Search Results (378)

300M ultra-high-strength steel for critical load-bearing components such as aircraft landing gear requires a better balance of strength, ductility, and toughness. However, the effect of partitioning temperature on the microstructural evolution and mechanical property balance of Q-P-treated 300M steel under a fixed interrupted quenching condition remains unclear. In this work, 300M steel was subjected to quenching–partitioning treatment with interrupted quenching at 220 °C for 300 s, followed by partitioning at 250–400 °C for 1 h. As the partitioning temperature increased, the yield strength and ultimate tensile strength decreased from 1599 MPa to 1499 MPa and from 1987 MPa to 1801 MPa, respectively, whereas the elongation to failure and impact toughness increased from 11.52% to 16.50% and from 240 kJ·m⁻² to 271 kJ·m⁻². The microstructure remained lath-martensitic throughout, while higher partitioning temperature promoted martensite recovery, reduced dislocation density, and caused precipitate coarsening. Retained austenite remained mainly between martensite laths and exhibited both morphology variation and a non-monotonic diffraction response. Within the investigated window, partitioning at 350 °C gave the most favorable combination of strength, ductility, and impact toughness. These results establish the partitioning temperature dependence of microstructural evolution and mechanical property balance in Q-P-treated 300M steel, and provide guidance for heat treatment optimization. Full article

A novel Fe-based alloy, designated as AMSD, was designed using a machine-learning-assisted high-throughput strategy, and it was successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing without crack formation. This work systematically investigated the effects of post-process cooling rates on the microstructure and mechanical performance of the LPBF-fabricated AMSD alloy. After solution treatment at 1200 °C for 2 h, two cooling conditions, namely air cooling (AC) and water quenching (WQ), were applied, followed by aging at 500 °C for 24 h. It was found that the as-built (AB) alloy exhibited a typical cellular structure, epitaxial columnar grains, and a continuous intercellular segregation network. Post-processing eliminated the segregation network and promoted a more homogeneous microstructure with multiscale precipitates. Compared with AC condition, WQ preserved a finer and denser population of grain-boundary borides and achieved a superior strength–ductility balance, with a UTS of 1072 ± 15 MPa and an elongation of 18.2 ± 0.3% achieved. In contrast, the AC sample exhibited a higher UTS of 1436 ± 45 MPa but lower ductility. These results demonstrate that post-process cooling rates play a key role in regulating precipitate evolution and mechanical performance in LPBF Fe-based alloys. Full article

The effects of Ti/Nb microalloying-induced MC-type carbide precipitation and tempered microstructure evolution on the dry-sliding wear behavior of low-carbon martensitic wear-resistant steels were systematically investigated. Three experimental steels with different microalloying strategies (0.04Ti, 0.1Ti, and 0.04Ti/Nb) were subjected to quenching and subsequent tempering. Microstructural features, carbide characteristics, and mechanical properties were characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing, and impact testing, while wear performance was evaluated by pin-on-disk tests under dry-sliding conditions. The results indicate that wear resistance is governed by the combined effects of tempered martensite stability and MC-type carbide precipitation. Low-temperature tempering effectively reduces the wear mass loss of Ti-containing steels by enhancing their resistance to abrasive shear deformation while maintaining sufficient toughness. In contrast, the Nb-containing steel exhibits a stage-dependent wear response associated with the formation and destabilization of oxide-derived third-body debris during sliding. (Nb,Ti)C precipitates act as microscale load-bearing units, contributing to strength enhancement and subsurface damage suppression, but their influence on wear behavior strongly depends on tempering temperature. The dominant wear mechanism is abrasive micro-cutting, accompanied by fatigue-induced spalling and oxidation-assisted damage at later stages. These results demonstrate that wear performance cannot be correlated with hardness alone, but instead requires the coordinated optimization of carbide precipitation and tempered microstructural stability. This work provides microstructural guidance for the design of microalloyed martensitic wear-resistant steels. Full article

The preparation of new magnetic materials is important because of their potential application in various electronic components. In the present work, the synthesis of glass-crystalline materials in the system Na₂O-MnO-SiO₂-Fe₂O₃ prepared by applying melt-quenching is reported. The phase composition as studied by X-ray diffraction and Raman spectroscopy reveals the precipitation of monophase Mn_xFe_3−xO₄ based solid solutions. The microstructure is studied by scanning electron and optical microscopy and shows bulk crystallization and the presence of polygon-shaped as well as of dendritic crystals, depending on the iron oxide concentration and used raw materials. Mössbauer spectra show that in the amorphous matrix the Fe ions are mainly present as Fe³⁺ in tetrahedral coordination and as Fe³⁺ in a solid solution with the composition Mn_xFe_3−xO₄. The simultaneous presence of MnFe₂O₄ (jacobsite) and a Mn-containing solid solution based on Fe₃O₄ (magnetite) is suggested. The room temperature magnetic properties were studied by vibrating sample magnetometer and reveal ferrimagnetic properties for all investigated glass-crystalline materials. Full article

A Ce-doped photocatalytic composite with easy solid–liquid separation capability was prepared and a heterojunction was constructed between BiVO₄ and Fe₃O₄ via a co-precipitation method. A variety of characterization techniques were employed, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), as well as other related methods. Its photocatalytic performance for the degradation of Rhodamine B (RhB) was also studied. The results indicate that the photocatalytic efficiency of BiVO₄/Fe₃O₄ is 1.4 times that of the pure BiVO₄ matrix. In particular, the photocatalytic efficiency of Ce_1.5%-BiVO₄/Fe₃O₄ was 2.2 times higher than that of the pure BiVO₄ matrix, and a 100% degradation rate of RhB was achieved within 30 min. The introduction of Fe₃O₄ not only forms a heterojunction with BiVO₄, increasing the active sites and surface oxygen vacancies of the material and effectively suppressing the recombination of photogenerated electron (e^-)-hole (h⁺) pairs, but it also enables the rapid separation of the material from the wastewater solution by the magnetic properties of Fe₃O₄. Additionally, the partial substitution of Ce for Bi in the BiVO₄ lattice reduces the bandgap energy, which enhances the utilization efficiency of visible light and improves the photocatalytic performance of the composite material. The mechanism of RhB degradation by Ce_1.5%-BiVO₄/Fe₃O₄ composite materials is also analyzed in this study. Quenching experiments and EPR tests revealed that h⁺ and ${·\mathrm{O}}_2^{-}$ were the primary reactive species in the degradation process. Full article

Large-scale reuse of copper tailings can mitigate environmental hazards and recover strategic elements; this work investigates the feasibility of producing foam glass-ceramics with high copper-tailing content (>70 wt%) by tuning the CaO/SiO₂ ratio to couple melt viscosity and crystallisation. The comprehensive utilisation of these tailings helps mitigate environmental pollution and enhance resource efficiency. In this study, foam glass-ceramics with varying CaO/SiO₂ ratios were synthesised through melt quenching followed by foaming heat treatment. The effects of different CaO/SiO₂ ratios on the foaming behaviour, crystallisation, and microstructure were investigated using DSC, FTIR, viscosity, XRD, SEM, and CT. The results indicate that increasing the CaO/SiO₂ ratio disrupts the three-dimensional network structure of the glass, which lowers the glass viscosity and influences the bubble size and distribution in the foam glass-ceramics. Additionally, the increased CaO content promotes crystal precipitation and enhances the compressive strength of the foam glass-ceramics. At a CaO/SiO₂ mass ratio of 0.22, the foam glass-ceramics exhibited the lower bulk density (240 kg/m³) and thermal conductivity (0.07 W/m·K). The materials also demonstrated good water absorption and compressive strength. This study highlights the potential of using copper tailings in foam glass-ceramics to improve their overall performance, offering promising energy-saving and environmentally friendly solutions. Full article

The research described in this article is a continuation of a series of studies on biocompatible materials, focused on finding the optimal alloy composition and heat treatment regimes. The use of materials with a low Young’s modulus ensures the long-term safety of the implant by reducing the stress shielding effect, which causes bone resorption. This work investigates the effect of alloying with niobium in the range of (8–10) at. % on the Ti-38Zr alloy, specifically its structure, mechanical properties, Young’s modulus, and superelasticity. In this study, plates of the Ti-38Zr-(8-10)Nb (at. %) alloy were investigated after quenching and subsequent annealing. In Ti-38Zr-(8-10)Nb alloys, quenching from 600 °C fixes the β-phase of Ti. In alloys with (8-9)Nb, this is a metastable β-phase, as evidenced by its superelastic behavior under cyclic tension. Annealing at 400 °C leads to a clear decomposition of the quenched high-temperature β-phase in Ti-38Zr-(8-9)Nb alloys into β- and α′-phases. Based on the mechanical test results, it can be inferred that the precipitation of the brittle ω-phase and the α′-phase occur concurrently, since annealing at 400 °C causes a pronounced embrittlement of the Ti-38Zr-(8–9)Nb alloys (with elongation dropping from ~15% to 0.7–2.5%, respectively) alongside a substantial increase in strength (from 500 MPa to 1010 MPa). For the Ti-38Zr-10Nb alloy, the ductility also declines but remains within acceptable limits (from ~14% to ~10%), while the strength rises from 520 MPa to 630 MPa. The Young’s modulus of the Ti-38Zr-(8-10)Nb alloy after quenching is ~80 GPa. After annealing, it increases to 95 GPa for alloys with (8-9)Nb, while for 10Nb it remains at approximately 80 GPa. Full article

Chelating agents can extend the operational pH range of iron-based advanced oxidation processes, yet comprehensive studies on chelated Fe-activated persulfate systems for textile dye degradation remain scarce. This study establishes an integrated framework for optimizing Fe(II)/persulfate (PS) systems using chelating ligands and hybrid energy inputs under near-neutral conditions. Among the tested systems, Fe(II)/PS complexed with citric acid (CA) exhibited superior performance, achieving ~91% dye removal within 20 min at pH 6.5 under optimized conditions (1.25 mM Fe(II), 10 mM PS, 0.1 mM CA). Chelation stabilized Fe redox cycling and prevented precipitation, enabling effective catalysis across pH 3–10. Optimal CA/Fe and Fe/PS ratios (0.1:1.25 and 1.25:10) yielded ~96% decolorization and 67.65% TOC removal in 60 min, while excessive chelation reduced activity. Transition metal screening (Mn(II), Zn(II), Cu(II), Co(II), and Ni(II) confirmed Fe(II) as the most effective activator, providing removal efficiencies up to 3.2-fold higher than competing metals. Mixed-dye experiments showed competitive degradation, with >37% color removal after 60 min for ternary dye mixtures. Mineralization reached ~92% TOC reduction after 120 min, indicating deep oxidation beyond chromophore cleavage. Reactive species quenching revealed a mixed oxidation mechanism involving ^•OH radicals and high-valent Fe(IV) species. Hybrid assistance improved mineralization, with UVC increasing TOC removal by 15.6%, while solar irradiation provided moderate enhancement under low-energy input. In contrast, low-power ultrasound (40 kHz, 60 W) delivered only 17.6 W acoustic power to the solution and did not improve performance due to limited cavitation and mixing. This work thus contributes a robust platform for advancing chelated iron-persulfate oxidation systems toward practical, effective treatment of recalcitrant dye-contaminated wastewaters under near-neutral conditions. Full article

The study systematically investigates the effect of molybdenum (Mo) content (0.70–1.57 wt.%) on the microstructure and mechanical properties of quenched and tempered martensitic steel for ultra-high-strength and -toughness oil well pipes. The results demonstrate that increasing the Mo content substantially enhances the strength of the steel. The yield strength (YS) increases from 1135 MPa to 1233 MPa, the ultimate tensile strength (UTS) rises from 1176 MPa to 1285 MPa, and the elongation after fracture is marginally improved to 19%. However, the low-temperature impact energy (AKV₂) of the steel at −20 °C exhibits a pronounced decrease, from 117 J to 36 J. Mo refines the multi-scale martensitic microstructure, increases the fraction of high-angle grain boundaries (HAGBs) and dislocation density, and promotes the precipitation of three types of carbides. Quantitative analysis indicates that grain refinement strengthening is the predominant factor contributing to the enhancement of steel strength. The decline in the steel’s resistance to low temperatures is attributed to the separation of coarse, blocky M₃C-type carbides at the grain boundaries. This results in the accumulation of stress at these boundaries, leading to a transformation in the steel’s fracture mode from ductile to brittle. Full article

Elastocaloric cooling, which leverages stress-induced phase transformation in shape memory materials, represents a sustainable and energy-efficient alternative to conventional vapor-compression cooling systems. Central to optimizing these materials is understanding how thermal processing history dictates phase formation, microstructure, and thermal properties. In this study, we investigated the (Ni₅₀Mn_31.5Ti₁₈)_99.8B_0.2 compound synthesized via vacuum induction melting and arc melting, followed by water quenching. Induction melting results in needle-like, boron-rich precipitates within the martensite lattice. In contrast, vacuum arc melting promoted precipitate growth at the grain boundaries. The vacuum arc melting sample exhibits ~82% martensite phase fraction, a near-ambient transformation temperature of ~277 K, a large transition entropy change of ~75 J·kg⁻¹·K⁻¹, and moderate thermal hysteresis of ~24 K. These results underscore the pivotal role of thermal history in tailoring phase stability and transformation thermodynamics, providing essential design guidelines for subsequent mechanical performance optimization in elastocaloric shape memory alloys for energy-efficient and sustainable thermal management applications. Full article

This study systematically investigates the influence of quenching (850–910 °C) and tempering (160–280 °C) temperatures on the microstructural evolution and mechanical properties of a novel low-alloy ultra-high-strength martensitic steel (UHSMS). Comprehensive microstructural characterization combined with mechanical testing demonstrates that quenching at 880 °C results in the finest martensitic laths and the highest dislocation density, leading to an excellent strength–toughness balance. Subsequent tempering treatments reveal that the specimen tempered at 200 °C achieves an optimal combination of properties, with a yield strength of 1517 MPa, ultimate tensile strength of 2017 MPa, elongation of 10.4%, and impact toughness of 80.3 J/cm². This optimum is mechanistically linked to a cooperative effect where the fine tempered martensitic structure and stable film-like retained austenite (RA) enhance toughness and ductility, while the nano-scale precipitates (forming during the ε→θ carbide transition) simultaneously provide substantial precipitation strengthening, thereby minimizing the strength sacrifice typically associated with improved toughness. Furthermore, the 200 °C tempered specimen exhibits the largest shear lip on the tensile fracture surface and the maximum dimple size on the impact fracture surface, indicative of a high plastic strain capacity and excellent crack propagation resistance. Full article

In this work, the effects of Nb and Mo additions on the precipitation behavior and strengthening mechanisms of three ultra-low carbon Ti-Mo-Nb steels with a predominantly ferritic microstructure were investigated under two different thermo-mechanical processing (TMP) routes. A water-quenching step after hot rolling followed by furnace cooling was found to refine the average precipitate size and increase their volume fraction, leading to a significant strength improvement. Specifically, this process increased the yield strength by approximately 110~180 MPa, reaching levels above 750 MPa, with the 22Mo-Nb steel achieving a peak ultimate tensile strength of ~790 MPa. The precipitates exhibited dispersed, interphase, and grain boundary morphologies, none of which correlated directly with the TMP route or steel composition. While variations in Mo content showed little influence on precipitate characteristics, the addition of Nb markedly promoted precipitation. The strength of these Ti-Mo-Nb ferritic steels is primarily determined by precipitation strengthening. Through optimized TMP parameters and microalloying additions, the overall precipitation strengthening contribution was elevated to the 300~400 MPa range. Full article

To synergistically enhance the strength and toughness of low-alloy cast steels, a quenching–partitioning–tempering (Q-P-T) heat treatment process was specifically performed based on the “Constrained Carbon Equilibrium” thermodynamic model. The effects of partitioning temperature on microstructure and mechanical properties were examined. The Q-P(210)-T approach successfully produced an ultra-high strength cast steel (48SiNiMnCrMoAl6-4-4-3-8-14) with a tensile strength exceeding 2000 MPa and an elongation greater than 19.0%. The microstructure of this cast steel consists of tempered martensite (TM), bainite, ferrite, and retained austenite (RA). During tensile deformation, dislocations from adjacent martensite are absorbed by the film-like RA, thereby alleviating stress concentration induced by dislocations. Meanwhile, the transformation-induced plasticity (TRIP) effect of the RA significantly enhances the toughness of the cast steel. Furthermore, the ultra-high strength of the cast steel is jointly ensured by the fine crystalline strengthening of the martensite and the precipitation strengthening of the transitional carbides in the microstructure of the cast steel. This work provides a good reference for the development of high-performance cast steels. Full article

High-chromium cast iron is widely used in cement, mining and metallurgy, but its as-cast state has defects such as coarse carbides, uneven distribution and severe elemental segregation, resulting in insufficient toughness and poor wear stability. Taking Cr20 type high-chromium cast iron as the research object, two sample groups (without/with La) were designed. XRD, OM, SEM, EDS, mechanical property tests and impact wear experiments were used to study the effects of La addition and different quenching temperatures (900 °C, 950 °C, 1000 °C, 1050 °C) on its properties. The results show that La does not change the phase composition but refines carbides, alleviates segregation and promotes secondary carbide precipitation. Suitable heat treatment enhances properties, while excessive temperature (1050 °C) causes performance degradation. Sample 2 (with La, quenched at 1000 °C) has the optimal comprehensive properties, with superior hardness, impact energy and wear resistance. This study provides an experimental basis and technical reference for optimizing high-chromium cast iron properties. Full article

A novel Ag₃PO₄/BiVO₄ heterojunction was synthesized via a combined hydrothermal–in situ precipitation method. With an optimal Bi:Ag molar ratio of 1:2 and after calcination at 200 °C for 22 h, 0.9 g of this composite reduced the chemical oxygen demand (COD) of landfill leachate tailwater from 232 mg·L⁻¹ to 142 mg·L⁻¹ and its UV₂₅₄ absorbance from 0.22 to 0.156 under visible light irradiation within 140 min. The material exhibited a bandgap of 2.56 eV, along with enhanced visible-light absorption and improved charge-carrier separation efficiency. In the Ag₃PO₄/BiVO₄/peroxymonosulfate (PMS)/visible light system, using 0.5 g of catalyst and 2.0 g·L⁻¹ of PMS at pH 11 reduced the COD from 242 mg·L⁻¹ to 138 mg·L⁻¹. A subsequent two-stage treatment process, integrating the Ag₃PO₄/BiVO₄/PMS/vis and P25/UV process, achieved a final tailwater COD of 90 mg·L⁻¹—meeting standard discharge limits—and a 69.5% removal of humic-like substances. The heterojunction catalyst retained its activity over four consecutive cycles. Radical quenching experiments and electron paramagnetic resonance (EPR) spectroscopy identified photogenerated holes (h⁺), hydroxyl radicals(·OH), and sulfate radicals (SO₄⁻·) as the primary reactive species. Gas chromatography–mass spectrometry (GC–MS) analysis identified intermediate organic compounds and proposed plausible degradation pathways. These results support a reaction mechanism in which h⁺ oxidizes H₂O to generate ·OH, while PMS accepts electrons to produce SO₄⁻· and further ·OH radicals, leading to effective pollutant mineralization. Collectively, this solar-driven, sulfate radical-based advanced oxidation process offers an energy-efficient strategy with reduced chemical consumption for the sustainable treatment of refractory wastewater. Full article