Abstract: Effects of the crystallochemical factors on amorphous state formation in the Ni−Nb-based systems are studied. Alloys with compositions (Ni, Co, Fe)−(Nb, Ta, V, Mo+Zr) are prepared by rapid melt quenching method with various cooling rates. It was found that at given preparation conditions and at certain atomic size factor, glass forming ability depends on factor of electron concentration was defined as number of s+d electrons per atom. Atomic size factor is necessary take into account, too. High glass forming ability of Ni−Nb alloys are attributed to formation possibility of two distinct E93 type phases.
Abstract: This work is focused on a development and research of a new lead-free Sn-Mg solder, alloy compatible with the human body. Tin and magnesium are biocompatible elements which do not cause an inflammation or allergic reactions with living tissues. We have prepared the Sn97Mg3 solder (wt. %) by a rapid solidification of its melt on a copper wheel (melt-spinning technique). This solder may find applications in electronic devices for intracorporeal utilisation. The microstructure of the prepared solder exhibits a heterogeneous distribution of the SnMg2 intermetallic particles within the β-Sn matrix. Structure of the solder was studied by an in-situ high energy X-ray diffraction experiment (energy of an X-ray photon: 60 keV) where 2D XRD patterns were collected from the sample in the temperature range from 298 K to 566 K. The experiment was performed at a high brilliance 3rd generation synchrotron source of radiation (PETRA III storage ring, DESY, Hamburg, Germany) at the P02 undulator beamline. From the measured X-ray diffraction data by applying the Rietveld refinement technique we have obtained thermal volume expansion data, mean positions of atoms as well as isotropic atomic displacement parameters of the constituent SnMg2 and the β-Sn crystalline phases. Thermal behaviour was studied by differential scanning calorimetry at heating rates of 5, 15, 30 and 60 K.min-1 and compared with the measured X-ray data. Our main goal lies in a preparation of a lead-free solder with fine grain structure made exclusively of biocompatible elements. We demonstrated that the rapid melt solidification technique leads to in an improvement and better thermal stability of this alloy.
Abstract: The process of producing a composite material hybrid powder-laser-casting method. Developed new design of the mixing reactor. On the basis of mathematical methods of modeling examined of hydro-and gas-dynamic conditions for obtaining the suspension of the aluminum melt. Investigated the trajectory of moving particles in gas and liquid flows. Comprehensively studied the regularities of formation and stability of structural phase components in the composite material of aluminum alloy, which was obtained hybrid powder-laser-casting method. We show the possibility to control the porosity of the obtained composite material using the process parameters of the developed hybrid method.
Abstract: In this paper, we investigated the process of rotary forging of commercially pure copper grade M2 using standard and special-shaped anvils and presented the results of studies obtained by the method of numerical and physical modeling. It is established that the use of anvils with special geometric shapes provides a higher level of accumulated strain and the formation of more dispersed structural states with the same elongation ratio under conditions of multi-cycle processing . The formation of a finer structure in its turn increases the hardness and strength of the material. In addition, the special shape of the anvils provides a positive field of values of the Lode-Nadai coefficient in the cross section of the samples, predominantly in a range of 0.3-0.7 and, correspondingly, a more "comfortable" stress state close to non-uniform all-round compression, which contributes to increasing technological plasticity.
Abstract: Hydrogen storage in its solid state is one of the main challenges for mobile and stationary applications. Some metal hydrides are potential candidates for energy storage. This is an experimental research, which represents a contribution to the study of Hydrogen storage in its solid state, by studying the influence of the proportional substitution of V for Zr in the stoichiometric ratio Zr2-XVXFe (X=0.0, 0.1 y 0.2). Results indicate that the synthesis process generates a multi-phase type microstructure, and the absorption and desorption kinetic is less than 5 minutes at room temperature, in line with the parameters established by the United States Department of Energy; however, it is clear that the desorption capacity decreases.
Abstract: The paper presents the results of a study the hydrogen effect on the structural-phase transformations and the superelasticity in binary ultrafine-grained (UFG) TiNi based alloy after diffusion redistribution hydrogen as a result of aging at room temperature. The redistribution of hydrogen in the process of long-term aging after electrolytic hydrogenation of UFG wire specimens the Ti49,1Ni50,9 (at.%) stabilizes the B2 structure. Superelasticity in samples aged at room temperature after hydrogenation is significantly deteriorated.
Abstract: Effects of severe plastic deformation by isothermal сryorolling with a strain of e~2 and subsequent natural and artificial aging on the structure and resistance to intergranular corrosion (IGC) of the preliminary quenched 2024 aluminum alloy of standard and Zr modified compositions were investigated. Increasing the temperature of aging leads to decreasing the alloy IGC resistance due to precipitation of more stable strengthening S-phase (Al2CuMg), rising difference of electrochemical potentials at grain and subgrain boundaries. Zr additions, оn the opposite, significantly increased the alloy IGC resistance in both naturally and artificially aged conditions, reducing its depth and intensity. The main structural factor, influencing the alloy corrosion behavior, is excess phases: their composition, volume fraction and distribution.
Abstract: In this comparative study, the structural and superelastic characteristics of two thermomechanically treated metastable Ti-Nb based (Ti-22Nb-6Zr) and Ti-Zr based (Ti-18Zr-14Nb and Ti-18Zr-13Nb-2Ta (at. %)) alloy systems were studied. To study the influence of room temperature storage on the functional properties of these two alloy systems, the alloys were subjected to a multistage testing routine consisting of four ten-cycle loading-unloading testing series alternated with three room temperature ageing periods (1, 5 and 20 days). Based on microstructure-properties relationships, it was shown that for each alloy system, the forward stress-induced martensitic transformation was essentially dependent on the material microstructure, whereas the subsequent reverse martenstic transformation was controlled by the material composition. The Ti-Zr based alloys demonstrated more stable functional behavior than their Ti-Nb based counterparts. More specifically Ti-18Zr-13Nb-2Ta, subjected to a combination of cyclic training alternated with room temperature ageing showed a significant improvement in superelastic behavior with small accumulated strains and narrow stress hysteresis.
Abstract: Gas atomization powders (GAP) chemical composition which corresponds to the first area of the phase equilibrium, and the fraction that ensures a cooling rate of a separate powder particle of more than 103K/s contains an amorphous component of two types: the first (AC1) has a chemical composition similar to that of the alloy; and the second (AC2) has a chemical composition of the triple eutectic. AC1 is mostly localized on the surface of the powder particles (in the form of layers, shells, nodules) or are detected in the whole volume of the spherical powder particles with its size less than 5 μm. The authors hold that during gas atomization, powder particles of this size have a cooling rate ≥ 105 K/s. Alloys having a similar chemical composition at similar cooling rates are also amorphized by quenching from the liquid state. This proves that an amorphous alloy of the first type is formed directly from a supercooled melt. While AC2 (enriched by Nd) is formed on the border or in the between the crystal phase Fe14Nd2B of the remaining (after primary crystallization during the primary phase) melt enriched by the moment of the solidification of Nd.