Journal of Mining and Metallurgy, Section B: Metallurgy

Effect of copper addition on the microstructure, mechanical, thermal, and magnetic properties of Fe-Ni-Cu alloys

2025-12-31T10:13:05+01:00

In this study, FeNiCu alloys with two different copper contents were produced by arc melting. The aim was to investigate the effects of Cu content on the microstructural, mechanical, thermal, and Mössbauer properties of the alloys. Microstructures were examined using SEM micrographs. Vickers hardness tests were conducted to evaluate mechanical strength. Thermal behavior was analyzed using DSC. Magnetic characteristics were studied by Mössbauer spectroscopy. SEM analysis showed the presence of martensitic structures in both alloys, with the alloy containing more Cu exhibiting a higher amount of martensite. Hardness increased from 169.1 HV to 190.2 HV as Cu content increased. DSC results confirmed the martensitic transformation. The alloy with higher Cu content showed a higher transformation temperature and greater transformation energy released. Mössbauer spectra indicated the presence of both magnetically ordered and non-ordered phases in both alloys. Hyperfine parameters demonstrated changes in the local atomic environment due to Cu addition. The weak singlet obtained was associated with the FCC phase. The two sextets were attributed to ferromagnetic BCC phases arising from different environments of the Fe atom. The other sextet, with a low internal magnetic field of around 18 T, was ascribed to possible Ni- and/or Cu-rich surroundings of the Fe atom. Overall, increasing Cu in the alloy altered the microstructure, improved hardness, shifted the martensitic transformation temperature, and modified the magnetic hyperfine interactions. These results may aid in designing advanced Fe-based materials for structural and magnetic applications.

Effects of welding parameters on percentage dilution and mechanical properties in welded joints of ultra-high hardness armour steels

2025-12-31T10:13:05+01:00

This study investigates the effects of Gas Metal Arc Welding (GMAW) parameters—specifically welding speed and stick-out—on the dilution and mechanical properties of welded joints composed of ultra-high hardness quenched and tempered (UHH-Q&T) armor steel and austenitic stainless steel filler metal. An optimization methodology was used to set constant parameters, including wire diameter, gas flow rate, welding voltage, and wire feed speed, based on equipment capabilities. Experimental trials varied welding speed and electrode stick-out while maintaining a constant current through inductance control. Although the welding parameters affected the melted base and filler metal areas, the dilution percentage remained unaffected. The correlation between dilution and welding current was validated. Microstructural and mechanical analyses confirmed the consistent behavior of the welded joints under the tested conditions.

The influence of cold, warm and hot deformation on microstructure and mechanical properties of Inconel 718 superalloy

2025-12-31T10:13:06+01:00

This study systematically examines the influence of precipitation on the microstructural and mechanical properties of Inconel 718 superalloy in as-received, solution heat-treated, peak-aged, and overaged conditions. Cold, warm, and hot deformation tests were performed at 25 °C, 400 °C and 800 °C using a constant strain rate of 5.55 × 10⁻⁴ s⁻¹. The results indicated dynamic strain aging during warm deformation at 400 °C in all investigated conditions. However, at temperatures above 400 °C, a pronounced reduction in strength was observed, accompanied by a corresponding increase in elongation for most conditions. Notably, the solution heat-treated samples exhibited anomalous behavior, showing an increase in Rp0.2 after deformation at 800 °C. This suggests the occurrence of dynamic precipitation during hot deformation in the solution heat-treated samples.

Oxidation and property evolution of AISI T5 steel under varying heat treatments

2025-12-31T10:13:06+01:00

This study evaluates the effect of heat treatment on the mechanical, tribological, and oxidation behavior of AISI T5 steel. The chemical composition was first characterized using spectroscopy and SEM. A two-year oxidation test conducted in humid and relatively dry atmospheres showed strong environmental sensitivity: in humid air, the oxidation rate reached 11.27×10^-2 P/P₀ per month with a sharp increase after 25 days, whereas in dry air it remained below1.35×10^-2 P/P₀ per month, following a linear and nearly flat trend indicative of a protective oxide scale.

Heat treatment significantly increased hardness from 34.15 ± 0.59 HRC (untreated) to 62.70 ± 0.66 and 60.80 ± 0.48 HRC for water and oil quenched steels, respectively. Impact strength decreased accordingly, with oil quenching offering the best hardness-toughness balance (60.8 HRC, 2.08 Kcv). Instrumented indentation confirmed substantial surface strengthening, with HIT rising to 17.39 ± 0.29 GPa (Q. Water) and 7.68 ± 0.12 GPa (Q. Oil). Under dry sliding, wear rates were reduced by 81.3% (Q. Water) and 62.5% (Q. Oil), with faster run-in in the water-quenched condition. XRD revealed tempered martensite with Fe₃W₃C/Cr₇C₃ (Q. Water) and Co₃W₃C (Q. Oil), consistent with thermal conditions. This study provides new experimental data on the effects of 15-minute austenitization followed by oil or water quenching on the properties of AISI T5 steel, highlighting its potential for process optimization.

Extraction of vanadium from pet-coke gasification cinder: Part 1 leaching kinetics studies in sulphuric acid medium

2025-12-31T10:13:06+01:00

Petcoke cinder is a solid by-product generated during the gasification of petcoke, accounting for three to five percent of the petroleum coke mass. It commonly contains valuable metals like V, Ni, Al, and Fe, highlighting the resource's potential for vanadium extraction. Thus, it can be regarded as an emerging secondary source of vanadium and other critical metals. The conventional pyro-cum-hydrometallurgical process for vanadium recovery relied on alkali roasting, which was not only energy-intensive but also contributed to greenhouse gas emissions. Considering environmental concerns and high energy consumption, the current study embodies a state-of-the-art development of an economically viable process for extracting V from petcoke gasification cinders. This paper examines the method of sulfuric acid-leaching of vanadium from gasification cinders and the effects of various parameters, including acid concentration, temperature, process duration, percentage of H₂O₂, amount of sodium dodecyl sulfate (SDS), and solid-liquid phase ratios. The maximum vanadium yield of 95.62% was achieved under optimal conditions of sulfuric acid concentration, temperature, time, S/L ratio, and amounts of H₂O₂ and SDS, which were determined to be 4M, 90°C, 3 hours, 20%, and 6%, respectively. The shrinking surface-controlled model was employed to investigate leaching kinetics. The reaction order concerning sulfuric acid concentrations was found to be 1.29. According to the Arrhenius equation, the evaluated apparent activation energy for leaching was approximately 27.67 kJ/mol, and the empirical equation representing the acid leaching kinetics of vanadium is identified as 1-(1-α)^1/3 = kt = (9.261 X 10³) [H₂SO₄]^1.2916exp[-27674/RT] T.

The influence of Cu content on microstructure and mechanical properties of PM-fabricated Ti-18Nb-xCu alloy

2025-12-31T10:13:06+01:00

This research investigated the influence of varying copper (Cu) concentrations (0, 5, 7, and 9 wt.%)on the sintering behaviour, microstructural development, and mechanical characteristics of Ti-18Nb alloy, fabricated through conventional powder metallurgy. Under specific sintering conditions (1150°C for 5 hours), Cu addition led to a more homogeneous microstructure and promoted the complete dissolution of Nb particles. X-ray diffraction (XRD) analysis confirmed the presence of alpha (α) and beta (β) Ti phases, along with the Ti₂Cu phase, with its peak intensity increasing as Cu content rose. Mechanical properties were significantly enhanced by Cu addition. Yield strength increased almost linearly with Cu content. Compressive strength notably increased with 7 wt.% Cu, reaching 980 MPa, and slightly exceeded this value with 9 wt.% Cu. Hardness values increased due to solid solution strengthening in the α-Ti phase and the precipitation of the Ti₂Cu phase, with the highest hardness (222 HV) observed in the 7 wt.% Cu alloy. The elastic modulus initially increased with 5 wt.% Cu, then subsequently decreased with further Cu additions; the Ti-18Nb-7Cu alloy exhibited the lowest elastic modulus at 13.34 GPa. Furthermore, the resilience of the alloys improved with the formation of the Ti₂Cu phase, and a maximum value of 13.15 MJ m⁻³ was achieved.

The influence of nickel grade and its occurrence state on high pressure acid leaching behavior of lateritic nickel ores

2025-12-31T10:13:06+01:00

This research evaluates the effects of nickel grade and occurrence state on the leaching behavior of lateritic nickel ores using high-pressure acid leaching (HPAL) at 250 °C with sulfuric acid. Three ores were selected for the study: Ore 1 (ultra-low-grade limonite, 0.73 wt.% Ni), Ore 2 (limonite, 1.34 wt.% Ni), and Ore 3 (saprolite, 2.00 wt.% Ni). Mineralogical studies (XRD, SEM, and EPMA) were conducted to provide insight into nickel-hosting phases and characteristics of the ore matrix. A higher nickel grade does not necessarily result in higher extraction. Ore 1 had the lowest nickel grade but achieved the highest extraction of Ni (97.25%) and Co (98.49%) under experimental conditions using an acid-to-ore (A/O) ratio of 0.40. This significant Ni extraction is attributed to nickel's structural substitution in goethite, an iron oxide mineral that dissolves readily under the HPAL process. Ore 2 also contains goethite as the dominant phase and achieved similarly high recoveries of Ni (97%) and Co (98%), however, Co recovery decreased slightly under higher acid conditions due to co-precipitation with hematite. Ore 3 had the highest nickel grade but the lowest leaching efficiency (<90% Ni). The generally low recoveries may be attributed to nickel being hosted in both goethite (a leachable phase) and lizardite (a less leachable phase). The silicate matrix of lizardite and its elevated magnesium content restricted the effective acid range and thus diminished nickel selectivity during the HPAL leaching process. The results highlight that the mineralogical occurrence state of nickel is more important than nickel grade in determining leaching performance. Therefore, low-grade limonite ores with favorable mineralogy can serve as potential feed sources for environmentally friendly sustainable nickel hydrometallurgical extraction.

Evolution of microstructure under different homogenization conditions and its effect on recrystallization processes during hot rolling of AA5182 alloy

2025-12-31T10:13:07+01:00

This study investigates microstructure development of AA5182 Al-Mg alloy under various homogenization conditions and how these conditions affect recrystallization processes and texture development during the laboratory hot-rolling. Homogenization treatments were conducted for 16 h at 490°C and at 550°C for various times. Scanning electron microscopy (SEM) characterization including energy-dispersive X-ray spectroscopy (EDX) revealed the presence of Al₃(Fe,Mn) and Al_m(Fe,Mn) phases as Fe/Mn-bearing microconstituents in as-cast state. These transformed into Al₆(Fe,Mn) and α-Al(Fe,Mn)Si during homogenization treatments. The treatments also led to precipitation of Al₆(Mn,Fe) and α-Al(Fe,Mn)Si dispersoid particles. Results of electron backscattered diffraction (EBSD) indicated that a weak deformation texture was present after the hot-rolling. The morphology of grains and degree of restoration were significantly influenced by homogenization conditions. The distribution and density of dispersoids had a strong effect on the mechanisms of recovery and recrystallization.

Dissolution kinetic mechanisms of FeCr₂O₄ spinel in MgO-Al₂O₃-SiO₂ slag system: Elemental dissolution and component diffusion

2025-12-31T10:13:07+01:00

The molten chromite reduction direct alloying process serves as a pivotal metallurgical technology in stainless steel production, offering advantages such as reduced carbon consumption and improved production efficiency. In this study, to reveal the dissolution mechanism of chromite, pure phase of synthetic FeCr₂O₄, the main component of chromite, was used to replace chromite with complex compositions. The dissolution kinetics of FeCr₂O₄ in MgO-Al₂O₃-SiO₂ slag were systematically investigated as functions of stirring intensity, MgO/ SiO₂, and temperature, revealing its non-isothermal reactive dissolution characteristics. Experimental results demonstrated that the solubility of Cr₂O₃ exhibited a trend of initial increase followed by subsequent decrease as the MgO/SiO₂ mass ratio increased. The maximum solubility was observed at a MgO/SiO₂ mass ratio of 0.56. Additionally, temperature-related studies indicated that the dissolution of FeCr₂O₄ is progressively enhanced with increasing temperature under elevated thermal conditions (1500-1600 ℃). Meanwhile, scanning electron microscopy (SEM) analyses confirmed that the interfacial reaction between FeCr₂O₄ and slag components generated MgAl₂O₄, MgCr₂O₄ and MgO-xFeO solid solution, forming a boundary layer on the surface of unreacted FeCr₂O₄.The dissolution reaction on the surface of FeCr₂O₄ was the rate-controlling step in the dissolution process. The calculated activation energy of the dissolution process was 65.43 kJ·mol^-1.

Algorithm to optimize thermodynamic parameters: A review

2025-12-31T10:13:07+01:00

Computational thermodynamics provides essential information for materials design. The CALPHAD (CALculation of PHAse Diagrams) method based on thermodynamic databases can be used for thermodynamic optimization and for calculating phase diagrams and thermodynamic properties in multicomponent systems. This article reviews the algorithms implemented in software for optimizing thermodynamic parameters. These software tools offer strong support for developing accurate thermodynamic databases. Recent advances in software and algorithms for thermodynamic parameter optimization are summarized, and their respective characteristics and potential limitations are analyzed. Finally, the development trends of software and algorithms for thermodynamic parameter optimization are discussed. This review will help interested readers understand the principles of thermodynamic optimization and contribute to the advancement of related algorithms.