Materials Science Forum Vol. 946

Abstract: The effect of Nb content on microstructure, mechanical properties and phase formation in as-melt and annealed binary Ti-Nb alloys were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. The content of Nb varied in the range 25-35 mass % leading to significant changes in the microstructure. The annealed and furnace-cooled binary Ti-Nb samples exhibited HCP martensitic α` phase at a Nb content below 27.5 mass % and metastable BCC β phase at higher contents of Nb. The mechanical properties of alloys depended strongly on the Nb content and type of the dominating phase.

Abstract: Article presents an experimental study result of milling coarse strontium hexaferrite in beater mill with formation of magneto fluidized bed and without it. Magneto fluidized bed is formed by mutually perpendicular constant and alternating gradient magnetic fields. We studied the dynamics of particle size distribution from milling time and parameters of magnetic fields. Microstructure dynamics of strontium hexaferrite powder particles milled in various regimes was studied by X-ray diffraction methods. Milling efficiency and energy efficiency of milling process were studied in conditions with and without powder fluidization by magnetic fields. Analysis of experimental data showed advantages of milling in magneto fluidized bed in increased efficiency, particle size distribution homogeneity and powder chemical activity because of lattice micro-stresses.

Abstract: It is shown that for the formation of Fe₂Al₅ intermetallic coatings on the steel surface the aluminized layer obtained by explosion welding must be subjected to a double heat treatment (660 °C, 3 h + 640 °C, 3 h). The first heat treatment ensures the necessary size of the diffusion zone, and the second leads to the formation of a main crack at the interface of Fe₂Al₅ and FeAl₃ intermetallides, which allows to separate the unreacted layer of aluminum and form a coating with hardness of 10 GPa. To form Fe₂Al₅ intermetallic coating on the steel surface, the aluminized layer, which is immersed in the melt, must be heat treated at 800 °C. The alloying of the diffusion zone by Si and Cu with the replacement of aluminum by the AK12M2 alloy leads to a decrease in the thickness of the diffusion zone and the appearance of additional phases of Al₇Fe₂Si and (Al,Si)₅Fe₃ in its composition. The duration of the subsequent heat treatment at 800 °C for complete dissolution of the surface layer increases the hardness of the resulting coating on the basis of a solid solution of Si in Fe₂Al₅ is 7.5-8 GPa.

Abstract: The data on the occurrence of martensitic transformation in steel under the action of a magnetic field were obtained by the electric resistivity method. The obtained data indicate the possibility of stress-assisted martensite formation in the temperature range of M_s-M_d (in which superplasticity of austenite is observed). This possibility is due to the magnetic heterogeneity of austenite. Nanosized regions with a ferromagnetic order are present in the paramagnetic matrix. They can perceive the energy of the external magnetic field through the magnetostrictive stresses and change the fields of the elastic forces in the crystal lattice. All this leads to a decrease in the energy of formation of the nucleation center.

Abstract: The relationship between the phase composition and the Young’s modulus in quenched PT-7M, Ti-6Al-7Nb, BT16 titanium alloys has been studied using the structural analysis, thermodynamic calculations in the Thermo-Calc software and micro-indentation. It is found that the nature of the change in the Young’s modulus in the investigated titanium alloys after quenching from the two-phase α+β-region depends on the chemical composition of the alloy, which determines the nature of the observed metastable phases (α', α", ω, β). The correlation between the extreme change in the Young’s modulus from the quenching temperature and the so-called interatomic bonding force (F_b) calculated from the electronic structure parameters of the α, α', β phases was shown for the Ti-6Al-7Nb alloy. The relationship between the limits of the Young’s modulus of the investigated alloys during quenching with the level of their alloying with α-and β-stabilizers is shown.

Abstract: The work is devoted to studying the polished surface state of K8 optical glass by ellipsometry, IR spectroscopy and surface roughness measurement methods. It is shown that for chemically stable K8 glass the change of the surface state is insignificant, that is caused by its composition.

Abstract: In this article we justify the economic feasibility of using thermos-cyclic treatment of casing from economically alloyed steel 09G2S to produce the strength group Q125, in accordance with API 5CT. It was confirmed by the experiment that using a four-fold thermal cyclic quenching followed by a low-temperature tempering from the low-alloyed pre-eutectoid steel, it is possible to produce mechanical properties at the level: tensile strength 1068 MPa, conditional yield strength 1002 MPa, elongation 11.2 % and absorbed energy 64 Joules. In addition, an economic evaluation of the application in the production of high-strength casings from steel 09G2S, which allows reducing production costs by at least 11 %, due to thermal cycling.

Abstract: The paper presents experimental results of wear resistance measurements of anti-friction coatings of bimetal fluid-film bearings. As a result, nature and peculiarities of wear process of anti-friction coatings and steel base have been identified. An analysis of antifriction properties of studied copper-based coatings is presented. The paper also features recommendations for application of the studied coatings obtained by means of gas-flame spraying.

Abstract: A second-order regression polynomial model is offered, taking into account a pair components interaction for TCLE calculation of low-melting glasses in system MgSO₄-KPO₃-Na₂B₄O₇. The analysis of the obtained model is carried out. The results adequacy, obtained by modeling in comparison with the experimental data, is shown. It is established that the square pair interaction of the MgSO₄-KPO₃ and MgSO₄-Na₂B₄O₇ components, when modeling this system, can be neglected.

Abstract: Strontium hexaferrite is a well-known material, due to its application in microelectronics. This paper is devoted to strontium hexaferrite single crystals, obtained by the spontaneous crystallization technique with sodium based flux. SrFe₁₂O₁₉ crystals were grounded, pressed to the tablets, and crystals cell parameters were measured by thermal X-ray diffraction technique. Coefficient of thermal expansion calculated from the X-ray thermal diffraction data is in a good agreement with dilatometric measurements.