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Metals, Volume 11, Issue 5 (May 2021) – 173 articles

Cover Story (view full-size image): The degradation behavior and biocompatibility of molybdenum (Mo) were investigated. After immersion in simulated body fluid for 28 days at 37 °C, the degradation product layers were examined with optical microscopy and REM/EDX analysis. The degradation product layer was non-passivating, uniform, slowly soluble, and it released molybdate ions (MoO42−). A dissolution rate of 10 µm/year was derived from ion concentration measurements. Apoptosis and necrosis assays with human endothelial and smooth muscle cell lines showed that Mo is tolerated at concentrations relevant for implant applications. Mo is also colonizable by those cell lines. Consequently, Mo is a promising biomaterial for resorbable implants due to its favorable mechanical properties, uniform degradation, and good biocompatibility. View this paper.
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Article
Solidification Pattern of Si-Alloyed, Inoculated Ductile Cast Irons, Evaluated by Thermal Analysis
Metals 2021, 11(5), 846; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050846 - 20 May 2021
Viewed by 418
Abstract
The solidification cooling curve itself as well as its first derivative, and related temperatures, reported to the calculated equilibrium temperatures in stable and metastable solidification systems, are used to predict the solidification characteristics of the cast iron. Silicon, as the most representative cast [...] Read more.
The solidification cooling curve itself as well as its first derivative, and related temperatures, reported to the calculated equilibrium temperatures in stable and metastable solidification systems, are used to predict the solidification characteristics of the cast iron. Silicon, as the most representative cast iron element, and inoculation, as graphitizing metallurgical treatment, have a major influence on the transition from the liquid to the solid state. Six experimental programs are performed, with Si content typically for non-alloyed (<3.0% Si), low (3.0–3.5% Si) and medium alloyed (4.5–5.5% Si) ductile cast irons, as Si-content increasing, and inoculation simultaneous effects. Silicon is an important influencing factor, but the base and minor elements also affect the equilibrium eutectic temperatures, much more in the Fe-C-Si-Xi stable system (15–20 °C) than in the metastable system (5–10 °C), comparing with their calculation based only on a Si effect (Fe-C-Si system). The highest positive effect of inoculation is visible in non-Si alloyed cast irons (2.5% Si): 9–15 °C for the eutectic reaction and 3 to 4 times increased at the end of solidification (37–47 °C). Increased Si content decreases inoculation power to 7–9 °C for low alloying grade (up to 3.5% Si), with the lowest contribution at more than 4.5% Si (0.3–2.0 °C). 2.5–3.5% Si ductile cast irons are more sensitive to high solidification undercooling, especially at the end of solidification (but with a higher efficiency of inoculation), compared to 4.5–5.5% Si ductile cast irons, at a lower undercooling level, and at lower inoculation contribution, as well. Full article
(This article belongs to the Special Issue Recent Advances in Cast Irons)
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Article
Radiation Effects in Amorphous Metallic Alloys as Revealed by Mössbauer Spectrometry: Part I. Neutron Irradiation
Metals 2021, 11(5), 845; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050845 - 20 May 2021
Viewed by 387
Abstract
Iron-based amorphous metallic alloys (AMAs) of several compositions were exposed to neutron irradiation with fluences of up to 1019 n/cm2. These materials exhibit excellent magnetic properties which predetermine them for use in electronic devices operated also in radiation-exposed environments. Response [...] Read more.
Iron-based amorphous metallic alloys (AMAs) of several compositions were exposed to neutron irradiation with fluences of up to 1019 n/cm2. These materials exhibit excellent magnetic properties which predetermine them for use in electronic devices operated also in radiation-exposed environments. Response of the studied AMAs to neutron irradiation is followed by Mössbauer spectrometry which probes the local microstructure. Neutron irradiation leads to rearrangement of constituent atoms, their clustering, and formation of stress centers. The observed modifications of topological short-range order result in changes of spectral parameters including average hyperfine magnetic field, B, standard deviation of the distribution of hyperfine fields, and position of the net magnetic moment. After irradiation, especially differences in B-values develop in two opposite directions. This apparent controversy can be explained by formation of specific atomic pairs with different exchange interactions, which depend on the composition of the samples. Part II of this paper will be devoted to radiation effects caused in Fe-based AMAs by ion irradiation. Full article
(This article belongs to the Special Issue Radiation Effects in Steels and Alloys)
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Article
The Improvement of Bonding Strength of W/Cu Joints via Nano-Treatment of the W Surface
Metals 2021, 11(5), 844; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050844 - 20 May 2021
Viewed by 366
Abstract
W/Cu joining is key for the fabrication of plasma-facing compounds of fusion reactors. In this work, W and Cu are joined through three steps: (1) hydrothermal treatment and reduction annealing (i.e., nano-treatment), (2) Cu plating and annealing in a pure H2 atmosphere, [...] Read more.
W/Cu joining is key for the fabrication of plasma-facing compounds of fusion reactors. In this work, W and Cu are joined through three steps: (1) hydrothermal treatment and reduction annealing (i.e., nano-treatment), (2) Cu plating and annealing in a pure H2 atmosphere, and (3) W/Cu bonding at 980 °C for 3 h. After nano-treatment, nanosheets structure can be found on the W substrate surface. The tensile strength of the W/Cu joint prepared via nano-treatment reaches as high as approximately 93 MPa, which increases by about 60% compared with the one without nano-treatment. The microhardness curves exhibited continuous variations along the W/Cu interface. The TEM images show that the W/Cu interface is compact without any cracks or voids. This work may also be applied for enhancing bonding strength in other immiscible materials. Full article
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Article
Strategy for Surface Post-Processing of AISI 316L Additively Manufactured by Powder Bed Fusion Using Ultrasonic Nanocrystal Surface Modification
Metals 2021, 11(5), 843; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050843 - 20 May 2021
Viewed by 398
Abstract
Ultrasonic nanocrystal surface modification (UNSM) technology was applied to the surfaces of specimens additively manufactured by powder bed fusion (PBF). The changes in roughness and hardness due to the UNSM were set as objective functions, and the optimal conditions for the main parameters [...] Read more.
Ultrasonic nanocrystal surface modification (UNSM) technology was applied to the surfaces of specimens additively manufactured by powder bed fusion (PBF). The changes in roughness and hardness due to the UNSM were set as objective functions, and the optimal conditions for the main parameters were derived through the response surface method (RSM) and Box–Behnken design (BBD). Regression analysis-based mathematical models for predicting the surface hardness and roughness are presented and validated. The RSM results show that the surface roughness is highly dependent on the load and ball tip diameter, and the surface roughness significantly improves as the inter-pass interval and ball tip diameter decrease. Through BBD and ANOVA, the optimal conditions for the improvement of surface characteristics were found to be a load of 40 N, inter-pass interval of 10 μm, and ball tip diameter of 2.38 m. The surface treated under these optimal conditions exhibited a hardness of 497 Hv and surface roughness of 1.32 μm, which were significantly improved compared to the values for an untreated specimen. In addition, it was confirmed that the grains are significantly refined after UNSM, and scratch resistance increases for the top layer of the surface directly affected by the UNSM horn. Full article
(This article belongs to the Special Issue Surface Modification of Metallic Materials for Wear and Fatigue)
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Article
Study on Ultra-High Temperature Contact Solution Treatment of Al–Zn–Mg–Cu Alloys
Metals 2021, 11(5), 842; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050842 - 20 May 2021
Viewed by 366
Abstract
Contact solution treatment (CST) of Al–Zn–Mg–Cu alloys can shorten solution time to within 40 s in comparison with 1800 s with traditional solution treatment using a heating furnace. Heating temperature is the key factor in solution treatment. Considering the short heating time of [...] Read more.
Contact solution treatment (CST) of Al–Zn–Mg–Cu alloys can shorten solution time to within 40 s in comparison with 1800 s with traditional solution treatment using a heating furnace. Heating temperature is the key factor in solution treatment. Considering the short heating time of CST, the ultra-high solution temperature over 500 °C of Al–Zn–Mg–Cu alloys was studied in this work. The effects of solution temperatures on the microstructures and the mechanical properties were investigated. The evolution of the second phases was explored and the strengthening mechanisms were also quantitatively evaluated. The results showed that solution time could be reduced to 10 s with the solution temperature of 535 °C due to the increasing dissolution rate of the second phase and the tensile strength of the aged specimen could reach 545 MPa. Precipitation strengthening was the main strengthening mechanism, accounting for 75.4% of the total strength. Over-burning of grain boundaries occurred when the solution temperature increased to 555 °C, leading to the deterioration of the strength. Full article
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Article
Effect of Gas Bubbling Filtration Treatment Conditions on Melt Quality of AlSiMgCu Alloy
Metals 2021, 11(5), 841; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050841 - 20 May 2021
Viewed by 383
Abstract
In this study, the optimal conditions of gas bubbling filtration (GBF) treatment for securing highly-clean molten Al-Si-Mg-Cu alloy were identified. The effects of GBF treatment time and stabilization time on the degree of molten metal cleanliness were examined by measuring melt quality parameters [...] Read more.
In this study, the optimal conditions of gas bubbling filtration (GBF) treatment for securing highly-clean molten Al-Si-Mg-Cu alloy were identified. The effects of GBF treatment time and stabilization time on the degree of molten metal cleanliness were examined by measuring melt quality parameters such as density index, bifilm index, porosity, and the amount of dissolved hydrogen [H]. A high melt quality was achieved when GBF treatment was performed on 10 kg melt for more than 10 min (i.e., 1 L gas/kg melt). However, as the stabilization holding time after GBF treatment increased to 10, 20, and 30 min, the melt quality degraded. GBF treatment for 30 min had a similar effect to treatment for 10 min, and the degree of deterioration of melt quality during the stabilization time was also similar. Considering the economics, 10 min GBF treatment and short holding time are required. Observations of the shape and volume of the largest pore suggested the cause of defect formation and confirmed that the volume of the largest pore can be used as an index of the melt quality. Full article
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Article
MEROS Dust Quality of Different Plants and Its Potential Further Uses
Metals 2021, 11(5), 840; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050840 - 20 May 2021
Viewed by 444
Abstract
Sintering is a process of agglomeration of fine particles into porous sinters for blast furnaces. During the sintering process, high volumes of sinter plant gas containing high loads of dust, SO2 and NOX and toxic pollutants, such as heavy metals (e.g., [...] Read more.
Sintering is a process of agglomeration of fine particles into porous sinters for blast furnaces. During the sintering process, high volumes of sinter plant gas containing high loads of dust, SO2 and NOX and toxic pollutants, such as heavy metals (e.g., Hg, Pb, Cr and Cd) and PCDD/F, are emitted. The objective of this study was to characterize dusts of different plants as the basis for suggestions of reutilization and treatment options. Dusts, eluates and residues were produced and DOC, T-N, ions and heavy metals were analyzed. The results show that dusts from different plants are very similar in terms of DOC, T-N, Mg, Ca and many heavy metals and only differ in criteria such as suspended solids and ions such as K, Na, Cl and SO4. Based on the high levels of alkalis and low levels of iron, direct recycling into the sinter or furnace process is not recommended. The dissolution of the soluble substances in water reduces the MEROS dust by 90% of the weight and extracts the alkalis. The remaining wastewater needs to be treated to reduce DOC, T-N and some heavy metals. The solid residues can be recycled into the sinter to reduce potential PCDD/F, which are attached to the activated carbon. Full article
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Article
Investigation on the Reaction Behaviour of Partially Reduced Iron under Blast Furnace Conditions
Metals 2021, 11(5), 839; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050839 - 20 May 2021
Viewed by 351
Abstract
The reaction behaviour of partially reduced iron (PRI) was studied to understand the effect of PRI utilisation in the blast furnace process. For quantitative analysis, the reaction behaviour of PRI under typical operating conditions of a blast furnace was measured using the thermogravimetric [...] Read more.
The reaction behaviour of partially reduced iron (PRI) was studied to understand the effect of PRI utilisation in the blast furnace process. For quantitative analysis, the reaction behaviour of PRI under typical operating conditions of a blast furnace was measured using the thermogravimetric method along with the reduction behaviour of hematite and sinter. Experimental results indicated that the reoxidation behaviour of the PRI under the conditions of the upper shaft of the blast furnace retarded the indirect reduction rate in the lower shaft. The rate constants derived from the grain model, experimental results of scanning electron microscopy, and porosimetry analysis indicated that the phenomenon of reduction retardation of PRI under the conditions of the lower shaft originated owing to the reoxidation of PRI, resulting in the blockage of pores. The reaction behaviour considering the reaction characteristics of PRI was derived under conventional blast furnace conditions. Full article
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Article
A Comprehensive Study of Dynamic Recrystallization Behavior of Mg Alloy with 3 wt.% Bi Addition
Metals 2021, 11(5), 838; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050838 - 20 May 2021
Viewed by 363
Abstract
The effect of the addition of bismuth on the dynamic recrystallization (DRX) behavior of the matrix has been investigated by comparing coarse grain pure Mg with the addition of 3 wt.% Bi, using a uniaxial compression test in the temperature range of 473–623 [...] Read more.
The effect of the addition of bismuth on the dynamic recrystallization (DRX) behavior of the matrix has been investigated by comparing coarse grain pure Mg with the addition of 3 wt.% Bi, using a uniaxial compression test in the temperature range of 473–623 K and the strain rate of 0.01–10 s−1. The constitutive equation, processing map, microstructure, and texture evolution of the Mg-3Bi alloy were systematically investigated. The results showed that the Bi addition could refine the grain size and accelerate the DRX process. The DRX kinetics is discussed in detail, accompanied by extensive characterization employing EBSD analysis. The DRX of the Mg-3Bi alloy depended on the deformation temperature rather than the strain rate. The {10–12} tensile twin appeared at 573 K/0.01–0.1 s−1, and discontinuous DRX (DDRX), continuous DRX (CDRX) as the main mechanism in the case of 573 K/0.01 s−1, while the dominant mechanism was DDRX when deformation temperature and strain rate increased. Particle-stimulated nucleation (PSN) was also involved in the DRX of this new RE-free Mg alloy. Full article
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Article
Hot Deformation Behavior and Hot Rolling Properties of a Nano-Y2O3 Addition Near-α Titanium Alloy
Metals 2021, 11(5), 837; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050837 - 19 May 2021
Viewed by 427
Abstract
The hot deformation behavior and hot rolling based on the hot processing map of a nano-Y2O3 addition near-α titanium alloy were investigated. The isothermal compression tests were conducted at various deformation temperatures (950–1070 °C) and strain rates (0.001–1 s−1 [...] Read more.
The hot deformation behavior and hot rolling based on the hot processing map of a nano-Y2O3 addition near-α titanium alloy were investigated. The isothermal compression tests were conducted at various deformation temperatures (950–1070 °C) and strain rates (0.001–1 s−1), up to a true strain of 1.2. The flow stress was strongly dependent on deformation temperature and strain rate, decreasing with increased temperature and decreased strain rate. The average activation energy was 657.8 kJ/mol and 405.9 kJ/mol in (α + β) and β region, respectively. The high activation energy and peak stress were contributed to the Y2O3 particles and refractory elements comparing with other alloys and composites. The deformation mechanisms in the (α + β) region were dynamic recovery and spheroidization of α phase, while the β phase field was mainly controlled by the dynamic recrystallization and dynamic recovery of β grains. Moreover, the constitutive equation based on Norton–Hoff equation and hot processing map were also obtained. Through the optimal processing window determined by the hot processing map at true strains of 0.2, 0.4 and 0.6, the alloy sheet with multi-pass hot rolling (1050 °C/0.03–1 s−1) was received directly from the as-cast alloy. The ultimate tensile strength and yield strength of the alloy sheet were 1168 MPa and 1091 MPa at room temperature, and 642 MPa and 535 MPa at 650 °C, respectively, which performs some advantages in current research. Full article
(This article belongs to the Special Issue Casting and Rolling of Alloys)
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Review
Duplex Stainless Steels—Alloys for the 21st Century
Metals 2021, 11(5), 836; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050836 - 19 May 2021
Viewed by 454
Abstract
Duplex stainless steels were first manufactured early in the 20th century, but it was the introduction in the 1970s of the argon-oxygen decarburisation (AOD) steel making process and the addition of nitrogen to these steels, that made the alloys stronger, more weldable and [...] Read more.
Duplex stainless steels were first manufactured early in the 20th century, but it was the introduction in the 1970s of the argon-oxygen decarburisation (AOD) steel making process and the addition of nitrogen to these steels, that made the alloys stronger, more weldable and more corrosion resistant. Today, duplex stainless steels can be categorised into four main groups, i.e., “lean”, “standard”, “super”, and “hyper” duplex types. These groups cover a range of compositions and properties, but they all have in common a microstructure consisting of roughly equal proportions of austenite and ferrite, high strength, good toughness and good corrosion resistance, especially to stress corrosion cracking (SCC) compared with similar austenitic stainless steels. Moreover, the development of a duplex stainless-steel microstructure requires lower levels of nickel in the composition than for a corresponding austenitic stainless steel with comparable pitting and crevice corrosion resistance, hence they cost less. This makes duplex stainless steels a very versatile and attractive group of alloys both commercially and technically. There are applications where duplex grades can be used as lower cost through-life options, in preference to coated carbon steels, a range of other stainless steels, and in some cases nickel alloys. This cost benefit is further emphasised if the design engineer can use the higher strength of duplex grades to construct vessels and pipework of lower wall thickness than would be the case if an austenitic grade or nickel alloy was being used. Hence, we find duplex stainless steels are widely used in many industries. In this paper their use in three industrial applications is reviewed, namely marine, heat exchangers, and the chemical and process industries. The corrosion resistance in the relevant fluids is discussed and some case histories highlight both successes and potential problems with duplex alloys in these industries. The paper shows how duplex stainless steels can provide cost-effective solutions in corrosive environments, and why they will be a standard corrosion resistant alloy (CRA) for many industries through the 21st century. Full article
(This article belongs to the Special Issue Corrosion and Protection of Stainless Steels)
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Article
Fatigue Behavior of Hybrid Components Containing Maraging Steel Parts Produced by Laser Powder Bed Fusion
Metals 2021, 11(5), 835; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050835 - 19 May 2021
Viewed by 377
Abstract
This investigation concerns about of fatigue behavior under controlled loading and under strain control for hybrid specimens with parts produced with conventional processes in steel AISI H13 and the stainless steel AISI 420 and the rest part produced by laser powder bed fusion [...] Read more.
This investigation concerns about of fatigue behavior under controlled loading and under strain control for hybrid specimens with parts produced with conventional processes in steel AISI H13 and the stainless steel AISI 420 and the rest part produced by laser powder bed fusion in AISI 18Ni300 steel. The controlled loading tests were performed in constant and variable amplitude. Fatigue failure of hybrid samples occurs mostly in laser-melted parts, initiated around the surface, in many cases with multi-nucleation and propagated predominantly between the deposited layers. Fatigue strength of hybrid parts, tested under displacement control is similar, but for specimens tested under load control the fatigue strength the fatigue strength of hybrid specimens is progressively lesser than laser powder bed fusion samples. Despite a tendency to obtain conservative predictions, Miner’s law predicts reasonably the fatigue lives under block loadings. The interface between materials presented an excellent joining and fatigue strength because the fatigue failure of hybrid samples occurred mostly in laser melted parts out of the interface. Full article
(This article belongs to the Special Issue Fatigue and Fracture Mechanics of Metals)
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Article
Mechanical Behavior Evaluation of Tempcore and Hybrid Reinforcing Steel Bars via a Proposed Fatigue Damage Index in Long Terms
Metals 2021, 11(5), 834; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050834 - 19 May 2021
Viewed by 437
Abstract
As it is widely known, corrosion constitutes a major deterioration factor for reinforced concrete structures which are located in coastal areas. This phenomenon, combined with repeated loads and, especially, intense seismic events, negatively affect their useful service life. It is well known that [...] Read more.
As it is widely known, corrosion constitutes a major deterioration factor for reinforced concrete structures which are located in coastal areas. This phenomenon, combined with repeated loads and, especially, intense seismic events, negatively affect their useful service life. It is well known that the microstructure of steel reinforcing bars has a significant impact either on their corrosion resistance or on their fatigue life. In the present manuscript, an effort has been made to study the effect of corrosive factors on fatigue response for two types of steel reinforcement: Tempcore steel B reinforcing bars and a new-generation, dual-phase (DP) steel F reinforcement. The findings of this experimental study showed that DP steel reinforcement’s rate of degradation due to corrosion seemed apparently lighter than Tempcore B with respect to its capacity to bear repeated loads to a satisfactory degree after corrosion. For this purpose, based on a quality material index that characterizes the mechanical performance of materials, an extended damage material indicator for fatigue conditions is similarly proposed for evaluating and classifying these two types of rebars in terms of material quality and durability. The outcomes of this investigation demonstrated the feasibility of fatigue damage indicators in the production cycle as well as at different exposure times, once corrosion phenomena had left their mark in steel reinforcement. Full article
(This article belongs to the Special Issue Corrosion Effects on Durability of RC Structures)
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Article
Machine Learning-Based Models for the Estimation of the Energy Consumption in Metal Forming Processes
Metals 2021, 11(5), 833; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050833 - 19 May 2021
Viewed by 476
Abstract
This research provides an insight on the performances of machine learning (ML)-based algorithms for the estimation of the energy consumption in metal forming processes and is applied to the radial-axial ring rolling process. To define the mutual influence between ring geometry, process settings, [...] Read more.
This research provides an insight on the performances of machine learning (ML)-based algorithms for the estimation of the energy consumption in metal forming processes and is applied to the radial-axial ring rolling process. To define the mutual influence between ring geometry, process settings, and ring rolling mill geometries with the resulting energy consumption, measured in terms of the force integral over the processing time (FIOT), FEM simulations have been implemented in the commercial SW Simufact Forming 15. A total of 380 finite element simulations with rings ranging from 650 mm < DF < 2000 mm have been implemented and constitute the bulk of the training and validation datasets. Both finite element simulation settings (input), as well as the FI (output), have been utilized for the training of eight machine learning models, implemented with Python scripts. The results allow defining that the Gradient Boosting (GB) method is the most reliable for the FIOT prediction in forming processes, being its maximum and average errors equal to 9.03% and 3.18%, respectively. The trained ML models have been also applied to own and literature experimental cases, showing a maximum and average error equal to 8.00% and 5.70%, respectively, thus proving once again its reliability. Full article
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Article
Process Optimization and Microstructure Analysis to Understand Laser Powder Bed Fusion of 316L Stainless Steel
Metals 2021, 11(5), 832; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050832 - 19 May 2021
Viewed by 499
Abstract
The microstructural development of 316L stainless steel (SS) was investigated over a wide range of systematically varied laser powder bed fusion (LPBF) parameters, such as laser power, scan speed, hatch spacing and volumetric energy density. Relative density, melt pool width and depth, and [...] Read more.
The microstructural development of 316L stainless steel (SS) was investigated over a wide range of systematically varied laser powder bed fusion (LPBF) parameters, such as laser power, scan speed, hatch spacing and volumetric energy density. Relative density, melt pool width and depth, and the size of sub-grain cellular structure were quantified and related to the temperature field estimated by Rosenthal solution. Use of volumetric energy density between 46 and 127 J/mm3 produced nearly fully dense (≥99.8%) samples, and this included the best parameter set: power = 200 W; scan speed = 800 mm/s; hatch spacing = 0.12 mm; slice thickness = 0.03; energy density = 69 J/mm3). Cooling rate of 105 to 107 K/s was estimated base on the size of cellular structure within melt pools. Using the optimized LPBF parameters, the as-built 316L SS had, on average, yield strength of 563 MPa, Young’s modulus of 179 GPa, tensile strength of 710 MPa, and 48% strain at failure. Full article
(This article belongs to the Special Issue Optimization of Metal Additive Manufacturing Processes)
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Article
Investigation on Laser Welding of Al Ribbon to Cu Sheet: Weldability, Microstructure, and Mechanical and Electrical Properties
Metals 2021, 11(5), 831; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050831 - 19 May 2021
Viewed by 437
Abstract
The pulsed laser welding of Al ribbon to Cu sheet was investigated for the electrical interconnections in power electronic modules. The various experimental conditions with the different laser powers, scan speeds, and heat inputs were employed for obtaining the defect-free Al/Cu joints. During [...] Read more.
The pulsed laser welding of Al ribbon to Cu sheet was investigated for the electrical interconnections in power electronic modules. The various experimental conditions with the different laser powers, scan speeds, and heat inputs were employed for obtaining the defect-free Al/Cu joints. During the Al/Cu laser welding, the intermetallic compounds were formed in the welding zone. An electron probe microanalyzer and transmission electron microscopy confirmed the phases of intermetallic compounds, which were found to be Al4Cu9, Al2Cu, AlCu, etc. The computational fluid dynamics simulation revealed that the Marangoni effect induced the circulation of the molten pool, resulting in the mixture of Al and Cu and the formation of swirl-like structures at the Al/Cu joints. The tensile shear strengths and electrical resistances of the Al/Cu joints were measured, and they showed a strong correlation with the welding area. A decrease in mechanical strength and an increase in electrical resistance were measured with increasing the welding area of Al/Cu joints. Moreover, the process window for the defect-free Al/Cu joints was developed, and the experimental conditions for Al/Cu laser braze-welding were examined to minimize the intermetallic compounds formation at the Al/Cu joints. Full article
(This article belongs to the Special Issue Numerical Simulation of Metals Welding Process)
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Article
Creep Behavior of Diffusion-Welded Alloy 617
Metals 2021, 11(5), 830; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050830 - 19 May 2021
Viewed by 453
Abstract
Plate-type heat exchangers are anticipated to be used in the next-generation nuclear industry, and solid-state diffusion welding is a critical technology for building plate-type heat exchangers with high integrity. In this study, we manufactured a diffusion weldment and evaluated its creep behavior. Microscopic [...] Read more.
Plate-type heat exchangers are anticipated to be used in the next-generation nuclear industry, and solid-state diffusion welding is a critical technology for building plate-type heat exchangers with high integrity. In this study, we manufactured a diffusion weldment and evaluated its creep behavior. Microscopic analysis revealed that Al-rich oxides were developed along the interface, significantly impeding grain-boundary movement across the interface. Oxide-containing planar grain boundaries resulted in premature brittle fracture at the interface with less than 9% creep strain under all test conditions. The time to rupture and time to 1% creep strain of the diffusion weldment were less than those of the as-received alloy, while the slopes in double-logarithmic plots were almost identical for both alloys. In a Larson–Miller parameter study, the stress to rupture of the diffusion weldment reached 95.59% of that of the as-received alloy, whereas the stress to 1% creep strain steeply decreased in the low-stress range. Full article
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Review
Neutron Scattering as a Powerful Tool to Investigate Magnetic Shape Memory Alloys: A Review
Metals 2021, 11(5), 829; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050829 - 18 May 2021
Viewed by 463
Abstract
Magnetic shape memory alloys (MSMAs) are an interesting class of smart materials characterized by undergoing macroscopic deformations upon the application of a pertinent stimulus: temperature, stress and/or external magnetic fields. Since the deformation is rapid and contactless, these materials are being extensively investigated [...] Read more.
Magnetic shape memory alloys (MSMAs) are an interesting class of smart materials characterized by undergoing macroscopic deformations upon the application of a pertinent stimulus: temperature, stress and/or external magnetic fields. Since the deformation is rapid and contactless, these materials are being extensively investigated for a plethora of applications, such as sensors and actuators for the medical, automotive and space industries, energy harvesting and damping devices, among others. These materials also exhibit a giant magnetocaloric effect, whereby they are very promising for magnetic refrigeration. The applications in which they can be used are extremely dependent on the material properties, which are, in turn, greatly conditioned by the structure, atomic ordering and magnetism of a material. Particularly, exploring the material structure is essential in order to push forward the current application limitations of the MSMAs. Among the wide range of available characterization tools, neutron scattering techniques stand out in acquiring advanced knowledge about the structure and magnetism of these alloys. Throughout this manuscript, a comprehensive review about the characterization of MSMAs using neutron techniques is presented. Several elastic neutron scattering techniques will be explained and exemplified, covering neutron imaging techniques—such as radiography, tomography and texture diffractometry; diffraction techniques—magnetic (polarized neutron) diffraction, powder neutron diffraction and single crystal neutron diffraction, reflectometry and small angle neutron scattering. This will be complemented with a few examples where inelastic neutron scattering has been employed to obtain information about the phonon dispersion in MSMAs. Full article
(This article belongs to the Special Issue Recent Development in Magnetic Shape Memory Alloys)
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Review
Vanadium and Melanoma: A Systematic Review
Metals 2021, 11(5), 828; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050828 - 18 May 2021
Viewed by 452
Abstract
The application of metals in biological systems has been a rapidly growing branch of science. Vanadium has been investigated and reported as an anticancer agent. Melanoma is the most aggressive type of skin cancer, the incidence of which has been increasing annually worldwide. [...] Read more.
The application of metals in biological systems has been a rapidly growing branch of science. Vanadium has been investigated and reported as an anticancer agent. Melanoma is the most aggressive type of skin cancer, the incidence of which has been increasing annually worldwide. It is of paramount importance to identify novel pharmacological agents for melanoma treatment. Herein, a systematic review of publications including “Melanoma and Vanadium” was performed. Nine vanadium articles in several melanoma cells lines such as human A375, human CN-mel and murine B16F10, as well as in vivo studies, are described. Vanadium-based compounds with anticancer activity against melanoma include: (1) oxidovanadium(IV); (2) XMenes; (3) vanadium pentoxide, (4) oxidovanadium(IV) pyridinonate compounds; (5) vanadate; (6) polysaccharides vanadium(IV/V) complexes; (7) mixed-metal binuclear ruthenium(II)–vanadium(IV) complexes; (8) pyridoxal-based oxidovanadium(IV) complexes and (9) functionalized nanoparticles of yttrium vanadate doped with europium. Vanadium compounds and/or vanadium materials show potential anticancer activities that may be used as a useful approach to treat melanoma. Full article
(This article belongs to the Special Issue The Biological Applications of Metals and Metal Complexes)
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Article
Development of Lightweight Magnesium/Glass Micro Balloon Syntactic Foams Using Microwave Approach with Superior Thermal and Mechanical Properties
Metals 2021, 11(5), 827; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050827 - 18 May 2021
Viewed by 478
Abstract
Magnesium matrix syntactic foams (MgMSFs) are emerging lightweight materials with unique capabilities to exhibit remarkable thermal, acoustic, and mechanical properties. In the current study, lightweight glass micro balloon (GMB)-reinforced Mg syntactic foams were synthesized via the powder metallurgy technique using hybrid microwave sintering. [...] Read more.
Magnesium matrix syntactic foams (MgMSFs) are emerging lightweight materials with unique capabilities to exhibit remarkable thermal, acoustic, and mechanical properties. In the current study, lightweight glass micro balloon (GMB)-reinforced Mg syntactic foams were synthesized via the powder metallurgy technique using hybrid microwave sintering. The processing employed in the study yielded MgMSFs with refined grain sizes, no secondary phases, and reasonably uniform distributions of hollow reinforcement particles. The developed MgMSFs exhibited densities 8%, 16%, and 26% lower than that of the pure Mg. The coefficient of thermal expansion reduced (up to 20%) while the ignition resistance improved (up to 20 °C) with the amount of GMB in the magnesium matrix. The MgMSFs also exhibited a progressive increase in hardness with the amount of GMB. Although the MgMSFs showed a decrease in the yield strength with the addition of GMB hollow particles, the ultimate compression strength, fracture strain, and energy absorption capabilities increased noticeably. The best ultimate compression strength at 321 MPa, which was ~26% higher than that of the pure Mg, was displayed by the Mg-5GMB composite, while the Mg-20GMB composite showed the best fracture strain and energy absorption capability, which were higher by ~39 and 65%, respectively, when compared to pure Mg. The specific strength of all composites remained superior to that of monolithic magnesium. Particular efforts were made in the present study to interrelate the processing, microstructural features, and properties of MgMSFs. Full article
(This article belongs to the Special Issue Lightweight Metals: Process, Microstructure, and Properties)
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Communication
Effect of Scanning Strategy in the L-PBF Process of 18Ni300 Maraging Steel
Metals 2021, 11(5), 826; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050826 - 18 May 2021
Viewed by 417
Abstract
Maraging steels are good candidates for the laser powder bed fusion process (L-PBF), also known as Selective Laser Melting, due to excellent weldability and resistance to quench cracking. Powders physical and chemical characteristics dominate the final microstructure and properties of the printed parts, [...] Read more.
Maraging steels are good candidates for the laser powder bed fusion process (L-PBF), also known as Selective Laser Melting, due to excellent weldability and resistance to quench cracking. Powders physical and chemical characteristics dominate the final microstructure and properties of the printed parts, that are also heavily influenced by the process parameters. In this study, the effects of the scanning strategies on dimensions, average surface roughness, density and material hardness were evaluated, keeping the powder type and the volumetric energy density (Andrew number) constant. The effects of the scanning strategy on these properties are far less understood than on other important ones, like residual stresses and distortion, strongly affected by the scanning strategy. In this study, parallel stripes, chessboard and hexagonal pattern strategies were studied, keeping the Andrew number constant but varying the interlayer rotation. In general, the hexagonal strategy underperformed compared to the chessboard and the stripes ones. Full article
(This article belongs to the Section Additive Manufacturing)
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Communication
Determination of the Li Distribution in Synthetic Recycling Slag with SIMS
Metals 2021, 11(5), 825; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050825 - 18 May 2021
Viewed by 272
Abstract
The recovery of technically important elements like lithium from slag of pyrometallurgical recycling of lithium traction batteries will be very important in future due to the expected increasing demand of this element with the upcoming world-wide implementation of electro mobility. Therefore, the investigation [...] Read more.
The recovery of technically important elements like lithium from slag of pyrometallurgical recycling of lithium traction batteries will be very important in future due to the expected increasing demand of this element with the upcoming world-wide implementation of electro mobility. Therefore, the investigation of possibilities to recover lithium from pyrometallurgical slag from the recycling of lithium traction batteries is mandatory. In this context, the EnAM (engineered artificial mineral) approach is very promising. Solidified melt of synthetic recycling slag with the compounds Li2O-MgO-Al2O3-SiO2-CaO-MnO contains various Li-bearing phases including spinel solid solution, Li-aluminate and eucryptite-like Li-alumosilicate. Most probably, the Ca-alumosilicate matrix (melilite-like solid solution) incorporates lithium as well. These compounds can be determined and calculated to an acceptable approximation with electron probe microanalysis (EPMA). Nevertheless, an adequate precise measurement of lithium is virtually impossible due to the extremely low fluorescence yield and long wavelength of Li Kα. Secondary mass spectrometry (SIMS) can be used to fill this gap in the analytical assessment of the slag. Therefore, the combination of these two analytical methods can distinctively improve the mineralogical and chemical characterization of lithium-containing solidified (slag) melt. Full article
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Article
Deformation Behavior and Microstructural Evolution of Inconel 625 Superalloy during the Hot Compression Process
Metals 2021, 11(5), 824; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050824 - 18 May 2021
Viewed by 315
Abstract
Hot deformation behavior and the microstructural evolution of Inconel 625 superalloy plates are investigated by hot compression tests in a range of working temperatures (800–1050 °C) and strain rates (0.001–1 s−1). The microstructural observation shows that a strong <110> texture forms [...] Read more.
Hot deformation behavior and the microstructural evolution of Inconel 625 superalloy plates are investigated by hot compression tests in a range of working temperatures (800–1050 °C) and strain rates (0.001–1 s−1). The microstructural observation shows that a strong <110> texture forms when the processing temperature is below 950 °C, whose intensity decreases with the increases of the temperature, and it disappears when compressing above 950 °C. During the compression test, twin-related dynamic recrystallization (DRX) occurs in the investigated temperature range, and the intensity of twin-related DRX increases with the increases of the temperature. In addition, as the temperature increases, the intensity of continuum DRX decreases. Full article
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Article
Thermophysical Properties of the Fe48Cr15Mo14C15B6Y2 Alloy in Liquid State
Metals 2021, 11(5), 823; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050823 - 18 May 2021
Viewed by 369
Abstract
In this work, the physical properties of Fe48Cr15Mo14C15B6Y2 alloy in liquid state at high temperature are studied. It was observed that the basic physical characteristics of the alloy, such as viscosity, electrical [...] Read more.
In this work, the physical properties of Fe48Cr15Mo14C15B6Y2 alloy in liquid state at high temperature are studied. It was observed that the basic physical characteristics of the alloy, such as viscosity, electrical resistivity, and density, decrease with an increase of the temperature to 1700 °C. An abnormal increasing rate of viscosity for Fe48Cr15Mo14C15B6Y2 alloy in the temperature range from 1360 to 1550 °C was noted. The measurement of the electrical resistivity and density did not reveal any anomalies in the same temperature range. Full article
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Article
Digital Scanning of Welds and Influence of Sampling Resolution on the Predicted Fatigue Performance: Modelling, Experiment and Simulation
Metals 2021, 11(5), 822; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050822 - 18 May 2021
Viewed by 353
Abstract
Digital weld quality assurance systems are increasingly used to capture local geometrical variations that can be detrimental for the fatigue strength of welded components. In this study, a method is proposed to determine the required scanning sampling resolution for proper fatigue assessment. Based [...] Read more.
Digital weld quality assurance systems are increasingly used to capture local geometrical variations that can be detrimental for the fatigue strength of welded components. In this study, a method is proposed to determine the required scanning sampling resolution for proper fatigue assessment. Based on FE analysis of laser-scanned welded joints, fatigue failure probabilities are computed using a Weakest-link fatigue model with experimentally determined parameters. By down-sampling of the scanning data in the FE simulations, it is shown that the uncertainty and error in the fatigue failure probability prediction increases with decreased sampling resolution. The required sampling resolution is thereafter determined by setting an allowable error in the predicted failure probability. A sampling resolution of 200 to 250 μm has been shown to be adequate for the fatigue-loaded welded joints investigated in the current study. The resolution requirements can be directly incorporated in production for continuous quality assurance of welded structures. The proposed probabilistic model used to derive the resolution requirement accurately captures the experimental fatigue strength distribution, with a correlation coefficient of 0.9 between model and experimental failure probabilities. This work therefore brings novelty by deriving sampling resolution requirements based on the influence of stochastic topographical variations on the fatigue strength distribution. Full article
(This article belongs to the Special Issue Technological Aspects in Fatigue Design of Metallic Structures)
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Article
Study on High-Temperature Mechanical Properties of Fe–Mn–C–Al TWIP/TRIP Steel
Metals 2021, 11(5), 821; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050821 - 18 May 2021
Viewed by 341
Abstract
In this study, high-temperature tensile tests were carried out on a Gleeble-3500 thermal simulator under a strain rate of ε = 1 × 10−3 s−1 in the temperature range of 600–1310 °C. The hot deformation process of Fe–15.3Mn–0.58C–2.3Al TWIP/TRIP at different [...] Read more.
In this study, high-temperature tensile tests were carried out on a Gleeble-3500 thermal simulator under a strain rate of ε = 1 × 10−3 s−1 in the temperature range of 600–1310 °C. The hot deformation process of Fe–15.3Mn–0.58C–2.3Al TWIP/TRIP at different temperatures was studied. In the whole tested temperature range, the reduction of area ranged from 47.3 to 89.4% and reached the maximum value of 89.4% at 1275 °C. Assuming that 60% reduction of area is relative ductility trough, the high-temperature ductility trough was from 1275 °C to the melting point temperature, the medium-temperature ductility trough was 1000–1250 °C, and the low-temperature ductility trough was around 600 °C. The phase transformation process of the steel was analyzed by Thermo-Calc thermodynamics software. It was found that ferrite transformation occurred at 646 °C, and the austenite was softened by a small amount of ferrite, resulting in the reduction of thermoplastic and formation of the low-temperature ductility trough. However, the small difference in thermoplasticity in the low-temperature ductility trough was attributed to the small amount of ferrite and the low transformation temperature of ferrite. The tensile fracture at different temperatures was characterized by means of optical microscopy and scanning electron microscopy. It was found that there were Al2O3, AlN, MnO, and MnS(Se) impurities in the fracture. The abnormal points of thermoplasticity showed that the inclusions had a significant effect on the high-temperature mechanical properties. The results of EBSD local orientation difference analysis showed that the temperature range with good plasticity was around 1275 °C. Under large deformation extent, the phase difference in the internal position of the grain was larger than that in the grain boundary. The defect density in the grain was large, and the high dislocation density was the main deformation mechanism in the high-temperature tensile process. Full article
(This article belongs to the Special Issue Recent Developments in Medium and High Manganese Steels)
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Article
Hydrometallurgical Recycling Process for Mobile Phone Printed Circuit Boards Using Ozone
Metals 2021, 11(5), 820; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050820 - 18 May 2021
Viewed by 474
Abstract
Printed circuit boards (PCBs) can be an important source of non-ferrous metals (Al, Sn, Zn, and Ni) and precious metals (Au, Ag, Cu, and Pd). With the continuous increase in demand for metals due to the depletion of ores, recycling of this waste [...] Read more.
Printed circuit boards (PCBs) can be an important source of non-ferrous metals (Al, Sn, Zn, and Ni) and precious metals (Au, Ag, Cu, and Pd). With the continuous increase in demand for metals due to the depletion of ores, recycling of this waste is becoming an attractive alternative. The printed circuits also contain hazardous metals, such as Pb, Hg, As, and Cd. Due to the huge increase in the amount of e-waste, the processing of printed circuit boards for metal recovery and proper handling of hazardous substances has a positive effect on the environment. Pyrometallurgical and hydrometallurgical methods are used for the treatment of this waste. Various oxidizing agents are used in the hydrometallurgical processes, including ozone. PCBs from mobile phones were assessed for the recovery of Cu, Sn, and precious metals. The ground and sieved materials were leached in nitric acid, hydrochloric acid, and sulfuric acid at various process parameters, such as leaching time, leaching agent, and temperature. It was found that the best result was obtained using hydrochloric acid with the addition of ozone at 353 K for a period of 4 h to obtain 68.45 g/dm3 of copper. Preliminary results of electrolysis and cementation are also presented. Full article
(This article belongs to the Special Issue Leaching and Recycling of Metals)
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Article
The Effect of Aging on Precipitates, Mechanical and Magnetic Properties of Fe-21Cr-15Ni-6Mn-Nb Low Magnetic Stainless Steel
Metals 2021, 11(5), 819; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050819 - 18 May 2021
Viewed by 319
Abstract
The effect of aging on the precipitates, mechanical and magnetic properties of Fe-21Cr-15Ni-6Mn-Nb low magnetic stainless steel were investigated. The steel was aged at 550–750 °C for 2 h after solution heat treatment at 1100 °C for 1 h. During the aging treatment, [...] Read more.
The effect of aging on the precipitates, mechanical and magnetic properties of Fe-21Cr-15Ni-6Mn-Nb low magnetic stainless steel were investigated. The steel was aged at 550–750 °C for 2 h after solution heat treatment at 1100 °C for 1 h. During the aging treatment, the (Nb, V)(C, N) particles gradually precipitated in the grain, which were coherent or semi-coherent with the matrix. When the aging temperature was beyond 650 °C, the coarsening rate of (Nb, V)(C, N) particles increase rapidly and the coherent orientation between (Nb, V)(C, N) particles and the matrix was lost gradually. Meanwhile, coarse M23C6 was distributed at the grain boundary with chain shape, which was non-coherent with the matrix. The coarsening behavior of (Nb, V)(C, N) precipitates in the grain was analyzed, and the size of the particles precipitated after aging treatment at 650°C for different time was calculated and studied. After aging treatment at 650 °C for 2 h, the yield strength and tensile strength of the stainless steel was 705.6 MPa and 1002.3 MPa, the elongation and the relative magnetic permeability was 37.8% and 1.0035, respectively. Full article
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Article
A Mixed Numerical-Experimental Method to Characterize Metal-Polymer Interfaces for Crash Applications
Metals 2021, 11(5), 818; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050818 - 18 May 2021
Viewed by 327
Abstract
Metallic (M) and polymer (P) materials as layered hybrid metal-polymer-metal (MPM) sandwiches offer a wide range of applications by combining the advantages of both material classes. The interfaces between the materials have a considerable impact on the resulting mechanical properties of the composite [...] Read more.
Metallic (M) and polymer (P) materials as layered hybrid metal-polymer-metal (MPM) sandwiches offer a wide range of applications by combining the advantages of both material classes. The interfaces between the materials have a considerable impact on the resulting mechanical properties of the composite and its structural performance. Besides the fact that the experimental methods to determine the properties of the single constituents are well established, the characterization of interface failure behavior between dissimilar materials is very challenging. In this study, a mixed numerical–experimental approach for the determination of the mode I energy release rate is investigated. Using the example of an interface between a steel (St) and a thermoplastic polyolefin (PP/PE), the process of specimen development, experimental parameter determination, and numerical calibration is presented. A modified design of the Double Cantilever Beam (DCB) is utilized to characterize the interlaminar properties and a tailored experimental setup is presented. For this, an inverse calibration method is used by employing numerical studies using cohesive elements and the explicit solver of LS-DYNA based on the force-displacement and crack propagation results. Full article
(This article belongs to the Special Issue Characterization and Monitoring of Metal-CFRP-Hybrid Structures)
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Article
Comparative Study of MnO2 Dissolution from Black Copper Minerals and Manganese Nodules in an Acid Medium
Metals 2021, 11(5), 817; https://0-doi-org.brum.beds.ac.uk/10.3390/met11050817 - 18 May 2021
Cited by 1 | Viewed by 397
Abstract
The low grade of copper deposits and the use of the froth flotation process have caused excessive tailing production. In recent years, experts have looked for new alternative methods to improve this situation. Black copper minerals are abundant resources not exploited by large-scale [...] Read more.
The low grade of copper deposits and the use of the froth flotation process have caused excessive tailing production. In recent years, experts have looked for new alternative methods to improve this situation. Black copper minerals are abundant resources not exploited by large-scale copper mining and possess high Mn concentrations. On the other hand, manganese nodules are submarine resources and show high concentrations of Cu, Ni, Fe, and, mainly, Mn. However, both mineral resources are refractory to conventional leaching processes, and so a reducing agent is necessary for their treatment. We studied the use of tailings obtained from the flotation of foundry slags with a high content of Fe3O4 as reducing agents at different MnO2/tailings ratios and H2SO4 concentrations. Mn dissolution was compared in marine nodule and black copper minerals samples. It was found that higher Mn dissolutions are obtained from marine nodules, likely due to the acid consumption created by Cu dissolution from black copper minerals. The remnant elements in manganese nodules were leached under an oxidant condition. Full article
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