Search Results (117)

A novel strategy has been developed for extracting value-added resources from iron-lean, high-alumina- and -silica-containing red muds (RMs). With little or no recycling, such RMs are generally destined for waste dumps. Detailed results are presented on the carbothermic reduction of 100% RM (29.3 wt.% Fe₂O₃, 22.2 wt.% Al₂O₃, 20.0 wt.% SiO₂, 1.2 wt.% CaO, 12.2 wt.% Na₂O) and its 2:1 blends with Fe₂O₃ and red mill scale (MS). Synthetic graphite was used as the reductant. Carbothermic reduction of RM and blends was carried out in a Tamman resistance furnace at 1650 °C for 20 min in an Ar atmosphere. Reduction residues were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental mapping and X-ray diffraction (XRD). Small amounts of Fe₃Si alloys, alumina, SiC and other oxide-based residuals were detected in the carbothermic residue of 100% RM. A number of large metallic droplets of Fe–Si alloys were observed for RM/Fe₂O₃ blends; no aluminium was detected in these metallic droplets. A clear segregation of alumina was observed as a separate phase. For the RM/red MS blends, a number of metallic Fe–Si droplets were seen embedded in an alumina matrix in the form of a cermet. This study has shown the regeneration of alumina and the formation of alumina-based cermets, Fe–Si alloys and SiC during carbothermic reduction of RM and its blends. This innovative recycling strategy could be used for extracting value-added resources from iron-lean RMs, thereby enhancing process productivity, cost-effectiveness of alumina regeneration, waste utilization and sustainable developments in the field. Full article

Diverging from conventional dephosphorization approaches, this study employs a novel pre-reduction and smelting separation (PR-SS) to efficiently co-recover iron and phosphorus from high-phosphorus oolitic iron ore, directly yielding Fe–P alloy, and the Fe–P alloy shows potential as feedstock for high-phosphorus weathering steel or wear-resistant cast iron, indicating promising application prospects. Using oolitic magnetite concentrate (52.06% Fe, 0.37% P) as feedstock, optimized conditions including pre-reduction at 1050 °C for 2 h with C/Fe mass ratio of 2, followed by smelting separation at 1550 °C for 20 min with 5% coke, produced a metallic phase containing 99.24% Fe and 0.73% P. Iron and phosphorus recoveries reached 99.73% and 99.15%, respectively. EPMA microanalysis confirmed spatial correlation between iron and phosphorus in the metallic phase, with undetectable phosphorus signals in vitreous slag. This evidence suggests preferential phosphorus enrichment through interfacial mass transfer along the pathway of the slag phase to the metal interface and finally the iron matrix, forming homogeneous Fe–P solid solutions. The phosphorus migration mechanism involves sequential stages: apatite lattice decomposition liberates reactive P₂O₅ under SiO₂/Al₂O₃ influence; slag–iron interfacial co-reduction generates Fe₃P intermediates; Fe₃P incorporation into the iron matrix establishes stable solid solutions. Full article

A novel and cost-effective methodology is introduced for the precise prediction of the melting time of metals and alloys in a 700 W domestic microwave oven, using a hybrid SiC–graphite susceptor to ensure efficient heating without direct interaction with microwaves. The study includes experimental trials with multiple alloys (Sn–Bi, Zn, Zamak, and Al–Si, among others) and variable masses, whose results made it possible to construct a dimensionless model, trained with XGBoost on easily measurable thermophysical properties (specific heat, density, thermal conductivity, mass, and melting temperature). The model achieves high accuracy, with a relative error below 5%, and metrics of MAE = 4.8 s, RMSE = 6.1 s, and R² = 0.9996. The generalization of the model to different microwave powers (600–1100 W) is also validated through analytical adjustment, without the need for additional experiments. The proposal is implemented as a Python application with a graphical interface, suitable for any academic or teaching laboratory, and its performance is compared with classical models. This approach effectively contributes to the democratization of thermal testing of metals in educational and research settings with limited resources, providing thermodynamic rigor and advanced artificial intelligence tools. Full article

With the ongoing development of lightweight automobiles, research on new aluminum alloys and welding technology has gained significant attention. Friction stir welding (FSW) is a solid-state joining technique for welding aluminum alloys without melting. In this study, novel squeeze-cast Al-Si-Mg-Fe-Zn alloys with different Zn contents (0, 3.4, 6.5, and 8.3 wt%) were friction stir welded (FSWed) at a translational speed of 200 mm/min and a rotational speed of 800 rpm. These parameters were chosen based on the observations of visually sound welds, defect-free and fine-grained microstructures, homogeneous secondary phase distribution, and low roughness. Zn can affect the microstructure of Al-Si-Mg-Fe-Zn alloys, including the grain size and the content of secondary phases, leading to different mechanical and corrosion behavior. Adding different Zn contents with Mg forms the various amount of MgZn₂, which has a significant strengthening effect on the alloys. Softening observed in the weld zones of the alloys with 0, 3.4, and 6.5 wt% Zn is primarily attributed to the reduction in Kernel Average Misorientation (KAM) and a decrease in the Si phase and MgZn₂. Consequently, the mechanical strengths of the FSWed joints are lower as compared to the base material. Conversely, the FSWed alloy with 8.3 wt% Zn exhibited enhanced mechanical properties, with hardness of 116.3 HV_0.2, yield strength (YS) of 184.4 MPa, ultimate tensile strength (UTS) of 226.9 MP, percent elongation (EL%) of 1.78%, and a strength coefficient exceeding 100%, indicating that the joint retains the strength of the as-cast one, due to refined grains and more uniformly dispersed secondary phases. The highest corrosion resistance of the FSWed alloy with 6.5%Zn is due to the smallest grain size and KAM, without MgZn₂ and the highest percentage of {111} texture (24.8%). Full article

Interpenetrating phase composites (IPCs) have demonstrated tremendous potential across various fields, particularly those based on triply periodic minimal surface (TPMS) structures, whose uniquely interwoven lattice architectures have attracted widespread attention. However, current research on the dynamic mechanical properties of such IPC remains limited, and their impact resistance and damage mechanisms are yet to be thoroughly understood. In this study, a novel design of two volume fractions of IPCs based on the TPMS IWP configuration is developed using Python-based parametric modeling, with the Ti6Al4V alloy TPMS scaffolds fabricated via selective laser melting (SLM) and the AlSi12 reinforcing phase through infiltration casting. The influence of Ti alloy volume fraction and strain rate on the dynamic mechanical behavior of the Ti/Al IPC is systematically investigated using a split Hopkinson pressure bar (SHPB) experimental setup. Microscopic characterization validates the effectiveness and reliability of the proposed IPC fabrication method. Results show that the increasing Ti alloy volume fraction significantly affects the dynamic mechanical properties of the IPC, and IPCs with different Ti alloy volume fractions exhibit contrasting mechanical behaviors under increasing strain rates, attributed to the dominance of different constituent phases. This study enhances the understanding of the dynamic behavior of TPMS-based IPCs and offers a promising route for the development of high-performance energy-absorbing materials. Full article

The application fields of high-temperature titanium alloys are mainly concentrated in the aerospace, defense and military industries, such as the high-temperature parts of rocket and aircraft engines, missile cases, tail rudders, etc., which can greatly reduce the weight of aircraft while resisting high temperatures. However, traditional high-temperature titanium alloys containing multiple types of elements (more than six) have a complex impact on the solidification, deformation, and phase transformation processes of the alloys, which greatly increases the difficulty of casting and deformation manufacturing of aerospace and military components. Therefore, developing low-component high-temperature titanium alloys suitable for hot processing and forming is urgent. This study used data augmentation (Gaussian noise) to expedite the development of a novel quinary high-temperature titanium alloy. Utilizing data augmentation, the generalization abilities of four machine learning models (XGBoost, RF, AdaBoost, Lasso) were effectively improved, with the XGBoost model demonstrating superior prediction accuracy (with an R² value of 0.94, an RMSE of 53.31, and an MAE of 42.93 in the test set). Based on this model, a novel Ti-7.2Al-1.8Mo-2.0Nb-0.4Si (wt.%) alloy was designed and experimentally validated. The UTS of the alloy at 600 °C was 629 MPa, closely aligning with the value (649 MPa) predicted by the model, with an error of 3.2%. Compared to as-cast Ti1100 and Ti6242S alloy (both containing six elements), the novel quinary alloy has considerable high-temperature (600 °C) mechanical properties and fewer components. The microstructure analysis revealed that the designed alloy was an α+β type alloy, featuring a typical Widmanstätten structure. The fracture form of the alloy was a mixture of brittle and ductile fracture at both room and high temperatures. Full article

The precision casting of nickel-based single-crystal superalloys imposes stringent requirements on the high-temperature stability and chemical inertness of ceramic shell face coats. To address the issue of traditional EC95 shells (95% Al₂O₃–5% SiO₂) being prone to react with the alloy melt at elevated temperatures, thereby inducing casting defects, this study proposes a lanthanide oxide-based ceramic face coat material. Three distinct powders—LaAlO₃ (LA), LaAlO₃/La₂Si₂O₇ (LAS), and LaAl₁₁O₁₈/La₂Si₂O₇/Al₂O₃ (LA11S)—are successfully prepared through solid-phase sintering of the La₂O₃-Al₂O₃-SiO₂ ternary system. Their slurry properties, shell sintering processes, and high-temperature performance are systematically investigated. The results demonstrate that optimal slurry coating effectiveness is achieved when LA powder is processed with a liquid-to-powder ratio of 3:1 and a particle size of 300 mesh. While LA shells show no cracking at 1300 °C, their face coats fail above 1400 °C due to the formation of a La₂Si₂O₇ phase. In contrast, LAS and LA11S shells suppress cracking through the La₂Si₂O₇ and LaAl₁₁O₁₈ phases, respectively, exhibiting exceptionally high-temperature stability at 1400 °C and 1500 °C. All three shells meet the high-temperature strength requirements for CMSX-4 single-crystal alloy casting. Interfacial reaction analysis and Gibbs free energy calculations reveal that Al₂O₃-forming reactions occur between the novel shells and alloy melt, accompanied by minor dissolution erosion without other chemical side reactions. This work provides a high-performance face coat material solution for investment casting of nickel-based superalloys. Full article

The present study aims to investigate the microstructural evolution and local mechanical properties of an AlFe18Si8Cr5Ni2 alloy processed via Powder Bed Fusion–Laser-Based Manufacturing (PBF-LB/M). Designed with a focus on sustainability, this alloy was produced by deriving the necessary elements from AlSi10Mg and 304L steel, two of the most widely used alloys and, consequently, among the easiest materials to source from machining scrap. By leveraging iron, chromium, and nickel from these widespread standard compositions, the alloy mitigates the detrimental effects of Fe contamination in Al-based alloys while simultaneously enhancing mechanical performance. A comprehensive investigation of the impact of rapid solidification and thermal cycling offered novel insights into phase stability, elemental distribution, and local mechanical behavior. In particular, microstructural analyses using scanning electron microscopy (SEM), field emission SEM, energy-dispersive X-ray spectroscopy, X-ray diffraction, and differential scanning calorimetry revealed significant phase modifications post PBF-LB/M processing, including Fe-rich acicular phase segregation at melt pool boundaries and enhanced strengthening phase formation. In addition, nanoindentation mapping was used to demonstrate the correlation between microstructural heterogeneity and local mechanical properties. The findings contribute to a deeper understanding of Al-Fe-Si-Cr-Ni alloy changes after the interaction with the laser, supporting the development of high-performance, sustainable Al-based materials for PBF-LB/M applications. Full article

The creation of coatings by the cathodic arc evaporation method has outstanding advantages: these coatings are highly durable and wear-resistant, especially since the method has an intense ionization process and the atoms can penetrate deep into the surface substrates, resulting in excellent adhesion. Furthermore, this approach provides precise control over the chemical composition and thickness of the coating, ensuring consistent quality across the entire surface. However, uneven evaporation and ejection of molten metal droplets from the cathode during cathode arc deposition produce particles and droplets, resulting in an uneven coating surface. This study presents a new design for a magnetically controlled cathode arc source to effectively reduce particles and droplets during the cathodic arc deposition of multi-component alloy targets for nitride-based hard coatings. The study compares the performance of a new source with a conventional magnetic-controlled arc source for depositing TiAlNbSiN and AlCrSiN films. In the conventional source, the magnetic field is generated by a permanent magnet (PM), whereas in the new source, it is generated and controlled using an electromagnet (EM). Both films are produced using multi-component alloy targets (TiAlNbSi and AlCrSi) with identical composition ratios. The plasma characteristics of the two different arc sources are investigated using an optical emission spectrometer (OES), and the surface morphology, structural characteristics, deposition rate, uniformity, and surface roughness (Sa) are examined using scanning electron microscopy (SEM). When the EM was applied to have high plasma density, the hardness of the TiAlNbSiN film deposited with the novel arc source measured 31.2 ± 1.9 GPa, which is higher than that of the PM arc source (28.3 ± 1.4 GPa). In contrast, the AlCrSiN film created using a typical arc source exhibited a hardness of only 25.5 ± 0.6 GPa. This lower hardness may be due to insufficient ion kinetic energy to enhance stress blocking and increase hardness, or the presence of the h-AlN phase in the film, which was not detected by XRD. The electromagnet arc source, with its adequate ion bombardment velocity, facilitated a complementary effect between grain growth and stress blocking, leading to a remarkable hardness of 32.6 ± 0.5 GPa. Full article

To enhance the mechanical properties of 6082 aluminum alloy, a novel Sc- and Zr-microalloyed 6082 alloy was fabricated through squeeze casting technology. Microalloying with Sc and Zr substantially refined the microstructure of alloy, achieving an average grain size of 136.36 μm—a 31.7% reduction compared to the baseline 6082 alloy. Furthermore, the addition of Sc and Zr effectively refined the coarse AlFeMnSi intermetallic phases, mitigating their inherent brittleness. The Sc/Zr-modified alloy exhibited delayed age-hardening kinetics, requiring 100% longer aging time to reach peak hardness due to Sc/Zr-induced retardation of β’’-phase precipitation. The optimized alloy demonstrated better mechanical properties, showing 10.4%, 8.0%, and 71.8% enhancements in yield strength, ultimate tensile strength, and elongation, respectively, over the non-microalloyed counterpart. The squeeze-cast Sc/Zr-modified alloy valve body showed yield strength exceeding 300 MPa and elongation above 10% across various sections, which verifies the effectiveness of this integrated microalloying and forming approach. Full article

Ferrosilicon (FeSi) is a commercially important material with multiple uses in metallurgical processes. Recently, in an attempt to reduce the carbon impact of the FeSi production process, researchers have proposed using recycled Si recovered from electronic waste in the production of FeSi. However, Si recovered from electronic waste usually contains Al, Cu, and Sn as impurities. Hence, FeSi alloys produced with recycled Si from electronic waste may contain all these elements in varying proportions. Al, Cu, and Sn have been explored as alloying elements to produce alloys with Fe. FeSiAl alloys have also been studied recently for their superior properties. In this work, a multicomponent FeSiAlCuSn alloy is produced, and the phases formed at different temperatures are analyzed using different phase identification techniques. We also analyze the hardness of the multicomponent alloy to find any deviation from the standard FeSi alloy without the additional alloying elements. Understanding the phases and the composition of such alloys may help design future multi-component or high-entropy alloys involving Fe, Si, Al, Cu, and Sn for specific applications. Full article

Al 7075 alloy (AA7075) exhibits excellent strength yet poses significant challenges for additive manufacturing (AM) due to its complex composition and propensity for defects during rapid solidification. To address these issues, this study introduces a novel AA7075 containing a small amount of Si fabricated by selective laser melting (SLM). Despite concerns about reduced melt-pool stability at low Si content, the alloy was successfully processed into defect-minimized samples. Systematic evaluations of as-built and heat-treated (direct aging, solid-solution, T6) samples revealed distinct microstructural evolution and clear improvements in mechanical properties and corrosion resistance. Specifically, as-built and direct aging conditions showed high strength but limited ductility and pronounced galvanic corrosion due to inhomogeneous microstructures. Conversely, solid-solution and T6 treatments effectively homogenized the microstructure, significantly enhancing ductility and reducing corrosion susceptibility, with the T6-treated samples exhibiting the most balanced mechanical and electrochemical performance. By maintaining a favorable microstructural balance while minimizing Si-induced brittleness, the low-Si AA7075 demonstrates improved SLM processability and robust performance. These findings offer a new pathway for optimizing AM aluminum alloys through tailored heat treatments. Full article

The Al-Ti-C alloy is the most widely used grain refiner for Al-7Si alloys. However, TiC particles in Al-7Si alloys tend to aggregate and settle, thereby reducing their refinement efficiency. In the present paper, a novel Al-3Ti-4.35La master alloy was developed, and its influence on the stability of TiC particles in Al-7Si alloys was investigated by XRD, SEM, and TEM. The results show that when the Al-TiC alloy is added to the Al-7Si alloy, TiC will accumulate and settle obviously after holding the alloy for a certain time (15 min, 30 min, and 60 min). When the Al-TiC alloy and the Al-3Ti-4.35La master alloy are added to the Al-7Si alloy, the aggregation and settlement of TiC are weakened under the same holding time. Additionally, the refinement effect of TiC is enhanced. The Ti and La elements dissolved by Ti₂Al₂₀La in the Al-3Ti-4.35La master alloy are absorbed on the surface of the TiC particles, which improves the wettability between the TiC particles and the aluminum melt, reduces the agglomeration and sedimentation of TiC particles in the aluminum melt, and improves its stability. Full article

The present study developed a novel approach for transforming red mud (RM) into soft magnetic materials (SMMs) for applications in advanced electrical devices in the form of Fe-Si and Fe-Si-Al alloys. A total of ten blends were prepared based on two RMs, three iron oxide additives (Fe₂O₃, black and red mill scales), alumina and carbonaceous reductants in a range of proportions. Carbothermic reduction of the blends was carried out in a vertical Tamman resistance furnace at 1600–1650 °C for 30 min in an argon atmosphere; synthetic graphite was used as a reductant. Reaction products were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF) and X-ray diffraction (XRD). Significant amounts of Fe-rich metallic droplets/regions of different grain sizes (0.5 to 500 μm) were produced in these studies. The formation of Fe-Si alloys with Si contents from 3.9 to 6.7 wt.% was achieved in 8 out of 10 blends; the optimal levels of Si for SMMs ranged from 3.2 to 6.5 wt.%. There was clear evidence for the formation of Fe-Si-Al (up to 1.8 wt.% Al) alloys in 4 out of 10 blends. In addition to lowering operating challenges associated with RM processing, blending of RMs with iron oxide additives and alumina presents a novel recycling approach for converting RMs into valuable SMMs for possible emerging applications in renewable energy, storage, electrical vehicles and other fields. Along with reducing RM stockpiles across the globe, this approach is expected to improve resource efficiency, mitigating environmental impacts while generating economic benefits. Full article

The present research focuses on enhancing the mechanical properties and the electrical conductivity of alloys corresponding to the Al-Mg-Zn (two different compositions) and Al-Mg-Si systems, compared with the commercial 6201-T8 and 1350-H16 alloys, by using a novel approach based on T8 tempering (solution heat treated, cold worked, then artificially aged). After T8 tempering, the Al-Mg-Zn and Al-Mg-Si alloy systems show a better combination of electrical and mechanical properties, with an enhancement of the electrical conductivity by about 2.8% compared to that of 1350 alloy and 13% higher than for the 6201 alloy series. All studied alloys exhibit better mechanical properties than 1350-H16 and are similar to those of 6201-T8. Full article