Metallurgist最新文献

Aluminum alloys based on alternative alloying systems, particularly Al–Ca eutectic alloys, offer a favorable combination of castability, mechanical performance, and corrosion resistance. A key step in developing such alloys is reducing the time and labor inputs required to obtain a promising composition with the desired set of properties, a task partially addressed through thermodynamic modeling software. In this article, various machine learning methods, including linear regression, decision trees, and two types of gradient boosting, are applied to optimize alloys within a composition–property relationship framework. The database comprised 250 cast aluminum alloys based on Al–(Si, Ca, Ni, REM, Mg, Cu) systems described in scientific publications, with data on chemical composition, hot tearing susceptibility, hardness, and strength. The most effective method for predicting the mechanical and casting properties of as-cast alloys was identified by comparing predicted and experimental values on a hold-out dataset. The best results were achieved with Yandex’s CatBoost gradient boosting model, built on open-source code and modified for the purposes of this study. Differences between predicted and measured values are illustrated using alumocalcium alloys as an example.

Local thinning of the pipe wall thickness may occur during continuous rolling with a retained mandrel at the rear end of the pipes, which can be detected by ultrasonic testing. The characteristics that classify this local thinning as a surface defect have been identified. Primary factors contributing to these defects include an increased contact area between the metal and the mandrel at the rear end of the pipes, additional tensile stress in the metal, and non-uniform friction conditions at the contact surface between the metal and the mandrel.

High-temperature nickel alloys are promising materials for the construction of components in high-temperature nuclear power installations. However, these alloys are classified as difficult-to-weld materials, which limits their application. This study presents the results of mechanical property and microstructure analyses of welded nickel alloy joints (grades CrNi80MoTiAl- VI, CrNi80MoTiNb+Y-VI, EK198-VI, and EK199-VI) in their as-received state and after thermal aging.

Study aimed at determining the optimal hydrogen concentrations and conditions for hydrogenation annealing in the hydrogen plasticization of titanium alloy chips of different groups are presented. Due to the large total surface area and thinness of the chips, as well as the developed surface of chip waste, it is expected that the effect of hydrogen plasticization will be maximized in this specific case. The hydrogen plasticization of various types of titanium alloy chips, including VT1‑0, VT3‑1, and VT5, was studied. The characteristics of thermocompression processing of different types of chips formed after various mechanical processes were identified. The Russian software complex Quartoform QForm, which implements the finite element analysis method, was used to conduct mathematical modeling of the compaction and consolidation processes of chips. Further, the briquetting and thermocompression of titanium alloy chips was investigated. The optimal hydrogen saturation concentrations for different grades of titanium alloys were determined. At these concentrations, the chip material exhibits maximum plasticity and minimal resistance to deformation. Further increases in hydrogen concentration led to hydrogen embrittlement of the titanium alloys. Additionally, the study found that the maximum effect of hydrogen plasticization on titanium alloy chips of all types occurs under conditions of hot thermocompression processing.

The specifics of mass transfer, structure, and properties of electrospark-deposited coatings on steel 20Kh13 substrates using electrodes SHIM-40NAOKn (TiC − NiAl + ZrO₂^nano) and SHIM-11OKn (TiB₂ − NiAl + ZrO₂^nano) have been studied. The coatings were analyzed using X‑ray diffraction, scanning electron microscopy, energy-dispersive X‑ray spectroscopy, optical microscopy, and hardness testing. Tribological tests were carried out according to the “pin-on-disk” method, and heat resistance of the coatings was studied. It was found that the use of SHIM-40NAOKn electrodes results in cathode mass gain during the first 7 min of treatment, while the use of SHIM-11OKn electrodes leads to cathode mass loss during the entire 10 min of treatment. Substrate coatings formed by electrospark deposition exhibit 100% continuity and a thickness of 35–50 μm. The coating hardness ranges from 8.5 to 11.0 GPa. The use of SHS-electrodes made it possible to increase the hardness of the surface layer by more than 5 times, wear resistance—by 1.6 times, and heat resistance—by 1.9 times (800 °C, 32 h).

The parameters of the cast structure in the columnar crystallization zone were investigated in a section perpendicular to the wide face of continuous cast slabs of varying thickness. The distribution of the main cast grain parameters across the thickness of continuous cast low-alloy steel slabs is presented. A method for evaluating the degree of the columnar structure development is proposed. It was found that the influence of steel overheating on the development of the columnar structure decreases as slab thickness increases.

The effect of plasma quenching on the structure and corrosion resistance of 65G structural steel was investigated. Gravimetric corrosion tests were performed to measure mass loss before and after heat treatment and to determine the area affected by corrosion. This paper presents the experimental methodology, corrosion rate calculations, and analysis of the results. The results showed that plasma quenching can significantly alter the surface structure and thereby affect corrosion resistance in aggressive environments.

This paper presents a theoretical study—based on previously granted patents—of a new type of spherical metal casting mold capable of withstanding ultra-high internal gas pressures (up to 1000 MPa). The mold is a prefabricated, multi-part spherical structure preloaded into a prestressed state.

A mathematical model of the structure’s response to internal gas pressure is developed using the linear theory of elasticity. The stress–strain state is evaluated for each structural element. The resulting system of equations is solved numerically using a validated finite-difference method.

A test configuration was considered. The mutual interaction between structural components is examined, along with the influence of each component on the crack resistance of the overall system. The numerical results are presented as stress and displacement plots.

A comparison of the energy parameters of melts in arc steelmaking furnaces with capacities of 100 and 180 t of metal, EAF-100 and EAF-180 respectively, was performed. The calculations showed that, when using scrap metal as the charge, the coefficient of useful heat utilization from the arcs in the EAF-100 furnace is 0.78–0.80 and the specific electricity consumption is 360 kWh/t. Under similar conditions in the EAF-180 furnace, the corresponding values are 0.70 and 390 kWh/t, respectively. The lower arc efficiency and higher specific electricity consumption of the EAF-180 compared to the EAF-100 are caused by the greater distance of the arcs from the furnace walls and the necessity of operating with arcs that are not fully submerged in the bath. This results in radiated heat flux to the charge on the slopes. In the EAF-100, heat conduction from the hot zones under the arcs to the charge on the slopes is sufficient to melt the charge; the arcs are fully submerged in the slag, resulting in high arc efficiency and low specific electricity consumption.

In this study, fibers from industrial titanium alloy VT6 were obtained by pendent drop melt extraction. These rapidly solidified fibers are of interest for the production of porous titanium materials used as dampers, filters, or medical implants. To obtain such materials, the authors have analyzed the microstructure, phase composition, and mechanical properties of the rapidly solidified fibers and obtained porous sintered samples, the characteristics of which have also been studied. Sintering was carried out at 750–950 °C for 2 h. The structure and phase composition were analyzed by optical and electron microscopy, as well as by X‑ray diffraction analysis. The mechanical properties were studied by measuring microhardness and tensile strength (fibers), or by performing compression testing and determining the proportional limit depending on the sintering temperature (sintered materials). It was found that rapid solidification leads to the formation of a metastable phase composition of the alloy, represented by the martensitic α’-phase and β‑phase. The rapidly solidified fibers exhibit high microhardness (447.4 HV), as well as good ductility during tension and cold pressing. It has been established that heating and sintering lead to the martensite breakdown and formation of a lamellar microstructure of the (α+β)-alloy. Temperature greatly affects the morphology of the structure. Higher sintering temperatures also lead to a reduced number of defects in the sintered contact zone, along with an increase in contact size, and an improvement in compressive strength.