Russian Metallurgy (Metally)最新文献

Abstract—

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—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.

Abstract

The trends in the development of a technology for the production of the hot gas path parts of a gas turbine engine (GTE) by directional solidification from superalloys are considered. The existing special-purpose equipment used in Russia, the United States, Germany and other countries to produce blades with a directional and single-crystal structure is analyzed. The prospects of directional solidification with a liquid metal cooler in the production of GTE blades for both modern and promising GTEs are clearly demonstrated.

Abstract—Relations are proposed for calculating combined conditions for drawing with heating during metal forming. The workpiece material is taken to be anisotropic and viscoplastic. The extremum upper-boundary plasticity theorem and the damage kinetics equations of a deformed material are used. Calculated data are obtained.

Abstract—An algorithm for estimating the yield strength increment as a result of solid-solution and precipitation hardening of the surface-alloyed layers in iron, which are formed during combined saturation with a nitride-forming metal (Cr, V, Ti, W, Mo) and nitrogen. The input parameter for the estimating calculations is the alloying metal concentration in iron, which is quantitatively related to the structural factors of hardening, namely, the concentration of dissolved nitrogen and the volume fraction of precipitated nitrides. A high degree of correlation is found between the calculated hardening parameters and the microhardness of the modified layers in armco iron after diffusion metallization (by chromium, titanium, and vanadium) and nitriding.

Abstract

Currently, additive technologies, in particular, electric arc growth as the most universal and productive, are used to produce individual machine parts. The problem of studying the process of structure formation in alloys during electric arc additive growth to ensure the necessary parameters of the microstructure of a material and its mechanical properties is challenging. 09G2S steel samples for research are fabricated on a developed test bench implementing the technology of 3D printing by electric arc surfacing, microstructural studies on an optical microscope are used, and microhardness measurements are carried out. The features of structure formation in a 09G2S alloy during additive electric arc growth have been determined, and controlled parameters have been identified to ensure the necessary parameters of the structure and, consequently, the mechanical properties of the alloy. The heat input of the surfacing process and the temperature of a thermal cycle are found to play a significant role in the structure formation in the material. The conducted research and established dependences make it possible to control the structural state of 09G2S steel during cladding to ensure the required parameters of its microstructure and mechanical properties.

Abstract—The implantation of aluminum ions into the surface layer of a VT6 titanium alloy and the deposition of an aluminum thin film on the alloy surface by magnetron sputtering with subsequent ion-beam mixing by argon ions are studied. The evolution of the composition of the ion-alloyed layer in the VT6 titanium alloy after aluminum-ion implantation is demonstrated.

Abstract

Heat treatment conditions are chosen in accordance with alloys and production method of blanks and parts made from them. The heat treatment of parts produced from aluminum alloys is based on the fact that, as the temperature decreases, the solubility of many elements in solid aluminum deceases. The aim of the present study is to investigate the effect of heat treatment conditions of a wrought aluminum alloy on its structure and properties and, based on the data, to choose more rational technological heat treatment conditions.

Abstract

The results of experimental studies of the composition, structure, and properties of a lead–antimony alloy sintered from an electroerosive powder formed in distilled water are presented. Spark plasma sintering used to synthesize products from the powder produced by electrodispersion of an SSu-3 alloy is shown to manufacture alloys for the production of current lead plates for acid batteries due to the confirmed anticorrosive properties improved compared to the initial alloys.

Abstract—The formation of slag binders, which ensure the strength properties of iron ore pellets during reduction, is studied. The formation of dicalcium ferrite, which is not reduced, has been found. The formation of an irreducible binder, namely, dicalcium silicate (belite) is also discovered. However, this compound is characterized by low strength properties and cannot provide high metallurgical properties of the pellets. We decided to continue the search for the binders that provide high strength properties of pellets during reduction.