stoichiometry indicating a very low content of detrimental Tb4+ ions. The obtained results suggest that laser ablation in Ar gas flow is a promising technique for synthesizing Tb2 O3 nanoparticles suitable for further fabrication of advanced magnetooptical ceramics. © 2022, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.

A scheme is proposed that explains the appearance of several β-solid solutions that differ in chemical composition when the VST3553 alloy with the addition of tin and zirconium is heated to a temperature of 750 °C. It is shown that heating to a higher temperature of 770 °C contributes to more intense diffusion redistribution of alloying elements and the disappearance of this phenomenon., Предложена схема, объясняющая появление нескольких β-твердых растворов, отличающихся друг от друга по химическому составу при нагреве сплава VST3553 с добавками олова и циркония до температуры 750 °C. Показано, что нагрев до более высокой температуры 770 °C способствует более интенсивному протеканию диффузионного перераспределения легирующих элементов и исчезновению этого явления.

Solid-state amorphization process on Fe–3 %Si–0,5 %Cu alloy surface with thermostable MgO coating was observed at continuous annealing in 600–1060 °C temperature interval. Diffusion amorphization simulation has been suggested. Fe (Si) solid solution is being amorphizated because of Mg2Si complexes is transferring therein., Терморентгенографическим методом на поверхности сплава Fe-3 %Si–0,5 %Cu c термостойким покрытием MgO при непрерывном отжиге в интервале температур 600–1060 °C наблюдался процесс аморфизации из твердого состояния. Предложена модель диффузионной аморфизации твердого раствора Fe (Si) за счет перехода в него комплексов Mg2Si, образующихся в результате восстановления оксидов водородом.

The study of the processes occurring in the surface layer of the MgO coated commercial alloy Fe-3%Si-0.5%Cu (grain oriented electrical steel) demonstrated that the amorphous phase in the form of a Fe-based solid solution is formed during continuous heating in the 95%N2 + 5%H2 atmosphere. For the purposes of this study, the following methods were used: non-ambient XRD at 20 –1060°C with heating and cooling at a rate of 0.5 dps, layer-by-layer chemical analysis performed by a glow discharge analyzer, scanning electron microscopy and energy dispersive X-ray spectroscopy. ThermoCalc software was used to calculate the potential phase equilibrium states. The amorphous phase was formed in the α → γ transformation temperature range, when the heating rates were altered in the surface layer of 1 µm initially consisted of a solid α-Fe-based solution with ~1– 2 wt.% Si with (MgFe)2 SiO4, (MgFe)O, SiO2 oxide inclusions. We suppose that (MgFe)2 SiO4 oxides are partly reduced by H2 to Mg2 Si molecular complexes, which become solid solutions in the temperature range of the metastability of the α-Fe crystal lattice with subsequent amorphization as an alternative to the α → γ transition. The amorphous state is obtained at 920 – 960°C and is retained both at subsequent heating (to 1060°C) and cooling (to 20°С), which is super-stable compared to the established metallic glasses. The composition of the amorphous phase can be described by the formula Fe89.5 Si6 Mg4 Cu0.5. © 2020, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.

The material for investigation was a ribbon with an amorphous structure obtained by the melt spinning technique from a melt of molybdenum-modified Finemet-type high-permeability Fe72.5Cu1Nb2Mo1.5Si14B9 alloy. Using the methods of non-ambient X-ray diffraction, calorimetry, and dilatometry, temperature intervals of transformations during the transition of material from the amorphous state to the nanocrystalline one with subsequent recrystallization were determined. Each method was characterized by its own heating rate: 1 K / min for the non-ambient X-ray diffraction, 30 K / min for calorimetry, and 20 K / min for dilatometry. Regardless of the heating rate, phase and structure transformations (crystallization and recrystallization, respectively) were observed sequentially. With decreasing heating rate, the crystallization temperature significantly decreased and the recrystallization temperature slightly decreased. Specific heats of crystallization (386 kJ / mol) and recrystallization (88 kJ / mol) were calculated from calorimetry data. Basing on the results of X-ray diffraction and calorimetric studies, the possibility of using the structural unit model was analyzed to describe the amorphous state. It was supposed that any condensed state of the material (amorphous, nanocrystalline and recrystallized) were distinguished by different sizes of coherent scattering regions (CSRs). The lower estimate of coherent scattering regions size was made from the X-ray diffraction halo width for the amorphous state and (110) diffraction line broadening for polycrystals. The Wigner-Seitz cell (truncated octahedron) containing one atom has been adopted as a structural unit. Specific heats of transformations were compared to the values of energies related to the transitions of atoms from CSR borders to lattice sites. Satisfactory applicability of the structural unit model for the description of the amorphous state was demonstrated. © 2019, Institute for Metals Superplasticity Problems

The material of the study was (α + β) -titanium alloy VT16. Samples were quenched from different temperatures and then they were heated in situ on X-ray diffractometer. It has been established that the period “b” of the orthorhombic martensite lattice showed negative values of the coefficient of thermal expansion during heating.

The effect of copper and manganese on the amorphization process in the surface layer of a technical Fe-3% Si alloy during annealing in the α → γ transition temperature range was determined by x-ray phase analysis. The presence of 0.5 wt. % Cu and 0.3 wt. % Mn in the initial Fe-3% Si solid solution significantly enhances the amorphization process that occurs when heated in the temperature range 920... 960∘C as an alternative to the α → γ phase transformation. The effect of amplification of amorphization is both in obtaining a larger amount of material in the amorphous state, and in the appearance of two amorphous phases, differing in average interatomic distance. The composition of the amorphous phase is approximately described as Fe89Si6Mg4Mn0.5Cu0.5 in the presence of Cu and Mn atoms and Fe90Si6Mg4 in the case of their absence in the amorphous layer.

This paper is devoted to study a structure of SiC-based materials using ultrasonic tomography method. The SiC-based materials were fabricated from preceramic paper using spark plasma sintering (SPS) method. Also as part of the study the Young's modulus and density of sintered materials were determined and the effect of sintering pressure changing to this parameters value was investigated. The preceramic paper is a composite material including a matrix of organic cellulose fibers and inorganic powder filler (SiC). The sintering temperature and pressure were 2373 K and 20-40 MPa, respectively. The holding time for the sintering process was 10 min. The density of sintered materials was investigated by the hydrostatic weighing method. Ultrasonic tomography was implemented using of single-channel sensor at 10 MHz frequency. © Published under licence by IOP Publishing Ltd.

Critical points of amorphous alloy of Fe-Si-Nb-Cu-Mo-B system was determined using the non-ambient x-ray diffraction method. The sample with amorphous structure was produced by planar flow casting process. Temperature range of alloy nanocrystalline state was established. © 2019, National University of Science and Technology MISIS. All rights reserved.