Acta Metallurgica Sinica-English Letters最新文献

The development of high-performance transition metal sulfide (TMS)/carbon composites to replace conventional graphite anode remains a critical challenge for advancing lithium-ion batteries (LIBs). In this study, a facile self-sacrifice template method is developed to prepare FeS encapsulated into N, S co-doped carbon (FeS/NSC) composite using melamine-cyanuric acid (MCA) supermolecule as a multifunctional template precursor. The function of MCA supermolecule for material synthesis is explored, revealing its special function as a dispersant, dopant and pore-forming agent. Furthermore, the effect of Fe source dosage on the morphology, structure and composition of the final products is explored. The resultant FeS/NSC-0.1 (where 0.1 represents the mass of added Fe source) exhibits the most optimal proportion, characterized by a good dispersion status of FeS within the NSC matrix, effective N, S co-doping and ample porosity. Benefiting from these merits, the FeS/NSC-0.1 anode demonstrates significantly improved cycling stability and rate capability when compared to the counterparts. Undoubtedly, this work offers a universal method to produce advanced transition metal sulfide/carbon composite electrodes for energy storage and conversion systems.

This study systematically investigates the hot deformation behavior and microstructural evolution of CoNiV medium-entropy alloy (MEA) in the temperature range of 950–1100 °C and strain rates of 0.001–1 s⁻¹. The Arrhenius model and machine learning model were developed to forecast flow stresses at various conditions. The predictive capability of both models was assessed using the coefficients of determination (R²), average absolute relative error (AARE), and root mean square error (RMSE). The findings show that the osprey optimization algorithm convolutional neural network (OOA-CNN) model outperforms the Arrhenius model, achieving a high R² value of 0.99959 and lower AARE and RMSE values. The flow stress that the OOA-CNN model predicted was used to generate power dissipation maps and instability maps under different strains. Finally, combining the processing map and microstructure characterization, the ideal processing domain was identified as 1100 °C at strain rates of 0.01–0.1 s⁻¹. This study provided key insights into optimizing the hot working process of CoNiV MEA.

The corrosion behavior of 304LN austenitic stainless steel in supercritical CO₂ at 650 °C was investigated. The results show that 304LN follows Wagner’s law kinetics, forming a protective oxide film consisting of SiO₂, (Cr, Mn)₃O₄, and Cr₂O₃ from the inner to outer layers. A shallow carburization depth of approximately 130 nm indicates excellent resistance to carburization. The roles of key elements in 18/8 austenitic stainless steel represented by 304LN, such as Cr, Ni, and Si, were analyzed, highlighting their contributions to anti-carburization performance and corrosion resistance under harsh conditions.

A novel oxide-dispersion-strengthened (ODS) die steel was fabricated by mechanical alloying and hot consolidation. Annealing and quench-tempering treatments both obtained an ultra-fine grain structure (mean size: 310–330 nm) with an ultra-high density of ultra-fine Y-Al-O nano-oxides (number density: ~ (1–1.5) × 10²³ m⁻³, mean size: 5.1–7.2 nm). Prolonged thermal exposure further induced the new, highly dense precipitation of ultra-fine Y-Zr-O nano-oxides. Both nano-oxides tended to be wrapped up with a B2-NiAl nano-shells. Although the quench-tempered sample showed much higher room-temperature strength (yield strength = 1393 ± 40 MPa and ultimate tensile strength = 1774 ± 11 MPa) and slightly lower elongation (elongation = 13.6% ± 0.6%) than the annealed sample (YS = 988 ± 7 MPa, UTS = 1490 ± 12 MPa, and EL = 15.2% ± 1.1%), both samples exhibited better strength-ductility synergy at room temperature and much higher thermal stabilities at high temperatures (600–700 °C) than all those conventional hot-work die steels, which makes the new ODS steel highly promising for advanced hot-work mold and die applications at high temperatures above 600 °C.

The mechanical anisotropy on extruded AZ31 magnesium alloy bar has been investigated by combining experimental measurement and crystal plasticity modeling. Monotonic tension and compression are conducted in four loading directions with the oblique angle φ of 0°, 30°, 60° and 90° from extrusion radial direction to extrusion direction, and are also simulated by visco-plastic self-consistent model with considering twinning and detwinning scheme at the first time. The simulation results are well in agreement with the corresponding experimental data. Combined with the Schmid factor (SF), the anisotropic mechanical behaviors including yield strength, ultimate strength and strain hardening rate are interpreted with the predicted relative activities of deformation modes, texture evolution and twin volume fraction. With the loading angle varying from 0° to 90°, it is found that prismatic slip becomes the primary deformation mode with the decreasing relative activities of basal slip and extension twinning in tension. While the deformation mechanism is more complex in compression: Extension twinning gets great activation at the beginning of the deformation, especially under compression along 90°; basal slip and pyramidal < c + a > slip dominate the late deformation of compression along 0° and 30°, while basal slip and prismatic slip are dominated modes in compression along 60° and 90°. Additionally, different ({{{10}stackrel{{-}}{1}{{2}}}}) twinning behaviors with two or three and one or two pairs of twin variants being activated in tension along 30° and compression along 90°, respectively, have a close correlation with the texture evolution to coordinate plastic deformation. The activation of ({{{10}stackrel{{-}}{1}{{2}}}}) twinning, which varies with the loading angle φ, results in the increased trend of strain hardening rate. Following the exhausting of twinning, non-basal slips with the highest SF become the primary deformation mode subsequently, contributing to the decreasing trend in hardening behavior and the anisotropy of ultimate strength.

Sodium-ion batteries are receiving more and more attention due to their low cost and abundant sodium storage capacity, and are considered to be a promising alternative to lithium-ion batteries. A large number of studies have shown that constructing heterostructures are considered an effective strategy to solve the hysteresis problem of electronic and ion dynamics in sodium-ion battery anode materials. Herein, a nickel–cobalt bimetallic coordination polymer (NiCoCP) was synthesized using a coprecipitation method, and a CoSe₂@NiSe₂ cross-stacked structure was obtained through high-temperature carbonization and selenization processes. CoSe₂@NiSe₂ has a unique heterostructure and carbon film, which synergistically increases a large number of adsorption sites and alleviates the diffusion energy barrier, thereby improving the rapid diffusion kinetics of Na⁺ ions. It has superior rate performance and long-lasting cycle life. For sodium-ion batteries (SIBs), the specific capacity of CoSe₂@NiSe₂ is around 460 mA h g⁻¹ after 400 cycles at 1.0 A g⁻¹. For potassium-ion batteries (PIBs), CoSe₂@NiSe₂ also exhibits excellent cycling stability, maintaining a specific capacity of 160 mA h g⁻¹ after 700 cycles at 1.0 A g⁻¹. This study provides a new way to prepare metal selenide heterostructure as the promising anode material for SIBs.

This work studies the impact of the carbon diffusion on the growth kinetics of austenite and the solute segregation, by utilizing the phase-field (PF) method to simulate the solidification of a Fe–C binary alloy. It is revealed that increasing the ratio of the carbon diffusion coefficient in solid to that in liquid is advantageous in reducing the solute segregation, and a novel microsegregation model is developed based on the quantitative analysis of the results from PF simulations. The simplified one-dimensional diffusion simulation is employed to analyse the quantitative relationship between the parameters of the proposed microsegregation model and the properties of materials. The universality and reliability of the new microsegregation model are then validated by comparing with the experimental data of various alloy systems. These findings contribute to our comprehension of the fundamental theory of solidification and also provide a potential and promising approach to controlling the solidification microstructure.

In the present study, a simple but effective two-step annealing processing strategy via manipulating the austenite reversion path is proposed to obtain a large fraction of retained austenite in low-Mn medium-Mn steels. Initially, the Fe–3Mn–0.2C–1.5Si (wt%) steel is intercritically annealed to form Mn-enriched lamellar martensite precursors. Subsequently, the austenite reversion transformation is manipulated to occur within the martensite lamellae during the second annealing process, resulting in an ultra-fine duplex microstructure of laminated austenite and ferrite. This process can not only allow a large fraction of austenite to be retained in low-Mn medium-Mn steels, but also increase the elongation by up to 41% without sacrificing the strength level compared to the conventional annealing.

Metastable β titanium alloy is an ideal material for lightweight and high strength due to its excellent comprehensive mechanical properties. However, overcoming the trade-off relation between strength and ductility remains a significant challenge. In this study, the mechanical properties of Ti-38644 alloy were optimized by introducing a heterogeneous bi-grain bi-lamella (BG-BL) structure through a well-designed combination of rolling, drawing and heat treatment. The results demonstrate that the present BG-BL Ti-38644 alloy shows a tensile strength of ~ 1500 MPa and a total elongation of 18%. In particular, the high strength-elongation combination of the BG-BL Ti-38644 alloy breakthroughs the trade-off relation in all the titanium alloys available. The recrystallized grains with low dislocation enhance the ductility of the Ti-38644 alloy, while the highly distorted elongated grains mainly contribute to the high strength. The present study provides a new principle for designing Ti alloys with superior strength and ductility.

Nanocrystalline alloys often exhibit unusual thermal stability as a consequence of kinetic and thermodynamic barriers to grain growth. However, the physical mechanisms governing alloy stability need to be identified. In this work, we found that grain boundary (GB) relaxation renders Ni–W alloyed films relatively stable at low annealing temperature, while twinning-mediated grain growth occurs via dislocation-GB/twin boundary (TB) interactions as the annealing temperature increases. At a relatively low temperature, TB strengthening plays a dominant role in plastic deformation, whereas precipitation strengthening gradually controls the deformation mechanism with the increase of annealing temperature. Our findings provide evidence for improving mechanical property through alloying and microstructure design, and have a crucial guiding significance in material selection and miniaturized applications such as Micro Electro Mechanical Systems.