Formation Of Structural-phase States Research Articles

Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

Formation of Structural-Phase State and Elastic and Durometric Properties of Biocompatible Cold-Rolled Titanium Ti–Nb–Zr-Based Alloys during Aging

Formation of Structural-Phase States in Ag–Cu Bimetallic Nanoparticles Produced By Electrical Explosion of Wires

Formation of Structural-Phase States in Ag–Cu Bimetallic Nanoparticles Produced By Electrical Explosion of Wires

Formation of Structural-Phase State in a Cobalt-Chromium-Molybdenum Alloy by Selective Laser Melting

Heat resistant cobalt-based alloys have found a specific niche in the present-day mechanical engineering due to their unique properties. To begin with, cobalt-based alloys are used as corrosion, heat and wear resistant materials intended for aggressive environments and operation at extreme temperatures, e.g. blades, nozzles, swirlers, rings and other elements of turbines and internal combustion engines. Traditional molding methods applied in the mechanical engineering fail to provide necessary operational and technological characteristics of aforementioned machine parts. Owing to selective laser melting it is possible to reduce a production time and manufacturing costs for machine elements with a complex physical configuration and generate an alloy with an extraordinary structure, which is not found in traditionally combined compounds. A structure of cobalt exists in two crystal modifications: a hexagonal close-packed epsilon phase, a low-temperature phase and a face-centered cubic lattice gamma phase, a high-temperature phase. The alloy hardness is directly related to an amount of a low-temperature phase. The laser melting shortens a laser beam impact time on a powder composition due to a higher power and laser travelling speed. A high value of heat conductivity seems to be the reason for rapid solidification and cooling, which, in their turn, increase a percent of an alpha-martensite phase in an alloy and improve the hardness and wear resistance of machine parts. The reported paper summarizes studies aimed at the development of a stable phase structure three-component alloy (Сo-66 mass % Cr-6 mass % Mo) based on the cobalt-chromium-molybdenum system and mixed up via selective laser melting.

Структурно-фазовое состояние и остаточные напряжения в сварном соединении сплава ВТ20, полученном электронно-лучевой сваркой

Структурно-фазовое состояние и остаточные напряжения в сварном соединении сплава ВТ20, полученном электронно-лучевой сваркой

Formation of Structural-Phase States in Alumina Ceramics VK-95 by Sintering in a Constant Magnetic Field

Formation of Structural-Phase States in Alumina Ceramics VK-95 by Sintering in a Constant Magnetic Field

Hardening mechanisms of steels with bainite and martensite structures

Martensite and bainite are the most complex structures being formed in steel in heat treatment including the quantitative interpretation. On frequent occasions, the application field of these steels includes the operation at high static and dynamic compression stresses. The thorough and comprehensive analysis of the materials’ structure after different types of treatment enables to use them competently for the manufacturing of the parts and structures providing them with the necessary complex of physical and mechanical properties. The factor determining the mechanical properties of the materials are the structure of solid solution, presence of nano-dimentional particles of the second phases, dislocation substructure, types and location of various boundaries and internal stress fields. For successful control of the formation of structural phase states and mechanical properties of the material it is necessary to know the quantitative laws and the cold hardening mechanisms of steels of different structural classes at active plastic deformation. By methods of transmission electron diffraction microscopy the analysis of cold hardening of 38CrNi3MoV steel with martensite and 30Cr2Ni-2MoV steel with bainite structures at active plastic compression deformation to 26 % and 36 %, respectively, was done in the research. The contributions caused by intraphase boundaries, dislocation substructure, carbide phases, atoms of alloying elements and long-range stress fields are considered. It is established that the substructural hardening (caused by the internal long-range stress fields) and solid solution strengthening (caused by carbon atoms) give largest contribution to cold hardening of 38CrNi3MoV hardened steel. For normalization of 30Cr2Ni2MoV steel hardening also takes place at the expense of the internal stress field’s action, at the penetration of carbon atoms to the ferrite crystal lattice as well as at the structural fragmentation with the deformation degree higher than 26 %. The dislocation substructure and the particles of carbide phase make comparatively small contribution to the hardening of these steels. It is shown that the cause of bainite steel softening at large (more than 15 %) degrees of deformation is connected with the activation of deformation microtwinning process.

Формирование структурно-фазовых состояний, дефектной субструктуры и свойств поверхности термомеханически упрочнённой низкоуглеродистой стали

Формирование структурно-фазовых состояний, дефектной субструктуры и свойств поверхности термомеханически упрочнённой низкоуглеродистой стали

Nanostructuring and Physical Properties of Metal-Ceramic Composites With a Different Content the Ceramic Components

A comparative analysis of the microstructure and durability of hard-alloy plates treated with high-energy pulsed electron beam generated from the plasma of argon or xenon in steel cutting was conducted. It is shown that the choice of the plasma gas to generate electron from the cathode plasma-filled setting for pulsed electron-beam irradiation has a significant influence on the formation of structural-phase state in the surface layer and the durability of hard-alloy plates in steel cutting.

Formation of structure-phase states and dislocation substructures during thermomechanical hardening of Fe–0.09C–2Mn–1Si steel

3 Results of investigations of the structure-phase state and dislocation substructure formation during thermomechanical hardening of Fe-0.09C-2Mn-1Si steel in different regimes are presented. Methods of transmission electron microscopy reveal the formation of gradient states characterized by regular changes of the structure, phase composition, types, and parameters of the dislocation substructures over the structure cross section.

Formation of structure-phase states in gradient layers of 20X2H4A steel after nitrocementation

Formation of structure-phase states in gradient layers of 20X2H4A steel after nitrocementation

Formation of structural-phase states of the surface of Hadfield steel

989 By studying the deformation of a surface layer, we may judge its interaction in a joint, predict its effectiveness, and recommend methods of hardening this layer so as to improve wear resistance. In the present work, we study the formation of the structure and phase composition in ultrasonically modified surface layers of Γ 13 Hadfield steel, in dry friction [1, 2]. The samples are tested on a 2168UMT1 unit in conditions corresponding to shaft–bush, end-seal, and disk–cam junctions. The test parameters are as follows: pressure up to 4 MPa; slip rate up to 0.3 m/s; test time up to 6 h. Ultrasonic hardening is by means of a 20-W 160UZTK-18/22-0/25 unit (frequency 22 kHz, amplitude 15 μ m) [3]. This unit ensures plastic deformation at depths up to 700 μ m. The samples are investigated by X-ray structural and X-ray phase analysis and by optical microscopy. In the initial state, the Hadfield steel has an austenitic structure and consists of a single phase (Fig. 1). The X-ray diagrams of the samples after tribological tests at 3 MPa are characterized not only by broadening of the γ phase but also by the appearance of reflections close to 2 θ = 40 ° , which correspond to cementite Fe–Mn–C (Fig. 1, curve 2 ). The appearance of new phases may evidently be due to considerable heat liberation at the surface. The appearance of a faint reflex close to 2 θ = 77 ° is due to α -phase formation in friction. Whereas the hardness in the initial state is 3200 MPa, it is 8400 ± 200 MPa at the frictional surface. This cannot be associated with the formation of deformational martensite but is determined by changes in the fine structure, as noted in [4].