Russian Metallurgy (Metally)最新文献

In this study, the thermodynamic properties and phase transformations of Ti–Al–V alloys were investigated through simulations using the CALPHAD methodology, and the thermodynamic calculations were further validated with experimental data reported in the scientific literature. Phase diagrams and time–temperature–transformation (TTT) diagrams were generated to evaluate the effects of varying Aluminum (5–6–7 wt %) and Vanadium (3–4–5 wt %) contents on the stability and transformation kinetics of the α, β, and Ti₃Al phases. To observe changes in both α and β phases, simulations were performed by varying Aluminum (α stabilizer) and Vanadium (β stabilizer) concentrations within critical ranges associated with phase transformations. This approach was designed to enable a comprehensive study that allowed the observation of all variable effects under equilibrium and non-equilibrium conditions. The simulations revealed that increasing Aluminum content enhances the stability of the α phase while leading to earlier precipitation of the Ti₃Al phase, which is associated with brittle behavior. When Aluminum content exceeds 6 wt %, the Ti₃Al transformation time drops below the maximum aging limit of 24 h for α + β alloys, reaching critical levels. Additionally, increasing Vanadium content was found to improve the stability of the β phase. Below 3.1 wt % Vanadium, the β phase was not thermodynamically stable and did not form in certain temperature ranges, whereas above 3.1 wt %, the β phase formed continuously across all temperatures. This finding established 3.1 wt % as a critical threshold for achieving β phase continuity. These results highlight the importance of identifying critical alloying element ratios to optimize the mechanical and thermal performance of Ti–Al–V alloys. In conclusion, this study provides a comprehensive resource for understanding the effects of alloying elements on the thermodynamic properties of titanium alloys, with phase transformations effectively visualized through detailed graphical representations.

A review has been conducted to determine current research directions in three-high rolling and piercing of steel billets. The billets are made of carbon, low-, medium-, and high-alloy steels. Investigations related to billet fracture processes are important. Fracture is found to be both ring-shaped and axial. Results on qualitative and quantitative estimation of a microstructure and the influence of three-high screw rolling on mechanical properties are presented. A submicron structural state has been achieved in a number of works; an increase in yield strength and tensile strength and a decrease in relative elongation have been detected in all studies. Some works detected the influence of three-high screw rolling on impact toughness. Compared to rolling, piercing has been studied much less frequently. The change in the grain size across the wall thickness and the changes in the hardness and the mechanical properties are investigated.

In the present work, the microstructural evolution and mechanical properties of the high-entropy alloy CoCrFeMnNi were investigated after severe plastic deformation by high-pressure torsion (HPT) at 20 and 300°C, as well as after additional post-deformation annealing at 300°C for 1 h. It was established that HPT at 20°C leads to the formation of an ultrafine-grained structure with an average grain size of ~40 nm and a high defect density, which results in an increase in microhardness up to 600 HV and in tensile strength up to 1820 MPa, accompanied by a reduction in ductility to ~3%. Increasing the HPT temperature to 300°C causes the average grain size to grow to ~400 nm due to the activation of dynamic recrystallization processes. At the same time, the precipitation of nanoscale particles is observed, which provides dispersion strengthening and contributes to an increase in ductility up to 12% while maintaining a high strength of ~1486 MPa. Additional post-deformation annealing at 300°C for 1 h leads to partial relaxation of the defect structure and stabilization of equilibrium grains, accompanied by a reduction in strength to ~1000 MPa and an increase in ductility up to 20%. Thus, it has been shown that adjusting the parameters of thermomechanical treatment enables targeted control over the contributions of different strengthening mechanisms (grain boundary, dislocation, and dispersion) and allows achieving the desired balance of strength and ductility in the CoCrFeMnNi alloy. The results demonstrate the feasibility of tailoring the strength–ductility balance of the CoCrFeMnNi alloy through optimization of thermomechanical processing parameters.

This study investigates the thermal and energy efficiency of a multi-stage hot forming process for producing high-aspect-ratio hollow cylindrical components from AISI 1060 steel. The process integrates hot backward extrusion and subsequent ironing, simulated using Deform-3D under thermo-mechanical coupling conditions. Three key forming parameters—initial billet temperature, deformation degree (i.e., reduction in area/strain), and punch speed were systematically varied according to a Box–Behnken Design (BBD). The responses considered were the heat loss ratio after extrusion (HLR_extr), total heat loss ratio over the complete forming sequence (HLR_total), and total forming energy consumption (U_total). Reduced regression models were developed and validated using ANOVA, achieving high predictive accuracy (R² > 0.98). Multi-objective optimization using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was performed to minimize all three objectives under the constraint that the final average billet temperature remained within 850–900°C. The resulting Pareto front revealed clear trade-offs between thermal retention and energy demand, with selected solutions offering either minimal energy consumption or minimal total heat loss. The findings highlight the dominant influence of billet temperature and punch speed on both heat retention and energy efficiency, providing practical guidelines for parameter selection in industrial multi-stage hot forming of medium-carbon steels.

In this work, the mechanisms of cascade collapse were investigated using molecular dynamics simulation method for copper. For this purpose, the simulations were carried out using the molecular dynamics code MOLDYCASK. In addition to the density difference between the surrounding crystal and the molten zone, the difference in atomic density, quantified by the initial vacancy concentration, plays a critical role in cascade collapse as it directly influences vacancy transport and atomic diffusion during the thermal spike stage. Vacancy transport during the cascade thermal spike stage is determined by mean square displacement (MSD), the enhancement of mean square displacement due to an introduction of vacancies into the cascade volume. At the melting point of the material, mean square displacement is affected by the coefficient of vacancy diffusion, which is heavily influenced by initial vacancy density rather than deposited energy density.

In this paper, a kinetic model for the reduction process by solid carbon of MnO in high-carbon ferromanganese slags using fractional differential equations (FDE) was developed, the relationship between fractional order, fractional rate constant and temperature was determined, and the accuracy of the fractional order model was verified. The fractional order q is 0.892, 0.808, and 0.522, at 1450, 1500, and 1600°C respectively, and the fractional rate constant k_q 1.176E-03, 2.856E-03, and 3.477E-02. A linear relationship exists between the fractional order and the temperature and an exponential relationship exists with the fractional rate constant. Comparing the conversion factors calculated from the FDE and previous model with the experimental values, the RMSE were 0.005 and 0.029, respectively, and the r² 0.999 and 0.980. This means the FDE model is more accurate. The apparent activation energy of the MnO reduction process calculated using the model was 181.1 kJ/mol.

Laser annealing of structural steels is often used for surface hardening or coating deposition through remelting of the surface layer that leads to better microstructure parameters and mechanical properties. In this paper, an analysis of microstructure selection is performed under non-equilibrium conditions of rapid solidification. The microstructure selection map (MSM) is constructed as a function of the solidification velocity and local temperature gradient. A transition to structureless solidification is determined in the vicinity of the velocity of absolute morphological stability of the advancing front.

This study investigates crack formation mechanisms in gradient layers composed of stainless steel 03Х17Н14М3 (AISI 316L) and aluminum bronze BraZh9-1 (UNS C61800), fabricated via direct energy deposition (DED). The objective was to identify the factors responsible for cracking in the Fe–Cu system and to develop mitigation strategies with potential applications in aerospace, mechanical engineering, and nuclear power industries. Three structural configurations were produced: two with bronze-to-steel mass ratios of 50 : 50 and 70 : 30, respectively, and one comprising sandwich-like architectures with alternating layers. Comprehensive characterization—including microstructural analysis, X-ray diffraction (XRD), mechanical testing with digital image correlation (DIC), fractography, and neutron diffraction (ND)—was employed. Results indicate that cracking arises primarily from mismatches in coefficients of thermal expansion and thermal conductivity, limited mutual solubility between Fe and Cu, formation of brittle intermetallic phases, and residual stress accumulation. Gradual compositional transitions (graded interfaces), as well as sandwich-type layering, substantially reduce crack susceptibility compared to sharp, abrupt material boundaries. To mitigate cracking, the following practical measures are proposed: (i) implementation of gradient transitions incorporating Ni-based intermediate layers; and (ii) optimization of DED process parameters—specifically, reduced laser scanning speed and preheating of the substrate. This work provides novel insights for the DED-based fabrication of gradient multimaterial composites and offers actionable engineering solutions to suppress crack formation.

Amorphous Fe–Ni–Nb–B alloys with different iron/nickel ratios and different boron concentrations were obtained in the form of ribbons by planar flow method. All the ribbons were found to be X-ray amorphous, and their crystallization occurs in one or two stages depending on chemical composition. The onset crystallization temperature depends significantly on iron/nickel ratio and boron content in the samples. Magnetic susceptibility of the samples was studied at heating from amorphous state to crystalline and liquid states (in a high temperature region) and subsequent cooling. An anomalous increase of magnetic susceptibility was detected during heating in the temperature range of 1000–1100 K. This can be associated with the decomposition of metastable (Fe,Ni)₂₃B₆ phase. Some parameters of the electronic structure in Fe–Ni–Nb–B melts: paramagnetic Curie temperature, effective magnetic moment per atom and density of electron states at Fermi level were calculated from the experimental data.