Metals

14 pages, 4531 KiB

Open AccessArticle

Phase Transformations and Tellurium Recovery from Technical Copper Telluride by Oxidative-Distillate Roasting at 0.67 kPa

by Alina Nitsenko, Xeniya Linnik, Valeriy Volodin, Farkhat Tuleutay, Nurila Burabaeva, Sergey Trebukhov and Galiya Ruzakhunova

Metals 2022, 12(10), 1774; https://doi.org/10.3390/met12101774 - 21 Oct 2022

Cited by 1 | Viewed by 1508

Abstract

This paper presents the results of a study of phase transformations occurring in copper-telluride by-products during its processing of oxidation-distillate roasting at low pressure. The results show that copper telluride is oxidized through intermediate compounds to the most stable tellurate (Cu₃TeO [...] Read more.

This paper presents the results of a study of phase transformations occurring in copper-telluride by-products during its processing of oxidation-distillate roasting at low pressure. The results show that copper telluride is oxidized through intermediate compounds to the most stable tellurate (Cu₃TeO₆) at low temperatures. The increase in the roasting temperature above 900 °C and the presence of an oxidizer favor the copper orthotellurate decomposition. Thus, the tellurium extraction rate is 90–93% at a temperature of 1000 °C, the oxidant flow rate is 2.2 × 10⁻² m³/m²·s, and the roasting time is 60–90 min. One of the decomposition products is copper oxide alloy, which is the basis of the residue. The second product is tellurium in oxide form, which evaporates and then condenses in the cold zone of the condenser in crystalline form. The main constituent phase of the condensate is tellurium oxide (TeO₂), which can be further processed during one operation to elemental chalcogen by thermal reduction or electrolytic method. Full article

(This article belongs to the Special Issue Recovery of Valuable Metals from Industrial By-Products)

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16 pages, 5403 KiB

Open AccessArticle

Features of Cathodic Plasma Electrolytic Nitrocarburizing of Low-Carbon Steel in an Aqueous Electrolyte of Ammonium Nitrate and Glycerin

by Ivan Tambovskiy, Tatiana Mukhacheva, Ilya Gorokhov, Igor Suminov, Sergey Silkin, Ilya Dyakov, Sergei Kusmanov and Sergey Grigoriev

Metals 2022, 12(10), 1773; https://doi.org/10.3390/met12101773 - 21 Oct 2022

Cited by 5 | Viewed by 1106

Abstract

The possibility of using an aqueous non-toxic electrolyte of ammonium nitrate and glycerin for the cathodic plasma electrolytic nitrocarburizing of low-carbon steel is considered in this paper. Surface morphology and roughness, element and phase compositions, and microhardness of the modified layer were investigated. [...] Read more.

The possibility of using an aqueous non-toxic electrolyte of ammonium nitrate and glycerin for the cathodic plasma electrolytic nitrocarburizing of low-carbon steel is considered in this paper. Surface morphology and roughness, element and phase compositions, and microhardness of the modified layer were investigated. Kinetic calculations of the processes of nitrogen and carbon diffusion into the steel surface are proposed, taking into account their mutual influence. Wear resistance was studied under dry friction conditions with tool alloy steel as a counter-body. Corrosion studies are performed using potentiodynamic polarization curves in 3.5% sodium chloride solution. The plasma electrolytic nitrocarburizing in an aqueous electrolyte with ammonium nitrate and glycerin is established to increase surface hardness up to 980 HV due to the formation of a nitrocarburized layer with 1.35 ± 0.12% carbon and 0.32 ± 0.08% nitrogen concentration. The influence of erosion in electrolyte plasma and high-temperature oxidation on the morphology and surface roughness is shown. The presence of a dense oxide layer, low surface roughness, and high hardness of the diffusion layer favor a decrease in the friction coefficient by 1.3 times, weight wear by 1.8 times and corrosion current density by 1.4 times. Full article

(This article belongs to the Special Issue Machining of Advanced Cutting Materials: Fundamentals, Modeling and Applications)

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21 pages, 8270 KiB

Open AccessArticle

Degassing of Aluminum Alloy Melts by High Shear Melt Conditioning Technology: An Overview

by Jaime Lazaro-Nebreda, Jayesh B. Patel, Ewan Lordan, Yijie Zhang, Erdem Karakulak, Kawther Al-Helal, Geoff M. Scamans and Zhongyun Fan

Metals 2022, 12(10), 1772; https://doi.org/10.3390/met12101772 - 21 Oct 2022

Cited by 5 | Viewed by 4472

Abstract

The search for more efficient methods for degassing aluminum alloy melts has always been of great interest for the metal industry because the presence of hydrogen and oxides in the melts’ prior casting was detrimental to the integrity and properties of the final [...] Read more.

The search for more efficient methods for degassing aluminum alloy melts has always been of great interest for the metal industry because the presence of hydrogen and oxides in the melts’ prior casting was detrimental to the integrity and properties of the final products. In this work, we present an overview of the progress and key findings from the research and development of an innovative High Shear Melt Conditioning (HSMC) degassing technology during the Liquid Metal Engineering (LiME) Research Hub project. Compared to conventional rotary degassing, this novel technique was capable of working at higher rotor speeds to efficiently break and disperse the naturally occurring oxide bifilms in the melt and to capture and disperse each supplied inert gas bubble into many tiny bubbles throughout the whole melt. This resulted in the elimination of the need to degas fluxes to remove the oxides in the melt, the reduction in the gas flow required to reach the same level of hydrogen removal rate, and the minimization of the regassing effect after processing. The increased process efficiency allowed for reduced melt processing costs and, at the same time, improved the melt quality, which resulted in fewer defects and improved mechanical properties. Full article

(This article belongs to the Special Issue Heterogeneous Nucleation, Grain Initiation and Grain Refinement: Reports from the LiME Research Hub in the UK)

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2 pages, 167 KiB

Open AccessEditorial

Microstructure, Mechanical Properties and Solidification Behavior of Metals and Alloys

by Crystopher Brito

Metals 2022, 12(10), 1771; https://doi.org/10.3390/met12101771 - 21 Oct 2022

Viewed by 915

Abstract

The microstructure constitutes one of the pillars of the materials tetrahedron [...] Full article

(This article belongs to the Special Issue Microstructure, Mechanical Properties and Solidification Behavior of Metals and Alloys)

33 pages, 9749 KiB

Open AccessArticle

Microstructure-Based Modelling of Flow and Fracture Behavior of Tailored Microstructures of Ductibor^® 1000-AS Steel

by Pedram Samadian, Armin Abedini, Clifford Butcher and Michael J. Worswick

Metals 2022, 12(10), 1770; https://doi.org/10.3390/met12101770 - 21 Oct 2022

Cited by 3 | Viewed by 1818

Abstract

Emerging grades of press-hardening steels such as Ductibor^® 1000-AS are now commercially available for use within tailor-welded blanks (TWBs) to enhance ductility and energy absorption in hot-stamped automotive structural components. This study examines the constitutive (hardening) response and fracture limits of Ductibor [...] Read more.

Emerging grades of press-hardening steels such as Ductibor^® 1000-AS are now commercially available for use within tailor-welded blanks (TWBs) to enhance ductility and energy absorption in hot-stamped automotive structural components. This study examines the constitutive (hardening) response and fracture limits of Ductibor^® 1000-AS as functions of the as-quenched microstructure after hot stamping. Three different microstructures consisting of bainite and martensite were obtained by hot stamping with die temperatures of 25 °C, 350 °C, and 450 °C. Mechanical characterization was performed to determine the hardening curves and plane-stress fracture loci for the different quench conditions (cooling rates). Uniaxial-tension and shear tests were conducted to experimentally capture the hardening response to large strain levels. Shear, conical hole-expansion, plane-strain notch tension, and Nakazima tests were carried out to evaluate the stress-state dependence of fracture. A mean-field homogenization (MFH) scheme was applied to model the constitutive and fracture behavior of the mixed-phase microstructures. A dislocation-based hardening model was adopted for the individual phases, which accounts for material chemistry, inter-phase carbon partitioning, and dislocation evolution. The per-phase fracture modelling was executed using a phenomenological damage index based upon the stress state within each phase. The results revealed that the 25 °C hot-stamped material condition with a fully martensite microstructure exhibited the highest level of strength and the lowest degree of ductility. As bainite was formed in the final microstructure by quenching at higher die temperatures, the strength decreased, while the ductility increased. The predicted constitutive and fracture responses in the hot-stamped microstructures were in line with the measured data. Accordingly, the established numerical strategy was extended to predict the mechanical behavior of Ductibor^® 1000-AS for a broad range of intermediate as-quenched microstructures. Full article

(This article belongs to the Special Issue Hot Sheet Metal Forming of High Performance Materials)

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13 pages, 8790 KiB

Open AccessArticle

Simulation Study of Ultrasonic Elliptical Vibration Cutting of TiC Particle-Reinforced Titanium Matrix Composites

by Haixiang Huan, Wenqiang Xu, Biao Zhao, Ke Zhang, Jianfei Pu and Chilei Zhu

Metals 2022, 12(10), 1769; https://doi.org/10.3390/met12101769 - 21 Oct 2022

Cited by 6 | Viewed by 1280

Abstract

In order to investigate the characteristics of elliptical ultrasonic vibration cutting of TiC particle-reinforced titanium matrix composites, a two-dimensional thermodynamic coupled finite element cutting model was established based on the Johnson-Cook intrinsic structure model using ABAQUS simulation software, and the changes in cutting [...] Read more.

In order to investigate the characteristics of elliptical ultrasonic vibration cutting of TiC particle-reinforced titanium matrix composites, a two-dimensional thermodynamic coupled finite element cutting model was established based on the Johnson-Cook intrinsic structure model using ABAQUS simulation software, and the changes in cutting force, cutting temperature, machined surface shape, and particle fragmentation were obtained under the traditional cutting method and ultrasonic elliptical vibration cutting method. The results show that under the same process parameters, ultrasonic elliptical vibration cutting is better than conventional cutting in terms of surface profile; the stress direction tends to be horizontal during cutting and the TiC particles are mainly removed by cutting off. The average cutting force is significantly lower than conventional cutting, with a maximum reduction of 60%. The cutting temperature is also reduced, with a reduction of approximately 17.6%. Full article

(This article belongs to the Special Issue Advanced Metal Cutting Technology and Tools)

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8 pages, 4245 KiB

Open AccessArticle

Sn-0.7Cu-10Bi Solder Modification Strategy by Cr Addition

by Pin Han, Zhenpo Lu and Xuping Zhang

Metals 2022, 12(10), 1768; https://doi.org/10.3390/met12101768 - 21 Oct 2022

Cited by 1 | Viewed by 1230

Abstract

The application of Sn-0.7Cu-based composite solder in electronic packaging is limited due to its high melting point, poor wettability and low mechanical properties. Herein, we propose a strategy of adding Bi and Cr to improve the solderability of Sn-0.7Cu lead-free solder. The results [...] Read more.

The application of Sn-0.7Cu-based composite solder in electronic packaging is limited due to its high melting point, poor wettability and low mechanical properties. Herein, we propose a strategy of adding Bi and Cr to improve the solderability of Sn-0.7Cu lead-free solder. The results show that the addition of Bi reduces the melting point of the composite solder. Moreover, the Cr particles adsorb at the interface between solder and substrate, thereby reducing the wetting angle of the composite solder. The wetting angle reaches a minimum value of 25.84° when the content of Cr is 0.2 wt.%. The addition of Bi and Cr changes the microstructure of the composite solder. The nucleation rate of β-Sn rises with the increase of Cr content, thus decreasing the size of β-Sn. Furthermore, the addition of Bi and Cr reduces the thickness of the intermetallic compounds (IMCs). This is due to the adsorption of Bi and Cr at the interface of IMCs hinders the atomic diffusion channels and inhibits the growth of IMCs. Full article

(This article belongs to the Special Issue New Welding Materials and Green Joint Technology)

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14 pages, 4334 KiB

Open AccessArticle

Effect of Deep Cryogenic Treatment on the Artificial Ageing Behavior of SiCp–AA2009 Composite

by Zhenxiao Wang, Jie Chen, Baosheng Liu, Ran Pan, Yuan Gao and Yong Li

Metals 2022, 12(10), 1767; https://doi.org/10.3390/met12101767 - 20 Oct 2022

Cited by 2 | Viewed by 1280

Abstract

The effect of deep cryogenic treatment (DCT) on the artificial ageing kinetics of a SiC particles reinforced aluminum alloy composite (SiCp-Al) is experimentally studied in this paper. The evolutions of both macro-properties (i.e., yield strength and ultimate tensile strength) and microstructures (precipitates) have [...] Read more.

The effect of deep cryogenic treatment (DCT) on the artificial ageing kinetics of a SiC particles reinforced aluminum alloy composite (SiCp-Al) is experimentally studied in this paper. The evolutions of both macro-properties (i.e., yield strength and ultimate tensile strength) and microstructures (precipitates) have been investigated by a set of hardness tests, tensile tests, and microstructural observations (scanning electron microscope, SEM and transmission electron microscope, TEM) for a SiCp-Al composite material with conventional heat treatment (solution heat treatment + quenching + artificial ageing, CHT) or DCT (solution heat treatment + quenching + deep cryogenic + artificial ageing). The results show that SiCp could significantly accelerate the ageing kinetics of the composites. Meanwhile, compared with CHT conditions, DCT can further improve the yield strength (YS) and ultimate tensile strength (UTS) of the composite materials after artificial ageing. The microstructures show that DCT induces the generation of more thinner

θ

′ precipitates homogeneously distributed in the grains during artificial ageing compared with corresponding CHT conditions. A quantified analysis has been performed based on the microstructural data, and the calculated results further support the indication that the strengthening effect in DCT compared with CHT is mainly contributed by corresponding precipitation behavior. Full article

(This article belongs to the Special Issue Microstructural Evolution and Mechanical Properties of Aluminum Alloys)

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9 pages, 2037 KiB

Open AccessArticle

Effect of Natural Ageing on Subsequent Artificial Ageing of AA7075 Aluminum Alloy

by Cheng-Ling Tai, Po-Jui Tai, Ting-Jung Hsiao, Po-Han Chiu, Chien-Yu Tseng, Tzu-Ching Tsao, Tsai-Fu Chung, Yo-Lun Yang, Chih-Yuan Chen, Shing-Hoa Wang and Jer-Ren Yang

Metals 2022, 12(10), 1766; https://doi.org/10.3390/met12101766 - 20 Oct 2022

Cited by 4 | Viewed by 1699

Abstract

The effects of natural ageing treatment prior to artificial ageing treatment on the microstructures and mechanical properties of AA7075 Al-5.7Zn-2.6Mg-1.5Cu-0.18Cr-0.08Mn-0.05Si-0.17Fe (wt.%) aluminum alloy have been investigated. The hardness of solution-treated samples (91.0 HV) profoundly increased to 146.8 HV after 7 days of natural [...] Read more.

The effects of natural ageing treatment prior to artificial ageing treatment on the microstructures and mechanical properties of AA7075 Al-5.7Zn-2.6Mg-1.5Cu-0.18Cr-0.08Mn-0.05Si-0.17Fe (wt.%) aluminum alloy have been investigated. The hardness of solution-treated samples (91.0 HV) profoundly increased to 146.8 HV after 7 days of natural ageing. The purpose of the present work was to examine the kinetic hardening evolution in subsequent artificial ageing treatments of samples naturally aged for 7 days and their counterparts without natural ageing. The former were labelled as NA-7d samples, and the latter, NA-0d samples. After artificial ageing at 120 °C for 2 h, the hardness of NA-0d samples increased rapidly to 148.2 HV, which was approximately the same as that of the specimens with natural ageing for 7 days, compensating for the prior state of lower hardness without natural ageing. After being treated at 120 °C for 16 h, the ultimate tensile strength (UTS) and yield strength (YS) of NA-7d reached the highest value, respectively, 601 MPa and 539 MPa, followed by a slight decrement of UTS when aged to 24 h. On the other hand, NA-0d specimens aged at 120 °C for 16 and 24 h showed nearly the same UTS (598 MPa); the former possessed YS of 538 MPa, and the latter, 545 MPa. The results presumably reveal that the peak ageing condition for NA-0d samples can be achieved under 24 h ageing at 120 °C. Under the same treatment at 120 °C for 24 h, the size of η’ phase in NA-7d sample (with a length of 4.96 nm) coarsened and grew larger than that in NA-0d sample (with a length of 3.46 nm). In addition, some η’ phase in the NA-7d sample was found to be transformed into the η₂ phase. The results indicated that the naturally aged specimens (NA-7d) reached the peak ageing condition earlier, but did not significantly enhance the UTS in AA7075 aluminum alloy, as compared to the samples without prior natural ageing (NA-0d). Full article

(This article belongs to the Special Issue Microstructural Characterization of Metallic Materials)

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8 pages, 2627 KiB

Open AccessCommunication

High Manganese TWIP Steel with Increased Corrosion Resistance

by Pavel Podany, Tomas Gregor, Tomas Studecky and Crtomir Donik

Metals 2022, 12(10), 1765; https://doi.org/10.3390/met12101765 - 20 Oct 2022

Cited by 1 | Viewed by 1296

Abstract

The paper describes the development of austenitic steel with the TWIP effect, which is alloyed with chromium to increase corrosion resistance. The experimental heat of this steel was cast in an experimental melting furnace and subsequently subjected to hot and cold rolling. After [...] Read more.

The paper describes the development of austenitic steel with the TWIP effect, which is alloyed with chromium to increase corrosion resistance. The experimental heat of this steel was cast in an experimental melting furnace and subsequently subjected to hot and cold rolling. After cold rolling, the appropriate recrystallization annealing temperature was applied to obtain the optimal austenitic grain size. X-ray diffraction proved that the steel contains a fully austenitic structure. After recrystallization annealing, the sheets achieved a TS of more than 950 MPa with an elongation of 40%. The corrosion resistance of this steel is increased with the addition of chromium. Full article

(This article belongs to the Special Issue Microstructures and Mechanical Properties of TRIP/TWIP Steels)

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17 pages, 10683 KiB

Open AccessArticle

Fabrication, Microstructure, and Physico-Mechanical Properties of Fe–Cr–Ni–Mo–W High-Entropy Alloys from Elemental Powders

by Alexander Yurievich Ivannikov, Ivan Konstantinovich Grebennikov, Yulia Alexandrovna Klychevskikh, Anna Vladimirovna Mikhailova, Konstantin Victorovich Sergienko, Mikhail Alexandrovich Kaplan, Anton Sergeevich Lysenkov and Mikhail Anatolievich Sevostyanov

Metals 2022, 12(10), 1764; https://doi.org/10.3390/met12101764 - 20 Oct 2022

Viewed by 1281

Abstract

In this work, 35Fe30Cr20Ni10Mo5W (wt.%) and 30Fe30Cr20Ni10Mo10W (wt.%) high-entropy alloys were fabricated using a powder metallurgy route. Powder mixtures for a hot-pressure process were obtained by the mixing and mechanical alloying of elemental powders. Mechanical alloying was carried out for 1, 2.5, 5, [...] Read more.

In this work, 35Fe30Cr20Ni10Mo5W (wt.%) and 30Fe30Cr20Ni10Mo10W (wt.%) high-entropy alloys were fabricated using a powder metallurgy route. Powder mixtures for a hot-pressure process were obtained by the mixing and mechanical alloying of elemental powders. Mechanical alloying was carried out for 1, 2.5, 5, and 10 h. X-ray phase analysis of the powder mixtures showed that with increasing time of mechanical alloying, Face-Centered Cubic (FCC), Body-Centered Cubic (BCC), and nickel–iron intermetallic phases were formed in the structure, and the volume content of molybdenum and tungsten decreased. The hot-pressing was carried out at a pressure of 30 MPa and a temperature of 1200 °C for 30 min. The maximum densities of 8.14 ± 0.02 and 8.40 ± 0.01 g/cm³ and compressive strengths of 2430 ± 30 MPa and 2460 ± 35 MPa for consolidated materials were achieved using powder mixtures after 10 h of mechanical milling, for compositions with 5 wt.% W and 10 wt.% W, respectively. The workpieces fabricated with a pressure-assisted sintering process from milled powders were found to consist of FCC, BCC, and sigma phases. Full article

(This article belongs to the Section Powder Metallurgy)

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15 pages, 6857 KiB

Open AccessArticle

Corrosion Behavior of Mg-xGd-1Zn-0.4Zr Alloys with Different Gd Additions for Biomedical Application

by Xue Geng, Jiahao Jiang and Xiaobo Zhang

Metals 2022, 12(10), 1763; https://doi.org/10.3390/met12101763 - 20 Oct 2022

Cited by 7 | Viewed by 1279

Abstract

In recent years, Mg alloys have attracted increased attention for biomedical application owing to their good biodegradability, biocompatibility, and biomechanical properties. However, rapid corrosion is still one of the most common limitations for their implanted application. In this work, the microstructure and corrosion [...] Read more.

In recent years, Mg alloys have attracted increased attention for biomedical application owing to their good biodegradability, biocompatibility, and biomechanical properties. However, rapid corrosion is still one of the most common limitations for their implanted application. In this work, the microstructure and corrosion behavior of the solution- and aging-treated Mg-xGd-1Zn-0.4Zr (x = 3, 6, and 9 wt%, denoted as GZ31K, GZ61K, and GZ91K, respectively) alloys were studied using optical microscope (OM), scanning electron microscope (SEM), immersion tests, electrochemical tests, and quasi in situ corrosion method. The results show that block Gd-rich precipitates and needle-like Zr-Zn-rich precipitates are formed as well as α-Mg matrix. With the increase in Gd content, the precipitates increase and the grain size first reduces and then increases. Corrosion experiment results show that the GZ61K alloy has the best corrosion resistance and the GZ91K alloy shows the highest corrosion rate among the three alloys in simulated body fluid (SBF). It is found that α-Mg is preferentially corroded and the precipitates have better corrosion resistance as compared to the α-Mg matrix. The GZ61K alloy with the corrosion rate of 0.23 mm/y in SBF shows a promising prospect for biomedical application. Full article

(This article belongs to the Special Issue Corrosion Science and Engineering: Recent Research, Insights, and Challenges)

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20 pages, 9029 KiB

Open AccessArticle

External Illumination Enables Coaxial Sensing of Surface and Subsurface Molten Pool Geometry in LPBF

by Leonardo Caprio, Ali Gökhan Demir and Barbara Previtali

Metals 2022, 12(10), 1762; https://doi.org/10.3390/met12101762 - 20 Oct 2022

Cited by 2 | Viewed by 1769

Abstract

Laser powder bed fusion (LPBF) attracts the attention of high-end manufacturing sectors for its capability of depositing free-form components with elevated mechanical properties. However, due to the intrinsic nature of the feedstock material and the interaction with the laser beam, the process is [...] Read more.

Laser powder bed fusion (LPBF) attracts the attention of high-end manufacturing sectors for its capability of depositing free-form components with elevated mechanical properties. However, due to the intrinsic nature of the feedstock material and the interaction with the laser beam, the process is prone to defect formation and manufacturing inaccuracies. Therefore, the development of a monitoring architecture capable of measuring the geometrical features of the process tool (i.e., the melt pool generated by the laser-material interaction) is of paramount importance. This information may then be exploited to evaluate process stability. In this work, a high-speed camera was implemented coaxially in the optical chain of an LPBF system to extrapolate the geometrical features of the molten pool surface and its oscillatory behaviour, with elevated spatial and temporal resolution. A secondary light source was tested in both coaxial and off-axis configuration to dominate process emission and assess optimal illumination conditions for extracting the molten pool’s geometrical features. Preliminary results showed that the off-axis configuration of the illumination light enabled direct measurement of the molten pool surface geometry. A newly developed image processing algorithm based on illuminated images obtained via the coaxial observation frame was employed to provide automated identification of the melt pool geometry. Moreover, bright reflections of the external illumination over the melt surface could be clearly observed and used to characterise the oscillatory motion of the molten material. This information may therefore be taken as an indirect indicator of the molten pool penetration depth, hence providing information regarding the subsurface geometry. A successive experimental investigation showed the capability of the monitoring architecture to resolve the molten pool’s length, width and area with elevated acquisition frequency. Molten pool surface oscillations in the kHz range could be correlated to the penetration depth while the molten pool width measured via the high-speed imaging setup corresponded to the track width of the depositions. Hence, the methodological approach for the concurrent measurement of the molten pool’s geometry in three spatial dimensions was demonstrated and may be used to track the stability of LPBF depositions. Full article

(This article belongs to the Special Issue Additive Manufacturing of Architected Metallic Materials)

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14 pages, 5753 KiB

Open AccessArticle

Preparation of High-Precision Dimension Seamless Thick-Walled Pipe by New Cold Rolling Process

by Ran Li, Xuewei Zhang, Cheng Zhang, Jiaming Wang and Jinfeng Huang

Metals 2022, 12(10), 1761; https://doi.org/10.3390/met12101761 - 19 Oct 2022

Cited by 1 | Viewed by 1217

Abstract

In this study, the cold rolling test on the quenched-tempered hot working die steel pipe with an outer diameter/thickness ratio of no greater than 3 was performed. The evolutionary trend of microstructure was examined by a combination of the microscope, SEM, and EBSD [...] Read more.

In this study, the cold rolling test on the quenched-tempered hot working die steel pipe with an outer diameter/thickness ratio of no greater than 3 was performed. The evolutionary trend of microstructure was examined by a combination of the microscope, SEM, and EBSD tests. The effect of feed rate on the inner wall roughness of rolled pipe was analyzed by means of white light interference. According to the experimental results, the maximum normal pressure per unit area increases from 1046.7 MPa to 1113.2 MPa with the rise in feed rate from 1 mm/stroke to 6 mm/stroke. Meanwhile, the inner wall roughness of the pipe declines from 0.285 μm to 0.146 μm after rolling. When the feed rate reaches 2 mm/stroke, the maximum normal pressure per unit area is 1058.4 MPa, which causes a significant plastic deformation to the inner wall of the pipe, and the average roughness below 0.2 μm. The microstructure of the pipe is dominated by tempered sorbite whether before or after rolling, and the grain size before rolling is 16.22 μm on average. After cold rolling, the longitudinal structure is deformed along the direction of rolling, in which the average grain size is 24.31 μm. With the increase in deformation work-hardening behavior in the rolling process, the tensile strength improves from 1134 MPa to 1178 MPa, the yield strength increases from 985 MPa to 1125 MPa, and the room temperature impact energy diminishes from 58 J to 52.5 J. After vacuum tempering at 600 °C, it is difficult to eliminate the deformed band microstructure along the rolling direction completely. However, the grain size is reduced after cold rolling, no coarsening occurs, and the impact toughness increases from 52.5 J to 60.5 J. With the recovery of the original microstructure, the mechanical properties are restored to the before rolling level. Full article

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15 pages, 7301 KiB

Open AccessArticle

Corrosion Resistance of Mg(OH)₂/Mn(OH)₂ Hydroxide Film on ZK60 Mg Alloy

by Yongmin Wang, Zhuangzhuang Li, Yan Wang, Tianyi Sun and Zhixin Ba

Metals 2022, 12(10), 1760; https://doi.org/10.3390/met12101760 - 19 Oct 2022

Cited by 2 | Viewed by 1448

Abstract

This study aims to prepare hydroxide films on the surface of ZK60 magnesium alloy to improve the corrosion resistance of the latter. The hydroxide films were fabricated with a facile hydrothermal method using Mg(NO₃)₂ and Mn(NO₃)₂ aqueous [...] Read more.

This study aims to prepare hydroxide films on the surface of ZK60 magnesium alloy to improve the corrosion resistance of the latter. The hydroxide films were fabricated with a facile hydrothermal method using Mg(NO₃)₂ and Mn(NO₃)₂ aqueous solutions. The treatment temperature was maintained at 353 K, while the treatment time was 6 h, 12 h, and 24 h. X-ray diffraction (XRD) and Fourier transform-infrared (FT-IR) spectroscopy demonstrated that the films were composed of a mixture of Mg(OH)₂ and Mn(OH)₂. As revealed by scanning electron microscopy (SEM), each film grew from an incomplete lamellar structure to a thick lamellar structure at changing treatment times. The corrosion current density of the 12 h film sample immersed in a simulated body fluid (SBF) reached 3.07 × 10⁻⁷ A·cm⁻², which was approximately two orders of magnitude lower than that of the ZK60 magnesium alloy substrate (3.04 × 10⁻⁵ A·cm⁻²). In addition, the hydrogen evolution experiment showed that, even after 168 h of immersion, the 12 h film sample could still provide protection for the substrate. Full article

(This article belongs to the Special Issue Advanced Biomedical Materials)

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12 pages, 17615 KiB

Open AccessArticle

Kinetics of Low-Grade Scheelite Leaching with a Mixture of Sodium Phosphate and Sodium Fluoride

by Liang Yang, Chaoyang Li, Caifang Cao, Xiang Xue, Dandan Gong and Linsheng Wan

Metals 2022, 12(10), 1759; https://doi.org/10.3390/met12101759 - 19 Oct 2022

Viewed by 1151

Abstract

The current technology of leaching low-grade scheelite with sodium hydroxide or sodium carbonate has the disadvantages of large leaching reagent dosage and low leaching efficiency of tungsten. In order to extract scheelite efficiently, the kinetics of low-grade scheelite leaching with a mixture of [...] Read more.

The current technology of leaching low-grade scheelite with sodium hydroxide or sodium carbonate has the disadvantages of large leaching reagent dosage and low leaching efficiency of tungsten. In order to extract scheelite efficiently, the kinetics of low-grade scheelite leaching with a mixture of sodium phosphate and sodium fluoride was investigated. In this study, the effects of temperature, phosphate concentration, and fluoride ion concentration on the leaching rate of tungsten were investigated. Our results showed that the leaching rate of tungsten was greatly influenced by the temperature and less affected by the concentration of phosphate and fluorine ions. The leaching process was controlled by a chemical reaction with an apparent activation energy value of 51 ± 0.2 kJ/mol. The apparent reaction orders with respect to phosphate and fluorine ions were 0.49 and 0.11, respectively. The reaction product calcium fluorophosphate was a loose, rod-like crystal, which would not tightly wrap on the surface of scheelite to prevent the diffusion process. The leaching kinetics of low-grade scheelite was in accordance with the shrinking core model, and the corresponding kinetic equation was also established. Full article

(This article belongs to the Special Issue Metal Recovery from Secondary Resources)

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12 pages, 2908 KiB

Open AccessFeature PaperArticle

Precipitation Behavior of Carbides and Its Effect on the Microstructure and Mechanical Properties of 15CrNi3MoV Steel

by Xin Yao, Jie Huang, Yanxin Qiao, Mingyue Sun, Bing Wang and Bin Xu

Metals 2022, 12(10), 1758; https://doi.org/10.3390/met12101758 - 19 Oct 2022

Cited by 4 | Viewed by 2107

Abstract

In this study, quenching and tempering were employed to achieve the optimal match of strength and toughness of the high-strength low-alloy (HSLA) 15CrNi3MoV steel. The effect of the tempering temperature on the microstructure evolution and the carbides precipitation of the steel was also [...] Read more.

In this study, quenching and tempering were employed to achieve the optimal match of strength and toughness of the high-strength low-alloy (HSLA) 15CrNi3MoV steel. The effect of the tempering temperature on the microstructure evolution and the carbides precipitation of the steel was also investigated using scanning electron microscopy (SEM), a X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The results showed that after tempering at different temperatures, the microstructure of 15CrNi3MoV steel was tempered martensite. During the tempering process, the M₃C carbides precipitated on the ferrite matrix, the needle-like carbides accumulated and grew into a short rodlike shape or a granular shape with the increase of the tempering temperature. Subsequently, the strength and hardness of the steel showed a downward trend, and the elongation and the low temperature impact toughness showed an upward trend. The tensile strength and yield strength of the steel tempered at 650 °C decreased dramatically compared with the steel tempered at 550 °C, while the elongation increased rapidly. Considering the influence of the microstructure and the carbides and the demand for mechanical properties, the optimal tempering temperature is about 600 °C. Full article

(This article belongs to the Topic Properties of the Corroding Interface)

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13 pages, 3191 KiB

Open AccessArticle

Crystal Plasticity Model Analysis of the Effect of Short-Range Order on Strength-Plasticity of Medium Entropy Alloys

by Chen Li, Fuhua Cao, Yan Chen, Haiying Wang and Lanhong Dai

Metals 2022, 12(10), 1757; https://doi.org/10.3390/met12101757 - 19 Oct 2022

Cited by 2 | Viewed by 1396

Abstract

Numerous studies have demonstrated the widespread presence of chemical short-range order (SRO) in medium and high entropy alloys (M/HEAs). However, the mechanism of their influence on macroscopic mechanical behavior remains to be understood. In this paper, we propose a novel dislocation-based model of [...] Read more.

Numerous studies have demonstrated the widespread presence of chemical short-range order (SRO) in medium and high entropy alloys (M/HEAs). However, the mechanism of their influence on macroscopic mechanical behavior remains to be understood. In this paper, we propose a novel dislocation-based model of crystal plasticity, by considering both the dislocation blocking and coplanar slip induced by SRO. The effect of SRO on the plastic deformation of CoCrNi MEAs was investigated. We found that the yield strength increases monotonically with increasing SRO-induced slip resistance, but the elongation first appeared to increase and then decreased. Further analysis suggested that the plastic elongation is a result of the competition between grain rotation-induced deformation coordination and stress concentration, which depends on the slip resistance of the SRO. Full article

(This article belongs to the Special Issue Deformation Behavior and Mechanical Properties of High Entropy Alloys)

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14 pages, 4101 KiB

Open AccessArticle

Development of a Sustainable Metallurgical Process to Valorize Copper Smelting Wastes with Olive Stones-Based Biochar

by Aitziber Adrados, Mikel Merchán, Alejandro Obregón, Antxon Artola, Jon Ander Iparraguirre, Maider García de Cortázar, David Eguizabal and Hary Demey

Metals 2022, 12(10), 1756; https://doi.org/10.3390/met12101756 - 19 Oct 2022

Cited by 2 | Viewed by 1730

Abstract

Flue dust waste coming from a copper (Cu) smelting company has been valorized using a newly developed metallurgical process with the aim of recovering a dust concentrated in valuable metals, such as lead (Pb) and zinc (Zn), and studying the feasibility of replacing [...] Read more.

Flue dust waste coming from a copper (Cu) smelting company has been valorized using a newly developed metallurgical process with the aim of recovering a dust concentrated in valuable metals, such as lead (Pb) and zinc (Zn), and studying the feasibility of replacing anthracite with biochar as reducing agent. Metallurgical trials using different mixtures of reducing agents have been performed in a furnace at 1400 °C. This furnace employs a high-power thermal plasma (HPTP) system as energy source. Using copper as the base metal, pellets containing a mixture of the waste, different reducing agents, and binder were introduced into the furnace for their dissolution. Recovery yields in the range of 45–85 wt.% for Pb and Zn were obtained in the flue dusts. All the trials proved the effectiveness of the developed process to enrich the flue dusts in valuable metals, including those only using biochar as reducing agent. Further trials will be carried out in order to better control the parameters involved in the metallurgical process developed and improve its efficiency. Full article

(This article belongs to the Special Issue Sustainable Metallurgical Processes for Metallic Waste Valorization)

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16 pages, 6427 KiB

Open AccessArticle

Structure, Mechanical and Physical Properties of Cu/Al–10% La Composite Produced by Rotary Forging

by Stanislav O. Rogachev, Roman V. Sundeev, Vladimir A. Andreev, Nikolay V. Andreev, Denis V. Ten, Evgeniy V. Nikolaev, Natalia Yu. Tabachkova and Vladimir M. Khatkevich

Metals 2022, 12(10), 1755; https://doi.org/10.3390/met12101755 - 19 Oct 2022

Cited by 3 | Viewed by 1183

Abstract

The influence of cold rotary forging on the mechanical properties of the Cu/Al–10% La composite, depending on the billet’s reduction ratio, has been studied. The billet was forged from an original diameter of 20 mm to a final diameter of 2.5 mm ( [...] Read more.

The influence of cold rotary forging on the mechanical properties of the Cu/Al–10% La composite, depending on the billet’s reduction ratio, has been studied. The billet was forged from an original diameter of 20 mm to a final diameter of 2.5 mm (e = 4.16). It is shown that the formation of a predominantly subgrain structure with a high density of dislocations in a copper shell, and a predominantly ultrafine grain/subgrain structure in an aluminum rod provides an approximately two-fold increase in the strength of the composite material compared to its components. To clarify the mechanisms of deformation and fracture of the composite samples under tension, the acoustic emission technique was used. It is shown that by choosing the temperature of post-deformation annealing, it is possible to achieve the required balance between strength and plasticity of the composite samples. The electrical conductivity and coefficient of linear thermal expansion of the composite samples have been measured. Full article

(This article belongs to the Section Metal Matrix Composites)

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14 pages, 8267 KiB

Open AccessArticle

Kinetic Analysis of Isothermal and Non-Isothermal Reduction of Iron Ore Fines in Hydrogen Atmosphere

by Binbin Lyu, Guang Wang, Fan Yang, Haibin Zuo, Qingguo Xue and Jingsong Wang

Metals 2022, 12(10), 1754; https://doi.org/10.3390/met12101754 - 19 Oct 2022

Cited by 3 | Viewed by 1326

Abstract

Direct reduction of iron ore with H₂ has become an alternative technology for iron production that reduces pollutant emissions. The reduction kinetics of iron ore fines in an H₂ atmosphere under isothermal and non-isothermal conditions were studied by thermogravimetric analysis. X-ray [...] Read more.

Direct reduction of iron ore with H₂ has become an alternative technology for iron production that reduces pollutant emissions. The reduction kinetics of iron ore fines in an H₂ atmosphere under isothermal and non-isothermal conditions were studied by thermogravimetric analysis. X-ray diffraction and scanning electron microscopy were used to measure the mineral composition and analyse the morphology of the reduced fines, respectively. In the isothermal reduction experiment, it was found that the final reduction time was shorter, the higher the temperature, and the metallic iron particles formed a dense matrix structure. It is likely that the initial stages reduction process is the result of a combination of gaseous diffusion and interfacial chemical reaction mechanisms, and that the later stages a combination of interfacial chemical reaction and solid diffusion is the rate control mechanism. In the non-isothermal experiment, the heating rate had a significant effect on the reaction rate. The results show that the non-isothermal reduction proceeded through three stages: mixing control model, two-dimensional diffusion, and three-dimensional diffusion. Full article

(This article belongs to the Special Issue Innovation in Efficient and Sustainable Blast Furnace Ironmaking)

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18 pages, 11517 KiB

Open AccessFeature PaperArticle

The Dependence of the Strength of a Carbon Fiber/Aluminum Matrix Composite on the Interface Shear Strength between the Matrix and Fiber

by Sergei Galyshev and Bulat Atanov

Metals 2022, 12(10), 1753; https://doi.org/10.3390/met12101753 - 19 Oct 2022

Cited by 2 | Viewed by 1655

Abstract

Taking the example of a composite wire with an Al-25% Sn alloy matrix reinforced with carbon fiber, the dependence of composite bending strength on interface shear strength was determined. Samples of the composite wire with different interface shear strengths were obtained by heat [...] Read more.

Taking the example of a composite wire with an Al-25% Sn alloy matrix reinforced with carbon fiber, the dependence of composite bending strength on interface shear strength was determined. Samples of the composite wire with different interface shear strengths were obtained by heat treatment at temperatures from 300 to 600 °C. The highest bending strength of 2450 MPa was observed for composite wire samples with the lowest interface shear strength. With an increase in the shear strength of the interface, a decrease in the strength was observed. The study of the surface of carbon fiber extracted from the composite showed that heat treatment led to the formation of aluminum carbide crystals on the fiber surface, the size and number of which increased with increasing temperature. As a result, there was an increase in the shear strength of the interface. The evaluation of the work of fracture of a composite with different strengths of the interface between the matrix and the fiber demonstrated that as the strength of the interface increases, the work of fracture decreases, due to the premature fracture of the composite through crack propagation in one plane. Based on the experimental data, the refined mixture rule according to the Weibull distribution, and an assessment of the critical stress of crack propagation according to the Griffith–Orowan–Irwin concept, the dependence of composite strength on the shear strength of the interface was estimated. Due to this, the critical shear strength was calculated at which the greatest strength of the composite can be achieved, these values being 107 MPa and 2675 MPa, respectively. It is shown that the contribution of the work of overcoming the friction force to the total work of fracture at relatively small values of shear strength can be several times greater than the total contribution of all other types of energy. Full article

(This article belongs to the Special Issue Advances in Preparation Methods and Numerical Simulation of Composites: Formation and Properties)

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11 pages, 3921 KiB

Open AccessArticle

Electrochemical Corrosion Behavior of CrFeCoNi and CrMnFeCoNi Coatings in Salt Solution

by Caimei Wang, Yang Yu, Peng He, Jianjun Zhang, Xiaoyu Ma, Hua Zhang, Huizhao Li and Minghao Shao

Metals 2022, 12(10), 1752; https://doi.org/10.3390/met12101752 - 18 Oct 2022

Viewed by 1137

Abstract

CrFeCoNi and CrMnFeCoNi coatings were prepared by laser remelting method. The grain boundary characteristics distribution of both coatings was investigated by electron backscattered diffraction technique. The results showed that the CrFeCoNi coating exhibited higher fraction of low angle grain boundaries and Σ3 boundaries [...] Read more.

CrFeCoNi and CrMnFeCoNi coatings were prepared by laser remelting method. The grain boundary characteristics distribution of both coatings was investigated by electron backscattered diffraction technique. The results showed that the CrFeCoNi coating exhibited higher fraction of low angle grain boundaries and Σ3 boundaries compared to the CrMnFeCoNi coating. The corrosion properties of the CrFeCoNi and CrMnFeCoNi coatings in 3.5 wt% NaCl solution were identified by electrochemical method and localized electrochemical impedance spectroscopy technique. The results indicated that the CrFeCoNi coating had a higher corrosion resistance than the CrMnFeCoNi coating. The better corrosion resistance of the CrFeCoNi coating could be attributed to the high fraction of Σ3 boundaries and low fraction of the high angle boundaries. Full article

(This article belongs to the Special Issue Amorphous and High-Entropy Alloy Coatings)

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15 pages, 1251 KiB

Open AccessArticle

A Comprehensive Investigation on the Effects of Surface Finishing on the Resistance of Stainless Steel to Localized Corrosion

by Elena Messinese, Luca Casanova, Luca Paterlini, Fausto Capelli, Fabio Bolzoni, Marco Ormellese and Andrea Brenna

Metals 2022, 12(10), 1751; https://doi.org/10.3390/met12101751 - 18 Oct 2022

Cited by 16 | Viewed by 2306

Abstract

The present research investigates the influence of surface roughness imparted by cold surface finishing processes on the localized corrosion resistance of stainless steel. Five different alloys were studied: ferritic AISI 430, martensitic AISI 430F, austenitic AISI 303, AISI 304L, and AISI 316L. It [...] Read more.

The present research investigates the influence of surface roughness imparted by cold surface finishing processes on the localized corrosion resistance of stainless steel. Five different alloys were studied: ferritic AISI 430, martensitic AISI 430F, austenitic AISI 303, AISI 304L, and AISI 316L. It was demonstrated that the grinding process, executed on previously cold drawn bars, leads to an improvement in corrosion resistance according to the results obtained with electrochemical tests, namely, potentiostatic and potentiodynamic tests in chloride-rich environments, the salt spray test, and long-term exposure in urban and marine atmospheres. This allowed us to establish a trend among the different alloys regarding the resistance to pitting corrosion, which was assessed according to pitting potentials, critical chloride contents, and pitting initiation time. All the tests confirmed that surface finishing, as well as alloy chemical composition, is an important factor in controlling the corrosion resistance of stainless steel. Full article

(This article belongs to the Special Issue Corrosion and Protection of Stainless Steels)

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19 pages, 2570 KiB

Open AccessArticle

Development of Three-Dimensional LES Based Meshless Model of Continuous Casting of Steel

by Katarina Mramor, Robert Vertnik and Božidar Šarler

Metals 2022, 12(10), 1750; https://doi.org/10.3390/met12101750 - 18 Oct 2022

Cited by 6 | Viewed by 1149

Abstract

A large-eddy simulation (LES) based meshless model is developed for the three-dimensional (3D) problem of continuous casting (CC) of steel billet. The local collocation meshless method based on radial basis functions (RBF) is applied in 3D. The method applies scaled multiquadric (MQ) RBF [...] Read more.

A large-eddy simulation (LES) based meshless model is developed for the three-dimensional (3D) problem of continuous casting (CC) of steel billet. The local collocation meshless method based on radial basis functions (RBF) is applied in 3D. The method applies scaled multiquadric (MQ) RBF with a shape parameter on seven nodded local sub-domains. The incompressible turbulent fluid flow is described using mass, energy, and momentum conservation equations and the LES turbulence model. The solidification system is solved with the mixture continuum model. The Boussinesq approximation for buoyancy and the Darcy approximation for porous media are used. Chorin’s fractional step method is used to couple velocity and pressure. The microscopic model is closed with the lever rule model. The LES model is compared to the two-equation Low Re

k - ε

turbulence Reynolds Averaged Navier–Stokes (RANS) model in terms of temperature, velocity and computational times. The LES model resolves transient character of vortices which RANS-type turbulence models are unable to tackle. The computational cost of LES models is considerably higher than in RANS. On the other hand, it results in a much lower computational cost than the direct numerical simulation (DNS). The paper demonstrates the ability of the method to solve realistic industrial 3D examples. Trivial adjustment of nodal densities, high accuracy, and low numerical diffusivity are the main advantages of this meshless method. Full article

(This article belongs to the Special Issue Digitalization and Advanced Software Support of the Steelmaking Industry)

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22 pages, 8802 KiB

Open AccessArticle

Electrical Discharge Machining of Alumina Using Ni-Cr Coating and SnO Powder-Mixed Dielectric Medium

by Anna A. Okunkova, Marina A. Volosova, Elena Y. Kropotkina, Khaled Hamdy and Sergey N. Grigoriev

Metals 2022, 12(10), 1749; https://doi.org/10.3390/met12101749 - 18 Oct 2022

Cited by 7 | Viewed by 1568

Abstract

Aluminum-based ceramics exhibit excellent wear resistance and hot hardness that are suitable for various responsible applications allowing products to work under extreme mechanical and thermal loads (up to 1000 °C). The problem of high-precision forming complex-shaped parts is a known engineering challenge due [...] Read more.

Aluminum-based ceramics exhibit excellent wear resistance and hot hardness that are suitable for various responsible applications allowing products to work under extreme mechanical and thermal loads (up to 1000 °C). The problem of high-precision forming complex-shaped parts is a known engineering challenge due to the insulating properties of aluminum-containing ceramics and the formation of chemically active carbides in a hydrocarbon medium. The alternative approach for electrical discharge machining non-conductive sintered Al₂O₃ in the water-based medium using nickel-chrome plasma-vapor-deposed coating of 12 mm, SnO powder suspension (particle diameter of ⌀10 µm, concentration of 150 g/L), and brass wire-tool is proposed. The productivity was evaluated by calculating the material removal rate and discharge gap for various combinations of pulse frequency and duration. The maximal material removal rate of 0.0014 mm³/s was achieved for a pulse frequency of 30 kHz and pulse duration of 1.7–2.5 μs. The recommended value of the interelectrode gap is 48.0 ± 4.9 µm. The possibility of electrical discharge machining aluminum-containing insulating ceramics without using hydrocarbons, carbon and copper-group assisting measures was proposed and shown for the first time. The chemical content of the debris in the interelectrode gap between components of the materials was thermochemically analyzed. Full article

(This article belongs to the Special Issue Machining of Advanced Cutting Materials: Fundamentals, Modeling and Applications)

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13 pages, 3425 KiB

Open AccessArticle

Hydrogen Trapping in Laser Powder Bed Fusion 316L Stainless Steel

by Polina Metalnikov, Guy Ben-Hamu and Dan Eliezer

Metals 2022, 12(10), 1748; https://doi.org/10.3390/met12101748 - 18 Oct 2022

Cited by 6 | Viewed by 2062

Abstract

In this study, the hydrogen embrittlement (HE) of 316L stainless steel produced by laser powder bed fusion (L-PBF) was investigated by means of hydrogen trapping. The susceptibility of the material to HE is strongly connected to the interaction of hydrogen atoms with volumetric [...] Read more.

In this study, the hydrogen embrittlement (HE) of 316L stainless steel produced by laser powder bed fusion (L-PBF) was investigated by means of hydrogen trapping. The susceptibility of the material to HE is strongly connected to the interaction of hydrogen atoms with volumetric defects in the material. Trapping hydrogen in those defects affects its availability to critical locations where a hydrogen-induced crack can nucleate. Therefore, it is important to study the characteristics of hydrogen traps to better understand the behavior of the material in the hydrogen environment. The hydrogen was introduced into the material via electrochemical charging, and its interactions with various trapping sites were studied through thermal desorption spectroscopy (TDS). The obtained results were compared to conventionally produced 316L stainless steel, and the correlation between microstructure, characteristics of hydrogen traps, and susceptibility to HE is discussed. Full article

(This article belongs to the Special Issue Environmental Degradation of Structural Materials)

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8 pages, 2076 KiB

Open AccessArticle

Experimental Investigation of Isothermal Section in the La–Co–Ni System at 723 K

by Kailin Huang, Liming Xiao, Qingkai Yang, Lu Yang, Zhuobin Li, Zhao Lu, Qingrong Yao, Jianqiu Deng, Lichun Cheng, Caimin Huang, Qianxin Long, Jiang Wang and Huaiying Zhou

Metals 2022, 12(10), 1747; https://doi.org/10.3390/met12101747 - 17 Oct 2022

Cited by 2 | Viewed by 1157

Abstract

The isothermal section of the La–Co–Ni ternary system at 723 K has been constructed in this work by using X-ray diffraction (XRD), scanning electron microscopy, and energy dispersion spectroscopy techniques (SEM-EDS). The experimental results show no existence of ternary compounds at 723 K. [...] Read more.

The isothermal section of the La–Co–Ni ternary system at 723 K has been constructed in this work by using X-ray diffraction (XRD), scanning electron microscopy, and energy dispersion spectroscopy techniques (SEM-EDS). The experimental results show no existence of ternary compounds at 723 K. The isothermal section consists of 16 two-phase regions and 8 three-phase regions. La₃Co and La₃Ni, La₂Co₃ and La₂Ni₃, La₂Co₇ and La₂Ni₇, and LaCo₅ and LaNi₅ form a continuous solid solution. The ternary solid solubility of Ni in LaCo₁₃ phase and La₂Co_1.7 phase was determined to be 15.61 at.% and 9.61 at.%, respectively. The solid solubility of Co in the LaNi₃, La₇Ni₃, and LaNi phases was 18.07 at.%, 5.62 at.%, and 8.49 at.%, respectively. The present experimental results are important for the design of La(Fe,Si)₁₃-based magnetic refrigeration materials. Full article

(This article belongs to the Section Computation and Simulation on Metals)

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11 pages, 4088 KiB

Open AccessArticle

High-Temperature Oxidation of CrN/ZrN Multilayer Coatings

by Andrey Vorontsov, Andrey Filippov, Nickolay Shamarin, Evgeny Moskvichev, Olga Novitskaya, Evgenii Knyazhev, Yuliya Denisova, Andrei Leonov, Vladimir Denisov and Sergei Tarasov

Metals 2022, 12(10), 1746; https://doi.org/10.3390/met12101746 - 17 Oct 2022

Cited by 6 | Viewed by 1399

Abstract

Multilayer nitride coatings provide some of the best performance when in their use for the production of metalworking tools. In this work, vacuum-arc plasma-assisted deposited multilayer ZrN/CrN coatings with different numbers of constituent layers were characterized for high-temperature oxidization in air using weighing, [...] Read more.

Multilayer nitride coatings provide some of the best performance when in their use for the production of metalworking tools. In this work, vacuum-arc plasma-assisted deposited multilayer ZrN/CrN coatings with different numbers of constituent layers were characterized for high-temperature oxidization in air using weighing, confocal and scanning electron microscopy and synchrotron XRD. Oxidizing at 300 °C did not deteriorate the coating surfaces, while higher temperatures caused surface deterioration and oxidation accompanied by cracking, delamination and considerable mass gains. The coating with higher number of thinner layers showed higher oxidation resistance due to more prominent oxygen barrier effect. Full article

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10 pages, 11386 KiB

Open AccessArticle

Static Recrystallization Behavior of Low-Carbon Nb-V-Microalloyed Forging Steel

by Yang Zhao, Jiahao Zheng, Liqing Chen and Xianghua Liu

Metals 2022, 12(10), 1745; https://doi.org/10.3390/met12101745 - 17 Oct 2022

Cited by 5 | Viewed by 1243

Abstract

Static recrystallization is a method of tailoring the microstructure and mechanical properties of steels, which is important for microalloyed forging steels as the hot deformation process significantly affects their mechanical properties. In this paper, the static recrystallization behavior of a low-carbon Nb-V-microalloyed forging [...] Read more.

Static recrystallization is a method of tailoring the microstructure and mechanical properties of steels, which is important for microalloyed forging steels as the hot deformation process significantly affects their mechanical properties. In this paper, the static recrystallization behavior of a low-carbon Nb-V-microalloyed forging steel was investigated by double-pass hot compression tests at deformation temperature of 800–1100 °C and interruption time of 1–1000 s. The static recrystallization fractions were determined using the 2% offset method. The static recrystallization activation energy and the static recrystallization critical temperature (SRCT) of the experimental steel were determined. When the deformation temperature was higher than the SRCT, the recrystallization fraction curve conformed to the Avrami equation. When the deformation temperature was below the SRCT, the recrystallization curve appeared to plateau, which was caused by strain-induced precipitation. Before and after the plateau, the static recrystallization kinetics still obeyed the Avrami equation. Full article

(This article belongs to the Special Issue Advanced Technology in Microalloyed Steels)

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