Journal of Alloys and Metallurgical Systems最新文献

The current experimental work uses die casting, a liquid processing method, to create functionally graded material (FGM). To reduce the production of undesired intermetallic compounds, the FGM samples were created both with and without interfacing foil during the procedure. Mechanical properties including impact strength and microhardness were examined throughout the manufactured sample's cross-section. In addition, the interfacial bonding of FGM samples with and without an interacting foil was determined by estimating the shear strength. Analysis of the samples using X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveals the existence of compounds in the sample as well as the diffusion of Al and Zn particles from one side to the other. Compared to the FGM without foil, it is observed that the diffusion rate at the interface is regulated when the foil is present. In addition, it was found that, in contrast to pb foil, the inclusion of Ag foil limited the rate at which particles could move from one side to the other. Additionally, machining investigations are carried out at varying depths on both sides of the sample in the direction of the interface with the assistance of electric discharge machining.

This study aims to predict the various phases present in high entropy alloys (HEAs) and consequently classify their crystal structure employing multiple machine learning (ML) algorithms utilizing five thermodynamic, electronic and configurational parameters which are considered to be essential for the formation of HEA phases. The properties of a high entropy alloy can eventually be traced through accurate phase and crystal structure prediction, which is essential for selecting the ideal elements for designs. Twelve distinct ML algorithms were executed to predict the phases of HEAs, adopting an experimental database of 322 different HEAs, involving 33 amorphous (AM), 31 intermetallics (IM), and 258 solid solutions (SS) phases. Among the twelve ML models, Cat Boost Classifier displayed the optimum accuracy of 98.06 % for phase predictions. Further, crystal structure classification of the SS phase (body-centered cubic- BCC, face-centered cubic- FCC, and mixed body-centered and face-centered cubic- BCC+FCC) has endeavoured for better microstructure evolution using a different database containing of 194 additional HEAs data with 61 FCC, 76 BCC, and 57 BCC+FCC crystal structures and in comparison to the other models tested, the Gradient Boosting Classifier evolved with the highest accuracy of 86.90 %. An ensemble classifier was also introduced to improve the performance of the ML models, resulting in an accuracy increase to 98.70 % and 86.95 % for phase and crystal structure predictions, respectively. Additionally, the influence of parameters on model accuracy was determined independently.

To achieve a superior-quality weld, it is imperative to employ the appropriate welding parameters. In this study, the Taguchi-based technique for order of preference by similarity to ideal solution (TOPSIS) method has been used to improve the welding parameters such as current, voltage, and travel speed for metal inert gas (MIG) welding on the AA6063 aluminum alloy. Experiments have been performed to assess the hardness and strength characteristics of the joints. The assignment of the specimen was determined by the TOPSIS algorithm, which considers the specimen's performance score. The analysis of variance (ANOVA) approach was performed to identify the parameter with the highest significance level. A mathematical model has been established using a regression equation to establish a relationship between performance scores' signal-to-noise (S/N) ratio and process parameters. The optimal parameters for the butt joint welded using the MIG technique were determined to be a current of 120 A, a voltage of 20 V, and a travel speed of 3 cm/min. The ANOVA findings reveal that the current factor exhibits the highest level of statistical significance, accounting for 63 % of the observed variation. This was followed by voltage and travel speed, which contributed 24 % and 10.3 %, respectively. To ensure the validity of the findings, a confirmatory experiment was conducted using parameters optimized for analysis. The results of the confirmation indicate a strong alignment with the approach that was implemented.

The hot deformation behavior of Al-Zn/martensitic stainless steel particles-based composite (Al-Zn/6 %SSp), was examined in this study. The composite was tested using isothermal compression at 200–350 °C/0.01–10 s⁻¹ and a global strain of 0.5. From the results, it was noticed that the composite’s flow stress increased with strain rate increase and drop in temperature. The constitutive equation from the hot-worked composites resulted in an estimated activation energy of 226.27 kJ/mol, which was 58 % more than that for the self-diffusion of aluminum alloy (142 kJ/mol). These findings suggest dynamic recrystallization (DRX) as the dominant deformation mechanism, as confirmed from the microstructures of the hot worked samples mostly at high temperatures and strain rates. Work hardening was predicted to dominate the deformation process by the stress exponent (n) value of 10.36 (which exceeded 5), but this was inconsistent with the microstructural observations. Comparing the linear fitting of calculated flow stress data with the estimated flow stress yielded a correlation coefficient (R²) of approximately 0.97. This observation demonstrates an effective relationship involving the calculated stress with the computed stress value for the composite material that was fabricated. Based on the processing map analysis, the instability regime occurs at 200270 °C/0.01–10 s⁻¹. The stable domain established was at 280–340^◦C/0.01–10 s⁻¹ which is most suitable for achieving the best microstructural conditions for enhanced service performance.

The microstructure and grain refinement of Al-4.5Er-1Zr-1.5Ti master alloy were analyzed by the refinement experiment, OM, SEM and XRD. The results show that the grain size of pure aluminum is reduced from 14,000μm to 202μm by Al-4.5Er-1Zr-1.5Ti master alloy, which is mainly due to the nucleation promoted by Ti₂Al₂₀Er, Al₃Er and Al₃Ti. Plastic deformation further improves the refining effect of the material by improving the primary phase size, and the Al-4.5Er-1Zr-1.5Ti −2ARB can refine the pure aluminum from 202 mμm to 150μm, and the refinement was increased by 25.7 %. The master alloy showed a better refinement effect in Al-5Cu alloy than pure aluminum, with a grain size of 92μm and a refinement improvement of 97.8 %.

The challenge of making sponge iron, or direct reduced iron (DRI), is hard to overstate. These are a key feed for metallurgical operations while iron extraction sets these limits, which include scarcity of metallurgical coke, poor environmental impact, and high production cost. Thus, the non-contact direct reduction process of DRIs has the potential to significantly reduce carbon deposition and CO₂ emission from the ironmaking process. This work produced sponge iron from commercially acquired hematite ore using an alternative reducing agent (i.e. charcoal) under specified isothermal conditions. Comparative analysis of reaction kinetics models including Ginstein−Brounshtein and Shrinking core models was also performed to ascertain the resistances that control the reaction rate for reduction degree up to 98.1%. The reduction kinetics were found to be described by reaction control time and activation energies based on a shrinking core model as the reduction time lasted for 120 min at temperatures 843–1273 K. At temperatures above 973–1073 K, the rate-limiting step was found to be solely an interfacial chemical reaction process, with an apparent activation energy of 196.1 kJ/mol. In addition, a slowing trend was observed for iron ore sample sizes 10–20 mm as a result of ash layer infiltration around the inner-core structure of the DRI metal matrix. The DRI morphological characteristics were performed using Scanning Electron Microscopy (SEM) and Electron Dispersive Spectrometry (EDS) to ascertain the mineralogical and morphological properties of the DRI samples. The XRF analysis confirms that the raw iron ore sample is hematite. Its iron content is 70.04% metallic iron (TFe) which has 83.59% Fe₂O₃ The SEM/EDS image also revealed the presence of micropores on the DRI morphology. This indicates that the reduction ratio and swelling extent rise with the temperature and time. This happens for all DRI sizes. However, the EDS result confirms the presence of gangue elements within the DRI metal matrix and mineralogical structure. The DRI contains very high silicon content up to 33.90%. So, a fluxing experiment is needed using limestone (CaCO₃) or quicklime (CaO) quicklime to remove gangue (silicate, aluminate) from the DRI matrix. At the set reduction temperatures, the largest metallization degree of 93.05% at 1273 K for a reduction time of 120 min was achieved. This showed that the overall reduction process still follows the expected chronological order since the NDR process uses CO gas from preheated charcoal. This makes DRI be produced from raw hematite under non-contact reduction bases. Therefore, the NDR technique offers a viable option for sponge iron production in modern-day iron and steelmaking processes.

Herein, we report the fabrication of graphene nanoplatelets (GNPs) reinforced zinc-copper (ZnCu) matrix composite coatings on a stainless-steel substrate using electro-co-deposition technique. The influence of varying concentrations of GNPs in the acidic electrolyte bath on the microstructure, chemical composition, phase structure, hardness, wear resistance, corrosion resistance, and antibacterial activity of ZnCu/GNPs composite coating was investigated. The microhardness of the ZnCu/GNPs composite coating with a GNPs concentration of 100 mg/L is compared with pure ZnCu coating, which has a 90 % significant enhancement, while (50 mg/L) has 86 %, and (25 mg/L) has 50 %. Also, ZnCu/GNPs composite coating showed a wear loss of 10 mg for 100 mg/L GNPs sample with an increase in microhardness. The bacterial resistance assays were conducted against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results reveal a notable improvement in the anti-bacterial activity of the ZnCu/GNPs composite coating. The corrosion rate of the ZnCu/GNPs composite coating in 3.5 wt % NaCl solution steadily decreased when the concentration of GNPs in the electrolyte bath was increased to 100 mg/L. These findings hold great potential for various applications, including healthcare settings where preventing healthcare-associated infections is critical, public infrastructure to prolong the lifespan of structures, and marine coatings to protect against corrosion in harsh marine environments.

In this paper the microstructural features of the glass former Fe₆₈Cr₈Mo₄Nb₄B₁₆ coatings are unveiled and related to their electrochemical and tribological responses. The coating was mostly glassy with some embedded borides (M₃B₂, M₂B-tetragonal; M being the metallic elements of the alloy) and ferrite. The tribological behavior of the HVAF coated sample, characterized by a thickness of about 200 µm, ∼6% porosity and a Vickers hardness of 357 HV_0.5, was assessed in a sphere-on-plate configuration, revealing a specific wear rate of approximately 5 ×10⁻⁴ mm³∙N⁻¹m⁻¹. The wear mechanism was dominated by delamination caused by fragile intersplats. The corrosion resistance of HVAF coatings was evaluated in 0.6 M NaCl solution and compared with the results obtained for the crystalline Fe₆₈Cr₈Mo₄Nb₄B₁₆ ingot, produced by melting in an induction furnace, and for the AISI 1020 steel substrate. The HVAF coating showed satisfactory corrosion resistance compared to the carbon steel substrate and the crystalline ingot, with the highest corrosion potential, E_corr, values (−533 mV_SCE) and the lowest corrosion current density, i_corr, (10⁻⁶ A∙cm⁻²) followed by a clear passivation window upon anodic polarization in 0.6 M NaCl solution. Evaluations of HVAF coating showed a higher glassy content compared to the gas-atomized feedstock powders. This suggests that during spraying, certain particles were molten and experienced cooling rates adequate to inhibit crystallization, resulting in the freezing of the supercooled liquid. This phenomenon contributes to the good corrosion resistance observed in the present work and offers an opportunity to enhance the electrochemical behavior of HVAF coatings.

This study aims to observe the residual stress in a substrate and predict stress behavior during the laser deposition process (DED) using finite element analysis (FEA). The residual stress observed on the substrate surface indicated that stress variation during the deposition process increases with proximity to the deposition area, resulting in higher residual stress levels. Additionally, tensile residual stress tends to increase with the height of the deposition area. While variations in the deposition area size influenced the residual stress, consistent stress levels were observed at the same measurement points across different area sizes. The deposition process was simulated using FEA, which confirmed that stress behavior is influenced by melting and solidification cycles. The residual stress levels after cooling aligned well with those observed in actual experiments. Therefore, this study suggests that stress variations can be effectively predicted by simulating the deposition process prior to conducting actual experiments.

The increasing demand and complexities within the manufacturing sector to fabricate composite materials, particularly bimetallic products for the manufacturing industry, have led to the introduction of various joining processes. Notably, explosive welding which is a solid-state welding process has emerged as a highly advantageous technique for the fabrication of composite materials for lighter weight and durable vehicle components. This review aims to provide a comprehensive study of the explosive welding process. The complexities of the explosive welding methodology are explained, incorporating a comprehensive examination of the influence of experimental parameters on the mechanical and microstructural characteristics of the resultant welded composite materials. Additionally, the review consolidates current research pertaining to underwater explosive welding of bimetallic materials and the joining of different configurations using explosive welding. The challenges encountered during the welding process are discussed and solutions proposed by various researchers are presented.