Dielectric Switch of High Temperature Plastic Phase Transition in Two Organic Salts with Chiral Feature

Organic ionic plastic crystals (OIPCs) with high-temperature reversible dielectric switching properties and single chiral characteristics and various structural phase transformations provide more possibilities for different functional properties. Here, we successfully...

Preparation, composition, structure and properties of mechanically alloyed heat‑resistant steels

Despite a significant amount of work in the field of mechanically doped alloys and, above all, based on aluminum and copper, research aimed at creating mechanically doped alloys is extremely limited. In this regard, the following work aimed at to establishing the regularities of the formation of the phase composition, structure, and properties in the implementation of the technology for obtaining mechanically doped heat‑resistant steels, is important and relevant.The basis for the development of mechanically doped alloys were the results of long‑term research carried out at the Belarusian‑Russian University and aimed at studying mechanically and thermally activated structural phase transformations taking place at all the technological stages of obtaining mechanically doped metal alloys. In this article, in a generalized form the final research results are presented, revealing the patterns of these transformations, which are a reliable scientific basis for the creation of mechanically doped complex‑hardened heat‑resistant steels.

Structural phase transformations in welding high-alloyed titanium alloy

This article investigates the change in the phase composition and structural state during the thermal cycle of welding a high-alloyed titanium alloy. It is shown that structural-phase transformations in the welded joint occurring under the influence of the thermal and deformation cycle of welding lead to the formation of metastable phases, and its subsequent decomposition can lead to ductility losses. To bring the metal of the welded joint to an equilibrium state, stabilizing annealing is required.

STRUCTURAL-PHASE TRANSFORMATIONS IN FILMS AT THE INTERFACE OF THE HETEROSYSTEM “GLASS - CLUSTERS Ag-Pd” – Sn-Pb

Structural-phase transformations in films at the interface of the heterosystem "glass - Ag-Pd clusters" – Sn-Pb have been investigated. The relationship between these transformations and the initial system material component dispersion is established at the same film element temperature operating mode. It is shown that structural-phase transformations in contact elements of hybrid integrated circuits microelectronic devices, sensors and solar cells, etc. made of functional materials based on the specified heterosystem can lead to degradation processes and, as a consequence, to a decrease in the electronic product reliability.

Stress-Strain State and Structural-Phase Transformations of Metal Articles Obtained by Laser Shaping

The article analyses the effect of temperature distribution at different points of the irradiation zone on the nature of leakage of structural-phase transformations. The results of the X-structural analysis are given, which shows the presence of martensite and residual austenite in the treatment zone. The peculiarities of structural-phase transformations during laser heating are studied and their effect on strain value during laser shaping is determined. The results of experimental studies are given, according to which, if the mechanisms for forming the temperature gradient and polymorphic transformations (for 65G steel) operate in parallel, the amount of deformation is one third of the sample for which only the temperature gradient mechanism works (12Х18N10Т steel).

Features of Structural-Phase Transformations during Oxidation of Metals with Bulk Submicrocrystalline Structure and Fine Metal Powders

The oxidation processes for compact and powdery samples of titanium, copper, and molybdenum with different volume structure and dispersivity were studied using thermal analysis, electron microscopy, and X-ray diffraction. It is established that producing of metals with a modified structure under conditions of high-energy impact (severe plastic deformation, electric explosion of a thin wire) in accordance with intermediate annealing leads to an increase in the content of oxygen in the form of solid solutions and oxides; the oxide component’s share, form and localization within the material depend on physicochemical properties of both metal and oxide . It is shown that the structural-phase transformations of the oxide component during heating of fine-grained metals and powders have a significant effect on the parameters of the oxidation process of such materials. The thermally induced effects in the oxygen-containing components might play a critical role for the structure stability during long-term use of such materials under cyclic thermomechanical impacts.

Research of Heat Resistance and Thermophysical Properties of the Diffusion Zone Formed by Annealing by Contact Melting Mode of the Layered Metal-Intermetallic Composite of the Cu-Al System

The results of studying the effect of isothermal annealing on structural, phase transformations, and thermal diffusivity in the diffusion zone of a Cu-Al layered metal-intermetallic composite (LMIC), obtained using technology including explosion welding, pressure treatment and heat treatment, are presented. It was found that, at 530 °C (the highest temperature, excluding the formation of a liquid phase in this system) with a holding time of up to 1000 h, there are no structural phase transformations in the Al (Cu)/CuAl2 metal-intermetallic composition, and a slight increase in its mass is associated with the formation of a thin dense protective oxide film on the surface. The thermal diffusivity of Cu-Al LMIC, obtained after removal of copper residues from the surface of the diffusion zone, is 50–60 W/m×K, which is significantly lower than that of copper (410 W/m×K) and aluminum (220 W/m×K).

Structural-phase transformations in 0.34C–1CRr–1Ni–1Mo–Fe steel during plasma electrolytic hardening

Structural-phase transformations in 0.34C–1Cr–1Ni–1Mo–Fe steel during plasma electrolytic hardening were investigated. Electrolytic-plasma hardening of steel samples was carried out by surface quenching with rapid concentrated heating of the surface by plasma action and subsequent rapid cooling by heat removal from the depth of the sample by electrolyte jet. Plasma electrolytic hardening was carried out in the cathode mode in an electrolyte made from an aqueous solution containing 20 % sodium carbonate and 10 % carbamide. To study the structural-phase states of the modified layer, we used the method of transmission diffraction electron microscopy on thin foils. The study of steel samples was carried out before and after the plasma electrolytic hardening. Initially, the steel was a mixture of pearlite and ferrite grains. Surface hardening of 0.34C–1Cr–1Ni–1Mo–Fe ferrite-pearlite steel led to a change in the structural-phase state and the formation of a packet-lamellar martensite structure. It was found that PEH leads to distortion of the crystal lattice and the formation of long-range internal stresses, as well as to the release of small particles of cementite and carbide of M23C6 type, uniformly distributed throughout the volume of the material. Surface hardening led to the increase in all quantitative parameters of the fine structure (ρ, ρ ±, χ, σL, σd).

Chemically induced local lattice distortions versus structural phase transformations in compositionally complex alloys

Recent experiments show that the chemical composition of body-centered cubic (bcc) refractory high entropy alloys (HEAs) can be tuned to enable transformation-induced plasticity (TRIP), which significantly improves the ductility of these alloys. This calls for an accurate and efficient method to map the structural stability as a function of composition. A key challenge for atomistic simulations is to separate the structural transformation between the bcc and the ω phases from the intrinsic local lattice distortions in such chemically disordered alloys. To solve this issue, we develop a method that utilizes a symmetry analysis to detect differences in the crystal structures. Utilizing this method in combination with ab initio calculations, we demonstrate that local lattice distortions largely affect the phase stability of Ti–Zr–Hf–Ta and Ti–Zr–Nb–Hf–Ta HEAs. If relaxation effects are properly taken into account, the predicted compositions near the bcc–hcp energetic equilibrium are close to the experimental compositions, for which good strength and ductility due to the TRIP effect are observed.