Journal Description
Alloys
Alloys
is an international, peer-reviewed, open access journal on all aspects of alloys science and engineering, published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 19.4 days after submission; acceptance to publication is undertaken in 6.6 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
- Alloys is a companion journal of Metals.
Latest Articles
Research on the Corrosion Resistance and Cytotoxicity of Medical Forged Co-28Cr-6Mo Alloy
Alloys 2024, 3(4), 269-280; https://doi.org/10.3390/alloys3040016 - 18 Oct 2024
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Co-Cr-Mo alloy as a human body implant material has a long history, because of its excellent corrosion resistance and biocompatibility, and is widely used in human hip joint materials. Co-Cr-Mo alloy in the human body is often in a passivation state; the formation
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Co-Cr-Mo alloy as a human body implant material has a long history, because of its excellent corrosion resistance and biocompatibility, and is widely used in human hip joint materials. Co-Cr-Mo alloy in the human body is often in a passivation state; the formation of dense oxide film on the alloy surface prevents further corrosion of the alloy. The main component of the passivation film is the oxide of Cr, so a layer of oxide film formed by Cr on the surface of Co-Cr-Mo alloy is the reason for its good corrosion resistance. In biocompatibility, cytotoxicity is the first choice and necessary option for biological evaluation, and cytotoxicity can quickly detect the effect of materials on cells in a relatively short time. Therefore, this research conducted a comparative evaluation on the corrosion resistance and biocompatibility of forged Co-Cr-Mo alloys produced in domestic and foreign alloys in line with medical standards. Three simulated human body fluids and Princeton electrochemical station were selected for corrosion resistance experiments, and it was found that the corrosion resistance of four alloys in sodium citrate solution inside and outside China would be reduced. All the alloys exhibit secondary passivation behavior in Hanks solution, which improves the corrosion resistance of the alloys. According to the self-corrosion potential Ecorr analysis, the corrosion resistance of domestic B alloy is the best, while that of foreign R31537 alloy is poor. In the biocompatibility experiment, the biocompatibility of Co-Cr-Mo alloy was evaluated through the measurement of contact Angle and cytotoxicity reaction. The experimental results show that Co-Cr-Mo alloy is a hydrophilic material, and the contact Angle of foreign R31537 alloy is smaller, indicating that the surface of R31537 alloy is more suitable for cell adhesion and spreading. According to the qualitative and quantitative analysis of the cytotoxicity experiment, the toxic reaction grade of domestic A, B and R31537 alloy is grade 1, the toxic reaction grade of C alloy is grade 2, and C alloy has a slight toxic reaction.
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Open AccessArticle
Assessing the Corrosive Effects of Unmelted Particles in Additively Manufactured Ti6Al4V: A Study in Simulated Body Fluid
by
Surinder Pal, Xavier Velay and Waqas Saleem
Alloys 2024, 3(4), 257-268; https://doi.org/10.3390/alloys3040015 - 9 Oct 2024
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This study investigates the corrosion behavior of Grade 23 Ti6Al4V alloys produced through laser powder bed fusion (L-PBF) when exposed to simulated body fluid at room temperature, focusing on the role of unmelted particles. This research aims to understand how these microstructural features,
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This study investigates the corrosion behavior of Grade 23 Ti6Al4V alloys produced through laser powder bed fusion (L-PBF) when exposed to simulated body fluid at room temperature, focusing on the role of unmelted particles. This research aims to understand how these microstructural features, resulting from the additive manufacturing process, influence the corrosion resistance of the alloys. It was observed that unmelted particles serve as critical sites for initiating localized corrosion, including pitting, which significantly compromises the material’s overall durability. Electrochemical testing and detailed surface analysis revealed that these particles, alongside other defects such as voids, exacerbate the susceptibility to corrosion in biomedical environments where high material reliability is paramount. Weight loss measurements conducted over exposure periods of 48 h, 96 h, and 144 h demonstrated a progressive increase in corrosion, correlating with the presence of unmelted particles. These findings underscore the importance of optimizing L-PBF processing parameters to minimize the formation of unmelted particles, thereby enhancing corrosion resistance and extending the operational lifespan of Ti6Al4V implants in biomedical applications.
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Open AccessArticle
SHS-Hydrogenation, Thermal Dehydrogenation, and Plasma Spheroidization to Produce Spherical Titanium Powders from Titanium Sponge
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Nikita Cherezov, Andrey Fadeev, Andrey Samokhin and Mikhail Alymov
Alloys 2024, 3(3), 246-256; https://doi.org/10.3390/alloys3030014 - 17 Sep 2024
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Additive manufacturing is a promising and actively developing method for the synthesis of metal products. The development of techniques for the production of spherical powder particles with specified properties from metals and alloys represents a significant challenge in the field of additive manufacturing.
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Additive manufacturing is a promising and actively developing method for the synthesis of metal products. The development of techniques for the production of spherical powder particles with specified properties from metals and alloys represents a significant challenge in the field of additive manufacturing. A new method for the production of titanium powders with spherical particles has been proposed, including the method of hydrogenation and dehydrogenation with subsequent spheroidization in thermal plasma. Titanium sponge, used as a feedstock, was saturated with hydrogen using the energy-efficient self-propagating high-temperature synthesis (SHS) method. The resulting hydride was then mechanically ground and then dehydrogenated by thermal decomposition in a vacuum furnace. The resulting precursor was subjected to plasma treatment, which resulted in a product (titanium powder) with a high degree of spheroidization. The physical, chemical, and technological parameters of the titanium powders were investigated. It was found that the final product, spherical titanium powder, has the necessary properties for use in additive manufacturing technologies.
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Open AccessArticle
Production of Neutron-Absorbing Zirconium-Boron Alloy by Self-Propagating High-Temperature Synthesis and Its Refining via Electron Beam Melting
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Anatoly Mukhachev, Dmytro Yelatontsev, Olena Kharytonova and Nickolay Grechanyuk
Alloys 2024, 3(3), 232-245; https://doi.org/10.3390/alloys3030013 - 13 Sep 2024
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The paper presents the results of the study of the processes of self-propagating high-temperature synthesis of Zr-1%B alloy and its refining by electron beam melting. Experiments on the influence of boron’s amorphous and crystalline modifications on the safety parameters of the synthesis process
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The paper presents the results of the study of the processes of self-propagating high-temperature synthesis of Zr-1%B alloy and its refining by electron beam melting. Experiments on the influence of boron’s amorphous and crystalline modifications on the safety parameters of the synthesis process of Zr-1%B alloy necessitated the conversion of amorphous boron into crystalline form by electron beam melting, with an increase in its purity from 94% to 99.9%. High efficiency of vacuum induction and electron beam equipment was demonstrated, which provided a high purity of the Zr-1%B alloy of at least 99.9%. The alloy ingots had a uniform distribution of the alloying element (boron) all over the volume. The obtained alloy is suitable for the production of materials with thermal neutron capture cross-sections of up to 40 barns for neutron protection.
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Open AccessFeature PaperArticle
Microstructure and Properties of Complex Concentrated C14–MCr2 Laves, A15–M3X and D8m M5Si3 Intermetallics in a Refractory Complex Concentrated Alloy
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Nik Tankov, Claire Utton and Panos Tsakiropoulos
Alloys 2024, 3(3), 190-231; https://doi.org/10.3390/alloys3030012 - 2 Sep 2024
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Abstract: The refractory complex concentrated alloy (RCCA) 5Al–5Cr–5Ge–1Hf–6Mo–33Nb–19Si–20Ti–5Sn–1W (at.%) was studied in the as-cast and heat-treated conditions. The partitioning of solutes in the as-cast and heat-treated microstructures and relationships between solutes, between solutes and the parameters VEC and Δχ, and between these parameters,
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Abstract: The refractory complex concentrated alloy (RCCA) 5Al–5Cr–5Ge–1Hf–6Mo–33Nb–19Si–20Ti–5Sn–1W (at.%) was studied in the as-cast and heat-treated conditions. The partitioning of solutes in the as-cast and heat-treated microstructures and relationships between solutes, between solutes and the parameters VEC and Δχ, and between these parameters, most of which are reported for the first time for metallic UHTMs, were shown to be important for the properties of the stable phases A15–Nb3X and the D8m βNb5Si3. The nano-hardness and Young’s modulus of the A15–Nb3X and the D8m βNb5Si3 of the heat-treated alloy were measured using nanoindentation and changes in these properties per solute addition were discussed. The aforementioned relationships, the VEC versus Δχ maps and the VEC, Δχ, time, or VEC, Δχ, Young’s modulus or VEC, Δχ, nano-hardness diagrams of the phases in the as-cast and heat-treated alloy, and the properties of the two phases demonstrated the importance of synergy and entanglement of solutes, parameters and phases in the microstructure and properties of the RCCA. The significance of the new data and the synergy and entanglement of solutes and phases for the design of metallic ultra-high temperature materials were discussed.
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Open AccessArticle
The Activation of Magnesium Sintering by Zinc Addition
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Serhii Teslia, Mykyta Kovalenko, Mariia Teslia, Mykhailo Vterkovskiy, Ievgen Solodkyi, Petro Loboda and Tetiana Soloviova
Alloys 2024, 3(3), 178-189; https://doi.org/10.3390/alloys3030011 - 6 Aug 2024
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Light alloys based on magnesium are widely used in most areas of science and technology. However, magnesium powder alloys are quite difficult to sinter due to the stable film of oxides that counteracts diffusion. Therefore, finding a method to activate magnesium sintering is
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Light alloys based on magnesium are widely used in most areas of science and technology. However, magnesium powder alloys are quite difficult to sinter due to the stable film of oxides that counteracts diffusion. Therefore, finding a method to activate magnesium sintering is urgent. This study examines the effect of adding 5 wt. % and 10 wt. % zinc to the sintering pattern of magnesium powders at 430 °C; a dwell of 30 min was used to homogenize at the densification’s temperature. Scanning electron microscopy (SEM) was used to characterize the alloy’s microstructure, while the phase composition was characterized using X-ray diffraction (XRD) and energy dispersion spectroscopy (EDS). The sintering densities of Mg–5Zn and Mg–10Zn were found to be 88% and 92%, respectively. The results show that after sintering, a heterophase structure of the alloy is formed based on a solid solution and phases MgZn and Mg50Zn21. To establish the sintering mechanism, the interaction at the MgO and Zn melt phase interface was analyzed using the sessile drop method. The minimum contact angle—65°—was discovered at 500 °C with a 20 min holding time. It was demonstrated that the sintering process in the Mg–Zn system proceeds through the following stages: (1) penetration of zinc into oxide-free surfaces; (2) crystallization of a solid solution, intermetallics; and (3) the removal of magnesium oxide from the particle surface, with oxide particles deposited on the surface of the sample.
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Open AccessArticle
Reduction of Copper Smelting Slag by Carbon for Smelting Cu-Fe Alloy
by
Weijun Huang, Yajing Liu and Tao Jiang
Alloys 2024, 3(3), 164-177; https://doi.org/10.3390/alloys3030010 - 20 Jul 2024
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An innovative technology for the direct reduction of copper slag was studied while smelting Cu-Fe alloy by carbon to recover the main valuable elements from the copper smelting slag. The melting temperature of samples first decreased, followed by an increase in Fe3
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An innovative technology for the direct reduction of copper slag was studied while smelting Cu-Fe alloy by carbon to recover the main valuable elements from the copper smelting slag. The melting temperature of samples first decreased, followed by an increase in Fe3O4 content in slag. The melting temperature reached the minimum temperature of 1157 °C once the Fe3O4 content was about 8 wt%. The recovery rate of copper and iron first increased gradually, followed by a rapid increase in the modifier (CaO). Subsequently, the rise in the recovery rate slowed down. The reduction rate of copper and iron only increased by 1.61% and 1.05% from 5 wt% CaO to 10 wt% CaO, but significantly increased by 8.89% and 14.21% from 10 wt% CaO to 25 wt% CaO, and remained almost unchanged beyond 25 wt% CaO. This could be attributed to the reaction between modifier (CaO) and silicate in acidic copper slag to generate low melting point composite oxide while replacing free iron oxides, improving the melting properties and reduction reaction. Meanwhile, the recovery rates of copper and iron increased with the increase of reaction time, reaction temperature, and reduction agent in a certain range. To obtain good element yield, the optimum conditions for reducing copper and iron from the molten copper slag were determined to be 1500 °C, 14 wt% C, 20–25 wt% CaO, and 60–80 min. The recovery rates of iron and copper reached about 90% and 85%, and the contents of iron and copper in alloy reached about 91–93 wt% and 5–7 wt%, respectively. The tailing was mainly composed of Ca3Si3O9, Ca(Mg,Al)(Si,Al)2O6, and SiO2, which could be used as a raw material for cement and pelletizing.
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Open AccessEditorial
Preamble for the “Feature Paper Collection of Advanced Research on Alloys”
by
Nikki Stanford
Alloys 2024, 3(3), 161-163; https://doi.org/10.3390/alloys3030009 - 26 Jun 2024
Abstract
This year, several hot topics have emerged in alloy research and design; we have collected a few of these in this feature paper collection for your enjoyment [...]
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(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)
Open AccessArticle
Effect of Annealing Temperature on Microstructure and Properties of Solid Solution Extruded Mg–2.0Zn–1.0Y–0.5Zr Alloys
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Junguang He, Zhenfei Cheng, Jiuba Wen, Peiwu Tian, Wuyun Feng, Xiangyang Zheng and Yuan Gong
Alloys 2024, 3(2), 140-160; https://doi.org/10.3390/alloys3020008 - 23 May 2024
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In this investigation, the effects of different annealing temperatures (180, 200, 220, 240, 260, and 280 °C) on the microstructure evolution and properties of an extruded Mg–2.0Zn–1.0Y–0.5Zr (wt%) magnesium alloys were determined. Optical microscopy (OM), scanning electron microscopy (SEM), immersion corrosion, electrochemical corrosion
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In this investigation, the effects of different annealing temperatures (180, 200, 220, 240, 260, and 280 °C) on the microstructure evolution and properties of an extruded Mg–2.0Zn–1.0Y–0.5Zr (wt%) magnesium alloys were determined. Optical microscopy (OM), scanning electron microscopy (SEM), immersion corrosion, electrochemical corrosion experiments, and tensile testing were performed. Research has found that combining hot extrusion with subsequent low-temperature annealing significantly improves the strength, plasticity, and corrosion resistance of alloys due to grain refinement and a reduced dislocation density. The alloy was completely recrystallized at an annealing temperature of 240 °C for 4 h after solid solution extrusion, and the grains were fine and uniform, demonstrating the best comprehensive properties. Its corrosion rate, ultimate tensile strength, yield strength, and elongation were 0.454 ± 0.023 mm/y, 346.7 ± 8.9 MPa, 292.4 ± 6.9 MPa, and 19.0 ± 0.4%, respectively. The corrosion mechanism of the specimens under extruded and annealed conditions was analyzed. After annealing at 240 °C for 4 h, the dislocation and bimodal grain structure of the samples were almost eliminated, resulting in uniform and fine grains, which were conducive to the formation of a more uniform and denser oxide film, thus improving the corrosion resistance of the alloy.
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Open AccessArticle
First-Principles Study on Thermodynamic, Structural, Mechanical, Electronic, and Phonon Properties of tP16 Ru-Based Alloys
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Bhila Oliver Mnisi, Moseti Evans Benecha and Malebo Meriam Tibane
Alloys 2024, 3(2), 126-139; https://doi.org/10.3390/alloys3020007 - 15 Apr 2024
Cited by 2
Abstract
Transition metal-ruthenium alloys are promising candidates for ultra-high-temperature structural applications. However, the mechanical and electronic characteristics of these alloys are not well understood in the literature. This study uses first-principles density functional theory calculations to explore the structural, electronic, mechanical, and phonon properties
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Transition metal-ruthenium alloys are promising candidates for ultra-high-temperature structural applications. However, the mechanical and electronic characteristics of these alloys are not well understood in the literature. This study uses first-principles density functional theory calculations to explore the structural, electronic, mechanical, and phonon properties of X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) binary alloys in the tP16 crystallographic phase. We find that Mn3Ru, Sc3Ru, Ti3Ru, V3Ru, and Zn3Ru have negative heats of formation and hence are thermodynamically stable. Mechanical analysis (Cij) indicates that all tP16-X3Ru alloys are mechanically stable except, Fe3Ru and Cr3Ru. Moreover, these compounds exhibit ductility and possess high melting temperatures. Furthermore, phonon dispersion curves indicate that Cr3Ru, Co3Ru, Ni3Ru, and Cu3Ru are dynamically stable, while the electronic density of states reveals all the X3Ru alloys are metallic, with a significant overlap between the valence and conduction bands at the Fermi energy. These findings offer insights into the novel properties of the tP16 X3Ru intermetallic alloys for the exploration of high-temperature structural applications.
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(This article belongs to the Topic Microstructure and Properties in Metals and Alloys, 3rd Volume)
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Open AccessReview
Mechanism of Electropulsing Treatment Technology for Flow Stress of Metal Material: A Review
by
Bobo Lu, Kai Tang, Mingxia Wu, Yi Yang and Gang Yang
Alloys 2024, 3(1), 96-125; https://doi.org/10.3390/alloys3010006 - 21 Mar 2024
Cited by 3
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Residual stress is caused by non–uniform deformation caused by non–uniform force, heat and composition, which is of great significance in engineering applications. It is assumed that the residual stress is always the upper limit of the elastic limit, so the reduction of the
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Residual stress is caused by non–uniform deformation caused by non–uniform force, heat and composition, which is of great significance in engineering applications. It is assumed that the residual stress is always the upper limit of the elastic limit, so the reduction of the flow stress will reduce the residual elastic stress. It is particularly important to control the flow stress in metal materials. Compared with traditional methods, the use of electropulsing treatment (EPT) technology stands out due to its energy–efficient, highly effective, straightforward and pollution–free characteristics. However, there are different opinions about the mechanism of reducing flow stress through EPT due to the conflation of the effects from pulsed currents. Herein, a clear correlation is identified between induced stress levels and the application of pulsed electrical current. It was found that the decrease in flow stress is positively correlated with the current density and the duration of electrical contact and current action time. We first systematically and comprehensively summarize the influence mechanisms of EPT on dislocations, phase, textures and recrystallization. An analysis of Joule heating, electron wind effect, and thermal–induced stress within metal frameworks under the influence of pulsed currents was conducted. And the distribution of electric, thermal and stress fields under EPT are discussed in detail based on a finite element simulation (FES). Finally, some new insights into the issues and challenges of flow stress drops caused by EPT are proposed, which is critically important for advancing related mechanism research and the revision of theories and models.
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Open AccessFeature PaperArticle
On the Microstructure and Properties of Complex Concentrated bcc Solid Solution and Tetragonal D8m M5Si3 Silicide Phases in a Refractory Complex Concentrated Alloy
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Nik Tankov, Claire Utton and Panos Tsakiropoulos
Alloys 2024, 3(1), 59-95; https://doi.org/10.3390/alloys3010005 - 7 Mar 2024
Cited by 1
Abstract
In this work, the refractory complex concentrated alloy (RCCA) 3.5Al–4Cr–6Ge–1Hf–5Mo–36Nb–22Si–1.5Sn–20Ti–1W (at.%) was studied in the as cast and heat treated conditions (100 h or 200 h at 1500 °C). There was strong macrosegregation of Si in the 0.6 kg button/ingot of the cast
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In this work, the refractory complex concentrated alloy (RCCA) 3.5Al–4Cr–6Ge–1Hf–5Mo–36Nb–22Si–1.5Sn–20Ti–1W (at.%) was studied in the as cast and heat treated conditions (100 h or 200 h at 1500 °C). There was strong macrosegregation of Si in the 0.6 kg button/ingot of the cast alloy, in which A2 solid solution, D8m βNb5Si3, C14-NbCr2 Laves phase and Tiss and a ternary eutectic of the A2, D8m and C14 phases were formed. The partitioning of Ti in the as cast and heat treated microstructure and its relationships with other solutes was shown to be important for the properties of the A2 solid solution and the D8m βNb5Si3, which were the stable phases at 1500 °C. The near surface microstructure of the alloy was contaminated with oxygen after heat treatment under flowing Ar. For the aforementioned phases, it was shown, for the first time, that there are relationships between solutes, between solutes and the parameters VEC, Δχ and δ, between the said parameters, and between parameters and phase properties. For the contaminated with oxygen solid solution and silicide, trends in relationships between solutes, between solutes and oxygen content and between the aforementioned parameters and oxygen content also were shown for the first time. The nano-hardness and Young’s modulus of the A2 solid solution and the D8m βNb5Si3 of the as cast and heat-treated alloy were measured using nanoindentation. Changes of nano-hardness and Young’s modulus of the A2 solid solution and D8m βNb5Si3 per solute addition for this multiphase RCCA were discussed. The nano-hardness and Young’s modulus of the solid solution and the βNb5Si3, respectively, were 9.5 ± 0.2 GPa and 177.4 ± 5.5 GPa, and 17.55 ± 0.5 GPa and 250.27 ± 6.3 GPa after 200 h at 1500 °C. The aforementioned relationships and properties of the two phases demonstrated the importance of synergy and entanglement of solutes, parameters and phases in the microstructure and properties of the RCCA. Implications of synergy and entanglement for the design of metallic ultra-high temperature materials were emphasised.
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(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)
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Open AccessArticle
Oxidation of Fe35Mn21Ni20Cr12Al12 High Entropy Alloy in Dry Air
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Lamiaa Z. Mohamed, Sanaa S. Abd ElMoamen, Seung Jo Yoo and Mohamed Abdel-Hady Gepreel
Alloys 2024, 3(1), 43-58; https://doi.org/10.3390/alloys3010004 - 23 Feb 2024
Abstract
The isothermal oxidation of a Fe35Mn21Ni20Cr12Al12 high entropy alloy (HEA) was investigated in dry air for 50 h at 500, 600, and 700 °C after 90% cold rolling. The Fe35Mn21Ni
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The isothermal oxidation of a Fe35Mn21Ni20Cr12Al12 high entropy alloy (HEA) was investigated in dry air for 50 h at 500, 600, and 700 °C after 90% cold rolling. The Fe35Mn21Ni20Cr12Al12 HEA behaves according to the linear oxidation rate with rate constants of 1 × 10−6, 3 × 10−6, and 7 × 10−6 g/(cm2·s) for oxidation at 500 °C, 600 °C, and 700 °C, respectively. The activation energy for oxidation of the HEA was calculated to be 60.866 KJ/mole in the 500–700 °C temperature range. The surface morphology and phase identification of the oxide layers were characterized. The formation of MnO2, Mn2O3, Mn3O4, Cr2O3, and Al2O3 in the oxide layers along with Fe2O3 is the key to the oxidation mechanism. The elemental mapping and line EDX scans were performed to identify the oxidation mechanisms.
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(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)
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Open AccessArticle
Optical Properties of AgAu Alloy Clusters: Effect of Chemical Configuration along a Rearrangement Pathway
by
Hans-Christian Weissker and Florent Calvo
Alloys 2024, 3(1), 31-42; https://doi.org/10.3390/alloys3010003 - 20 Feb 2024
Abstract
Gold and silver are, for all their chemical similarities, optically very different. Small Ag clusters show a localized surface-plasmon resonance (LSPR), whereas in Au clusters smaller than about 300 atoms, the resonance is absent due to the coupling with the interband transitions from
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Gold and silver are, for all their chemical similarities, optically very different. Small Ag clusters show a localized surface-plasmon resonance (LSPR), whereas in Au clusters smaller than about 300 atoms, the resonance is absent due to the coupling with the interband transitions from the d electrons. This opens the possibility of tuning the cluster properties depending on their composition and chemical configuration. Earlier work on AgAu alloy clusters has shown that the outermost shell of atoms is crucial to their overall optical properties. In the present contribution, we consider the optical spectroscopic properties associated with the structural rearrangement in 55-atom AgAu alloy clusters in which the core transforms from pure silver to pure gold. Calculations using time-dependent density-functional theory are complemented by an in-depth study of the subtle effects that the chemical configuration has on the details of the materials’ d bands. Although the cluster surface remains alloyed, the geometrical changes translate into strong variations in the optical properties.
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(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)
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Open AccessArticle
Exploring Synergistic Effect on the Stability of Ni-, Pd-, Ir-Doped TiN (N = 1–15) Nanoparticles
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Tshegofatso Phaahla, Phuti Ngoepe and Hasani Chauke
Alloys 2024, 3(1), 15-30; https://doi.org/10.3390/alloys3010002 - 26 Jan 2024
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Bimetallic nanoclusters have attracted great interest due to their ability to enhance the catalytic properties of nanoclusters through synergetic effects that emerge from the combination of the metal nanocluster with different transition metal (TM) species. However, their indefinite composition and broad distribution hinder
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Bimetallic nanoclusters have attracted great interest due to their ability to enhance the catalytic properties of nanoclusters through synergetic effects that emerge from the combination of the metal nanocluster with different transition metal (TM) species. However, their indefinite composition and broad distribution hinder the insightful understanding of the interaction between these invasive metals in bimetallic doped nanoalloys. In this study, we report a density functional theory calculation with the PBEsol exchange-correlation functional for 16-atom TiN−1TM (TM = Ni, Ir, Pd) nanoalloys, which provides new insights into the synergetic effect of these invasive metals. The probe into the effect of these metal impurities revealed that the replacement of a Ti atom with Ni, Ir and Pd enhances the relative stability of the nanoalloys, and the maximum stability for a lower bimetallic composition is reached for Ti4Ir, Ti5Pd and Ti7Ni. The most stable nanoalloy is reached for the Ti12Ir cluster in comparison with the Ti12Pd and Ti12Ni clusters and pure Ti13 monoatomic nanocluster. This stability trend is as revealed well by both the binding energy and the dissociation energy. The average HOMO-LUMO gap for the bigger clusters revealed that the valence electrons in the HOMO can absorb lower energy, which is indicatory of a higher reactivity and lower stability. The quantum confinement is higher for the smaller clusters, which illustrates a higher stability and lower reactivity for those systems.
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Open AccessArticle
The Effect of the Environment on the Case Hardening Characteristics of AISI 1018 Steel during Cassava Leaf Pack Cyaniding
by
Renee Erica Gordon, Egwu Eric Kalu, Adelana Rasak Adetunji, Dorr Campbell and Peter N. Kalu
Alloys 2024, 3(1), 1-14; https://doi.org/10.3390/alloys3010001 - 31 Dec 2023
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As part of a comprehensive study on eco-friendly processing techniques, the influence of the heat treatment environment on the case hardening of AISI 1018 steel using pulverized cassava leaf was studied. The process was carried out at two different temperatures (850 °C and
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As part of a comprehensive study on eco-friendly processing techniques, the influence of the heat treatment environment on the case hardening of AISI 1018 steel using pulverized cassava leaf was studied. The process was carried out at two different temperatures (850 °C and 950 °C) and under three environmental conditions: Process 1, the control experiment, was carried out in air only; in Process 2, the medium comprised pulverized cassava leaves; and in Process 3 a combination of pulverized cassava leaves plus barium carbonate (BaCO3) was used as an energizer (CBC mixture). Vickers microhardness testing and scanning electron microscopy were used to evaluate the effect of the processing environment on the case hardening of the steel. As expected, regardless of the processing temperature, Process 1 resulted in little or no hardening of the steel surface. However, notable case hardening occurred when the steel specimens were subjected to either Process 2 or Process 3. Furthermore, the inclusion of barium carbonate in Process 3 significantly enhanced the case hardening effectiveness of the cassava leaf in terms of the rate of and maximum hardness achieved. A maximum enhancement was observed at 950 °C. After 1 h, the increase in hardness was 160% and 280% for Process 2 and Process 3, respectively. Upon increasing the processing time to 5 h, the increase in hardness due to Process 2 was raised to 254%, while that of Process 3 remained at approximately 280%. The diffusivity of AISI 1018 was calculated using the microhardness data. The diffusivity was highest in Process 2 samples with values of 1.568 × 10−9 m2/s at 850 °C and 1.893 × 10−9 m2/s at 950 °C. Effective case hardening of AISI 1018 steel was carried out using the medium of cassava leaf, without the addition of barium carbonate (BaCO3) as an energizer.
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Open AccessFeature PaperArticle
Modelling Microstructure in Casting of Steel via CALPHAD-Based ICME Approach
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Chunhui Luo, Karin Hansson, Zhili Song, Debbie Ågren, Ewa Sjöqvist Persson, Fredrik Cederholm and Changji Xuan
Alloys 2023, 2(4), 321-343; https://doi.org/10.3390/alloys2040021 - 28 Nov 2023
Abstract
Integrated computational materials engineering (ICME) is emerging as an increasingly powerful approach to integrate computational materials science tools into a holistic system and address the multiscale modeling challenges in the processing of advanced steels. This work aims at incorporating macroscopic model (finite element-based
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Integrated computational materials engineering (ICME) is emerging as an increasingly powerful approach to integrate computational materials science tools into a holistic system and address the multiscale modeling challenges in the processing of advanced steels. This work aims at incorporating macroscopic model (finite element-based thermal model) and microscopic model (CALPHAD-based microstructure model), building an industry-oriented computational tool (MICAST) for casting of steels. Two case studies were performed for solidification simulations of tool steel and stainless steel by using the CALPHAD approach (Thermo-Calc package and CALPHAD database). The predicted microsegregation results agree with the measured ones. In addition, two case studies were performed for continuous casting and ingot casting with selected steel grades, mold geometries and process conditions. The temperature distributions and histories in continuous casting and ingot casting process of steels were calculated using in-house finite-element code which is integrated in MICAST. The predicted temperature history from the casting process simulation was exported as input data for the DICTRA simulation of solidification. The resulting microsegregation by the DICTRA simulation can reflect the microstructure evolution in the real casting process. Current computational practice demonstrates that CALPHAD-based material models can be directly linked with casting process models to predict location-specific microstructures for smart material processing.
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(This article belongs to the Collection Feature Paper Collection of Advanced Research on Alloys)
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Open AccessFeature PaperArticle
Processing of Carbon Nanoparticle-Enriched AISI H11 Tool Steel Powder Mixtures in DED-LB/M for the AM of Forging Tools with Tailored Properties (Part II): Influence of Nanoscale Carbon Additives on Microstructure and Mechanical Properties
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Oliver Hentschel, Jan Kohlstruck, Pavel Krakhmalev, Dimitrios Nikas and Michael Schmidt
Alloys 2023, 2(4), 288-320; https://doi.org/10.3390/alloys2040020 - 14 Nov 2023
Cited by 2
Abstract
A promising approach for producing parts with outstanding properties in directed energy deposition (DED-LB/M) provides the application of tailored powder mixtures processed by applying in situ alloying strategies. In this work, DED-LB/M was used to manufacture multilayer specimens from AISI H11 steel powders
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A promising approach for producing parts with outstanding properties in directed energy deposition (DED-LB/M) provides the application of tailored powder mixtures processed by applying in situ alloying strategies. In this work, DED-LB/M was used to manufacture multilayer specimens from AISI H11 steel powders enriched with carbon nanoparticles (C-np) in concentrations of 0.1 wt.-% and 0.2 wt.-%. The scientific aim was to investigate the impact of C-np on the microstructural (particularly retained austenite content (RA-c) and grain size) and mechanical properties (specifically hardness and compression yield strength) of the manufactured specimens. It was shown that the addition of C-np to the H11 powder leads to a stronger distortion of martensite as well as significantly enhancing the RA-c. Furthermore, the C-np seem to favor the formation of finer martensite, as can be verified with XRD and EBSD. Under as-built conditions, the mean hardness increases from 653 ± 10 HV1 for the H11 sample to 770 ± 14 HV1 for the sample reinforced with 0.2 wt.-% C-np. At the same time, Y0.2% rises up from 1839 ± 61 MPa to 2134 ± 68 MPa. The hardness- and strength-increasing effect of the added C-np is retained even after heat treatment, similarly to the industrial standard.
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(This article belongs to the Special Issue Design of New Metallic Alloys for AM)
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Open AccessArticle
Investigation on the Optimal Amount of Y and B Elements in High-Temperature Titanium Alloy Ti-5.9Al-4Sn-3.9Zr-3.8Mo-0.4Si-xY-yB
by
Yingbo Zhang, Yuanhui Peng, Pu Zhang, Yunfeng Hu, Dongliang Wu and Xing Tu
Alloys 2023, 2(4), 271-287; https://doi.org/10.3390/alloys2040019 - 30 Oct 2023
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This article presents a novel and feasible approach for researching the quantity of the ceramic phase and component optimization in high-temperature titanium alloys with small trace amounts of ceramic phases. Different near-α titanium alloys with varying yttrium and boron contents were prepared through
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This article presents a novel and feasible approach for researching the quantity of the ceramic phase and component optimization in high-temperature titanium alloys with small trace amounts of ceramic phases. Different near-α titanium alloys with varying yttrium and boron contents were prepared through the utilization of a vacuum non-consumable arc furnace melting method. The alloy used was a Ti-5.9Al-4Sn-3.9Zr-3.8Mo-0.4Si base. Its microstructure, texture, mechanical properties, and fracture behavior were studied. The observation of the as-cast structure shows that the addition of different doses of trace Y and B elements significantly refines both the original β grains and α grains. Moreover, the addition of the B element transforms the Widmanstätten structure in the titanium alloy structure into a basketweave structure. The addition of Y can refine the grain structure, improve the uniformity of the matrix structure, and act as a strong deoxidizer, which will take away the oxygen in the matrix and purify it. The TiB whiskers generated with the addition of B promotes dynamic recrystallization behavior and leads to more equiaxed α grains being precipitated around them, resulting in a significant refinement of the microstructure of the as-cast alloy. After adding a small amount of B, the texture strength of the α phase is significantly reduced, indicating that TiB whiskers inhibit the formation of texture. After conducting performance screening and structure analysis, the study supplements the analysis of Y’s regulation of the titanium alloy structure. The regulation is primarily explained by combining the results of the analysis of boron content, phase diagram analysis, mechanical properties, and fracture analysis. The mechanical analysis introduces the unique load transfer strengthening of TiB whiskers combined with an analysis of high-temperature mechanical properties, as the threshold for addition. The optimal amounts of Y and B additions are 0.6 wt% and 0.8 wt%, respectively. The optimized alloy obtained under this condition can achieve a tensile strength of 950 Mpa at 500 °C without any plastic deformation or heat treatment.
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The Research on Ultrasonic Vibration Amplitudes in Ti6Al4V DED Additive Manufacturing
by
Wei Liu, Zhenchao Zhang, Suli Li and Chao Xu
Alloys 2023, 2(4), 256-270; https://doi.org/10.3390/alloys2040018 - 19 Oct 2023
Abstract
Ultrasonic-assisted Ti6Al4V Directed Energy Deposition (DED) additive manufacturing technology can improve the problem of uneven microstructure caused by laser heating and sudden cooling of the molten pool. In this paper, the numerical analysis and experimental verification methods were adopted. The influencing factors, such
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Ultrasonic-assisted Ti6Al4V Directed Energy Deposition (DED) additive manufacturing technology can improve the problem of uneven microstructure caused by laser heating and sudden cooling of the molten pool. In this paper, the numerical analysis and experimental verification methods were adopted. The influencing factors, such as the cavitations’ effect, sound flow enhancement effect, and sound flow thermal effect related to the ultrasonic assistance in the molten pool, were analyzed. After equating the energy of the ultrasound, the model of additive manufacturing was introduced in the form of a heat source. The temperature gradient changes during the solidification process of the molten pool with the addition of ultrasound assistance and the effect of ultrasonic vibration during the manufacturing process on its deposited state and microstructure of solution-aged formed parts were studied. The results showed that when the wire feeding rate is 5 mm/s and the laser scanning speed is 5 mm/s, the optimal laser power is 1000 W~1100 W, corresponding to the optimal ultrasonic amplitude of 120 μm. Then, by comparing the temperature field with the same amplitude of 0 μm (i.e., no ultrasonic vibration) and the microstructure of the formed parts, it was verified that ultrasonic vibration facilitates fluid flow in the molten pool, which could lead to a more uniform temperature distribution. This optimized approach not only enhances the understanding of the process but also contributes significantly to the advancement of related research endeavors.
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(This article belongs to the Topic Laser Welding of Metallic Materials)
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