Journal of Mining and Metallurgy, Section B: Metallurgy

Aluminium thermal reduction process for preparing ferrosilicon and alumina from fly ash

2026-07-02T12:59:33+02:00

There has been a focus on environmental protection and the recycling of solid waste resources, particularly fly ash and aluminum dross. Efforts to utilize fly ash efficiently have increased. In this paper, a process is introduced for producing alumina-rich slag and ferrosilicon alloy through aluminothermic reduction of fly ash with aluminium dross. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirm the formation of spherical ferrosilicon alloy encased in a loose, porous alumina matrix during the aluminothermic reduction process. Thermodynamic calculations indicated that the reduction temperature of SiO2 and mullite decreases in the presence of Fe2O3. Under conditions of 1673 K, a specific aluminium dross to fly ash ratio (A/F), and a reduction time of 20 minutes, the magnetic fraction contains 85.89% ferrosilicon, while the non-magnetic fraction has an alumina content of 79.42%. This process offers a solution with potential environmental and economic benefits for the application of fly ash and aluminum ash.

Influence of holding time during rapid tempering after rapid austenitization on the microstructure and mechanical properties of low carbon steel

2026-07-02T12:59:33+02:00

The rising demand for high-quality steel in construction, automotive, and other industrial sectors presents significant challenges, particularly regarding energy consumption and CO₂ emissions from large-scale production. This study explores the use of rapid tempering as a heat treatment strategy to enhance the mechanical properties of low carbon steel while potentially reducing the environmental footprint of steel manufacturing. Rapid tempering was performed following rapid austenitization at 1000 °C for 90 seconds using a 7-kW induction furnace, followed by quenching in ice water. Soaking times of 5, 15, and 20 seconds were applied during tempering, and results were compared with conventional heat treatment. The rapid tempering process resulted in a microstructure consisting of tempered martensite, with only slight morphological changes in the martensitic phase compared to conventional tempering, and the formation of markedly finer cementite precipitates. Mechanical testing demonstrated superior performance in rapid tempering, with the 5-second condition achieving the highest hardness (422.667 HV), tensile strength (1308.9 MPa), and yield strength (1270 MPa), while the 20-second condition yielded the highest toughness (139.336 J/cm²) and elongation (33.833%). Based on the balance among tensile strength, hardness, and toughness, the RA-RT 5- second specimen exhibited the most optimal mechanical performance.

Effects of scanning speed on mechanical, wear property, and corrosion behavior of CP-Ti fabricated by the selective laser melting technique

2026-07-02T12:59:33+02:00

In this study, CP-Ti was prepared using the selective laser melting (SLM) technique to systematically investigate the effect of scanning speed on microstructure, mechanical properties, wear properties, and corrosion behavior. The optimum relative density of 99.87±0.12% was achieved at a scanning speed of 800 mm/s, with corresponding tensile strength, yield strength, elongation, and hardness values of 543±17 MPa, 453±7 MPa, 14±1%, and 294±4 HV, respectively. Additionally, SLM-processed CP-Ti with optimum relative density exhibited the lowest wear rate (2.72×10^-7 mm²/N) and excellent corrosion resistance. These results indicate that CP-Ti with high relative density, strength, and hardness, low wear rate, and excellent corrosion resistance can be fabricated by controlling the scanning speed, making it well-suited for biomedical implant applications.

Optimization of smelting process of magnesium based on machine learning

2026-07-02T12:59:33+02:00

The traditional magnesium reduction process consumes a significant amount of energy, which contradicts China’s green and low-carbon development goals. Therefore, exploring more energy-efficient methods is crucial for environmental protection. The magnesium reduction rate is influenced by several factors, including gas flow rate, briquetting pressure, ferrosilicon content, reduction temperature, and reduction time. In this study, data analysis utilizing a machine learning algorithm: support vector machine (SVM)—was employed to predict the magnesium reduction rate. Given that energy-saving processes are a primary objective for enterprises, the processing was optimized using the particle swarm optimization (PSO) algorithm based on the SVM model, while maintaining a constant magnesium reduction rate. This optimization aims to reduce energy and gas consumption during the magnesium smelting process. Experimental verification of the magnesium reduction rate under the optimized processing conditions demonstrated that the application of machine learning algorithms can lead to resource savings in the magnesium reduction process. To further evaluate the environmental benefits of the optimized process, a Life Cycle Assessment (LCA) focusing on energy consumption and carbon dioxide (CO2) emissions was conducted. The LCA results indicate that the optimized process significantly reduces life cycle energy consumption (reduced by 5.33%) and CO2 emissions (reduced by 3.63%) compared with the initial process, providing precise environmental performance data for the promotion and application of magnesium alloys in lightweight structures.

A comparative study of mechanical behaviour of heat-treated 3D printed In-718 and ASTM F75 alloys across multiple length scales

2026-07-02T12:59:33+02:00

The hardness and strength of many alloys often differ when measured at the nano, micro, and macroscopic scales. Therefore, it is essential to study the mechanical behavior of important alloys across a wide range of length scales. In this work, we present a scenario in which two industrially significant alloys, In-718 and ASTM F75, exhibit different behaviors at the micro and macroscopic levels. Both alloys are promising candidates for similar applications in the aerospace and petroleum industries. The alloys were first 3D printed using selective laser melting (SLM) and then heat-treated in a vacuum. The average yield strength and percentage elongation (along the build direction) of the In-718 alloy were 29% and 19% higher, respectively, than those observed for the ASTM F75 alloy. The difference between the ultimate tensile strength (UTS) and Vickers hardness (at a load of 98 N) was almost negligible, i.e., less than 5%. In contrast to the Vickers hardness values of 3.9 GPa and 3.8 GPa, the average nanohardness of the In-718 and ASTM F75 alloys was 5.7 GPa and 7.6 GPa, respectively, which was substantially higher than their Vickers hardness. Furthermore, the ASTM F75 alloy demonstrated much better wear resistance in ScanningWear tests performed using a nanoindenter. The explanation for these differences and the similarities between macro- and nanomechanical behavior are presented in this work.

Structure, mechanical properties, and corrosion resistance of low-nickel nitrogen-alloyed austenite stainless steel

2026-07-02T12:59:33+02:00

This study investigates the structure, mechanical properties, and corrosion resistance of low-nickel nitrogen-alloyed austenitic stainless steels (Cr17Mn9Ni3N, 05Cr18Mn10Ni3N) as cost-effective alternatives to conventional AISI 304L and AISI 321 grades. The alloys were produced by vacuum induction melting with nitrogen introduced via nitrided ferrochrome. Microstructural analysis confirmed fully austenitic structures with finer grain sizes (ASTM No. 4.5–6.0) compared to conventional steels (ASTM No. 3.5–4.0). Mechanical testing revealed superior yield strength (~414 MPa) and tensile strength (~730–748 MPa) in nitrogen-alloyed steels, attributed to solid-solution strengthening by nitrogen. However, the impact toughness at cryogenic temperatures (-196°C) was reduced, and brittle facets were found on the fracture surface. Potentiodynamic polarization tests showed that AISI 304L steel exhibited a higher pitting potential. The pitting potentials of Cr17Mn9Ni3N and 05Cr18Mn10Ni3N steels were lower than that of AISI 304L but higher than that of AISI 321 steel. Economic analysis highlighted significant cost savings potential through nickel substitution with nitrogen. The results validate nitrogen-alloyed steels as viable alternatives for applications requiring high strength and corrosion resistance, though cryogenic applications require careful nickel content optimization.

Phase and roughness analysis of nanocrystalline coatings based on 310S steel with aluminum additions

2026-07-02T12:59:33+02:00

Aluminum alloying is commonly used to improve high-temperature oxidation resistance. In this study, Al was incorporated into nanocrystalline coatings produced by magnetron sputtering of 310S chromium–nickel steel. The effect of this addition on the phase composition and morphology of the coatings, which influence the formation of protective oxide layers under high-temperature conditions, was investigated. The coatings were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), with emphasis on surface roughness, as well as X-ray diffractometry (XRD) to determine crystallite size and phase composition. The results showed that the addition of aluminum affects phase stability in the coatings. At Al contents of 1–2 at.%, there is a twofold reduction in the fraction of the fcc phase in the coating (and its disappearance at 5 at.%), along with a similar decrease in surface roughness. At the same time, crystallite size increases while the nanocrystalline structure is retained, creating favorable conditions for the formation of dense Al₂O₃ oxide layers on the coatings.

Influence of growth velocity v and temperature gradient G on the interlamellar spacing λ of FeC unidirectionally crystallized eutectic

2026-07-02T12:59:34+02:00

The paper presents the results of investigations concerning the influence of growth velocity (v) and temperature gradient (G) on the interlamellar spacing (λ) in an irregular iron-carbon (Fe-C) eutectic unidirectionally crystallized. The aim of this study was to verify the growth model of D.J. Fisher and W. Kurz and to determine the relationship λ = f(v, G) based on experimental and numerical analysis. The crystallization process was carried out using the Bridgman-Stockbarger method with liquid metal cooling (LMC), and the structure was studied using optical microscopy and scanning electron microscopy. In parallel, numerical simulations were performed in ProCAST to determine the temperature gradient in the liquid at the crystallization front. The results showed that increasing the growth velocity at constant G leads to a decrease in interlamellar spacing λ, while at constant velocity a decrease in G results in an increase in λ. The experimental data obtained showed good agreement with the results of mathematical modelling, confirming the suitability of the W. Kurz and D.J. Fisher model in describing the crystallization of irregular Fe-C eutectic alloys.

Investigating the Al-Cr-La ternary system: Al-rich corner phase equilibria at 600 °C

2026-07-02T12:59:34+02:00

The phase equilibria of the ternary Al-Cr-La system were investigated in the Al-rich corner at 600 °C, with a minimum Al content of 98.77 at.%. The formed phases, transformation temperatures (specifically liquidus and solidus), and microstructure evolution were experimentally determined by isothermal annealing at 600 °C for 600 hours and by Differential Scanning Calorimetry (DSC) analysis. A Scanning Electron Microscope (SEM) equipped with Energy-Dispersive X-ray Spectroscopy (EDXS) was used to fully characterize the samples. The equilibrium microstructure consists of (Al), the binary phase Al45Cr7, and the ternary phase LaCr2Al20 in samples with increased Cr content (from 0.03 up to 1.12 at.%), while it consists of (Al), the mixture (Al) + Al11La3, and the ternary LaCr2Al20 phase in samples with increased La content (from 0.03 up to 0.45 at.%). It was observed that even a small amount of alloying elements leads to the formation of the ternary phase.

Extraction and recovery of zinc, potassium, and sodium from blast furnace dust by ultrasonic-assisted ammonia leaching

2026-07-02T12:59:34+02:00

To efficiently recover valuable elements (Zn, K, Na) from blast furnace dust (BFD) and address issues such as alkali metal enrichment and disrupted furnace operation caused by its direct reuse, ammonia leaching experiments were conducted in this study using an NH3·H2O–NH4HCO3 system combined with ultrasound and ammonium persulfate. Single-factor experiments were performed to investigate the effects of variables such as [NH3]T and solid-to-liquid ratio on the leaching efficiencies of Zn, K, and Na under ultrasonic conditions. Under the conditions of [NH3]T = 6 mol·L−1, a solid-to-liquid ratio of 1:6, [NH3]/[NH4+] = 1:1, 40 °C, and 90 W ultrasound power, the leaching efficiencies of Zn, K, and Na reached 90.73%, 91.45%, and 91.56%, respectively. Based on these results, the effect of ultrasound combined with 1 mol·L−1 ammonium persulfate on zinc leaching was further evaluated, and the Zn leaching efficiency increased to 95.16%, while the leaching efficiencies of K and Na slightly increased to 92.35% and 92.50%, respectively. The enhanced Zn leaching is reasonably attributed to the synergistic effects of ultrasonic intensification and persulfate oxidation, in which ultrasound promotes particle fragmentation and mass transfer, while activated ammonium persulfate generates SO4•⁻ radicals that facilitate the oxidation of refractory ZnS. Kinetic analysis indicated that Zn leaching was mainly controlled by the surface chemical reaction, and ultrasound reduced the apparent activation energy from 62.37 to 44.15 kJ·mol−1. This synergistic leaching process, with high selectivity and low cost, provides theoretical and technical references for BFD resource recovery.