Influence of the initial structural-phase state on inelastic and plastic strains behavior in coarse-grained samples of the Ti49.3Ni50.7 (at.%) alloy

The paper presents the experimental results of studies of the temperature dependence of inelastic and plastic strains during torsion of coarse-grained samples of the Ti49.3Ni50.7 (at.%) alloy. Investigations of the deformation behavior of the test alloy samples in the martensitic, two-phase and high-temperature states have been carried out. It is shown that the value of the summary inelastic strain reaches a maximum value of ∼ 18% under deformation of the samples in the martensitic and two-phase state, as well as in the temperature range of pre-transition phenomena.

Structure of tantalum coatings on NiTi substrate deposited by magnetron sputtering

The paper provides the results of studies of the structural-phase state of tantalum coatings prepared by magnetron deposition. The coatings were deposited on substrates made of titanium nickelide with a shape memory. The NiTi temperature during coating deposition did not exceed 100 °C. The structural-phase state of Ta was determined by X-ray diffraction at different stages of coating formation. It has been shown that at the initial stage of deposition, two-phase coatings (α- and β-Ta) are formed. The synthesis of the coating from Ta leads to the growth of interplanar distance of the B2 austenite phase in the crystallographic direction (100). The growth of interplanar spacing is caused by formation of microstresses during interaction with incident tantalum ions. The lattice parameters of the B19 ‘phase, responsible for appearance of the shape memory effect, do not change during deposition of the tantalum coating.

Study of the Structural-Phase State of Pipeline Welded Metal

The issues of research of structural changes as applied to welded joints of steam pipelines are considered. The results of metallographic analysis of structural changes in the metal of steam pipelines are presented. There was carried out the analysis for a number of samples cut from different sections of the steam line at different operating time under creep and low-cycle fatigue conditions. In the analyzing process of the images of micro sections, the relative content of the structural-phase components and their distribution in the metal were revealed. A comparative analysis of the statistical characteristics of the distribution and the relative content of structural components for different sections of the metal of welded joints with different operating time is carried out. A scientifically substantiated description of structural changes in the metal of various sections of samples of welded joints is given, as well as the possibility of extending the service life of elements of steam pipelines with a degraded structure and the presence of damageability. The most promising, in the opinion of the authors, directions of further research of samples to provide conditions for extending the service life of steam pipelines have been formulated and substantiated.

Influence of the Structural-Phase State of a Copper Substrate upon Modification with Titanium Ions on the Thermal Cyclic Resistance of a Coating Based on Zr-Y-O

The results of investigation of the surface of a copper substrate modified with titanium ions are presented. The phase composition, the structure, and the morphology of the surface of the copper alloy modified by titanium ions have been investigated by X-ray, SEM, and TEM. It has been established that there are the intermetallic phases of the Cu-Ti equilibrium diagram in the surface layer during the treatment of copper by the titanium ions. A multilevel micro- and nanoporous structure is formed in the modified layer. It has been established that the structure-phase state and morphology of the surface layers of copper directly effects on the thermocycler resistance and adhesion of the Zr-Y-O coating. The thermocyclic resistance of the Zr-Y-O coating increases by an order of magnitude, the adhesion to the substrate is 2 times if the substrate surface is treated with titanium ions for 6 min.

FEATURES OF THE STRUCTURAL PHASE STATE OF A FILM BASED ON A HIGH-ENTROPY AlNbTiZrCu ALLOY SYNTHESIZED BY DEPOSITION OF A MULTIELEMENT METAL PLASMA

В данной работе приведены результаты структурных исследований пленок толщиной до 5 мкм высокоэнтропийных сплавов системы AlNbTiZrCu . Пленки были синтезированы на металлических и металлокерамических подложках путем осаждения многоэлементной металлической плазмы, созданной электродуговым плазменно ассистированным одновременным независимым распылением нескольких катодов. Показано, что пленки являются слоистым материалом и имеют аморфнокристаллическую структуру. Установлено, что облучение пленок импульсным электронным пучком (18 кэВ, 20 Дж/см, 50 мкс, 3 имп., 0,3 с) сопровождается кристаллизацией материала. Показано, что в полученных пленках доминирует соединение состава AlNbTiZr с параметром решетки 0,32344 нм. На основе теоретических расчетов получены структурные данные кристаллической решетки AlTiZrNb и определены механические и термодинамические характеристики этого соединения. This paper presents the results of structural studies of films with a thickness of up to 5 microns of high-entropy alloys of the AlNbTiZrCu system. The films were synthesized on metal and cermet substrates by deposition of a multielement metal plasma created by electric arc plasma assisted simultaneous independent sputtering of several cathodes. It is shown that the films are a layered material and have an amorphous-crystalline structure. It was found that irradiation of films with a pulsed electron beam (18 keV, 20 J/cm, 50 gs, 3 imp., 0,3 s) is accompanied by crystallization of the material. It is shown that the resulting films are dominated by the compound of the AlNbTiZr composition with the lattice parameter of 0,32344 nm. On the basis of theoretical calculations, the structural data of the crystal AlTiZrNb lattice were obtained, mechanical and thermodynamic characteristics of this compound were determined.

The Effect of Cobalt on the Deformation Behaviour of a Porous TiNi-Based Alloy Obtained by Sintering

This research investigates the effect of cobalt on the deformation behaviour of a porous TiNi-based alloy that was obtained by sintering. Porous TiNi-based alloys with cobalt additives, accounting for 0–2 at. % and with a pitch of 0.5, were obtained. The structural-phase state of the porous material was researched by X-ray structural analysis. The effect of different amounts of Co (used as an alloying additive) on the deformation behaviour was investigated by tensile to fracture. The fractograms of fracture of the experimental samples were analysed using scanning electron microscopy. For the first time, the present research shows a diagram of the deformation of a porous TiNi-based alloy that was obtained by sintering under tensile. The stages of deformation were described according to the physical nature of the processes taking place. The effect of the cobalt-alloying additive on the change in the critical stress of martensitic shear was investigated. It was found that the behaviour of the concentration dependency of stress at concentrations under 1.5 at. % Co was determined by an increase in the stress in the TiNi solid solution. This phenomenon is attributed to the arrangement of Co atoms on the Ti sublattice, as well as an increase in the fraction of the B19′ phase in the matrix. The steep rise of the developed forces on the concentration dependency of the martensitic shear stress at 2 at. % Co is presumably attributed to the precipitation hardening of austenite due to the precipitation of finely dispersed coherent Ti3Ni4 phase following the decrease of fraction of martensite. An analysis of fractograms showed that as more cobalt was added, areas of fracture with traces of martensite plates of the B19′ phase started to prevail. At 2 at. % Co these plates fill almost the entire area of the fracture. The research findings presented in this work are of great importance, since they can be used to achieve the set of physical and mechanical properties required for the development of biocompatible materials for implantology.

Закономерности образования карбидов титана и вольфрама из продуктов электровзрывного разрушения проводников

A series of electrical explosions in propane-butane of single and strand-connected Ti and W conductors with various diameters was carried out. Electrophysical characteristics of the explosion revealed that resistive heating of conductors is characterized by two monotonically ascending sections on the voltage – current curves separated by a flat segment (plateau), which corresponds to relatively stable electrical resistivity of refractory metals in the liquid state. The energy deposited by changing the power input into the conductor during its resistive heating, which can be higher or lower than its sublimation energy and can be regulated by changing the external adjustable parameters of the discharge circuit, is a key indicator determining the structural-phase state of destructed and chemically synthesized products after the explosion. The conditions are achieved under which micro- and nano-sized powder products do not contain residual metals and consist of carbide phases completely (TiC with an average microhardness of 29580 MPa as a result of the titanium explosion and a mixture of W2C+WC1-х, in which stabilized high-temperature non-stoichiometric cubic carbide WC1-x dominates, with an average microhardness of 16770 MPa as a result of tungsten explosion).