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Metals, Volume 11, Issue 8 (August 2021) – 183 articles

Cover Story (view full-size image): A 3D-printable RS-333 Al–Mg–Si alloy has been successfully used by RUSAL for SLM fabrication of thermoregulatory casing for a gamma-ray detector mounted on a Yarilo satellite (Skoltech). SEM EBSD characterization, in-SEM mechanical testing, and nanoindentation reveal strong interrelation of grain microstructure–mechanical properties and elastic moduli anisotropy in the theoretically isotropic aluminum alloy. Fundamentally different grain patterns were formed along the growth (bouquets of columnar crystallites) and laser scanning directions (fine equiaxed grains). Optimal mechanical performance of lightweight structures is achievable by controlling the grain microstructure formation during a single SLM printing process. View this paper.
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Article
Entropy-Driven Grain Boundary Segregation: Prediction of the Phenomenon
Metals 2021, 11(8), 1331; https://doi.org/10.3390/met11081331 - 23 Aug 2021
Cited by 1 | Viewed by 741
Abstract
The question is formulated as to whether entropy-driven grain boundary segregation can exist. Such a phenomenon would be based on the assumption that a solute can segregate at the grain boundary sites that exhibit positive segregation energy (enthalpy) if the product of segregation [...] Read more.
The question is formulated as to whether entropy-driven grain boundary segregation can exist. Such a phenomenon would be based on the assumption that a solute can segregate at the grain boundary sites that exhibit positive segregation energy (enthalpy) if the product of segregation entropy and temperature is larger than this energy (enthalpy). The possibility of entropy-driven grain boundary segregation is discussed for several model examples in iron-based systems, which can serve as indirect evidence of the phenomenon. It is shown that entropy-driven grain boundary segregation would be a further step beyond the recently proposed entropy-dominated grain boundary segregation as it represents solute segregation at “anti-segregation” sites. Full article
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Article
Lead Electrodeposition from Triethylenetetramine Solution Containing Inhibitors
Metals 2021, 11(8), 1330; https://doi.org/10.3390/met11081330 - 23 Aug 2021
Cited by 1 | Viewed by 602
Abstract
Lead can be efficiently electrodeposited from a number of common leaching agents such as mineral acids, carboxylic acids, and bases (hydroxides and ammonia). This paper reports the possibility to deposit lead from a triethylenetetramine solution, which is also a powerful extracting agent for [...] Read more.
Lead can be efficiently electrodeposited from a number of common leaching agents such as mineral acids, carboxylic acids, and bases (hydroxides and ammonia). This paper reports the possibility to deposit lead from a triethylenetetramine solution, which is also a powerful extracting agent for lead sulfate. The high affinity of triethylenetetramine towards lead sulfate molecules makes it a promising candidate for lead recovery from various solid materials, including industrial secondary resources, sewages, and wastes. A popular methodology that can be found in the literature to recover metal from amine is based on purging a solution with carbon dioxide, resulting in lead carbonate precipitation. Here, the direct electrodeposition of lead from an amine solution was reported. The effects of the main process parameters, i.e., current density, temperature, and presence of additives, were examined to enhance the product quality. Bone glue, ethylene glycol, and polyvinylpyrolidone were used as perspective inhibitors of dendritic lead formation. It was shown that the addition of ethylene glycol can significantly reduce their formation as well as discoloration resulting from amine, producing lead metal with a 99.9% purity. Full article
(This article belongs to the Section Extractive Metallurgy)
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Article
Reductions of Intergranular Corrosion Resistance and Wear Resistance in a Ni-Cr-Mo-Based Superalloy by Aging-Treatment-Induced Precipitation
Metals 2021, 11(8), 1329; https://doi.org/10.3390/met11081329 - 23 Aug 2021
Viewed by 802
Abstract
Ni-Cr-Mo-based superalloy is widely used as a key component in many critical environments. To ensure that the manufacturing process does not impact the long-term service performance of these components, the aging precipitation behavior at different temperatures and its effect on intergranular corrosion (IGC) [...] Read more.
Ni-Cr-Mo-based superalloy is widely used as a key component in many critical environments. To ensure that the manufacturing process does not impact the long-term service performance of these components, the aging precipitation behavior at different temperatures and its effect on intergranular corrosion (IGC) resistance and wear resistance of a Ni-Cr-Mo-based C276 superalloy were investigated. The equilibrium phase diagram was calculated first using thermodynamic software to confirm the potential phases. Carbides of M6C were found to be formed at grain boundaries after aging at 800–850 °C for short-term treatment. The other two phases (μ phase and P phase) indicated in the phase diagram were not observed for the samples after aging treatment up to 15 h. Furthermore, double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were conducted to examine the IGC resistance. The degree of sensitization increased with the aging time and severe corrosion was found to occur at grain boundaries. For the first time, the influence of aging treatment on the wear behavior of this superalloy has been specifically studied. Concerning the hot processing of Ni-Cr-Mo-based C276 superalloy, these results indicate the importance of avoiding high-temperature heat treatment for long periods. Full article
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Article
Evaluation of Copper Leaching for Subsequent Recovery from the Waste Dumps of the Linares Mining District and Their Use for Construction Materials
Metals 2021, 11(8), 1328; https://doi.org/10.3390/met11081328 - 23 Aug 2021
Cited by 2 | Viewed by 594
Abstract
The development of the population’s well-being involves the use of different raw materials. However, metallic elements such as copper are currently scarce due to their intensive use in different sectors. Therefore, new sources of raw materials that provide these elements, are of lower [...] Read more.
The development of the population’s well-being involves the use of different raw materials. However, metallic elements such as copper are currently scarce due to their intensive use in different sectors. Therefore, new sources of raw materials that provide these elements, are of lower cost, and use waste for their extraction must be sought. For this reason, in this research, different waste dumps of the mining district of Linares (Spain) are studied to evaluate the existence of recoverable copper by hydrometallurgical techniques. The material from the waste dump selected as potentially viable is leached with different sulfuric acid solutions (0.25, 0.5, 1, and 2 mol) and at different times, obtaining copper concentrations usable for subsequent hydrometallurgical processes. In addition, in order to develop an environmental hydrometallurgy, the leach waste is characterized, and bituminous mixtures are made with it. The results of the present investigation showed that it was possible to recover 80% of the copper in the waste dumps of the Linares mining district with 1 and 2 mol solutions of sulfuric acid. At the same time, the waste from the leaching process was found to be suitable for use as an aggregate in bituminous mixtures. Therefore, bituminous mixtures were conformed, and it was obtained that the optimum percentage of bituminous emulsion was 6.95% for the proposed granulometry. This emulsion percentage, which corresponds to a residual bitumen percentage of 4.17%, showed particle loss test results of 14% and 18% after immersion. In addition, the stability test values for the Marshall test with the above-mentioned bitumen emulsion percentage and leaching waste showed a stability of 8.99 KN. This fact demonstrates the quality of the bituminous mixture made with the leaching waste for use in bituminous mixtures. Consequently, it can be affirmed that in the present investigation, a significant percentage of copper has been extracted from the waste dumps of the mining district of Linares (Spain) and that the waste after processing can be used in bituminous mixtures, there being a closed cycle of materials in which no waste is produced. Full article
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Article
Research on the Dynamic Compressive Deformation Behavior of 3D-Printed Ti6Al4V
Metals 2021, 11(8), 1327; https://doi.org/10.3390/met11081327 - 23 Aug 2021
Viewed by 520
Abstract
In this paper, the plastic flow and fracture behavior of 3D-printed Ti6Al4V (TC-4) alloy under different temperatures (289–1073 K) and strain rates (0.1–4100 s−1) were studied by using the MTS comprehensive experimental machine (MTS) and split Hopkinson pressure bar (SHPB) equipment. [...] Read more.
In this paper, the plastic flow and fracture behavior of 3D-printed Ti6Al4V (TC-4) alloy under different temperatures (289–1073 K) and strain rates (0.1–4100 s−1) were studied by using the MTS comprehensive experimental machine (MTS) and split Hopkinson pressure bar (SHPB) equipment. The patterns of the influence of temperature and strain rate on the plastic flow behavior of 3D-printed materials in different printing directions were analyzed and compared with those of the traditional TC-4. Based on the experimental data, the modified Johnson–Cook (J-C) constitutive model of 3D-printed TC-4 alloy was established, and the plastic deformation behavior of the material driven by detonation was studied by X-ray photography. The research results showed that under static loading conditions, the strength of the material (AM-P-TC-4) along the printing direction was much higher than the strength of the material perpendicular to the printing direction (AM-T-TC-4). However, there was no difference in material strength for different directions under dynamic loading. Second, under the same deformation conditions, the strength of the 3D-printed TC-4 alloy was considerably higher than that of the traditional TC-4 alloy, but adiabatic shear fracture could be more easily induced under dynamic compressive deformation conditions for the 3D-printed TC-4 alloy, and its fracture strain was substantially less than that of TC-4 alloys. The modified J-C constitutive model established in this paper could better describe the plastic flow behavior of the AM-P-TC-4 alloy under high temperature and high-strain rate deformation conditions. Full article
(This article belongs to the Topic Additive Manufacturing)
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Article
Deposition of Nickel-Based Superalloy Claddings on Low Alloy Structural Steel by Direct Laser Deposition
Metals 2021, 11(8), 1326; https://doi.org/10.3390/met11081326 - 22 Aug 2021
Cited by 6 | Viewed by 901
Abstract
In this study, direct laser deposition (DLD) of nickel-based superalloy powders (Inconel 625) on structural steel (42CrMo4) was analysed. Cladding layers were produced by varying the main processing conditions: laser power, scanning speed, feed rate, and preheating. The processing window was established based [...] Read more.
In this study, direct laser deposition (DLD) of nickel-based superalloy powders (Inconel 625) on structural steel (42CrMo4) was analysed. Cladding layers were produced by varying the main processing conditions: laser power, scanning speed, feed rate, and preheating. The processing window was established based on conditions that assured deposited layers without significant structural defects and a dilution between 15 and 30%. Scanning electron microscopy, energy dispersive spectroscopy, and electron backscatter diffraction were performed for microstructural characterisation. The Vickers hardness test was used to analyse the mechanical response of the optimised cladding layers. The results highlight the influence of preheating on the microstructure and mechanical responses, particularly in the heat-affected zone. Substrate preheating to 300 °C has a strong effect on the cladding/substrate interface region, affecting the microstructure and the hardness distribution. Preheating also reduced the formation of the deleterious Laves phase in the cladding and altered the martensite microstructure in the heat-affected zone, with a substantial decrease in hardness. Full article
(This article belongs to the Special Issue Additive Manufacturing Research and Applications)
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Article
Investigation of the Solid-Phase Joint of VT-14 Titanium Alloy with 12KH18N10T Stainless Steel Obtained by Diffusion Welding through Intermediate Layers
Metals 2021, 11(8), 1325; https://doi.org/10.3390/met11081325 - 22 Aug 2021
Viewed by 631
Abstract
This paper describes the technological process of manufacturing bimetallic billets, which are capable of operating at high pressures, high temperatures, and in corrosive environments, from VT-14 titanium alloy and 12KH18N10T stainless steel. To obtain a joint with a strength of at least 350 [...] Read more.
This paper describes the technological process of manufacturing bimetallic billets, which are capable of operating at high pressures, high temperatures, and in corrosive environments, from VT-14 titanium alloy and 12KH18N10T stainless steel. To obtain a joint with a strength of at least 350 MPa, the diffusion welding method was used, which makes it possible to obtain equal-strength joints using dissimilar materials. The connection of VT-14 titanium alloy with 12KH18N10T stainless steel after obtaining bimetallic billets with the desired properties was investigated. We studied the welded VT-14 and 12KH18N10T joint obtained by diffusion welding through intermediate spacers of niobium Nb (NbStrip-1) and copper Cu (M1). On the basis of our investigations, the optimum welding modes are as follows: welding temperature: 1137 K; welding pressure: 18 MPa; welding time: 1200 s. Mechanical tests, tightness tests, and metallographic, factographic, and micro-X-ray structural studies were carried out, the results of which indicate the effectiveness of the proposed approach. Full article
(This article belongs to the Section Metal Casting, Forming and Heat Treatment)
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Article
Investigation of Dissimilar Resistance Spot Welding Process of AISI 304 and AISI 1060 Steels with TLBO-ANFIS and Sensitivity Analysis
Metals 2021, 11(8), 1324; https://doi.org/10.3390/met11081324 - 21 Aug 2021
Cited by 2 | Viewed by 627
Abstract
In this work, the process of dissimilar resistance spot welding (RSW) for AISI 304 and AISI 1060 steel sheets is experimentally investigated. The effects of the main process parameters such as welding current, electrode force, welding cycle, and cooling cycle on the tensile-shear [...] Read more.
In this work, the process of dissimilar resistance spot welding (RSW) for AISI 304 and AISI 1060 steel sheets is experimentally investigated. The effects of the main process parameters such as welding current, electrode force, welding cycle, and cooling cycle on the tensile-shear strength (TSS) of dissimilar RSW joints are studied. To this aim, using a central composite experimental design based on response surface methodology (RSM), the experimental tests were performed. Furthermore, from the test results, an adaptive neuro-fuzzy inference system (ANFIS) was developed to model and estimate the TSS. The optimal parameters of the ANFIS system were obtained using a teaching-learning-based optimization (TLBO) algorithm. In order to model the process behavior, the results of experiments were used for the training (70% of the data) and testing (30% of the data) of the adaptive inference system. The accuracy of the obtained model was investigated via different plots and statistical criteria including root mean square error, correlation coefficient, and mean absolute percentage error. The findings show that the ANFIS network successfully predicts the TSS. In addition, the network error in estimating the TSS in the training and test section is equal to 0.08% and 5.87%, respectively. After modeling with TLBO-ANFIS, the effect of each input parameter on TSS of the dissimilar joints is quantitatively measured using the Sobol sensitivity analysis method. The results show that increasing in welding current and welding cycle leads to an increase in the TSS of joints. It is concluded that TSS decreases with increases in the electrode force and cooling cycle. Full article
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Article
Numerical Simulation and Experimental Investigation on 2205 Duplex Stainless Steel K-TIG Welded Joint
Metals 2021, 11(8), 1323; https://doi.org/10.3390/met11081323 - 21 Aug 2021
Cited by 1 | Viewed by 573
Abstract
In this paper, 8 mm thickness 2205 duplex stainless steel (DSS) plates were successfully welded using keyhole tungsten inert gas welding (K-TIG) welding, and numerical simulations were performed applying the finite element method. Three models of combined heat source were adopted to verify [...] Read more.
In this paper, 8 mm thickness 2205 duplex stainless steel (DSS) plates were successfully welded using keyhole tungsten inert gas welding (K-TIG) welding, and numerical simulations were performed applying the finite element method. Three models of combined heat source were adopted to verify accuracy of experiment. The welding process under different welding speeds were simulated, and the temperature field, molten pool shape, and thermal cycle curve were calculated. The welding simulation results show that a combined model consisting of the ellipsoid heat source and the conical heat source is more suitable for K-TIG welding. The results of the microstructure analysis of the welded joint showed that when the welding speed was increased from 280 mm/min to 340 mm/min, the austenite content and the ferrite and austenite grain size decreased. The evolution laws of welded joint morphologies, microstructure and grain sizes under different welding speed conditions were consistent with the analysis results of simulated molten pool morphologies, temperature field distributions and thermal cycle curves. It is proved that this kind of simulation method can effectively simulate the K-TIG welding process and ensure the welding quality, which is a guide for industrial applications. Full article
(This article belongs to the Section Metal Casting, Forming and Heat Treatment)
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Article
A First-Principles Study on Na and O Adsorption Behaviors on Mo (110) Surface
Metals 2021, 11(8), 1322; https://doi.org/10.3390/met11081322 - 20 Aug 2021
Cited by 1 | Viewed by 663
Abstract
Molybdenum-rhenium alloys are usually used as the wall materials for high-temperature heat pipes using liquid sodium as heat-transfer medium. The corrosion of Mo in liquid Na is a key challenge for heat pipes. In addition, oxygen impurity also plays an important role in [...] Read more.
Molybdenum-rhenium alloys are usually used as the wall materials for high-temperature heat pipes using liquid sodium as heat-transfer medium. The corrosion of Mo in liquid Na is a key challenge for heat pipes. In addition, oxygen impurity also plays an important role in affecting the alloy resistance to Na liquid. In this article, the adsorption and diffusion behaviors of Na atom on Mo (110) surface are theoretically studied using first-principles approach, and the effects of alloy Re and impurity O atoms are investigated. The result shows that the Re alloy atom can strengthen the attractive interactions between Na/O and the Mo substrate, and the existence of Na or O atom on the Mo surface can slower down the Na diffusion by increasing diffusion barrier. The surface vacancy formation energy is also calculated. For the Mo (110) surface, the Na/O co-adsorption can lead to a low vacancy formation energy of 0.47 eV, which indicates the dissolution of Mo is a potential corrosion mechanism in the liquid Na environment with O impurities. It is worth noting that Re substitution atom can protect the Mo surface by increasing the vacancy formation energy to 1.06 eV. Full article
(This article belongs to the Special Issue Numerical Modeling of Materials under Extreme Conditions)
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Article
Effect of Pre-Strain on Microstructure and Tensile Properties of Ti-6Al-4V at Elevated Temperature
Metals 2021, 11(8), 1321; https://doi.org/10.3390/met11081321 - 20 Aug 2021
Cited by 2 | Viewed by 765
Abstract
Research on pre-deformation influences on material properties in multistep hot forming is of important scientific interest. In this paper, hot tensile tests at 850 °C and a strain rate of 0.001 s−1 were performed to study the microstructural evolution and mechanical properties [...] Read more.
Research on pre-deformation influences on material properties in multistep hot forming is of important scientific interest. In this paper, hot tensile tests at 850 °C and a strain rate of 0.001 s−1 were performed to study the microstructural evolution and mechanical properties of Ti-6Al-4V with pre-strains at 0.05, 0.1 and 0.15. The tensile test results showed that the specimen with 0.05 pre-strain exhibited higher flow stress and larger elongation. Additionally, increasing the pre-strain resulted in a decrease in ultimate tensile strength (UTS) and elongation (EL). The EBSD results showed that the main deformation mechanism of Ti-6Al-4V was high-angle grain boundary sliding. Pre-strain promoted dynamic recrystallization (DRX) by increasing the deformation substructure. The refinement of grains and the eradication of dislocations enhanced the deformability, resulting in an increase in flow stress. Full article
(This article belongs to the Special Issue Titanium Alloys and Titanium-Based Matrix Composites)
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Article
Recovery of Pure Pd(II) from Spent Electroplating Solutions by Solvent Extraction with Ionic Liquids from Sulfuric Acid Leaching Solution of Cemented Pd
Metals 2021, 11(8), 1320; https://doi.org/10.3390/met11081320 - 20 Aug 2021
Cited by 1 | Viewed by 597
Abstract
Palladium (Pd) electroplating is widely practiced in the manufacture of advanced electronic devices. The Pd(II) present in spent electroplating solutions is treated by cementation with zinc (Zn) metal powder. In order to recover pure Pd from the cemented Pd, a process that consisted [...] Read more.
Palladium (Pd) electroplating is widely practiced in the manufacture of advanced electronic devices. The Pd(II) present in spent electroplating solutions is treated by cementation with zinc (Zn) metal powder. In order to recover pure Pd from the cemented Pd, a process that consisted of leaching followed by solvent extraction was investigated. For this purpose, solvent extraction experiments using synthesized ionic liquids (ILs) with organic and inorganic anions were performed to find separation conditions at which selective extraction of Pd(II) over Zn(II) from synthetic H2SO4 leaching solutions is possible. The concentration of sulfuric acid was varied from 0.5 to 9 M. The complete separation of Pd(II) over Zn(II) by ILs such as ALi–CY301 (N-methyl-N,N,N-trioctylammonium bis(2,4,4-trimethylpentyl) dithiophosphinic), ALi–SCN (N-methyl-N,N,N-trioctylammonium thiocyanate), ALi–I (N-methyl-N,N,N-trioctylammonium iodide) and ALi–Br (N-methyl-N,N,N-trioctylammonium bromide) depends on H2SO4 concentration, while ALi–LIX63 (N-methyl-N,N,N-trioctylammonium 5,8-diethyl-7-hydroxydodecane-6-oxime) and ALi–LIX84 (N-methyl-N,N,N-trioctylammonium 2-hydroxy-5-nonylacetophenone oxime) can completely separate Pd(II) irrespective of H2SO4 concentration. Additionally, the mixture of HCl and thiourea, aqua regia solution, NH3 solution and the mixture of NH4Cl and NH3 are powerful stripping agents for Pd(II) from the loaded ALi–LIX63/ALi–LIX84, ALi–CY301, ALi–Br/ALi–I and ALi–SCN, respectively. However, application of the separation conditions to the real 5 M sulfuric acid leaching solutions of cemented Pd indicated that it was difficult to separate the two ions by extraction with ALi–LIX63 and ALi–LIX84. Use of NaClO as an oxidizing agent during the sulfuric acid leaching of real cemented Pd resulted in an enhancement of Zn(II) extraction by ALi–LIX63 and ALi–LIX84. Therefore, removal of chloride ions from the sulfuric acid leaching solutions is necessary to apply the separation conditions obtained from synthetic sulfuric acid leaching solutions. Full article
(This article belongs to the Section Extractive Metallurgy)
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Article
Numerical Analysis of the Partial Penetration High Power Laser Beam Welding of Thick Sheets at High Process Speeds
Metals 2021, 11(8), 1319; https://doi.org/10.3390/met11081319 - 20 Aug 2021
Cited by 1 | Viewed by 690
Abstract
The present work is devoted to the numerical analysis of the high-power laser beam welding of thick sheets at different welding speeds. A three-dimensional transient multi-physics numerical model is developed, allowing for the prediction of the keyhole geometry and the final penetration depth. [...] Read more.
The present work is devoted to the numerical analysis of the high-power laser beam welding of thick sheets at different welding speeds. A three-dimensional transient multi-physics numerical model is developed, allowing for the prediction of the keyhole geometry and the final penetration depth. Two ray tracing algorithms are implemented and compared, namely a standard ray tracing approach and an approach using a virtual mesh refinement for a more accurate calculation of the reflection point. Both algorithms are found to provide sufficient accuracy for the prediction of the keyhole depth during laser beam welding with process speeds of up to 1.5mmin−1. However, with the standard algorithm, the penetration depth is underestimated by the model for a process speed of 2.5mmin−1 due to a trapping effect of the laser energy in the top region. In contrast, the virtually refined ray tracing approach results in high accuracy results for process speeds of both 1.5mmin−1 and 2.5mmin−1. A detailed study on the trapping effect is provided, accompanied by a benchmark including a predefined keyhole geometry with typical characteristics for the high-power laser beam welding of thick plates at high process speed, such as deep keyhole, inclined front keyhole wall, and a hump. Full article
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Article
Two-Stage Model for Fatigue Life Assessment of High Frequency Mechanical Impact (HFMI) Treated Welded Steel Details
Metals 2021, 11(8), 1318; https://doi.org/10.3390/met11081318 - 20 Aug 2021
Viewed by 951
Abstract
Welded steel details are critical components from the aspect of fatigue. Additional fatigue resistance can be achieved by the High-Frequency Mechanical Impact (HFMI) treatment. This treatment increases the crack initiation period by improving the weld geometry, introducing compressive residual stresses, and increasing the [...] Read more.
Welded steel details are critical components from the aspect of fatigue. Additional fatigue resistance can be achieved by the High-Frequency Mechanical Impact (HFMI) treatment. This treatment increases the crack initiation period by improving the weld geometry, introducing compressive residual stresses, and increasing the weld toe’s hardness. The study presented in this paper is based on the development and calibration of an Initiation–Propagation-based Two-Stage Model (TSM), which is, by the combination of different methods, suitable to separately consider crack initiation and crack propagation. It is shown that a TSM is able to predict the fatigue life of as-welded and HFMI-treated welded steel details, which is proven by comparing the calculated results with the results of tests on similar details given in the literature. A parametric study of the TSM is conducted for different steel grades in order to investigate the influence of steel strength and HFMI parameters on fatigue lives of a welded steel detail with longitudinal attachment. Full article
(This article belongs to the Special Issue Fatigue Failure Assessment of Metallic Materials)
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Article
The Effect of Immersion Corrosion Time on Electrochemical Corrosion Behavior and the Corrosion Mechanism of EH47 Ship Steel in Seawater
Metals 2021, 11(8), 1317; https://doi.org/10.3390/met11081317 - 20 Aug 2021
Cited by 1 | Viewed by 683
Abstract
In this paper, electrochemical corrosion tests and full immersion corrosion experiments were conducted in seawater at room temperature to investigate the electrochemical corrosion behavior and the corrosion mechanism of high-strength EH47. The polarization curve, EIS (electrochemical impedance spectroscopy), SEM (scanning electron microscope), and [...] Read more.
In this paper, electrochemical corrosion tests and full immersion corrosion experiments were conducted in seawater at room temperature to investigate the electrochemical corrosion behavior and the corrosion mechanism of high-strength EH47. The polarization curve, EIS (electrochemical impedance spectroscopy), SEM (scanning electron microscope), and EDS analyses were employed to analyze the results of the electrochemical corrosion process. The electrochemical corrosion experiments showed that the open circuit potential of EH47 decreases and then increases with an increase in total immersion time, with the minimum value obtained at 28 days. With an increase in immersion time, the corrosion current density (Icorr) of EH47 steel first decreases and then increases, with the minimum at about 28 days. This 28-day sample also showed the maximum capacitance arc radius, the maximum impedance and the minimum corrosion rate. In the seawater immersion test in the laboratory, the corrosion mechanism of EH47 steel in the initial stage of corrosion is mainly pitting corrosion, accompanied by a small amount of crevice corrosion with increased corrosion time. The corrosion products of EH47 steel after immersion in seawater for 30 days are mainly composed of FeOOH, Fe3O4 and Fe2O3. Full article
(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials)
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Article
A Crystal Plasticity Simulation on Strain-Induced Martensitic Transformation in Crystalline TRIP Steel by Coupling with Cellular Automata
Metals 2021, 11(8), 1316; https://doi.org/10.3390/met11081316 - 20 Aug 2021
Cited by 2 | Viewed by 774
Abstract
In transformation-induced plasticity (TRIP) steel, the strain-induced martensitic transformation (SIMT) has a close relationship with the shear band formation. At a small length scale such as that of a crystal, the explicit analysis of the shear band structure with the formed microstructure is [...] Read more.
In transformation-induced plasticity (TRIP) steel, the strain-induced martensitic transformation (SIMT) has a close relationship with the shear band formation. At a small length scale such as that of a crystal, the explicit analysis of the shear band structure with the formed microstructure is quite important for an adequate understanding of the SIMT. Here, a study on the microstructures formed by SIMT, related to shear band formation in both single and polycrystal TRIP steels, is presented. The constitutive equation for single crystal TRIP steel considering the transformation strain on each variant system is derived based on a rate-dependent crystal plasticity theory. To express the martensitic transformation, the cellular automata approach, including a transformation criterion acting as a local rule, is introduced. Numerical simulation is conducted with patterning processes of the martensitic phase at an infinite medium under the plane strain tension. It is found that the similar distributions of the plastic strain and the martensitic phase are dependent on the initial crystal orientation and appear as the shear band structures. In addition, the sizes of embryo and cell strongly influence the shear band formation and the martensitic volume fraction of crystal TRIP steel. Full article
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Article
Effects of Zr Content on the Microstructure and Performance of TiMoNbZrx High-Entropy Alloys
Metals 2021, 11(8), 1315; https://doi.org/10.3390/met11081315 - 19 Aug 2021
Cited by 2 | Viewed by 721
Abstract
TiMoNbZrx refractory high-entropy alloys were prepared by vacuum arc melting, and the influence of the Zr alloying element and its content on the phases, microstructure, mechanical properties, and wear resistance of TiMoNbZrx alloys was explored. It was found that the alloys [...] Read more.
TiMoNbZrx refractory high-entropy alloys were prepared by vacuum arc melting, and the influence of the Zr alloying element and its content on the phases, microstructure, mechanical properties, and wear resistance of TiMoNbZrx alloys was explored. It was found that the alloys after Zr addition were composed of a single BCC phase. Upon increasing the Zr content, the grain size of the as-cast alloy decreased first and then increased, and TiMoNbZr0.5 exhibited the smallest grain size. Adding an appropriate amount of Zr increased the strength and hardness of the alloys. TiMoNbZr0.5 exhibited the best wear resistance, with a friction coefficient of about 0.33. It also displayed the widest wear scar, the shallowest depth, and the greatest degree of wear on the grinding ball because of the formation of an oxide film during wear. Full article
(This article belongs to the Special Issue Advanced Refractory Alloys)
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Article
Application of Artificial Neural Network to the Prediction of Tensile Properties in High-Strength Low-Carbon Bainitic Steels
Metals 2021, 11(8), 1314; https://doi.org/10.3390/met11081314 - 19 Aug 2021
Cited by 2 | Viewed by 603
Abstract
An artificial neural network (ANN) model was designed to predict the tensile properties in high-strength, low-carbon bainitic steels with a focus on the fraction of constituents such as PF (polygonal ferrite), AF (acicular ferrite), GB (granular bainite), and BF (bainitic ferrite). The input [...] Read more.
An artificial neural network (ANN) model was designed to predict the tensile properties in high-strength, low-carbon bainitic steels with a focus on the fraction of constituents such as PF (polygonal ferrite), AF (acicular ferrite), GB (granular bainite), and BF (bainitic ferrite). The input parameters of the model were the fraction of constituents, while the output parameters of the model were composed of the yield strength, yield-to-tensile ratio, and uniform elongation. The ANN model to predict the tensile properties exhibited a higher accuracy than the multi linear regression (MLR) model. According to the average index of the relative importance for the input parameters, the yield strength, yield-to-tensile ratio, and uniform elongation could be effectively improved by increasing the fraction of AF, bainitic microstructures (AF, GB, and BF), and PF, respectively, in terms of the work hardening and dislocation slip behavior depending on their microstructural characteristics such as grain size and dislocation density. The ANN model is expected to provide a clearer understanding of the complex relationships between constituent fraction and tensile properties in high-strength, low-carbon bainitic steels. Full article
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Review
E-Waste Recycling and Resource Recovery: A Review on Technologies, Barriers and Enablers with a Focus on Oceania
Metals 2021, 11(8), 1313; https://doi.org/10.3390/met11081313 - 19 Aug 2021
Cited by 10 | Viewed by 2051
Abstract
Electronic e-waste (e-waste) is a growing problem worldwide. In 2019, total global production reached 53.6 million tons, and is estimated to increase to 74.7 million tons by 2030. This rapid increase is largely fuelled by higher consumption rates of electrical and electronic goods, [...] Read more.
Electronic e-waste (e-waste) is a growing problem worldwide. In 2019, total global production reached 53.6 million tons, and is estimated to increase to 74.7 million tons by 2030. This rapid increase is largely fuelled by higher consumption rates of electrical and electronic goods, shorter life cycles and fewer repair options. E-waste is classed as a hazardous substance, and if not collected and recycled properly, can have adverse environmental impacts. The recoverable material in e-waste represents significant economic value, with the total value of e-waste generated in 2019 estimated to be US $57 billion. Despite the inherent value of this waste, only 17.4% of e-waste was recycled globally in 2019, which highlights the need to establish proper recycling processes at a regional level. This review provides an overview of global e-waste production and current technologies for recycling e-waste and recovery of valuable material such as glass, plastic and metals. The paper also discusses the barriers and enablers influencing e-waste recycling with a specific focus on Oceania. Full article
(This article belongs to the Special Issue Processing and Characterization of Metal Containing Wastes)
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Correction
Correction: Torres et al. Leaching Chalcopyrite with High MnO2 and Chloride Concentrations. Metals 2020, 10, 107
Metals 2021, 11(8), 1312; https://doi.org/10.3390/met11081312 - 19 Aug 2021
Viewed by 422
Abstract
The authors wish to make the following corrections to this paper [...] Full article
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Article
Ground Structures-Based Topology Optimization of a Morphing Wing Using a Metaheuristic Algorithm
Metals 2021, 11(8), 1311; https://doi.org/10.3390/met11081311 - 19 Aug 2021
Cited by 2 | Viewed by 973
Abstract
This paper presents multi-objective topology and sizing optimization of a morphing wing structure. The purpose of this paper is to design a new aircraft wing structure with a tapered shape for ribs, spars, and skins including a torsion beam for external actuating torques, [...] Read more.
This paper presents multi-objective topology and sizing optimization of a morphing wing structure. The purpose of this paper is to design a new aircraft wing structure with a tapered shape for ribs, spars, and skins including a torsion beam for external actuating torques, which is anticipated to modify the aeroelastic characteristic of the aircraft wing using multi-objective optimization. Two multi-objective topology optimization problems are proposed employing ground element structures with high- and low-grid resolutions. The design problem is to minimize mass, maximize difference of lift effectiveness, and maximize the buckling factor of an aircraft wing subject to aeroelastic and structural constraints including lift effectiveness, critical speed, and buckling factors. The design variables include aircraft wing structure dimensions and thickness distribution. The proposed optimization problems are solved by an efficient multi-objective metaheuristic algorithm while the results are compared and discussed. The Pareto optimal fronts obtained for all tests were compared based on a hypervolume metric. The objective function values for Case I and Case II at 10 selected optimal solutions exhibit a range of structural mass as 115.3216–411.6250 kg, 125.0137–440.5869 kg, lift effectiveness as 1.0514–1.1451, 1.0834–1.1639 and bucking factor as 38.895–1133.1864 Hz, 158.1264–1844.4355 Hz, respectively. The best results reveal unconventional aircraft wing structures that can be manufactured using additive manufacturing. This research is expected to serve as a foundation for future research into multi-objective topology optimization of morphing wing structures based on the ground element framework. Full article
(This article belongs to the Special Issue Computational Advanced Metallic Materials Processing)
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Article
Effect of Hot Band on Texture Evolution and Plastic Anisotropy in Aluminium Alloys
Metals 2021, 11(8), 1310; https://doi.org/10.3390/met11081310 - 19 Aug 2021
Cited by 1 | Viewed by 638
Abstract
This contribution presents the evolution of crystallographic texture during thermomechanical processing of Al alloys. It is shown that the nature of crystallographic changes involved in deformation and recrystallization is strongly affected by the variety of initial (pre-rolling) state of a given metallic system. [...] Read more.
This contribution presents the evolution of crystallographic texture during thermomechanical processing of Al alloys. It is shown that the nature of crystallographic changes involved in deformation and recrystallization is strongly affected by the variety of initial (pre-rolling) state of a given metallic system. Four hot rolled Al strips of identical chemical composition and different textures were subjected to further thermomechanical processing with equal technological characteristics. Although the pre-rolling textures were first destroyed by the deformation, while annealing accounted for further qualitative and quantitative crystallographic changes in the investigated polycrystalline systems, it seems that there is still a great influence of the hot band texture on the texture dependent properties. Various qualitative and quantitative texture characteristics of annealed sheets ensured diverse Lanford value curves, which is a direct consequence of the crystallographic features developed in the hot bands. The Cube-dominated hot band ensured a strong V-shaped profile after cold rolling and subsequent recrystallization, whereas it was shown that a weak pre-rolling texture is more advantageous in terms of both normal and planar anisotropy. Full article
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Article
Radiation Effects in Amorphous Metallic Alloys as Revealed by Mössbauer Spectrometry: Part II. Ion Irradiation
Metals 2021, 11(8), 1309; https://doi.org/10.3390/met11081309 - 18 Aug 2021
Viewed by 527
Abstract
Due to their excellent magnetic properties, amorphous metallic alloys (AMAs) are considered for the construction of magnetic cores of radio-frequency cavities in accelerators. Here, they might be exposed to ion bombardment. The influence of irradiation by both light and heavy ions featuring low [...] Read more.
Due to their excellent magnetic properties, amorphous metallic alloys (AMAs) are considered for the construction of magnetic cores of radio-frequency cavities in accelerators. Here, they might be exposed to ion bombardment. The influence of irradiation by both light and heavy ions featuring low and high energies, respectively, is followed by the techniques of 57Fe Mössbauer spectrometry. Modifications of surface layers in selected Fe-containing AMAs after ion irradiation are unveiled by detection of conversion electrons and photons of characteristic radiation whereas those in their bulk are derived from standard transmission spectra. Rearrangement of microstructure which favors the formation of magnetically active regions, is observed in surface regions bombarded by light ions. Heavy ions caused pronounced effects in the orientation of net magnetization of the irradiated samples. No measurable impact upon short-range order arrangement was observed. Part I of this paper is devoted to radiation effects in Fe-based AMAs induced by neutron irradiation. Full article
(This article belongs to the Special Issue Radiation Effects in Steels and Alloys)
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Article
A Study on Determining Weld Joint Hardening and a Quality Evaluation Algorithm for 9% Nickel Weld Joints Using the Dilution Ratio of the Base Material in Fiber Laser Welding
Metals 2021, 11(8), 1308; https://doi.org/10.3390/met11081308 - 18 Aug 2021
Cited by 1 | Viewed by 613
Abstract
The demand for LNG-powered ships and related equipment is rapidly increasing among major domestic and foreign carriers due to the strengthened IMO regulations on the sulfur content of ship fuel oil. LNG operation in a cryogenic environment requires a storage tank and fuel [...] Read more.
The demand for LNG-powered ships and related equipment is rapidly increasing among major domestic and foreign carriers due to the strengthened IMO regulations on the sulfur content of ship fuel oil. LNG operation in a cryogenic environment requires a storage tank and fuel supply system that uses steel with excellent brittleness and fatigue strength. A ship using LNG is very sensitive to explosion and fire. For this reason, 9% Ni is often used, because ships require high quality products with special materials and structural technologies that ensure operability at cryogenic temperatures. However, research to derive uniform welding quality is urgent because the deterioration of weld quality in the 9% Ni steel welding process is caused by high process difficulty and differences in welding quality depending on a welder’s skill set. This study proposes a method to guarantee a uniform quality of 9% Ni steel in a fiber laser welding process by categorizing weld joint hardness according to the dilution ratio of a base material and establishing a standard for quantitative evaluation. Full article
(This article belongs to the Special Issue Welding Metallurgy)
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Article
The Effect of Multilayer Architecture and Ta Alloying on the Mechanical Performance of Ti-Al-N Coatings under Scratching and Uniaxial Tension
Metals 2021, 11(8), 1307; https://doi.org/10.3390/met11081307 - 18 Aug 2021
Viewed by 445
Abstract
The present work is focused on a comparative study of the effect of Ti-Al interlayers and Ta alloying on the mechanical behavior of Ti1−xAlxN coatings under normal contact pressure and in-plane straining. The contact loading of the samples was [...] Read more.
The present work is focused on a comparative study of the effect of Ti-Al interlayers and Ta alloying on the mechanical behavior of Ti1−xAlxN coatings under normal contact pressure and in-plane straining. The contact loading of the samples was carried out by scratch testing, while the in-plane tensile straining was performed by uniaxial tension of the coated steel substrates. The Ti0.45Al0.55N and Ti0.43Al0.45Ta0.12N monolithic coatings as well as the Ti0.45Al0.55N/Ti0.45Al0.55 multilayer coatings with different number and thickness of the layers were deposited by DC magnetron sputtering. It was found that the introduction of the ductile Ti0.45Al0.55 layers into the Ti0.45Al0.55N coating and alloying with Ta led to their significant toughening. The improved toughness of the Ti0.43Al0.45Ta0.12N coating coupled with high residual compressive stress and high hardness resulted in its strongest resistance to cracking under scratching and tensile straining among the coatings studied. The multilayer coating with the thickest metal layers exhibited the improved resistance to delamination under in-plane straining. Full article
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Article
Effect of V Addition on Microstructure and Mechanical Properties in C–Mn–Si Steels after Quenching and Partitioning Processes
Metals 2021, 11(8), 1306; https://doi.org/10.3390/met11081306 - 18 Aug 2021
Viewed by 528
Abstract
Three C-Si-Mn Q&P steels with different V addition after one-step and two-step quenching and partitioning (Q&P) processes were investigated by means of optical microstructure observation, X-ray diffraction (XRD) measurement, transmission electron microscopy (TEM) characterization and particle size distribution (PSD) analysis. The effect of [...] Read more.
Three C-Si-Mn Q&P steels with different V addition after one-step and two-step quenching and partitioning (Q&P) processes were investigated by means of optical microstructure observation, X-ray diffraction (XRD) measurement, transmission electron microscopy (TEM) characterization and particle size distribution (PSD) analysis. The effect of V addition on strength and ductility of the steels was elucidated by comparative analysis on the microstructure and mechanical properties as functions of partitioning time and temperature. For one-step Q&P treatment, the mechanical properties were mainly controlled by the tempering behavior of martensite during partitioning. V addition was helpful to mitigate the deterioration of mechanical properties by precipitation strengthening and grain refinement strengthening. For two-step Q&P treatment, the satisfying plasticity was attributed to the transformation-induced plasticity (TRIP) effect of retained austenite maintaining the high work hardening rate at high strain regime. The higher volume fraction of retained austenite with high stability resulted from the refined microstructure and the promoted carbon partitioning for the steel with 0.16 wt% V addition. However, the carbon consumption due to the formation of VC carbides led to the strength reduction of tempered martensite. Full article
(This article belongs to the Special Issue Strengthening Mechanisms of Metals and Alloys)
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Article
High-Strain Deformation and Spallation Strength of 09CrNi2MoCu Steel Obtained by Direct Laser Deposition
Metals 2021, 11(8), 1305; https://doi.org/10.3390/met11081305 - 18 Aug 2021
Cited by 6 | Viewed by 689
Abstract
In this work, the critical fracture stresses during spalling of high-strength steel 09CrNi2MoCu samples obtained by direct laser deposition (DLD) were measured under shock compression of up to ~5.5 GPa. The microstructure and mechanical properties of DLD steel samples in the initial state [...] Read more.
In this work, the critical fracture stresses during spalling of high-strength steel 09CrNi2MoCu samples obtained by direct laser deposition (DLD) were measured under shock compression of up to ~5.5 GPa. The microstructure and mechanical properties of DLD steel samples in the initial state and after heat treatment were studied and compared to traditional hot rolled one. The microstructural features of steel before and after heat treatment were revealed. The heat treatment modes of the deposit specimens on their strength properties under both static and dynamic loads have been investigated. The spall strength of the deposited specimens is somewhat lower than the strength of steel specimens after hot rolling regardless of their heat treatment. The minimum elastic limit of elasticity is exhibited by the deposit specimens. After heat treatment of the deposit samples, the elastic limit increases and approximately doubles. Subsequent heat treatment in the form of hardening and tempering allows obtaining strength properties under Hugoniot loads in traditional hot-rolled products. Full article
(This article belongs to the Special Issue Laser Processing of Metals and Alloys)
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Article
Effect of Solidification Rates at Sand Casting on the Mechanical Joinability of a Cast Aluminium Alloy
Metals 2021, 11(8), 1304; https://doi.org/10.3390/met11081304 - 17 Aug 2021
Cited by 4 | Viewed by 985
Abstract
Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials. As weight reduction is desired, these cast components are usually made from high-strength aluminium alloys of the [...] Read more.
Implementing the concept of mixed construction in modern automotive engineering requires the joining of sheet metal or extruded profiles with cast components made from different materials. As weight reduction is desired, these cast components are usually made from high-strength aluminium alloys of the Al-Si (Mn, Mg) system, which have limited weldability. The mechanical joinability of the cast components depends on their ductility, which is influenced by the microstructure. High-strength cast aluminium alloys have relatively low ductility, which leads to cracking of the joints. This limits the range of applications for cast aluminium alloys. In this study, an aluminium alloy of the Al-Si system AlSi9 is used to investigate relationships between solidification conditions during the sand casting process, microstructure, mechanical properties, and joinability. The demonstrator is a stepped plate with a minimum thickness of 2.0 mm and a maximum thickness of 4.0 mm, whereas the thickness difference between neighbour steps amounts to 0.5 mm. During casting trials, the solidification rates for different plate steps were measured. The microscopic investigations reveal a correlation between solidification rates and microstructure parameters such as secondary dendrite arm spacing. Furthermore, mechanical properties and the mechanical joinability are investigated. Full article
(This article belongs to the Special Issue Casting and Rolling of Alloys)
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Review
Analysis of Hydrogen Embrittlement on Aluminum Alloys for Vehicle-Mounted Hydrogen Storage Tanks: A Review
Metals 2021, 11(8), 1303; https://doi.org/10.3390/met11081303 - 17 Aug 2021
Cited by 1 | Viewed by 1204
Abstract
High-pressure hydrogen tanks which are composed of an aluminum alloy liner and a carbon fiber wound layer are currently the most popular means to store hydrogen on vehicles. Nevertheless, the aluminum alloy is easily affected by high-pressure hydrogen, which leads to the appearance [...] Read more.
High-pressure hydrogen tanks which are composed of an aluminum alloy liner and a carbon fiber wound layer are currently the most popular means to store hydrogen on vehicles. Nevertheless, the aluminum alloy is easily affected by high-pressure hydrogen, which leads to the appearance of hydrogen embrittlement (HE). Serious HE of hydrogen tank represents a huge dangers to the safety of vehicles and passengers. It is critical and timely to outline the mainstream approach and point out potential avenues for further investigation of HE. An analysis, including the mechanism (including hydrogen-enhanced local plasticity model, hydrogen-enhanced decohesion mechanism and hydrogen pressure theory), the detection (including slow strain rate test, linearly increasing stress test and so on) and methods for the prevention of HE on aluminum alloys of hydrogen vehicles (such as coating) are systematically presented in this work. Moreover, the entire experimental detection procedures for HE are expounded. Ultimately, the prevention measures are discussed in detail. It is believed that further prevention measures will rely on the integration of multiple prevention methods. Successfully solving this problem is of great significance to reduce the risk of failure of hydrogen storage tanks and improve the reliability of aluminum alloys for engineering applications in various industries including automotive and aerospace. Full article
(This article belongs to the Special Issue Forming of Aluminium Alloys)
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Review
Review of Recent Research on AlCoCrFeNi High-Entropy Alloy
Metals 2021, 11(8), 1302; https://doi.org/10.3390/met11081302 - 17 Aug 2021
Cited by 9 | Viewed by 1952
Abstract
High-entropy alloys (HEAs) have gained significant interest in recent years because of their outstanding properties. The AlCoCrFeNi alloy is one of the most studied HEAs. The effect of the manufacturing methods and heat treatment on the properties of the high-entropy AlCoCrFeNi alloy is [...] Read more.
High-entropy alloys (HEAs) have gained significant interest in recent years because of their outstanding properties. The AlCoCrFeNi alloy is one of the most studied HEAs. The effect of the manufacturing methods and heat treatment on the properties of the high-entropy AlCoCrFeNi alloy is under intense scrutiny. The effect of varying component content on properties of the alloy is frequently analysed. Aluminium is most popular due to its impact on alloy microstructure and occurrence of phases. Research is also conducted on the influence of alloying additives, such as boron and titanium, on the properties of the AlCoCrFeNi alloy. High-entropy alloys also have excellent mechanical properties at high temperatures. Excellent structural and functional properties make them suitable for application in the most demanding conditions. The research conducted on HEAs still provides a lot of new and valuable information on the properties and structures of these alloys. This article summarizes the most important information about HEAs, specifically the AlCoCrFeNi alloy. Full article
(This article belongs to the Special Issue Design of High-Entropy Alloys)
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