Key Engineering Materials Vol. 887

Abstract: The paper shows the possibility of using such quantitative characteristics of the element-oxygen chemical bond as the covalent character, metallic character and ionic character in substances to select a set of technological methods and develop a technology for nanomodification of natural bentonite aluminosilicates. The research results showed that thermal activation of bentonite at 200, 300, 380 and 400 °C with different modes of isothermal exposure (15, 30, 60, 120 minutes) does not significantly affect the efficiency of its modification with silicon (SS) and aluminum (AS) oxide nanoparticles, estimated by the increment of the compressive strength and the adsorption index for methylene blue. Obtaining a 46 % aqueous suspension of bentonite and modifying it with silicon and aluminum oxide nanoparticles followed by ultrasonic treatment after standing decreases the particle size by more than 4 times, which is a promising technological solution for improving the performance properties of ceramics, molding mixtures, adsorbents and other materials based on bentonite from various deposits.

Abstract: It was studied the structure of hard magnetic alloys Fe-Cr-Co and Al-Ni-Cu-Co-Fe manufactured by selective laser melting (SLM) from spherical powders smaller than 80 microns on the RussianSLM FACTORY unit. Powders were manufactured by melt atomization. At various scanning speeds and laser powers, samples were made to study the structure, magnetic and mechanical parameters. By constructing a hysteresis loop, data were obtained indicating an increase in the magnetic characteristics in SLM samples in comparison with similar ones obtained by foundry technology.

Abstract: The quantitative microstructure - impact toughness relationships in two batches of the same steel grade subjected to quenching and tempering (Q&T) have been established via characterization using EBSD technique and FIB visualization. The EBSD-based criterion for separation of structural constituents in microstructure of Q&T low carbon low alloy steels is proposed. Impact toughness differences between two steel batches subjected to nominally identical Q&T are caused by the changes in the volume fraction of structural constituents caused by various cooling conditions at quenching stage. High volume fraction of bainite containing more distorted bainitic ferrite and the highest amount of brittle cementite precipitates leads to the increase in strength and to the decrease in impact toughness.

Abstract: The study analyzes the specifics of modern metal processing technologies. The results of laboratory research for samples made from structural steel St3 with various heat treatment are presented. The results of mechanical tests, measurements of the relaxation coercive field force are shown. The processes that occur with the structure during heat treatment are studied and described. It is made by x-ray diffractograms and images obtained with raster electron and optical microscopes. The influence of structural changes on the relaxation coercive field force and mechanical parameters is described.

Abstract: The effect of high-dose aluminum implantation on the structural-phase state of the surface layer of titanium alloy VT6 with a fine structure (average grain size 2.3 μm) on the mechanical and corrosion properties has been investigated. It is shown that, as a result of ion irradiation, polyphase implanted layers based on α-titanium grains are formed, containing an intermetallic Ti₃Al phase along the grain boundaries of α-titanium. The modified surface layers are characterized by improved mechanical properties and corrosion resistance. The noted effect is enhanced by the use of preliminary helium implantation with a dose of 1.3 × 10¹⁷ ion / cm².

Abstract: The article presents studies of the structure and phase composition of aluminum alloys after ion implantation. It is shown that the effect of accelerated ions (Cu + Pb) (E = 30 keV, j = 100 μA / cm²) on an alloy without a cladding layer already at a dose of 10¹⁶ cm ^{- 2} leads to the formation of a developed subgrain structure in the initially deformed alloy. With an increase in the ion current density and radiation dose, the cellular structure of the implanted aluminum alloys becomes more regular - well-formed cells are observed practically throughout the entire volume of the sample under study. The average width of the dislocation-free regions reaches 2.5 μm with the width of the boundaries not exceeding 0.6 μm.

Abstract: Active development of the territories of Siberia and the Far East requires the use of materials that are able to work under the combined influence of low temperatures and a complex state. When operating equipment parts at low temperatures, it is necessary to take into account the impact of static and dynamic loads, as well as the influence of an external aggressive environment. The paper studies corrosion-resistant cold-resistant metastable austenitic steels, which are widely used for manufacturing parts of low-temperature equipment. Tests were performed to assess the strength and ductility characteristics of smooth samples and samples with annular notches for static stretching in the temperature range from 293 to 77 K.

Abstract: The article considers the effect of laser treatment of bearing steel on the change in the elasticity modulus and hardness of the steel SHH15SG. Multi-factor models were obtained that relate the output parameters to the power W of laser radiation, the longitudinal feed Spr of the laser beam and the distance L from the protective glass of the focusing head to the workpiece surface. According to the degree of reduction of the influence on the elastic modulus of steel SHH15SG subjected to laser treatment, these factors are arranged in a sequence: W, Spr, and L. With increasing W and L the modulus of elasticity and hardness of the treated surface layer increase. 3M-XYZ surface-graphs, 3M-XYZ contour-graphs of interactive influence of independent factors on the elastic modulus and hardness of the surface layer are constructed, which simplifies the procedure for assigning the processing mode. The research results are useful for manufacturing and design companies that implement laser technologies and create laser equipment.

Abstract: In the paper, the atomic structure of amorphous and nanocrystalline alloys of the electrolytically obtained CoP, NiP, CoNiP, CoW, and CoNiW systems has been studied. The structure was investigated by electron microscopy and diffraction using a Libra 200 HR FE transmission electron microscope at an accelerating voltage of 200 kV within a temperature range of 50-35 °C. The obtained radial atom distribution function and the coordination sphere radii are in good agreement with the data for the cobalt structure in the cubic and hexagonal modifications. The high coordination numbers of the third and fourth coordination spheres allow suggesting a predominantly cubic structure of the local atom environment in CoP samples but somewhat lower, which is explained by the presence of free volume and phosphorus atoms distorting the local structure. When heating, the near atomic order also corresponds to the cubic phase of cobalt, and the ordering occurs in the second, third, and fourth coordination spheres. The data obtained for CoNiP alloys indicate that by configuration, the local atomic environment is closer to the hexagonal structure of nickel. In general, the structure of the CoP-CoNiP system alloy films obtained by electrolytic deposition is already in one of the local minima of the total system energy, which is confirmed by the near atomic order similar to the cubic phase of cobalt or hexagonal phase of nickel. This determines the good stability of the structure and properties during thermal exposure.

Abstract: The paper presents the data obtained in the course of experimental studies on the production of rods from the Al-0.5% REM alloy using combined processing methods, such as combined rolling-extruding (CRE) and combined casting and rolling-extruding (CCRE). The variable parameters were the temperature of the ingot or melt, the degree of deformation and the strain rate. With the help of strain gauge equipment, experimental data were obtained on the forces acting on the rolls and the die of the CCRE-200 combined processing unit in the process of obtaining rods with a diameter of 5 and 9 mm. The estimation of the dependence of the mechanical properties of the rods on the variable factors has been carried out. The highest strength properties are possessed by a bar obtained by the CRE mode at a temperature T = 550 oC and a strain rate ξ = 0.74 s^-1. When comparing the temperature of pouring the metal, the highest strength properties are possessed by a rod with a diameter of 9 mm and 5 mm and a strain rate ξ = 0.74 s^-1. If compare in terms of the deformation rate, then the highest strength properties are possessed by a rod with a diameter of 5 mm and a deformation rate ξ = 1.49 s^-1. The plasticity of deformed semi-finished products in all modes is at a high level, which allows further processing.