Metal Science and Heat Treatment最新文献

Maps of the strain tensor component ε_yy and profiles of the distribution of ε_yy along the length of the sample plotted by the method of digital image correlation are used to study the evolution of ε_yy and the width b_b of the nucleating center, of the band nucleus and the band itself during tension of sample 1 of steel 08G2B exhibiting a high magnitude of the strain aging effect (SAE) after heating to T_h = 250°C; the results are compared to the data for sample 2 (T_h = 680°C) with low SAE. The experimental data obtained are used to reconstruct at the micro- (dislocation) level the process of formation and growth of the nucleating center and of the nucleus of the localized strain band emerging from it.

The effect of Zr content on the microstructure, martensitic transformation temperatures, mechanical properties, strain recovery characteristics, and corrosion resistance of the alloys of the Ti – 11V – 9.7Al – xZr system were investigated. It was revealed that with the addition of Zr, the structure of the alloy is gradually transforms from the α″-phase to the β-phase. The addition of Zr decreases the martensitic transformation temperatures of the Ti – 11V – 9.7Al – xZr alloy and significantly improves its yield strength and ductility. The full recovery of 6% strain is achieved in the Ti – 11V – 9.7Al – 5Zr alloy, which shows a high shape memory effect and superelasticity. When the content of Zr reaches 10 at.%, there is no shape memory effect reply. Electrochemical testing revealed that the Ti – 11V – 9.7Al – 5Zr alloy exhibits the best corrosion resistance, and a small amount of Zr addition enhances the corrosion resistance of the alloy.

This review summarizes the current progress and main methods of regulating multi-phase structures in steels, highlighting the potential application of pre-martensitic phase transformation in multi-phase structure regulation. Analyzing the factors influencing pre-martensitic phase transformation, not only fully demonstrates the effectiveness of this technique as an efficient strategy for multi-phase structure regulation but also reveals its significant advantages in refining microstructures and enhancing material mechanical properties. Additionally, technology’s role in accelerating the bainite transformation has been proven. The synergistic effect of carbon atom diffusion and dislocation movement during the pre-martensitic phase transformation process is specifically analyzed. Although the control of multi-phase structures through pre-martensitic phase transformation shows great prospects, some unresolved issues in research still exist. Directions for further exploration are indicated. Addressing these challenges in depth is crucial not only for understanding the complexity of the pre-martensitic transformation but also provides new ideas for the conscious customization of microstructures in practical industrial applications.

The effect of the annealing process parameters on the structure, phase composition and properties of new heat-resistant bearing steel VKS17-ID (M50NiL) is studied. Fractional factorial experiment with subsequent movement along the gradient is used to study the influence of the temperature, the hold time and the cooling scheme during annealing on the microstructure and hardness of steel. The obtained results can be helpful for choosing the mode of softening heat treatment of ring forgings in industrial production of bearings.

The features and patterns of variation of the nonequilibrium solubility of transition metals in aluminum in binary, ternary and more complex aluminum-based alloys are analyzed. The effect of multicomponent alloying is shown, in which the complication of the composition of the alloy by increasing the number of transition metals increases their nonequilibrium solubility in aluminum. It is established that the effect of the multicomponent alloying is implemented in the process of rapid crystallization (cooling rate 10³ – 10⁴ K/sec) and is caused by the increase in the crystallization rate due to intensification of the pre-crystallization supercooling.

The effect of corrosive environment on the resistance of drill pipes from aluminum alloys 1953T1 and D16T (2024) to static and cyclic loads is studied. After the 240-h autoclave exposure to an environment with mineralization 29.5 g/liter, the static mechanical properties of the D16T and 1953T1 alloys are reduced by 20 and 3%, respectively, compared to the initial values. However, under cyclic loading by a bending with rotation scheme, the negative effect of the corrosive environment with pH ≈ 10 on the endurance limit of the 1953T1 alloy is greater than that of the D16T alloy. After 1 × 10⁷ loading cycles in the corrosive environment, the endurance limit of both alloys is the same and equals 49 MPa, while for the air tests it is 216 and 179 MPa for alloys 1953T1 and D16T, respectively.

The structure and phase composition of pressed sections from alloy V-1977 after three-stage aging are studied using optical and transmission electron microscopy. The mechanical properties under tension and compression, the fatigue characteristics, the fracture toughness and the corrosion resistance are determined. The developed three-stage artificial aging mode makes it possible to obtain a high strength in combination with a good set of operational properties in semi-finished products from alloy V-1977. The use of pressed sections from high-strength aluminum alloy V-1977 in the T12 condition with increased strength (> 670 MPa) and fracture toughness (35 – 39 MPa · m^1/2 ) is expected to raise the weight efficiency and reliability of heavily loaded airframe components.

The possibility of formation of a wear-resistant surface layer on chromium-nickel stainless steel sheets by electron beam cladding of boron-containing powder mixtures is investigated. The heating is conducted by a beam of relativistic electrons released into the air atmosphere. The cladding is followed by hot rolling. The structure, the phase composition, the microhardness and the wear resistance of the boron-modified surface layer of the steel is determined. It is shown that the structure of the surface layer after the deformation depends on the composition of the deposited powder and determines the strength and ductility properties of the “modified layer – base metal” composition.

The effect of alloying of model alloys based on a Ti – 10Al binary alloy with additives of 1% molybdenum and niobium, 3% tin, and 4% zirconium quenched from the β-range on the formation of structure, martensite lattice parameters, hardness, and contact modulus of elasticity is studied using the methods of diffraction analysis, microindentation, and Rockwell hardness measurements. The method of synchronous thermal analysis is used to determine the stages of the phase transformations (α′→ α + α₂ + β, α₂ → α, α + β → β) and the development of oxidation in the quenched model alloys under continuous heating to 1200°C. It is shown that complex alloying of the Ti – 10Al alloy with Mo, Nb, Sn and Zr promotes (1) occurrence of processes of decomposition of α′-martensite at higher temperatures, (2) lowering of the temperature range of the α + β → β transformation and (3) convergence of the temperature intervals of the α₂ → β and α + β → β transformations up to their overlapping.

The effect of the duration of the exposure of alloy ZhS6U to hydrogen at 1473 K for 0, 15, 30, and 60 min on the chemical composition of the surface and internal layers is studied. It is shown that the surface layer of the alloy is oxidized by trace amounts of oxygen present in the hydrogen, while the inner layers do not undergo oxidation. At the same time, the Al content in the surface layer increases abnormally from 17 to 34% after 15 min, and the Cr and Ni contents decrease from 20 to 5% and from 62 to 20%, respectively, at a slight change in the Mo and Co contents. The abnormally high content of O₂ and Al in the surface layer is apparently a result of the high rate of oxidation of Al and of the diffusion of low-melting Al from the lower layers of the alloy to the upper thin porous Al₂O₃ film. The low Ni content in the surface layer indicates intense oxidation of nickel despite the previously formed gas-permeable Al₂O₃ film.