Russian Metallurgy (Metally)最新文献

The optimization of heat treatment of an anisotropic hard magnetic Fe–30Cr–16Co–1Sm powder alloy is performed by experimental design using the Statgraphics and Statistica software. After optimization, the remanence is B_r = 1.252 T, the coercive force is H_cB = 53.08 kA/m, and maximum energy product is (BH)_max = 36.8 kJ/m³. Adequate regression equations of the dependences of B_r, H_cB, and (BH)_max on the heat treatment parameters (holding time during isothermal thermomagnetic treatment (ITMT), cooling rate from the ITMT temperature to 580°C, and cooling rate from 580 to 500°C) within variations of selected parameters in corresponding phase spaces are obtained. The studied magnetic hysteretic properties of the Fe–30Cr–16Co–1Sm alloy exceed those of one of the most widely used commercial alloys, YuNDK4 (GOST 17809–72) [1], by more than 40% at a lower cobalt content.

The possibility of introduction of titanium carbide into a weldpool is studied. Titanium carbide forms in the metal deposit structure due to proper in situ alloying. However, the in situ technology is rather complicated because of difficulties associated with the impossibility of controlling the factors predetermining the alloying element redistribution between the carbide phase and the matrix. Therefore, attention is frequently given to the introduction of titanium carbide in the finished form (ex situ technology). Titanium carbide particles can be applied as a reinforcing phase in the preparation of wear-resistant coatings using this technology. Titanium carbide is not thermodynamically prone to decomposition and interaction with the chemical elements in the Fe–Ti–C system, demonstrating its high stability. However, experimental studies show that titanium carbide undergoes cracking and dissolution in a weldpool. This process is accompanied by the saturation of the metal with titanium and an increase in its hardness.

Abstract—The pricing environment of rare earth metals, which has a multidirectional character for different rare earth products, is reviewed. The potentially recoverable value of 1 kg rare earth metals is calculated for various foreign and Russian deposits. The level of unit cost of the rare earth products, which is taken as a basic comparative indicator, is revealed. An efficiency coefficient for manufacturing commercial rare earth products for various deposits has been proposed and calculated.

Abstract—The research on ultrasonic riveting has revealed that the application of vibrations enables a significant decrease in the riveting force and changes the deformation characteristics of a rivet. Initially, a rivet shank undergoes upsetting, and the gap between the rivet and the installation hole is filled with the deformed metal, and a closing head then forms. The joints formed by ultrasound-deformed D18 alloy rivets exhibit a considerable increase in the shear force.

The effect of repeated use of the chrome-calorizing powder mixture on the thickness and structure of the diffusion coating in the repair of gas turbine engine blades was investigated. The experimental study showed that reuse of the powder mixture results in a change in the mechanism of formation of the diffusion coating. The mechanism of sticking of the powder mixture during deposition of the protective coating on the turbine blades was determined.

The reported results of studying the thermal fatigue of superalloys by the Coffin method are analyzed after varying the plastic deformation in a cycle ε_pl by changing the constraint stiffness of free thermal deformation ε₀, which induces elastoplastic deformation Δε = ε_el + ε_pl in half-cycles equal to 0.6, 1.0, and 1.3%, according to the results of testing a ZhS6F superalloy. It is found that, in tests with Δε = 0.6%, plastic deformation ε_pl is absent, and elastic deformation ε_el completely compensates the entire constraint part of ε₀. In these tests, fracture cannot be considered as a result of thermal fatigue, since, according to the Coffin law, the existence of ε_pl is a necessary condition for it. In tests with full constraint ε₀ and Δε = ε₀ = 1.3% in both half-cycles, plastic deformation occurs, and the measured maximum compression stresses σ_comp and tensile stresses σ_t correspond to the values of the yield strength achieved in the temperature ranges of heating and cooling after removing ε_el of the preceding half-cycle. In tests with partial constraint of ε₀ (when Δε = 1.0%), the situation is ambiguous. In this case, the change in Δε with temperature includes plastic deformation, as TC maps show. However, the measured values of stresses σ_comp and σ_t are substantially lower than yield strength σ_y. The observed results and the existence of ε_pl cannot be explained because of the absence of required data. The results of the analysis carried out in this work show that the construction of the dependence of life N_f on ε_pl provided by the Coffin method using the data obtained in the tests considered above is impossible. Therefore, the reliability of numerous reference data on the dependence of N_f on ε_pl obtained before in identical tests on the same equipment needs a verification for many superalloys.

Abstract—The dependence of the Russian industry on the import of rare metals is considered. The volume of imports and their geographical structure, including those from the so-called “unfriendly countries,” are presented. The rare metals the prospects for replacing them with imports in the near future seem to be low are considered.

Abstract—The features and prospects of using nickel superalloys as structural materials for advanced reactor plants, in particular, molten salt reactor (MSR) are considered. The main limiting factors impeding the use of nickel superalloys under MSR operating conditions are considered. Information on new high-temperature EK198 and EK199 alloys, which have high radiation resistance and improved mechanical characteristics, is provided.

Abstract—A unique solution is proposed to solve the fundamental problem of studying the features of the formation and changes in the structure of aluminum alloys during solidification of the melt under cyclic thermomechanical treatment conditions. A setup is described that implements the thermomechanical effect on a solidifying melt. The methodology for studying the formation and changes in the microstructure of a solidifying metal under cyclic thermomechanical treatment conditions is described. The application of the proposed research methodology is exemplified by studying the solidification of the D1 alloy. Conclusions are drawn about the practical significance of the proposed research methodology.

Free cyanide ions should be replaced by thiocyanate ions to decrease the toxicity of a cyanic silver-plating electrolyte. This allows the process to occur at high working current densities with the formation of a fine-grained deposit. This structure is shown to be formed due to the discharge of a mixed cyanide–thiocyanate complex. However, black or yellow spots causing article rejection form on the silver coating surface after washing and subsequent drying at elevated temperature. The spots are insoluble silver products, which further worsen the physicochemical characteristics of the coating. These spots can be removed by both chemical and electrochemical methods. The final elemental analysis of the coating composition after product removal shows no elements except for silver. The deposit structure has also been improved.