Journal Description
Metals
Metals
is an international, peer-reviewed, open access journal published monthly online by MDPI. The Portuguese Society of Materials (SPM), and the Spanish Materials Society (SOCIEMAT) are affiliated with Metals and their members receive a discount on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Journal Rank: JCR - Q2 (Metallurgy & Metallurgical Engineering) / CiteScore - Q1 (Metals and Alloys)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the first half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journals for Metals include: Compounds and Alloys.
Impact Factor:
2.9 (2022);
5-Year Impact Factor:
2.9 (2022)
Latest Articles
Microstructure and Mechanical Properties of Friction Stir Lap Welding Joint of Al/CU Dissimilar Metals
Metals 2023, 13(12), 1969; https://doi.org/10.3390/met13121969 (registering DOI) - 03 Dec 2023
Abstract
In this paper, 5083 aluminum alloy and T2 copper were selected for the friction stir lap welding test. The effect of intermetallic compounds on the microstructure and properties of Al/Cu dissimilar metal lap joints was studied. The results showed that the circulating Al/Cu
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In this paper, 5083 aluminum alloy and T2 copper were selected for the friction stir lap welding test. The effect of intermetallic compounds on the microstructure and properties of Al/Cu dissimilar metal lap joints was studied. The results showed that the circulating Al/Cu composite structure was formed on the advancing side of the lap joint, and the Al/Cu staggered hook-like structure and copper-rich region were generated on the retreating side. There was no typical ‘onion ring’ structure in the joint. Element diffusion occurred at the interface of the joint, forming a thin and uniform interfacial layer of Al/Cu intermetallic compounds, thus achieving a well-metallurgical bond at the Al/Cu interface. There were the intermetallic compounds Al2Cu and Al4Cu9, without AlCu, in the lap joint. In addition, dynamic recrystallization occurred in the nugget zone, and higher dislocation density and dislocation entanglement were generated, which enhanced the deformation resistance in the nugget zone and increased the joint strength. The tensile test showed that the ductile–brittle mixed fracture occurred in the heat-affected zone on the advancing side of the aluminum plate, and the fracture had necking. The failure load of the lap joint was 4350 ± 30 N, about 80% of the aluminum base metal. The elongation of the Al/Cu dissimilar lap joint tensile specimen was 2.5%.
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(This article belongs to the Topic Development of Friction Stir Welding and Processing)
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Computational and Experimental Study on Failure Mechanism of a GTD-111 First-Stage Blade of an Industrial Gas Turbine
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, , , and
Metals 2023, 13(12), 1968; https://doi.org/10.3390/met13121968 - 01 Dec 2023
Abstract
This paper investigates the root cause of a recurring failure observed in the first-stage blades of an industrial gas turbine. The failure involves the loss of the trailing edge tip of the blades. The study employs a combination of metallographic analysis and computational
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This paper investigates the root cause of a recurring failure observed in the first-stage blades of an industrial gas turbine. The failure involves the loss of the trailing edge tip of the blades. The study employs a combination of metallographic analysis and computational simulations utilizing the finite element method and computational fluid dynamics. The metallographic analysis reveals significant degradation in the GTD-111 nickel-based superalloy within the region where the failure occurs. This degradation is characterized by the coarsening and coalescence of the gamma prime phase, which can be attributed to localized overheating. Additionally, the computational study enables the calculation of the trajectory, pressure, and temperature profiles of the hot gases, as well as the distribution of temperatures within the blade. These findings demonstrate that the cooling airflow is influenced by the hot gas flow, particularly in the vicinity of the fault location, owing to the orientation of the cooling ducts, which results in overheating in this area. Ultimately, the temperatures derived from the microstructural analysis using the Ostwald-ripening theory align remarkably well with the results obtained from the simulation, validating the accuracy of the computational model. By combining metallographic analysis and computational simulations, this study provides crucial insights into the failure mechanism of the first-stage blades.
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(This article belongs to the Section Computation and Simulation on Metals)
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Microstructural Characterization of In Situ Aluminum Matrix Composites with Interconnected Aluminum Nitride Produced by Arc Plasma-Induced Accelerated Volume Nitridation
Metals 2023, 13(12), 1967; https://doi.org/10.3390/met13121967 - 01 Dec 2023
Abstract
We present a strategy for fabricating aluminum (Al) matrix composites (AMCs) reinforced with interconnected aluminum nitride (AlN) via arc plasma-induced accelerated volume nitridation. AMCs with 10 vol.% AlN are formed in situ by the reaction between liquid Al alloy and nitrogen gas within
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We present a strategy for fabricating aluminum (Al) matrix composites (AMCs) reinforced with interconnected aluminum nitride (AlN) via arc plasma-induced accelerated volume nitridation. AMCs with 10 vol.% AlN are formed in situ by the reaction between liquid Al alloy and nitrogen gas within 1 min of arc melting, revealing very high formation rate of AlN (3.28 × 10−1 g/min·cm3). The rapid nitridation is attributed to the improved wettability and spontaneous infiltration of the melt, which results in the formation of AlN agglomerates and lamellas. In particular, Al-12Si/AlN composites exhibit over two times higher yield strength (195 MPa) than the Al/AlN composites (70 MPa) when compressed along the longitudinal direction to the lamellas. The coefficient of thermal expansion (CTE) is about 30% lower in the Al-12Si/AlN composites (17.0 × 10−6/K) than pure Al (23.6 × 10−6/K). This is attributed to the interconnected AlN architecture and Al–Si eutectic microstructure, which constrain the thermal expansion of the Al matrix. The present AMCs afford an attractive combination of specific thermal conductivity and CTE. These findings would facilitate the development of novel AMCs reinforced with interconnected AlN as cost-effective heat sink materials.
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(This article belongs to the Special Issue Nanostructured Metallic Materials: Preparation, Properties, and Applications)
Open AccessArticle
Different Primary Gas Flow Rates in Determining the Flattening Behavior of In-Flight Particles in Plasma-Sprayed NiCrBSi Coatings and the Resultant Microstructure and Hardness
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, , , , , , , and
Metals 2023, 13(12), 1966; https://doi.org/10.3390/met13121966 - 01 Dec 2023
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The flattening behavior of in-flight particles during plasma spraying is a highly intricate process affected by numerous factors. Therefore, in this work, in-flight particles (spherical NiCrBSi powder) were collected with the water quenching process, and the morphology and composition differences between the original
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The flattening behavior of in-flight particles during plasma spraying is a highly intricate process affected by numerous factors. Therefore, in this work, in-flight particles (spherical NiCrBSi powder) were collected with the water quenching process, and the morphology and composition differences between the original powder particles and the melted in-flight particles were observed using scanning electron microscopy (SEM). The particle size in various states was recorded and calculated. The internal structure of the particles was analyzed to elucidate their morphology and compositions under different flow rates of primary gas (FRPG). A coating with 1.25% porosity and a hardness of 767 HV0.5 was achieved at the FRPG of 80 L/min. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the microstructures of the obtained coatings. It was found that the as-sprayed coating had a certain amount of the amorphous phase. A noteworthy correlation was also established, wherein a decreased distance from the substrate, augmented spraying passes, and reduced amorphous phase content were interrelated. Concurrently, a noticeable influence of the tamping effect exerted by the in-flight particles on the coating was observed.
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Evaluation of the Applicability of Voltammetric Modes in Scanning Electrochemical Microscopy for In Situ Corrosion Characterisation of Copper-Based Materials
Metals 2023, 13(12), 1965; https://doi.org/10.3390/met13121965 - 01 Dec 2023
Abstract
Chemical imaging of corrosion processes involving copper species using scanning electrochemical microscopy has been hampered by the lack of soluble oxidation states for copper that can be achieved by amperometric conversion at the tip. Indeed, the only possibility is to reduce the corrosion
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Chemical imaging of corrosion processes involving copper species using scanning electrochemical microscopy has been hampered by the lack of soluble oxidation states for copper that can be achieved by amperometric conversion at the tip. Indeed, the only possibility is to reduce the corrosion products at the tip, thus modifying the chemical response of the electrode material and requiring subsequent redissolution of the copper deposits. Consequently, the limitations arising from the system prevented a full-scale quantification, requiring the development of new methodologies or the optimisation of those currently available, as we pursued with the present work. Therefore, the voltammetric behaviours of gold macro- and microelectrodes were evaluated with respect to the collection and redissolution of Cu2+ ions, with the aim of using them as sensing probes in scanning electrochemical microscopy (SECM) to investigate the activity of copper surfaces in acidic chloride-containing environments. Cyclic and square-wave voltammetric techniques were explored for copper collection and subsequent stripping on Au microelectrode tips in SECM with the objective to capture in situ image electrochemical reactivity distributions across copper surfaces undergoing corrosion.
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(This article belongs to the Special Issue Feature Paper Collection of “Current Challenges in Corrosion Research”)
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Parametric Investigation of the Effects of Electrical Discharge Machining on Plain D2 Steel
Metals 2023, 13(12), 1964; https://doi.org/10.3390/met13121964 - 01 Dec 2023
Abstract
Electrical discharge machining (EDM) has emerged as a pivotal non-conventional production technique due to its unique capability to machine without the cutting tool’s physical contact with the workpiece, making it apt for brittle, delicate, and complex materials. This research delved into the influence
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Electrical discharge machining (EDM) has emerged as a pivotal non-conventional production technique due to its unique capability to machine without the cutting tool’s physical contact with the workpiece, making it apt for brittle, delicate, and complex materials. This research delved into the influence of operational parameters—pulse duration (Ton), peak current (Ip), duty cycle (T), and gap voltage (Vg)—on machining attributes, namely material removal rate (MRR), electrode wear rate (EWR), and radial overcut (ROC) for AISI D2 steel. Utilizing the Taguchi L9 orthogonal array for experimental design, nine experiments were conducted, followed by signal-to-noise ratio (S/N ratio) computations. Key findings highlighted a 4.02 dB improvement in the S/N ratio for MRR, leading to a 29.13% improvement; a 10.35 dB enhancement in the S/N ratio for EWR, resulting in a 33.33% reduction; and a 2.20 dB increase in the S/N ratio for ROC, leading to a 28.57% increment. ANOVA analyses further underscored the predominant influence of all four parameters. The significance of these findings lies in optimizing the EDM process for increased efficiency, reduced tool wear, and enhanced precision, potentially leading to cost savings and improved production quality in industrial applications.
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(This article belongs to the Special Issue Optimization and Analysis of Metal Cutting Processes (Volume II))
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Effect of Al/Mg Ratio on the Microstructure and Phase Distribution of Zn-Al-Mg Coatings
Metals 2023, 13(12), 1963; https://doi.org/10.3390/met13121963 - 01 Dec 2023
Abstract
In contrast with studies such as those on the effect of a single elemental variable on Zn-Al-Mg coatings, Mg/Al is considered a variable parameter for evaluating the microstructure of Zn-Al-Mg coatings in this work, and the combined effect of the two elements is
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In contrast with studies such as those on the effect of a single elemental variable on Zn-Al-Mg coatings, Mg/Al is considered a variable parameter for evaluating the microstructure of Zn-Al-Mg coatings in this work, and the combined effect of the two elements is also taken into account. The Mg/Al ratios in the continuous hot-dip plating of low-alumina Zn-Al-Mg coatings were 0.63, 0.75, 1.00, 1.25, and 1.63. respectively, and the microstructures of the different coatings were observed using scanning electron microscopy (SEM). The surface elemental distributions of the coatings were analyzed with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis to understand the phase distributions of the coatings, which mainly consisted of a zinc monomeric phase, a binary eutectic phase (Zn/MgZn2), and a ternary eutectic phase (Zn/Al/MgZn2). Statistical calculations of the phase distributions in colored SEM images were performed using ImageJ-win64 software, comparative analysis of the solidification simulation results was carried out with thermodynamic simulation software (PANDAT-2023), and evaluation of the corrosion resistance of the platings was performed using macroscopic cyclic immersion corrosion experiments. The results show that with the increase in the Mg/Al ratio, the binary eutectic phase in the coatings gradually increased, the variation trend of the ternary eutectic phase was not obvious, and the corrosion resistance of the coatings gradually improved.
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(This article belongs to the Special Issue Feature Paper Collection of “Current Challenges in Corrosion Research”)
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Effect of CaO Content and Annealing Treatment on the Room-Temperature Mechanical Properties of AZ61 and AZ61-CaO Alloys
by
, , , , , and
Metals 2023, 13(12), 1962; https://doi.org/10.3390/met13121962 - 01 Dec 2023
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In the present study, the effect of homogenization treatment on the room-temperature mechanical performance of AZ61, AZ61-0.5CaO and AZ61-1CaO was thoroughly investigated. The as-rolled samples were homogenized at 400 °C for 1 h followed by furnace cooling. Microstructural characterization was carried out using
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In the present study, the effect of homogenization treatment on the room-temperature mechanical performance of AZ61, AZ61-0.5CaO and AZ61-1CaO was thoroughly investigated. The as-rolled samples were homogenized at 400 °C for 1 h followed by furnace cooling. Microstructural characterization was carried out using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). Moreover, room-temperature uniaxial tensile tests were carried out on the non-homogenized and homogenized samples along the rolling direction at the strain rate of 10−3 s−1. Microstructural analysis showed the presence of profuse twinning in non-homogenized samples and the twinning fraction was increased by the addition of CaO content. SEM showed the formation of precipitates in the AZ61-CaO alloys and TEM confirmed the precipitates to be (Mg, Al)2Ca. The room-temperature tensile tests showed that the mechanical properties of AZ61 were slightly reduced by the addition of CaO, which was attributed to the higher local stress concentration due to the twin–twin interactions. Furthermore, the homogenization treatment led to significant enhancement in the YS and UTS of AZ61-1CaO, which is related to the precipitation hardening induced by the intermetallic precipitates.
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Dilation Characteristics of 3D PBF-LB/M AlSi10Mg Alloy
Metals 2023, 13(12), 1961; https://doi.org/10.3390/met13121961 - 30 Nov 2023
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Application deployment of 3D-printed products represents a progressive area of industrial use of specific metal alloys. In parallel with starting points based on mechanical characteristics in the static and cyclic areas, dilation behavior is an important parameter. A typical application is, for example,
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Application deployment of 3D-printed products represents a progressive area of industrial use of specific metal alloys. In parallel with starting points based on mechanical characteristics in the static and cyclic areas, dilation behavior is an important parameter. A typical application is, for example, components in the aerospace sector, where the components are exposed for a short period to a significant temperature difference in both positive and negative values. Current industrial trends lead to the deployment of additive technologies for producing aircraft system components and instrument parts. Testing of AlSi10Mg alloy samples prepared by direct metal laser sintering, in the past DMLS, now according to the standard laser powder bed fusion (PBF-LB/M) method, is carried out by measuring dilation during a controlled temperature course. The AlSi10Mg alloy is used for mechanically less stressed components, from which a high accuracy of functional dimensions is usually required, which can be affected by dilation characteristics in a wide temperature range. Additively produced components have different dilation characteristics within an identical alloy, often dependent on the production method and orientation during 3D printing. The article presents the testing results and subsequent application characteristics of an additively produced aluminum alloy, considering dilation characteristics.
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The Effect of Pore Sealing in a Multilayer Si–O–Zr/Al2O3 Coating Designed to Protect Aluminium from Corrosion
Metals 2023, 13(12), 1960; https://doi.org/10.3390/met13121960 - 30 Nov 2023
Abstract
This study deals with the combination of two corrosion protection strategies for aluminium: barrier protection (provided by a 3.8 μm thick hybrid sol–gel coating) and aluminium pore sealing via the use of a 100 nm thick layer of aluminium oxide. A Si–O–Zr hybrid
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This study deals with the combination of two corrosion protection strategies for aluminium: barrier protection (provided by a 3.8 μm thick hybrid sol–gel coating) and aluminium pore sealing via the use of a 100 nm thick layer of aluminium oxide. A Si–O–Zr hybrid sol–gel coating (TMZ) was synthesised by combining two separately prepared sols (i) tetraethyl orthosilicate and 3-methacryloxypropyl trimethoxysilane and (ii) zirconium(IV) n-propoxide chelated with methacrylic acid. The synthesis of the Si–O–Zr hybrid sol–gel was evaluated at various stages using real-time infrared spectroscopy. A 100 nm thick Al2O3 film was prepared via thermal atomic layer deposition at 160 °C using trimethyl aluminium and water as precursors. The coating and film properties were assessed via focused ion beam/scanning electron microscopy coupled with energy-dispersive X-ray spectrometry. Sealing with the Al2O3 film did not affect the microstructure and composition of the underlying sol–gel coating. The coating’s corrosion performance in 0.1 M NaCl solution was evaluated using electrochemical impedance spectroscopy. Compared to individual coatings, the multilayer TMZ/Al2O3 coating ensured prolonged (more than three weeks) durable corrosion protection for the aluminium. The impedance magnitude increased by two orders compared to the uncoated substrate (|Z|10 mHz from 16 kΩ cm2 to almost 830 MΩ cm2). Thus, the pore sealing of the sol–gel coating using an ALD alumina film produced a protective multilayer coating system, with |Z|10 mHz remaining above 5 MΩ cm2 after four weeks in NaCl solution.
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(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials (Second Edition))
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Effect of Ti/Al Ratio on Precipitation Behavior during Aging of Ni-Cr-Co-Based Superalloys
Metals 2023, 13(12), 1959; https://doi.org/10.3390/met13121959 - 30 Nov 2023
Abstract
Precipitation behaviors of Ni-Cr-Co-based superalloys with different Ti/Al ratios aged at 750, 800, and 850 °C for up to 10,000 h were investigated using scanning and transmission electron microscopy. The Ti/Al ratio did not significantly affect the diameter of the γ′ phase. However,
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Precipitation behaviors of Ni-Cr-Co-based superalloys with different Ti/Al ratios aged at 750, 800, and 850 °C for up to 10,000 h were investigated using scanning and transmission electron microscopy. The Ti/Al ratio did not significantly affect the diameter of the γ′ phase. However, the volume fraction of the γ′ phase increased with increasing Ti/Al ratios. The η phase was not observed in alloys with a small Ti/Al ratio, whereas it was precipitated after aging at 850 °C for 1000 h in alloys with a Ti/Al ratio greater than 0.80. Higher aging temperatures and higher Ti/Al ratios led to faster η formation kinetics and accelerated the degradation of alloys. It is thought that the increase in hardness with an increase in the Ti/Al ratio is attributed to the effective inhibition of the γ′ phase on dislocation movement due to the increase in the volume fraction of the γ′ phase and an increase in the antiphase boundary (APB) energy.
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(This article belongs to the Topic Microstructure and Properties in Metals and Alloys, 2nd Volume)
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Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc
Metals 2023, 13(12), 1958; https://doi.org/10.3390/met13121958 - 30 Nov 2023
Abstract
The present work focuses on the investigation of protective coatings produced on zinc from chitosan (Chit) and an anionic dye, namely cresol red. Cresol red (CR) fulfills the basic requirements to be used as a corrosion inhibitor because it possesses a relatively high
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The present work focuses on the investigation of protective coatings produced on zinc from chitosan (Chit) and an anionic dye, namely cresol red. Cresol red (CR) fulfills the basic requirements to be used as a corrosion inhibitor because it possesses a relatively high molecular weight and includes in its structure oxygen and sulfur atoms as well as aromatic rings. Moreover, it is an anionic compound that can interact with positively charged chitosan to produce reinforced coatings for zinc anti-corrosion protection. The influence of cresol red as a possible corrosion inhibitor for zinc substrates was investigated either in solution or incorporated in Chit coatings. Two preparation methods for the coatings were used: (i) Chit coating impregnation by immersion in the CR solution after Chit deposition on Zn, and (ii) chitosan mixing with the CR solution before applying the dip-coating technique. Potentiodynamic polarization curves were used to determine the kinetic parameters of the corrosion process. Long-term measurements were carried out in wet/dry cyclic conditions by using electrochemical impedance spectroscopy. EIS measurements recorded in 0.2 g/L Na2SO4 at pH = 7 show an important increase in the impedance of the coatings occurring from the first until the fifty-fifth day in a row, in dry–wet cycles. This increase is due to the beneficial effect of CR incorporated in Chitosan and could be, at least partially, related to a consolidation of the Chit coating structure in the presence of CR by crosslinking between Chit and CR molecules. The structure of the coatings was studied, and the interactions between chitosan and cresol red were put into evidence by using FT-IR spectroscopy. Adhesion and wettability measurements were also carried out. The adhesion of Chit incorporating CR on Zn was better than that on glass substrates and reached ~99.99%, suggesting a better affinity of the chitosan coating towards the Zn substrate due to the existence of ZnO on the substrate surface. All the results show that CR could be used on zinc as a corrosion inhibitor incorporated in chitosan at basic pHs, but without taking advantage of its pH-indicating properties, which are lost due to the interactions occurring between the positively charged biopolymer and the negatively charged dye molecule. The preparation method of Chit coating impregnation with CR by immersion in the solution after deposition on Zn led to poorer results than the method in which chitosan was previously mixed with CR before applying the dip-coating technique.
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(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials (Second Edition))
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Investigation of Microstructure and Mechanical Properties of the Repaired Precipitation-Strengthened Ni-Based Superalloy via Laser Melting Deposition
Metals 2023, 13(12), 1957; https://doi.org/10.3390/met13121957 - 30 Nov 2023
Abstract
In this study, a typical γ′ phase precipitation-strengthened Ni-based superalloy DZ411 was repaired using an LMD-based repairing technique with an IN738LC superalloy, and crack-free samples were acquired. The mechanical properties and microstructure of different areas inside the repair sample were investigated, including the
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In this study, a typical γ′ phase precipitation-strengthened Ni-based superalloy DZ411 was repaired using an LMD-based repairing technique with an IN738LC superalloy, and crack-free samples were acquired. The mechanical properties and microstructure of different areas inside the repair sample were investigated, including the IN738LC deposit, the DZ411 substrate, and the interface between these two parts. The differences in mechanical properties between different areas were explained via analyzing fractography and KAM maps. It was found that the coarse carbides of the DZ411 substrate might lead to rapid cracking of grain boundaries, resulting in the worst mechanical properties of the DZ411 substrate. The IN738LC deposit demonstrated significantly superior mechanical properties in comparison to the DZ411 substrate. Its tensile strength exceeded that of the substrate by over 250 MPa, while its relative elongation after fracture was twice as great as that of the substrate. The excellent mechanical properties of the IN738LC deposit could be attributed to its fine microstructure, which resisted rapid cracking and generated a large number of GNDs during the plastic deformation process. For the interface between the deposit and substrate, although its hardness before the tensile test was low, it could also generate many GNDs during the plastic deformation process, hence exhibiting commendable mechanical properties. The research results show that using an LMD-based repairing technique with IN738LC superalloy to repair γ′ phase precipitation-strengthened Ni-based superalloy DZ411 is a feasible solution.
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(This article belongs to the Special Issue Additive Manufacturing of High Temperature Alloys)
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Fatigue Estimation Using Inverse Stamping
Metals 2023, 13(12), 1956; https://doi.org/10.3390/met13121956 - 29 Nov 2023
Abstract
Reverse engineering methods like 3D scanning are becoming common in engineering practice. These methods enable engineers to reproduce the original shape of a scanned part. If other properties are required, then other reverse engineering methods can follow. Estimation of fatigue is a tricky
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Reverse engineering methods like 3D scanning are becoming common in engineering practice. These methods enable engineers to reproduce the original shape of a scanned part. If other properties are required, then other reverse engineering methods can follow. Estimation of fatigue is a tricky task even if the material properties of the base material are known. Fatigue is influenced not only by material properties and the part’s shape but also by technological processes. Fast fatigue life estimation of stamped parts using reverse engineering methods is the target of this paper. The forming process, which has a crucial impact on the fatigue of stamped parts, is considered via inverse stamping. Adaptation of inverse stamping method from shell FEM meshes to volumetric meshes is included. The article also discusses the application of two methods, the Material Law for Steel Sheets (MLSS) and the Method of Variable Slopes (MVS). These methods adjust the fatigue curve based on effective plastic strain calculated by inverse stamping. Calculated results were compared with experimental results. In most situations, there is a good agreement between the calculations and the tests of the specimens without surface coatings. Sometimes, the calculated results are more conservative than the experiments. This is acceptable in component design in terms of reliability. When a Zn-Ni surface coating was applied, the fatigue life of the specimen decreased.
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(This article belongs to the Special Issue Advances in Modeling and Simulation in Metal Forming)
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Corrosion of Fixed Orthodontic Appliances: Causes, Concerns, and Mitigation Strategies
Metals 2023, 13(12), 1955; https://doi.org/10.3390/met13121955 - 29 Nov 2023
Abstract
The orthodontic supply market is a prosperous billion-dollar industry, driven by an increasing demand for orthodontic appliances. The supremacy of metallic first-generation biomaterials is evident for manufacturing brackets, archwires, bands, and other components due to their well-recognized chemical inertness, spontaneous passivation, biocompatibility, and
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The orthodontic supply market is a prosperous billion-dollar industry, driven by an increasing demand for orthodontic appliances. The supremacy of metallic first-generation biomaterials is evident for manufacturing brackets, archwires, bands, and other components due to their well-recognized chemical inertness, spontaneous passivation, biocompatibility, and favorable mechanical properties combination. However, the oral cavity is the ultimate corrosion-promoting environment for any metallic material. In this work, the general picture of the intraoral degradation of fixed orthodontic appliances is first addressed, from the causes to the harmful effects and their oral clinical implications. Current mitigation strategies are also pointed out, including the alloys’ bulk composition adjustment combined with new and advanced manufacturing processes and/or their surface treatment or coating deposition. The versatile use of thin films and coatings stands out with different deposition technologies: Many in vivo and in vitro efforts have been devoted to oral aging, from monolithic to composite architectures and micro- to nano-scale materials, to meet the best and safest oral practice demands. Unfortunately, literature data suggest that even the existing commercially available protective coatings have drawbacks and are fallible. Further multidisciplinary research is still required to effectively mitigate the corrosion behavior of fixed orthodontic appliances.
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(This article belongs to the Special Issue Feature Papers in Biobased and Biodegradable Metals)
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The Activation Energy of Viscous Flow and Liquid–Liquid Structure Transition in Co-B Alloys
Metals 2023, 13(12), 1954; https://doi.org/10.3390/met13121954 - 29 Nov 2023
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The temperature dependences of the kinematic viscosity during heating and cooling have been investigated in Co-B melts with a boron content of up to 30.8 at. A liquid–liquid structural transition was found, which is accompanied by an increase in the activation energy and
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The temperature dependences of the kinematic viscosity during heating and cooling have been investigated in Co-B melts with a boron content of up to 30.8 at. A liquid–liquid structural transition was found, which is accompanied by an increase in the activation energy and cluster size, as well as a significant decrease in the density of the melt. The liquid–liquid structural transition was associated with the formation of clusters with a short-range order of Co23B6 in the intermediate temperature region. At low and high temperatures, clusters of the order of an atomic size are active participants in the viscous flow. It was shown that with an increase in the cluster size, the activation energy increases and the viscosity of melts decreases. The formation of large Co23B6 clusters during the cooling of melt with low boron content leads to undercooling and the appearance of the transition temperature region with high activation energy, although this region does not exist during the heating stage.
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Designing Quaternary and Quinary Refractory-Based High-Entropy Alloys: Statistical Analysis of Their Lattice Distortion, Mechanical, and Thermal Properties
Metals 2023, 13(12), 1953; https://doi.org/10.3390/met13121953 - 29 Nov 2023
Abstract
The rapid evolution in materials science has resulted in a significant interest in high-entropy alloys (HEAs) for their unique properties. This study focuses on understanding both quaternary and quinary body-centered cubic (BCC) of 12 refractory-based HEAs, and on analysis of their electronic structures,
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The rapid evolution in materials science has resulted in a significant interest in high-entropy alloys (HEAs) for their unique properties. This study focuses on understanding both quaternary and quinary body-centered cubic (BCC) of 12 refractory-based HEAs, and on analysis of their electronic structures, lattice distortions, mechanical, and thermal properties. A comprehensive assessment is undertaken by means of density functional theory (DFT)-based first principles calculations. It is well known that multiple constituents lead to notable lattice distortions, especially in quinary HEAs. This distortion, in turn, has significant implications on the electronic structure that ultimately affect mechanical and thermal behaviors of these alloys such as ductility, lattice thermal conductivity, and toughness. Our in-depth analysis of their electronic structures revealed the role of valence electron concentration and its correlation with bond order and mechanical properties. Local lattice distortion (LD) was investigated for these 12 HEA models. M1 (WTiVZrHf), M7 (TiZrHfW), and M12 (TiZrHfVNb) have the highest LD whereas the models M3 (MoTaTiV), M5 (WTaCrV), M6 (MoNbTaW), and M9 (NbTaTiV) have the less LD. Furthermore, we investigated the thermal properties focusing on Debye temperature (ΘD), thermal conductivity (κ), Grüneisen parameter (γα), and dominant phonon wavelength (λdom). The NbTaTiV(M9) and TiVNbHf(M10) models have significantly reduced lattice thermal conductivities (κL). This reduction is due to the mass increase and strain fluctuations, which in turn signify lattice distortion. The findings not only provide an understanding of these promising materials but also offer guidance for the design of next-generation HEAs with properties tailored for potential specific applications.
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(This article belongs to the Special Issue Feature Papers in Entropic Alloys and Meta-Metals)
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Fabrication of Electron Beam Melted Titanium Aluminide: The Effects of Machining Parameters and Heat Treatment on Surface Roughness and Hardness
by
, , , , , , , and
Metals 2023, 13(12), 1952; https://doi.org/10.3390/met13121952 - 28 Nov 2023
Abstract
Titanium aluminide alloys have gained attention for their lightweight and high-performance properties, particularly in aerospace and automotive applications. Traditional manufacturing methods such as casting and forging have limitations on part size and complexity, but additive manufacturing (AM), specifically electron beam melting (EBM), has
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Titanium aluminide alloys have gained attention for their lightweight and high-performance properties, particularly in aerospace and automotive applications. Traditional manufacturing methods such as casting and forging have limitations on part size and complexity, but additive manufacturing (AM), specifically electron beam melting (EBM), has overcome these challenges. However, the surface quality of AM parts is not ideal for sensitive applications, so post-processing techniques such as machining are used to improve it. The combination of AM and machining is seen as a promising solution. However, research on optimizing machining parameters and their impact on surface quality characteristics is lacking. Limited studies exist on additively manufactured TiAl alloys, necessitating further investigation into surface roughness during EBM TiAl machining and its relationship to cutting speed. As-built and heat-treated TiAl samples undergo machining at different feed rates and surface speeds. Profilometer analysis reveals worsened surface roughness in both heat-treated and non-heat-treated specimens at certain machining conditions, with higher speeds exacerbating edge cracks and material pull-outs. The hardness of the machined surfaces remains consistent within the range of 32–33.1 HRC at condition 3C (45 SFM and 0.1 mm/tooth). As-built hardness remains unchanged with increasing spindle and cutting head speeds. Conversely, heat-treated condition 3C surfaces demonstrate greater hardness than condition 1A (15 SFM, and 0.04 mm/tooth), indicating increased hardness with varying feed and surface speeds. This suggests crack formation in the as-built condition is considered to be influenced by factors beyond hardness, such as deformation-related grain refinement/strain hardening, while hardness and the existence of the α2 phase play a more significant role in heat-treated surfaces.
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(This article belongs to the Special Issue Additive Manufacturing of Titanium Alloys 2022)
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Effect of Nanostructuring on Operational Properties of 316LVM Steel
by
, , , , , , , , and
Metals 2023, 13(12), 1951; https://doi.org/10.3390/met13121951 - 28 Nov 2023
Abstract
In this study, high-pressure torsion (HPT) was used to process austenitic 316LVM stainless steel at 20 °C and 400 °C. The effects of HPT on the microstructure, mechanical, and functional properties of the steel were investigated. By applying both HPT modes on the
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In this study, high-pressure torsion (HPT) was used to process austenitic 316LVM stainless steel at 20 °C and 400 °C. The effects of HPT on the microstructure, mechanical, and functional properties of the steel were investigated. By applying both HPT modes on the 316LVM steel, a nanocrystalline state with an average size of the structural elements of ~46–50 nm was achieved. The density of the dislocations and twins present in the austenite phase varied depending on the specific HPT conditions. Despite achieving a similar structural state after HPT, the deformation temperatures used has different effects on the mechanical and functional properties of the steel. After HPT at 20 °C, the yield strength of the 316L steel increased by more than nine times up to 1890 MPa, and the fatigue limit by more than two times up to 550 MPa, when compared to its coarse-grained counter-parts. After HPT at 20 °C, the 316LVM steel exhibited better ductility, higher low-cycle fatigue resistance, greater resistance to corrosion, and improved in vitro biocompatibility compared to processing at 400 °C. The reasons for the deterioration of the properties after HPT at 400 °C are discussed in the article.
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(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Improving Structural Integrity of Metals: From Bulk to Surface)
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Open AccessCommunication
Crystal Orientation and Dislocation Slip
Metals 2023, 13(12), 1950; https://doi.org/10.3390/met13121950 - 28 Nov 2023
Abstract
It is a widely held belief that dislocation slip has a direct effect on crystal orientation. Some of the confusion may be attributed to semantics when researchers are referring to related effects of dislocations on crystal orientation; either elastic bending due to constraints
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It is a widely held belief that dislocation slip has a direct effect on crystal orientation. Some of the confusion may be attributed to semantics when researchers are referring to related effects of dislocations on crystal orientation; either elastic bending due to constraints or the creation of geometrically necessary dislocations by climb. This communication highlights the distinction between the two and discusses why what is often imagined conflicts with what is real and possible. It is demonstrated that deformation-induced changes in the orientation of crystals are primarily limited to twinning and collections of geometrically necessary dislocations (GNDs), which in the most extreme cases are sub-grain boundaries. Alternate explanations for texture changes related to dislocation slip are provided, and they challenge the notion that grains can simply rotate because of dislocation slip through some undefined mechanism.
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(This article belongs to the Special Issue Feature Papers in Crystallography and Applications of Metallic Materials)
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