Metals

19 pages, 9314 KiB

Open AccessArticle

Fabrication, Microstructure, Mechanical, and Electrochemical Properties of NiMnFeCu High Entropy Alloy from Elemental Powders

by Ashok Kumar, Michael Mucalo, Leandro Bolzoni, Yiming Li, Fantao Kong and Fei Yang

Metals 2022, 12(1), 167; https://doi.org/10.3390/met12010167 - 17 Jan 2022

Cited by 8 | Viewed by 3219

Abstract

Transition metal based high entropy alloys (HEAs) are often used in electrocatalytic (water electrolysis) applications due to the synergistic effect operating among its constituent elements and unpaired electrons in d orbitals of the concerned metal. In this study, a low cost NiMnFeCu high [...] Read more.

Transition metal based high entropy alloys (HEAs) are often used in electrocatalytic (water electrolysis) applications due to the synergistic effect operating among its constituent elements and unpaired electrons in d orbitals of the concerned metal. In this study, a low cost NiMnFeCu high entropy alloy was successfully synthesised using the combined techniques of mechanical milling (MA) and vacuum sintering. X-ray diffraction was used to analyse the phase composition, optical microscopy, and scanning electron microscopy were used to characterise the fabricated material’s microstructure and chemical homogeneity, thermal, and mechanical properties were tested using the differential scanning calorimetry method and a universal testing machine, respectively. Electrochemical workstation was used to carry out preliminary electrochemical studies such as linear sweep voltammetry (LSV), cyclic voltammetry (CV) and chronoamperometry. The results showed that the as- sintered NiMnFeCu HEA possessed a single- phase FCC structure. The HEA NiMnFeCu sintered at 1050 °C (S4) and 1000 °C (S2) with a holding time of 2 h showed a yield strength of 516.3 MPa and 389.8 MPa, respectively, and the micro-hardness values were measured to be 233.45 ± 9 HV and 198.7 ± 8 HV, respectively. Preliminary electrochemical studies proved that the alloy sintered at 1000 °C (S2) with a holding time of 2 h exhibited excellent electrocatalytic properties with a measured overpotential of 322 mV at 10 mA cm⁻² at 100 cycles of CV and good stability for 10 h when compared to state-of-the-art electrocatalytic materials

{IrO}_{2}

and Ru

O_{2}

. This suggested that the HEA NiMnFeCu fabricated under the condition S2 could potentially be used for industrial-scale water electrolysis as it possesses permissible mechanical and good electrochemical properties. Full article

(This article belongs to the Special Issue Hot Forming/Processing of Metallic Materials)

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12 pages, 6050 KiB

Open AccessArticle

Influence of Magnetic Fields Assisted for Preparation of Ferromagnetic Mono- and Bi-Metallic Co and Co–V SHS Catalysts on Their Activity in Deep Oxidation and Hydrogenation of CO₂

by Elena Pugacheva, Vyacheslav Borshch, Svetlana Zhuk, Dmitrii Andreev, Denis Ikornikov, Olga Boyarchenko and Olga Golosova

Metals 2022, 12(1), 166; https://doi.org/10.3390/met12010166 - 17 Jan 2022

Viewed by 1694

Abstract

Co–Al and Co–V–Al intermetallics produced by centrifugal self-propagating high-temperature synthesis (SHS) were used as precursors for preparation of catalysts for deep oxidation and hydrogenation of CO₂. Leaching in NaOH solution and stabilization with H₂O₂ solution of precursors were [...] Read more.

Co–Al and Co–V–Al intermetallics produced by centrifugal self-propagating high-temperature synthesis (SHS) were used as precursors for preparation of catalysts for deep oxidation and hydrogenation of CO₂. Leaching in NaOH solution and stabilization with H₂O₂ solution of precursors were carried out in permanent magnetic field (MF) (0.24 Т) and alternating magnetic field (0.13 Т, 50 Hz). Prepared Co и Co–V (95Co–5V, 90Co–10V) granular catalysts with size of 100–300 µm were characterized by XRD, SEM, EDS, and BET method and revealed to have a scaly surface structure. It was shown that the type of MF affects phase composition and surface morphology, as well as specific surface and activity in deep oxidation of CO and hydrocarbons as an important part of the neutralization of gas emissions, and hydrogenation of CO₂, the processing of which would reduce atmospheric pollution with this greenhouse gas. Catalysts obtained in alternating MF was found to possess higher activity in the process of deep oxidation. Full article

(This article belongs to the Special Issue Metallothermic Reactions)

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21 pages, 25577 KiB

Open AccessReview

A Review on Thermophysical Property Assessment of Metal Oxide-Based Nanofluids: Industrial Perspectives

by Surendran V. Sujith, Hansoo Kim and Joonho Lee

Metals 2022, 12(1), 165; https://doi.org/10.3390/met12010165 - 17 Jan 2022

Cited by 25 | Viewed by 3365

Abstract

Energy consumption in the industrial sector can be significantly reduced by improving heat transfer rates in heat exchanger circuits, pool boiling, metal cutting industries, etc. Numerous energy-related issues can be overcome to a large extent by improving heat flow properties by utilizing nanofluids. [...] Read more.

Energy consumption in the industrial sector can be significantly reduced by improving heat transfer rates in heat exchanger circuits, pool boiling, metal cutting industries, etc. Numerous energy-related issues can be overcome to a large extent by improving heat flow properties by utilizing nanofluids. The present contribution reviews the improvement in thermophysical properties of metal oxide-based nanofluids. Key parameters affecting the thermophysical properties of nanofluids, such as particle volume fraction, temperature, particle size and various stabilizers, were reviewed. The importance of DLVO theory and zeta potential to control the electrostatic repulsion and pH values of nanofluids for stable nanofluid formulations were discussed. It has been observed that classical theories of thermal conductivity and viscosity cannot predict exact values for a wide range of variables. Therefore, various extensive correlations have been introduced to predict the thermophysical properties of nanofluids. In these correlations, individual dependent variables such as particle size, temperature, nanofluid layer thickness, and Brownian velocity of nanoparticles, etc. were considered for more accurate prediction. The heat transfer efficiencies of nanofluids to base fluids in the laminar and turbulent regimes have been discussed using various figures of merits. Finally, the scope of industrial applications of metal oxide-based nanofluids and future research opportunities have been discussed. Full article

(This article belongs to the Special Issue Thermo-Physical Properties of Metals and Oxides)

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12 pages, 6482 KiB

Open AccessArticle

Effect of Fe₂O₃ on the Crystallization Behavior of Glass-Ceramics Produced from Secondary Nickel Slag

by Xiaoming Li, Xuyuan Zang, Xiangdong Xing, Jinke Li, Yuwei Ma and Tao Li

Metals 2022, 12(1), 164; https://doi.org/10.3390/met12010164 - 17 Jan 2022

Cited by 9 | Viewed by 2273

Abstract

In this paper, glass-ceramics were prepared from secondary nickel slag by the melting method. The effects of Fe₂O₃ on the crystallization behavior of glass-ceramics were investigated by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The properties of glass-ceramics [...] Read more.

In this paper, glass-ceramics were prepared from secondary nickel slag by the melting method. The effects of Fe₂O₃ on the crystallization behavior of glass-ceramics were investigated by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The properties of glass-ceramics such as Vickers hardness, bending strength, and acid and alkali resistance were systematically discussed. The results indicate that the crystallization temperature (Tc) and transition temperature (Tg) of the glass show a trend of decreasing and then increasing with the increase in Fe₂O₃ content. The precipitation and refinement of the crystalline phase were promoted significantly when the Fe₂O₃ content was lower (≤9.32 wt%), while the crystallinity decreased slightly when the Fe₂O₃ content increased to 12.42 wt%. The promotion of crystal precipitation led to the depolymerization of the glass network. When the Fe₂O₃ content was 9.32 wt%, the sample exhibited the best crystallization ability, consisting of uniformly distributed anorthite, ferrobustamite and glass phases, while the Vickers hardness and bending strength were 11.42 GPa and 121 MPa, respectively. Full article

(This article belongs to the Special Issue Advances in Slag Metallurgy)

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Graphical abstract

20 pages, 6630 KiB

Open AccessArticle

Grain Scale Investigation of the Mechanical Anisotropic Behavior of Electron Beam Powder Bed Additively Manufactured Ti6Al4V Parts

by Md Jamal Mian, Jafar Razmi and Leila Ladani

Metals 2022, 12(1), 163; https://doi.org/10.3390/met12010163 - 17 Jan 2022

Cited by 5 | Viewed by 2328

Abstract

Numerous factors, including variable grain structures and different inherent defects, impact the mechanical behavior of Ti6Al4V parts fabricated using metal Additive Manufacturing (AM) processes. This study focuses on an in-depth analysis of how different microstructural features, such as crystallographic texture, grain size, grain [...] Read more.

Numerous factors, including variable grain structures and different inherent defects, impact the mechanical behavior of Ti6Al4V parts fabricated using metal Additive Manufacturing (AM) processes. This study focuses on an in-depth analysis of how different microstructural features, such as crystallographic texture, grain size, grain boundary misorientation angles, and inherent defects, as byproducts of the electron beam powder bed fusion (EB-PBF) AM process, impact its anisotropic mechanical behavior. Standard tensile testing, conducted on samples produced at different orientations relative to the build table, showed significant anisotropy in elastic-plastic constitutive characteristics. Furthermore, X-ray computed tomography (CT) and electron back-scattered diffraction (EBSD) analyses were conducted on as-built samples to assess the effects of inherent defects and microstructural anomalies on such behavior. The samples arranged vertically and parallel to build direction had an average porosity of 0.05%, while the horizontally built samples, which were perpendicular to the build direction, had an average porosity of 0.17%. Moreover, the vertical samples showed larger grain sizes, with an average of 6.6 µm, wider α lath sizes, a lower average misorientation angle, and subsequently lower strength values than the other two horizontal samples. Among the three strong preferred grain orientations of the α phases, <1 1

\bar{2}

1> and <1 1

\bar{2}

0> were dominant in the horizontally built samples, whereas the <0 0 0 1> orientation was dominant in vertically built samples. Finally, larger grain sizes and higher beta-phase volume ratios were observed in the areas located at distances further away from the build plate. This was possibly due to the change in thermal gradients, cooling rates, and some thermal annealing phenomena resultant from the elevated build chamber temperature. Full article

(This article belongs to the Special Issue Optimization of Metal Additive Manufacturing Processes)

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14 pages, 7607 KiB

Open AccessArticle

Inclusion Removements in a Bottom-Stirring Ladle with Novel Slot-Porous Matched Dual Plugs

by Xianglong Li, Shaoyan Hu, Deyong Wang, Tianpeng Qu, Guangjun Wu, Pei Zhang, Qi Quan, Xingzhi Zhou and Zhixiao Zhang

Metals 2022, 12(1), 162; https://doi.org/10.3390/met12010162 - 17 Jan 2022

Cited by 9 | Viewed by 2744

Abstract

The cleanness of steel has always been a big problem for secondary refining. In this work, a new method, which is coupled with slot and porous plugs, is proposed to improve the cleanness in steel. Water experiments and numerical simulations were performed to [...] Read more.

The cleanness of steel has always been a big problem for secondary refining. In this work, a new method, which is coupled with slot and porous plugs, is proposed to improve the cleanness in steel. Water experiments and numerical simulations were performed to study this effect. Results revealed that when using slot-porous plugs, the flow field was obviously asymmetrical, and the circulation flow was pushed towards the porous side. Then, the removement of inclusions was increased to about 22.7% percent, comparing with traditional two-slot bottom stirring and reducing the dead zone area near the bottom of the ladle; however, the mixing time delay was 16%, comparing with traditional plugs. Then, in order to explain the reason for these phenomena, we established a mathematical model through large eddy simulation and discrete particle modeling (DPM). Results shows that the asymmetry flow field awoke the recirculation flow downwards after using slot-porous plugs, which would homogenize the flow at the bottom, promoting floating in steel. What is more, the velocity near the free surface was lowered; therefore, it could also stabilize the surface velocity as well, which is also beneficial for removing inclusions as well. Full article

(This article belongs to the Special Issue Numerical Modeling of Metallurgical Processes: Continuous Casting and Electroslag Remelting)

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17 pages, 6615 KiB

Open AccessArticle

Characterisation of Compressive Behaviour of Low-Carbon and Third Generation Advanced High Strength Steel Sheets with Freely Movable Anti-buckling Bars

by Jaehoon Kim, Jaebong Jung, Taejoon Park, Daeyong Kim, Young Hoon Moon, Farhang Pourboghrat and Ji Hoon Kim

Metals 2022, 12(1), 161; https://doi.org/10.3390/met12010161 - 17 Jan 2022

Cited by 3 | Viewed by 2048

Abstract

Measuring the compressive behaviour of sheet materials is an important process for understanding the material behaviour and numerical simulation of metal forming. The application of side force on both surfaces of a specimen in the thickness direction is an effective way to prevent [...] Read more.

Measuring the compressive behaviour of sheet materials is an important process for understanding the material behaviour and numerical simulation of metal forming. The application of side force on both surfaces of a specimen in the thickness direction is an effective way to prevent buckling when conducting compressive tests. However, the side effects of side forces (such as the biaxial stress state and non-uniform deformation) make it difficult to interpret the measured data and derive the intrinsic compressive behaviour. It is even more difficult for materials with tension–compression asymmetry such as steels that undergo transformation-induced plasticity. In this study, a novel design for a sheet compression tester was developed with freely movable anti-buckling bars on both sides of the specimen to prevent buckling during in-plane compressive loading. Tensile and compressive tests under side force were conducted for low-carbon steel using the digital image correlation method. The raw tensile and compressive stress–strain data of the low-carbon steel showed apparent flow stress asymmetry of tension and compression, originating from the biaxial and thickness effects. A finite element method-based data correction procedure was suggested and validated for the low-carbon steel. The third generation advanced high strength steels showed intrinsic tension–compression asymmetry at room temperature whereas the asymmetry was significantly reduced at 175 °C. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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15 pages, 3431 KiB

Open AccessArticle

Influence of Bifilm Defects Generated during Mould Filling on the Tensile Properties of Al–Si–Mg Cast Alloys

by Mahmoud Ahmed El-Sayed, Khamis Essa and Hany Hassanin

Metals 2022, 12(1), 160; https://doi.org/10.3390/met12010160 - 16 Jan 2022

Cited by 3 | Viewed by 2325

Abstract

Entrapped double oxide film defects are known to be the most detrimental defects during the casting of aluminium alloys. In addition, hydrogen dissolved in the aluminium melt was suggested to pass into the defects to expand them and cause hydrogen porosity. In this [...] Read more.

Entrapped double oxide film defects are known to be the most detrimental defects during the casting of aluminium alloys. In addition, hydrogen dissolved in the aluminium melt was suggested to pass into the defects to expand them and cause hydrogen porosity. In this work, the effect of two important casting parameters (the filtration and hydrogen content) on the properties of Al–7 Si–0.3 Mg alloy castings was studied using a full factorial design of experiments approach. Casting properties such as the Weibull modulus and position parameter of the elongation and the tensile strength were considered as response parameters. The results suggested that adopting 10 PPI filters in the gating system resulted in a considerable boost of the Weibull moduli of the tensile strength and elongation due to the enhanced mould filling conditions that minimised the possibility of oxide film entrainment. In addition, the results showed that reducing the hydrogen content in the castings samples from 0.257 to 0.132 cm³/100 g Al was associated with a noticeable decrease in the size of bifilm defects with a corresponding improvement in the mechanical properties. Such significant effect of the process parameters studied on the casting properties suggests that the more careful and quiescent mould filling practice and the lower the hydrogen level of the casting, the higher the quality and reliability of the castings produced. Full article

(This article belongs to the Special Issue Casting and Forming of Light Alloys)

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22 pages, 5880 KiB

Open AccessArticle

Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

by Nicholas Olynik, Bin Cheng, David J. Sprouster, Chad M. Parish and Jason R. Trelewicz

Metals 2022, 12(1), 159; https://doi.org/10.3390/met12010159 - 15 Jan 2022

Cited by 6 | Viewed by 4092

Abstract

Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this [...] Read more.

Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders. Full article

(This article belongs to the Special Issue Tungsten and Tungsten Alloys)

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22 pages, 4147 KiB

Open AccessArticle

Manufacture of Defined Residual Stress Distributions in the Friction-Spinning Process: Investigations and Run-to-Run Predictive Control

by Frederik Dahms and Werner Homberg

Metals 2022, 12(1), 158; https://doi.org/10.3390/met12010158 - 15 Jan 2022

Cited by 4 | Viewed by 2176

Abstract

Friction-spinning as an innovative incremental forming process enables high degrees of deformation in the field of tube and sheet metal forming due to self-induced heat generation in the forming area. The complex thermomechanical conditions generate non-uniform residual stress distributions. In order to specifically [...] Read more.

Friction-spinning as an innovative incremental forming process enables high degrees of deformation in the field of tube and sheet metal forming due to self-induced heat generation in the forming area. The complex thermomechanical conditions generate non-uniform residual stress distributions. In order to specifically adjust these residual stress distributions, the influence of different process parameters on residual stress distributions in flanges formed by the friction-spinning of tubes is investigated using the design of experiments (DoE) method. The feed rate with an effect of −156 MPa/mm is the dominating control parameter for residual stress depth distribution in steel flange forming, whereas the rotation speed of the workpiece with an effect of 18 MPa/mm dominates the gradient of residual stress generation in the aluminium flange-forming process. A run-to-run predictive control system for the specific adjustment of residual stress distributions is proposed and validated. The predictive model provides an initial solution in the form of a parameter set, and the controlled feedback iteratively approaches the target value with new parameter sets recalculated on the basis of the deviation of the previous run. Residual stress measurements are carried out using the hole-drilling method and X-ray diffraction by the cosα-method. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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14 pages, 2900 KiB

Open AccessArticle

Mechanical Behaviour and Failure Mode of High Interstitially Alloyed Austenite under Combined Compression and Cyclic Torsion

by Timothy Ngeru, Dzhem Kurtulan, Ahmet Karkar and Stefanie Hanke

Metals 2022, 12(1), 157; https://doi.org/10.3390/met12010157 - 15 Jan 2022

Cited by 6 | Viewed by 2359

Abstract

Multiaxial stress states frequently occur in technical components and, due to the multitude of possible load situations and variations in behaviour of different materials, are to date not fully predictable. This is particularly the case when loads lie in the plastic range, when [...] Read more.

Multiaxial stress states frequently occur in technical components and, due to the multitude of possible load situations and variations in behaviour of different materials, are to date not fully predictable. This is particularly the case when loads lie in the plastic range, when strain accumulation, hardening and softening play a decisive role for the material reaction. This study therefore aims at adding to the understanding of material behaviour under complex load conditions. Fatigue tests conducted under cyclic torsional angles (5°, 7.5°, 10° and 15°), with superimposed axial static compression loads (250 MPa and 350 MPa), were carried out using smooth specimens at room temperature. A high nitrogen alloyed austenitic stainless steel (nickel free), was employed to determine not only the number of cycles to failure but particularly to aid in the understanding of the mechanical material reaction to the multiaxial stresses as well as modes of crack formation and growth. Experimental test results indicate that strain hardening occurs under the compressive strain, while at the same time cyclic softening is observable in the torsional shear stresses. Furthermore, the cracks’ nature is unusual with multiple branching and presence of cracks perpendicular in direction to the surface cracks, indicative of the varying multiaxial stress states across the samples’ cross section as cross slip is activated in different directions. In addition, it is believed that the static compressive stress facilitated the Stage I (mode II) crack to change direction from the axial direction to a plane perpendicular to the specimen’s axis. Full article

(This article belongs to the Special Issue Fatigue Behavior and Crack Mechanism of Metals and Alloys)

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15 pages, 13928 KiB

Open AccessArticle

First-Principles Calculations of Y-Si-O Nanoclusters and Effect of Si on Microstructure and Mechanical Properties of 12Cr ODS Steel in Vacuum Sintering System

by Feng Su, Guangtao Xu, Zhenhua Yao, Huachen Liu and Yikun Chen

Metals 2022, 12(1), 155; https://doi.org/10.3390/met12010155 - 15 Jan 2022

Cited by 1 | Viewed by 2091

Abstract

High density of thermally stable Y-Si-O nanoparticles dispersed in the Fe matrix play a primary role in oxide dispersion strengthened (ODS) steel. In this study, the binding energies of solutes Y, O and Si with vacancies have been calculated in the framework of [...] Read more.

High density of thermally stable Y-Si-O nanoparticles dispersed in the Fe matrix play a primary role in oxide dispersion strengthened (ODS) steel. In this study, the binding energies of solutes Y, O and Si with vacancies have been calculated in the framework of first-principles density functional theory. According to the calculations, any two solutes of Y, O and Si bound with each other strongly in the second nearest neighboring (NN) sites while not in 1NN. A vacancy (v) bounds strongly with Y and O in 1NN site. The binding sequence of solutes with v followed O-v → Y-v → Si-v, and the affinity of Y, Si and v with O followed O-Y → O-v → O-Si. The nucleation mechanism of Y-O-Si nanoclusters was determined, which gave the feasibility of adding Si to ODS steels. The core (consisting of Si and O)-shell (enriched Fe and Cr) structure of the microparticles was found in ODS steels containing Si, fabricated by mechanical alloying (MA) and vacuum sintering. Moreover the nanoparticles of monoclinic cubic Y₂O₃, Y₂SiO₅ and Y₂Si₂O₇ with sizes of 5~12 nm were observed in ODS steel. Si reduced the sintering temperature by maximizing densities and mechanical properties at a lower sintering temperature. The steel with 3 wt% Si was sintered at 1280 °C, exhibiting the best comprehensive mechanical properties. The tensile strength, hardness and relative density were 1025 MPa, 442.44 HV and 95.3%, respectively. Full article

(This article belongs to the Topic Metal Matrix Composites: Recent Advancements)

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18 pages, 8375 KiB

Open AccessArticle

Fatigue Assessment of Inconel 625 Produced by Directed Energy Deposition from Miniaturized Specimens

by Felipe Klein Fiorentin, Duarte Maciel, Jorge Gil, Miguel Figueiredo, Filippo Berto and Abílio de Jesus

Metals 2022, 12(1), 156; https://doi.org/10.3390/met12010156 - 14 Jan 2022

Cited by 11 | Viewed by 3561

Abstract

In recent years, the industrial application of Inconel 625 has grown significantly. This material is a nickel-base alloy, which is well known for its chemical resistance and mechanical properties, especially in high-temperature environments. The fatigue performance of parts produced via Metallic Additive Manufacturing [...] Read more.

In recent years, the industrial application of Inconel 625 has grown significantly. This material is a nickel-base alloy, which is well known for its chemical resistance and mechanical properties, especially in high-temperature environments. The fatigue performance of parts produced via Metallic Additive Manufacturing (MAM) heavily rely on their manufacturing parameters. Therefore, it is important to characterize the properties of alloys produced by a given set of parameters. The present work proposes a methodology for characterization of the mechanical properties of MAM parts, including the material production parametrization by Laser Directed Energy Deposition (DED). The methodology consists of the testing of miniaturized specimens, after their production in DED, supported by a numerical model developed and validated by experimental data for stress calculation. An extensive mechanical characterization, with emphasis on high-cycle fatigue, of Inconel 625 produced via DED is herein discussed. The results obtained using miniaturized specimens were in good agreement with standard-sized specimens, therefore validating the applied methodology even in the case of some plastic effects. Regarding the high-cycle fatigue properties, the samples produced via DED presented good fatigue performance, comparable with other competing Metallic Additive Manufactured (MAMed) and conventionally manufactured materials. Full article

(This article belongs to the Special Issue Fatigue Behavior Analysis of Metals and Alloys)

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13 pages, 2538 KiB

Open AccessArticle

Infrared Thermography for Investigation of Surface Quality in Dry Finish Turning of Ti6Al4V

by Manuela De Maddis, Vincenzo Lunetto, Valentino Razza and Pasquale Russo Spena

Metals 2022, 12(1), 154; https://doi.org/10.3390/met12010154 - 14 Jan 2022

Cited by 5 | Viewed by 2006

Abstract

The machining of titanium alloys always raises issues because of their peculiar chemical and physical characteristics as compared to traditional steel or aluminum alloys. A proper selection of parameters and their monitoring during the cutting operation makes it possible to minimize the surface [...] Read more.

The machining of titanium alloys always raises issues because of their peculiar chemical and physical characteristics as compared to traditional steel or aluminum alloys. A proper selection of parameters and their monitoring during the cutting operation makes it possible to minimize the surface roughness and cutting force. In this experimental study, infrared thermography was used as a control parameter of the surface roughness of Ti6A4V in dry finish turning. An analysis of variance was carried out to determine the effect of the main cutting parameters (cutting speed and feed rate) on the surface roughness and cutting temperature. In the examined range of the machining parameters, cutting speed and feed were found to have a primary effect on the surface roughness of the machined parts. Cutting speed also significantly affected the temperature of the cutting region, while feed was of second order. Higher cutting speeds and intermediate feed values gave the best surface roughness. A regression analysis defined some models to relate the cutting temperature and surface roughness to the machining parameters. Infrared thermography demonstrated that the cutting temperature could be related to roughness. Full article

(This article belongs to the Special Issue Advances in Titanium Alloys and Manufacturing and Processing Technologies)

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16 pages, 6465 KiB

Open AccessArticle

The Effect of Heavy-Duty Vehicle Crossings on the State of Stress of Buried Pipelines

by Ľubomír Gajdoš, Martin Šperl, Jan Kec and Petr Crha

Metals 2022, 12(1), 153; https://doi.org/10.3390/met12010153 - 14 Jan 2022

Cited by 2 | Viewed by 1976

Abstract

The aim of this article is to quantify the loads exerted by heavy-duty vehicles when crossing over buried pipeline. This problem arises in connection to the question pertaining to the use of protective sleeves (casings) applied to gas pipelines in regions with increased [...] Read more.

The aim of this article is to quantify the loads exerted by heavy-duty vehicles when crossing over buried pipeline. This problem arises in connection to the question pertaining to the use of protective sleeves (casings) applied to gas pipelines in regions with increased demands on pipeline operation safety. An experiment was conducted on a test pipe section made from L360NE pipeline steel equipped with strain gauges along the pipe perimeter, measuring strains in the axial and circumferential directions. Strain measurements were taken after back-filling the pipe trench, then during vehicle crossings over the empty pipe, and again after pressurizing the test pipe with air. Strain-based hoop stresses at the surface of the empty test pipe were found to exceed 30 MPa after back-filling the trench and increased to more than 40 MPa during the vehicle crossings. Similarly, axial stresses reached extremes of around 17 MPa in compression and 12 MPa in tension. Applying internal air pressure to the test pipe resulted in a reduced net effect on both the hoop and axial stresses. Full article

(This article belongs to the Special Issue Mechanical, Crack and Fatigue Properties of Tool Steel, Pipe Steel, and Laser Welded Steel)

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17 pages, 115015 KiB

Open AccessArticle

Superplastic Forming and Reaction Diffusion Bonding Process of Hollow Structural Component for Mg-Gd-Y-Zn-Zr Rare Earth Magnesium Alloy

by Peng Peng, Shaosong Jiang, Zhonghuan Qin and Zhen Lu

Metals 2022, 12(1), 152; https://doi.org/10.3390/met12010152 - 14 Jan 2022

Cited by 1 | Viewed by 2206

Abstract

This work fabricated a double hollow structural component of Mg-8.3Gd-2.9Y-0.8Zn-0.2Zr alloy by superplastic forming (SPF) and reaction-diffusion bonding (RDB). The superplastic characteristic and mechanical properties of Mg-8.3Gd-2.9Y-0.8Zn-0.2Zr alloy sheets at 250–450 °C were studied. Tensile tests showed that the maximum elongation of tensile [...] Read more.

This work fabricated a double hollow structural component of Mg-8.3Gd-2.9Y-0.8Zn-0.2Zr alloy by superplastic forming (SPF) and reaction-diffusion bonding (RDB). The superplastic characteristic and mechanical properties of Mg-8.3Gd-2.9Y-0.8Zn-0.2Zr alloy sheets at 250–450 °C were studied. Tensile tests showed that the maximum elongation of tensile specimens was about 1276.3% at 400 °C under a strain rate of 1 × 10⁻³ s⁻¹. Besides, the effect of bonding temperature and interface roughness on microstructure and mechanical properties of the reaction diffusion-bonded joints with a Cu interlayer was investigated. With the increase of temperature, the diffusion coefficient of Cu increases, and the diffusion transition region becomes wider, leading to tightening bonding of the joint. However, the bonding quality of the joint will deteriorate due to grain size growth at higher temperatures. Shear tests showed that the highest strength of the joints was 152 MPa (joint efficiency = 98.7%), which was performed at 460 °C. Full article

(This article belongs to the Special Issue Metal Forming—Hot Forming Technologies of Light Alloy Tubes and Sheets)

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16 pages, 4659 KiB

Open AccessArticle

Continuous Prediction Model of Carbon Content in 120 t Converter Blowing Process

by Dazhi Wang, Fang Gao, Lidong Xing, Jianhua Chu and Yanping Bao

Metals 2022, 12(1), 151; https://doi.org/10.3390/met12010151 - 14 Jan 2022

Cited by 7 | Viewed by 2376

Abstract

A continuous prediction model of carbon content of 120 t BOF is established in this paper. Based on the three-stage decarburization theory and combined with the production process of 120 t converter, the effects of oxygen lance height and top blowing oxygen flow [...] Read more.

A continuous prediction model of carbon content of 120 t BOF is established in this paper. Based on the three-stage decarburization theory and combined with the production process of 120 t converter, the effects of oxygen lance height and top blowing oxygen flow rate are also considered in the model. The explicit finite difference method is used to realize continuous prediction of carbon content in the converter blowing process. The model parameters such as ultimate carbon content in molten pool are calculated according to the actual data of 120 t BOF, which improves the hit rate of the model. Process verification and end-point verification for the continuous prediction model have been carried out, and the results of process verification indicate that the continuous prediction model established in the paper basically accords with the actual behavior of decarburization. Moreover, the hit ratio of the continuous prediction model reached 85% for the prediction of end-point carbon content within a tolerance of ±0.02%. Full article

(This article belongs to the Topic Processing, Analysis, Modelling and Mechanics of Materials and Structures)

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20 pages, 4828 KiB

Open AccessArticle

Corrosion Activity of Carbon Steel B450C and Low Chromium Ferritic Stainless Steel 430 in Chloride-Containing Cement Extract Solution

by Lucien Veleva, David Bonfil, Ángel Bacelis, Sebastian Feliu, Jr., Marina Cabrini and Sergio Lorenzi

Metals 2022, 12(1), 150; https://doi.org/10.3390/met12010150 - 14 Jan 2022

Cited by 3 | Viewed by 2715

Abstract

The carbon steel B450C and low chromium SS 430 ferritic samples were exposed for 30 days to chloride-containing (5 g L⁻¹ NaCL) cement extract solution. The initial pH ≈ 13.88 decreased to pH ≈ 9.6, associated mainly with the consumption of OH [...] Read more.

The carbon steel B450C and low chromium SS 430 ferritic samples were exposed for 30 days to chloride-containing (5 g L⁻¹ NaCL) cement extract solution. The initial pH ≈ 13.88 decreased to pH ≈ 9.6, associated mainly with the consumption of OH⁻ ions and the formation of γ-FeOOH, α-FeOOH, Fe₃O₄ and Cr(OH)₃, as suggested by XRD and XPS analysis, in the presence of CaCO₃ and NaCl crystals. The deep corrosion damages on B450C were observed around particles of Cu and S as local cathodes, while the first pitting events on the SS 430 surface appeared after 30 days of exposure. The change in the activity of each type of steel was provided by the potentiodynamic polarization curves (PDP). Two equivalent electrical circuits (EC) were proposed for quantitative analysis of EIS (Nyquist and Bode diagrams). The calculated polarization resistance (R_p), as an indicator of the stability of passive films, revealed that SS 430 presented relatively constant values, being two-three orders of magnitude higher than those of the carbon steel B450C. The calculated thickness (d) of the SS 430 passive layers was ≈0.5 nm and, in contrast, that of the B450C passive layers tends to disappear after 30 days. Full article

(This article belongs to the Special Issue Corrosion and Electrochemical Behaviors of Metals)

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18 pages, 5967 KiB

Open AccessArticle

Silver Nanoparticles: An Instantaneous Solution for Anticancer Activity against Human Liver (HepG2) and Breast (MCF-7) Cancer Cells

by Abdulaziz A. Al-Khedhairy and Rizwan Wahab

Metals 2022, 12(1), 148; https://doi.org/10.3390/met12010148 - 14 Jan 2022

Cited by 50 | Viewed by 5132

Abstract

Cancer is a cataclysmic disease that affects not only the target organ, but also the whole body. Metal-based nanoparticles (NPs) have recently emerged as a better option for the treatment of this deadly disease. Accordingly, the present work describes a means to control [...] Read more.

Cancer is a cataclysmic disease that affects not only the target organ, but also the whole body. Metal-based nanoparticles (NPs) have recently emerged as a better option for the treatment of this deadly disease. Accordingly, the present work describes a means to control the growth of cancer cells by using colloidal silver nanoparticles (AgNPs) processed via homemade solutions and the characterization of these materials. The AgNPs may become an instantaneous solution for the treatment of these deadly diseases and to minimize or remove these problems. The AgNPs exhibit excellent control of the growth rate of human liver (HepG2) and breast (MCF-7) cancer cells, even at a very low concentrations. The cytotoxic effects of AgNPs on HepG2 and MCF-7 cancer cells were dose dependent (2–200 μg/mL), as evaluated using MTT and NRU assays. The production of reactive oxygen species (ROS) was increased by 136% and 142% in HepG2 and MCF-7 cells treated with AgNPs, respectively. The quantitative polymerase chain reaction (qPCR) data for both cell types (HepG2 and MCF-7) after exposure to AgNPs showed up- and downregulation of the expression of apoptotic (p53, Bax, caspase-3) and anti-apoptotic (BCl2) genes; moreover, their roles were described. This work shows that NPs were successfully prepared and controlled the growth of both types of cancer cells. Full article

(This article belongs to the Special Issue The Biological Applications of Metals and Metal Complexes)

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15 pages, 10742 KiB

Open AccessArticle

Characterization of Waste Amidoxime Chelating Resin and Its Reutilization Performance in Adsorption of Pb(II), Cu(II), Cd(II) and Zn(II) Ions

by Chunhui Zheng, Chunlin He, Yingjie Yang, Toyohisa Fujita, Guifang Wang and Wenchao Yang

Metals 2022, 12(1), 149; https://doi.org/10.3390/met12010149 - 13 Jan 2022

Cited by 13 | Viewed by 2203

Abstract

The continuous expansion of the market demand and scale of commercial amidoxime chelating resins has caused large amounts of resin to be discarded around the world. In this study, the waste amidoxime chelating resin was reutilized as an adsorbent for the removal and [...] Read more.

The continuous expansion of the market demand and scale of commercial amidoxime chelating resins has caused large amounts of resin to be discarded around the world. In this study, the waste amidoxime chelating resin was reutilized as an adsorbent for the removal and recovery of Pb(II), Cu(II), Cd(II) and Zn(II) ions from aqueous solutions. The physical morphology and chemical composition of the waste amidoxime chelating resin (WAC-resin) from the factory was characterized by the elemental analyzer, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The influence of the initial metal ions concentration, contact time, temperature and the solution pH on the adsorption performance of the metal ions was explored by batch experiments. It was shown that the optimal pH was 4. Kinetic studies revealed that adsorption process corresponded with the pseudo-second-order kinetic model and the adsorption isotherm was consistent with the Langmuir model. At room temperature, the adsorption capacities of WAC-resin for Pb²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ reached 114.6, 93.4, 24.4 and 20.7 mg/g, respectively. Full article

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10 pages, 15226 KiB

Open AccessArticle

Kinetic Study of Oxide Growth at High Temperature in Low Carbon Steel

by Sixtos Antonio Arreola-Villa, Héctor Javier Vergara-Hernández, Gildardo Solorio-Diáz, Alejandro Pérez-Alvarado, Octavio Vázquez-Gómez and Gerardo Marx Chávez-Campos

Metals 2022, 12(1), 147; https://doi.org/10.3390/met12010147 - 13 Jan 2022

Cited by 7 | Viewed by 3302

Abstract

High-temperature surface oxidation kinetics were determined for low-carbon steel using a Joule heating device on hollow cylindrical specimens. The growth of the oxide layer was measured in situ between 800 and 1050

^{\circ}

C under isothermal oxidation conditions and in an air laboratory [...] Read more.

High-temperature surface oxidation kinetics were determined for low-carbon steel using a Joule heating device on hollow cylindrical specimens. The growth of the oxide layer was measured in situ between 800 and 1050

^{\circ}

C under isothermal oxidation conditions and in an air laboratory atmosphere (

O_{2}

= 20.3% and humidity = 42%). Through a laser and infrared measuring system, the expansion and temperature were measured continuously. From the data acquired, the oxidation kinetic parameters were obtained at different temperatures with a parabolic-type growth model to estimate the rate of oxide layer generation. The convergence degree of the data fitted with the oxidation model was acceptable and appropriately correlated with the experimental data. Finally, comparisons were made between the estimated kinetic parameters and those reported in the literature, observing that the activation energy values obtained are in the range of the reported values. Full article

(This article belongs to the Special Issue Study of the Formation of Oxides Layers on Alloy Surfaces and at the Oxide-Matrix Interfaces)

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14 pages, 10452 KiB

Open AccessArticle

Effect of Heat Treatment on the Cyclic Deforming Behavior of As-Extruded ZA81M Magnesium Alloy

by Tianjiao Luo, Jianguang Feng, Chenye Liu, Cong Wang, Yingju Li, Xiaohui Feng, Ce Zheng, Qiuyan Huang, Weirong Li and Yuansheng Yang

Metals 2022, 12(1), 146; https://doi.org/10.3390/met12010146 - 13 Jan 2022

Viewed by 1704

Abstract

In the present work, the effect of heat treatment on the cyclic deformation behavior of as-extruded ZA81M magnesium alloy was investigated. Two heat treatment conditions were applied to the as-extruded ZA81M alloy: a solution treatment (T4, 653 K for 40 h and quenched [...] Read more.

In the present work, the effect of heat treatment on the cyclic deformation behavior of as-extruded ZA81M magnesium alloy was investigated. Two heat treatment conditions were applied to the as-extruded ZA81M alloy: a solution treatment (T4, 653 K for 40 h and quenched with 298 K water) and a solution treatment plus artificial aging (T6, 348 K for 32 h (pre-aging at low temperature) and 453 K for 8 h (the second aging) and quenched with 353 K water). The results showed that the fine second phase precipitated after the aging treatment, the tensile yield strength of the T6-treated specimens increased, and the stress amplitude of T6-treated specimens was always higher than that of T4-treated specimens. The T6-treated specimens had a higher total strain energy density and a shorter fatigue life at a strain amplitude of 0.4%, and a lower total strain energy density and a longer fatigue life at a strain amplitude of 0.8%, compared to the T4-treated specimens. All fatigue cracks of the T4 and T6 ZA81M alloy were initiated at the second phase or along the grain boundary and propagated perpendicular to the loading direction. Full article

(This article belongs to the Special Issue Development and Applications of New Lightweighting Metal Technologies: High Strength Al and Mg Alloys)

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20 pages, 7282 KiB

Open AccessArticle

Damage-Based Assessment of the Fatigue Crack Initiation Site in High-Strength Steel Welded Joints Treated by HFMI

by Yuki Ono, Halid Can Yıldırım, Koji Kinoshita and Alain Nussbaumer

Metals 2022, 12(1), 145; https://doi.org/10.3390/met12010145 - 12 Jan 2022

Cited by 14 | Viewed by 3384

Abstract

This study aimed to identify the fatigue crack initiation site of high-frequency mechanical impact (HFMI)-treated high-strength steel welded joints subjected to high peak stresses; the impact of HFMI treatment residual stress relaxation being of particular interest. First, the compressive residual stresses induced by [...] Read more.

This study aimed to identify the fatigue crack initiation site of high-frequency mechanical impact (HFMI)-treated high-strength steel welded joints subjected to high peak stresses; the impact of HFMI treatment residual stress relaxation being of particular interest. First, the compressive residual stresses induced by HFMI treatment and their changes due to applied high peak stresses were quantified using advanced measurement techniques. Then, several features of crack initiation sites according to levels of applied peak stresses were identified through fracture surface observation of failed specimens. The relaxation behavior was simulated with finite element (FE) analyses incorporating the experimentally characterized residual stress field, load cycles including high peak load, improved weld geometry and non-linear material behavior. With local strain and local mean stress after relaxation, fatigue damage assessments along the surface of the HFMI groove were performed using the Smith–Watson–Topper (SWT) parameter to identify the critical location and compared with actual crack initiation sites. The obtained results demonstrate the shift of the crack initiation most prone position along the surface of the HFMI groove, resulting from a combination of stress concentration and residual stress relaxation effect. Full article

(This article belongs to the Special Issue Technological Aspects in Fatigue Design of Metallic Structures)

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4 pages, 186 KiB

Open AccessEditorial

Advances in Selective Flotation and Leaching Process in Metallurgy

by Ilhwan Park

Metals 2022, 12(1), 144; https://doi.org/10.3390/met12010144 - 12 Jan 2022

Cited by 3 | Viewed by 2033

Abstract

Metals are a finite resource that are necessary to maintain living standards in modern society, due to their countless applications, such as transportation vehicles, building and construction, household appliances, electronic devices, etc. [...] Full article

(This article belongs to the Special Issue Advances in Selective Flotation and Leaching Process in Metallurgy)

14 pages, 8594 KiB

Open AccessFeature PaperArticle

Compressive Rheological Behavior and Microstructure Evolution of a Semi-Solid CuSn10P1 Alloy at Medium Temperature and Low Strain

by Zhangxing Liu, Rongfeng Zhou, Wentao Xiong, Zilong He, Tao Liu and Yongkun Li

Metals 2022, 12(1), 143; https://doi.org/10.3390/met12010143 - 12 Jan 2022

Cited by 7 | Viewed by 1946

Abstract

Copper–tin alloys are widely used in the machining and molding of sleeves, bearings, bearing housings, gears, etc. They are a material used in heavy-duty, high-speed and high-temperature situations and subject to strong friction conditions due to their high strength, high modulus of elasticity, [...] Read more.

Copper–tin alloys are widely used in the machining and molding of sleeves, bearings, bearing housings, gears, etc. They are a material used in heavy-duty, high-speed and high-temperature situations and subject to strong friction conditions due to their high strength, high modulus of elasticity, low coefficient of friction and good wear and corrosion resistance. Although copper–tin alloys are excellent materials, a higher performance of mechanical parts is required under extreme operating conditions. Plastic deformation is an effective way to improve the overall performance of a workpiece. In this study, medium-temperature compression tests were performed on a semi-solid CuSn10P1 alloy using a Gleeble 1500D testing machine at different temperatures (350−440 °C) and strain rates (0.1−10 s⁻¹) to obtain its medium-temperature deformation characteristics. The experimental results show that the filamentary deformation marks appearing during the deformation are not single twins or slip lines, but a mixture of dislocations, stacking faults and twins. Within the experimental parameters, the filamentary deformation marks increase with increasing strain and decrease with increasing temperature. Twinning subdivides the grains into lamellar sheets, and dislocation aggregates are found near the twinning boundaries. The results of this study are expected to make a theoretical contribution to the forming of copper–tin alloys in post-processing processes such as rolling and forging. Full article

(This article belongs to the Topic Processing, Analysis, Modelling and Mechanics of Materials and Structures)

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20 pages, 6262 KiB

Open AccessArticle

A Comparative Study on the Microstructures and Mechanical Properties of Al-10Si-0.5Mg Alloys Prepared under Different Conditions

by Minghao Guo, Ming Sun, Junhui Huang and Song Pang

Metals 2022, 12(1), 142; https://doi.org/10.3390/met12010142 - 12 Jan 2022

Cited by 9 | Viewed by 3114

Abstract

Fabrication condition greatly influences the microstructures and properties of Al alloys. However, most of the available reports focus on a single fabrication technique, indicating there is still a lack of systematic comparisons among wider ranges of fabrication methods. In this paper, with conventional [...] Read more.

Fabrication condition greatly influences the microstructures and properties of Al alloys. However, most of the available reports focus on a single fabrication technique, indicating there is still a lack of systematic comparisons among wider ranges of fabrication methods. In this paper, with conventional casting (via sand/Fe/Cu mold) and additive manufacturing (AM, via selective laser melting, SLM) methods, the effects of cooling rate (Ṫ) on the microstructures and mechanical properties of hypoeutectic Al-10Si-0.5Mg alloy are systematically investigated. The results show that with increasing cooling rate from sand-mold condition to SLM condition, the grain size (d) is continuously refined from ~3522 ± 668 μm to ~10 μm, and the grain morphology is gradually refined from coarse dendrites to a mixed grain structure composed of columnar plus fine grains (~10 μm). The eutectic Si particles are effectively refined from blocky shape under sand/Fe-mold conditions to needle-like under Cu-mold conditions, and finally to fine fibrous network under SLM condition. The tensile yield strength and elongation is greatly improved from 125 ± 5 MPa (sand-mold) to 262 ± 3 MPa (SLM) and from 0.8 ± 0.2% (sand-mold) to 4.0 ± 0.2% (SLM), respectively. The strengthening mechanism is discussed, which is mainly ascribed to the continuous refinement of grains and Si particles and an increase in super-saturation of Al matrix with increasing cooling rate. Full article

(This article belongs to the Topic Processing, Analysis, Modelling and Mechanics of Materials and Structures)

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16 pages, 12324 KiB

Open AccessArticle

Experimental and Numerical Study on the Protective Behavior of Weldox 900 E Steel Plates Impacted by Blunt-Nosed Projectiles

by Yahui Shi, Ang Hu, Taisheng Du, Xinke Xiao and Bin Jia

Metals 2022, 12(1), 141; https://doi.org/10.3390/met12010141 - 12 Jan 2022

Cited by 6 | Viewed by 2341

Abstract

To demonstrate the importance of incorporating Lode angle into fracture criterion in predicting the penetration resistance of high-strength steel plates, ballistic tests of blunt-nosed projectiles with a diameter of 5.95 mm impacted 4 mm thick Weldox 900 E steel plates were conducted. Impacting [...] Read more.

To demonstrate the importance of incorporating Lode angle into fracture criterion in predicting the penetration resistance of high-strength steel plates, ballistic tests of blunt-nosed projectiles with a diameter of 5.95 mm impacted 4 mm thick Weldox 900 E steel plates were conducted. Impacting velocity range was 136.63~381.42 m/s. The fracture behavior and the ballistic limit velocities (BLVs) were obtained by fitting the initial-residual velocities of the projectiles. Subsequently, axisymmetric finite element (FE) models parallel to the tests were built by using Abaqus/Explicit software, and the Lode-independent Johnson–Cook (JC) and the Lode-dependent ASCE fracture criterion were incorporated into the finite element model for numerical simulation. Meanwhile, to verify the sensitivity of the mesh size in the numerical simulation, different mesh sizes were used in the shear plug area of the target. It can be found that Weldox 900 E steel has obvious mesh size sensitivity by comparing the experimental results and numerical simulation, and the JC fracture criterion and the ASCE fracture criterion predicted similar BLV for the same mesh size. Full article

(This article belongs to the Special Issue Failure Analysis in Metallic Materials)

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12 pages, 6292 KiB

Open AccessEditor’s ChoiceArticle

Performance of a Nozzle to Control Bath Level Oscillations and Turbulence of the Metal-Flux Interface in Slab Molds

by María Guadalupe González-Solórzano, Rodolfo Davila Morales, Javier Guarneros, Carlos Rodrigo Muñiz-Valdés and Alfonso Nájera Bastida

Metals 2022, 12(1), 140; https://doi.org/10.3390/met12010140 - 12 Jan 2022

Cited by 3 | Viewed by 1978

Abstract

The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the [...] Read more.

The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the bath levels during the experimental time. An ultrasonic transducer located in the mold, 20 mm below the meniscus, determines the velocities and the turbulent variables along with the distance from the narrow face to the position of the nozzle’s outer wall. These data, together with the mathematical simulations, demonstrated a high correlation of bath level oscillations and the time-dependent behavior of the discharging jets. The flow inside the mold shows low-frequency non-symmetric patterns without a severe turbulent in the meniscus. The source of this instability is the partial opening of the slide valve gate used to control the mass flow of liquid. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology)

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11 pages, 5402 KiB

Open AccessArticle

Microstructure and Fracture Toughness of Nitrided D2 Steels Using Potential-Controlled Nitriding

by Ki-Hong Kim, Won-Beom Lee, Tae-Hwan Kim and Seok-Won Son

Metals 2022, 12(1), 139; https://doi.org/10.3390/met12010139 - 11 Jan 2022

Cited by 8 | Viewed by 4012

Abstract

Potential-controlled nitriding is an effective technique for enhancing the life of steel molds and dies by improving their surface hardness and toughness against fatigue damage. In this study, the effect of the nitriding potential on the microstructure and fracture toughness of nitrided AISI [...] Read more.

Potential-controlled nitriding is an effective technique for enhancing the life of steel molds and dies by improving their surface hardness and toughness against fatigue damage. In this study, the effect of the nitriding potential on the microstructure and fracture toughness of nitrided AISI D2 steels was investigated. The nitrided layers were characterized by microhardness measurements, optical microscopy, and scanning electron microscopy, and their phases were identified by X-ray and electron backscatter diffraction. As the nitriding potential increased to 2.0 atm^−1/2, an increase in the surface hardness and fracture toughness was observed with the growth of the compound layer. However, both the surface hardness and the fracture toughness decreased at the higher nitriding potential of 5.0 atm^−1/2 owing to the increased porosity in the compound layers, which mainly consist of the ε (Fe_2–3N) phase. Additionally, by observing crack growth behavior, the fracture toughness was analyzed considering the material characteristics of the diffusion and compound layers. The fracture toughness was influenced by the location of the initial Palmqvist cracks due to the localized plastic deformation of the diffusion layer and increased crack length due to the porous compound layer. Full article

(This article belongs to the Topic Surface Treatments for Protecting from Fracture and Fatigue Damage)

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18 pages, 10019 KiB

Open AccessArticle

A Comparison of the Effects of Ultrasonic Cavitation on the Surfaces of 45 and 40Kh Steels

by Dmitriy S. Fatyukhin, Ravil I. Nigmetzyanov, Vyacheslav M. Prikhodko, Aleksandr V. Sukhov and Sergey K. Sundukov

Metals 2022, 12(1), 138; https://doi.org/10.3390/met12010138 - 11 Jan 2022

Cited by 18 | Viewed by 3497

Abstract

The ultrasonic treatment of metal products in liquid is used mainly to remove various kinds of contaminants from surfaces. The effects of ultrasound not only separate and remove contaminants, they also significantly impact the physical–mechanical and geometric properties of the surfaces of products [...] Read more.

The ultrasonic treatment of metal products in liquid is used mainly to remove various kinds of contaminants from surfaces. The effects of ultrasound not only separate and remove contaminants, they also significantly impact the physical–mechanical and geometric properties of the surfaces of products if there is enough time for treatment. The aim of this study was to compare the dynamics of ultrasonic cavitation effects on the surface properties of 45 (ASTM M1044; DIN C45; GB 45) and 40Kh (AISI 5140; DIN 41Cr4; GB 40Cr) structural steels. During the study, changes in the structure, roughness, sub-roughness, and microhardness values of these materials were observed. The results showed significant changes in the considered characteristics. It was found that the process of cavitation erosion involves at least 3 stages. In the first stage, the geometric properties of the surface slightly change with the accumulation of internal stresses and an increase in microhardness. The second stage is characterized by structure refinement, increased roughness and sub-microroughness, and the development of surface erosion. In the third stage, when a certain limiting state is reached, there are no noticeable changes in the surface properties. The lengths of these stages and the quantitative characteristics of erosion for the considered materials differ significantly. It was found that the time required to reach the limiting state was longer for carbon steel than for alloy steel. The results can be used to improve the cleaning process, as well as to form the required surface properties of structural steels. Full article

(This article belongs to the Special Issue Effect of Ultrasound on the Structure and Properties of Metallic Materials)

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