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Metals, Volume 9, Issue 4 (April 2019)

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Cover Story (view full-size image) Tundish filling operations are physically and mathematically simulated using three types of [...] Read more.
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Open AccessArticle
Hot Deformation Behavior and Microstructure Evolution of a TiBw/Near α-Ti Composite with Fine Matrix Microstructure
Metals 2019, 9(4), 481; https://doi.org/10.3390/met9040481
Received: 25 March 2019 / Revised: 23 April 2019 / Accepted: 24 April 2019 / Published: 25 April 2019
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Abstract
The hot deformation behavior and microstructure evolution of a 7.5 vol.% TiBw/near α-Ti composite with fine matrix microstructure were investigated under the deformation conditions in a temperature range of 800–950 °C and strain rate range of 0.001–1 s−1 using plane [...] Read more.
The hot deformation behavior and microstructure evolution of a 7.5 vol.% TiBw/near α-Ti composite with fine matrix microstructure were investigated under the deformation conditions in a temperature range of 800–950 °C and strain rate range of 0.001–1 s−1 using plane strain compression tests. The flow stress curves show different characteristics according to the various deformation conditions. At a higher strain rate (1 s−1), the flow stress of the composite continuously increases until a peak value is reached. The activation energy is 410.40 kJ/mol, much lower than the activation energy of as-sintered or as-forged composites. The decreased activation energy is ascribed to the breaking of the TiBw reinforcement during the multi-directional forging and the resultant fine matrix microstructure. Refined reinforcement and refined matrix microstructure significantly improve the hot deformation ability of the composite. The deformation conditions determine the morphology and fraction of α and β phases. At 800–900 °C and 0.01 s−1 the matrix α grains are much refined due to the continuous dynamic recrystallization (CDRX). The processing map is constructed based on the hot deformation behavior and microstructure evolution. The optimal hot processing window is determined to be 800–950 °C/0.001–0.01 s−1, which lead to CDRX of primary α grains or dynamic recovery (DRV) and dynamic recrystallization (DRX) of β phase. Full article
(This article belongs to the Special Issue Titanium Alloys: Processing and Properties)
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Open AccessFeature PaperArticle
Experimental and Numerical Investigations of the Development of Residual Stresses in Thermo-Mechanically Processed Cr-Alloyed Steel 1.3505
Metals 2019, 9(4), 480; https://doi.org/10.3390/met9040480
Received: 15 March 2019 / Revised: 12 April 2019 / Accepted: 14 April 2019 / Published: 25 April 2019
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Abstract
Residual stresses in components are a central issue in almost every manufacturing process, as they influence the performance of the final part. Regarding hot forming processes, there is a great potential for defining a targeted residual stress state, as many adjustment parameters, such [...] Read more.
Residual stresses in components are a central issue in almost every manufacturing process, as they influence the performance of the final part. Regarding hot forming processes, there is a great potential for defining a targeted residual stress state, as many adjustment parameters, such as deformation state or temperature profile, are available that influence residual stresses. To ensure appropriate numerical modeling of residual stresses in hot forming processes, comprehensive material characterization and suitable multiscale Finite Element (FE) simulations are required. In this paper, experimental and numerical investigations of thermo-mechanically processed steel alloy 1.3505 (DIN 100Cr6) are presented that serve as a basis for further optimization of numerically modeled residual stresses. For this purpose, cylindrical upsetting tests at high temperature with subsequently cooling of the parts in the media air or water are carried out. Additionally, the process is simulated on the macroscale and compared to the results based on the experimental investigations. Therefore, the experimentally processed specimens are examined regarding the resulting microstructure, distortions, and residual stresses. For the investigation on a smaller scale, a numerical model is set up based on the state-data of the macroscopic simulation and experiments, simulating the transformation of the microstructure using phase-field theory and FE analysis on micro- and meso-scopic level. Full article
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Open AccessArticle
Friction Surfacing of Aluminium Alloy 5083 on DH36 Steel Plate
Metals 2019, 9(4), 479; https://doi.org/10.3390/met9040479
Received: 19 March 2019 / Revised: 20 April 2019 / Accepted: 21 April 2019 / Published: 25 April 2019
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Abstract
In this work, friction surfacing (FS) of AA5083 on a DH36 steel substrate was experimentally studied. The process parameters such as rotation speed, travel speed and feed rate are of great significance to the success of the FS process. Seven friction surfaced plates [...] Read more.
In this work, friction surfacing (FS) of AA5083 on a DH36 steel substrate was experimentally studied. The process parameters such as rotation speed, travel speed and feed rate are of great significance to the success of the FS process. Seven friction surfaced plates with different combinations of parameters were examined. Optical microscopy, SEM and EDS were used to analyse the characteristics of the microstructure and composition of the interface between the surface and the substrate. The results show that the deposition surface quality decreased as the feed rate, travel speed and axial force increased. However, the bond strength increased with higher feed rate, higher rotation speed and lower travel speed. Elemental diffusion of Fe to AA5083 was established, and the intermetallic compound FeAl3 was produced in the interface. Full article
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Open AccessArticle
Influence of Size on the Fractal Dimension of Dislocation Microstructure
Metals 2019, 9(4), 478; https://doi.org/10.3390/met9040478
Received: 29 March 2019 / Revised: 19 April 2019 / Accepted: 20 April 2019 / Published: 25 April 2019
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Abstract
Three-dimensional (3D) discrete dislocation dynamics simulations are used to analyze the size effect on the fractal dimension of two-dimensional (2D) and 3D dislocation microstructure. 2D dislocation structures are analyzed first, and the calculated fractal dimension (n2) is found to be [...] Read more.
Three-dimensional (3D) discrete dislocation dynamics simulations are used to analyze the size effect on the fractal dimension of two-dimensional (2D) and 3D dislocation microstructure. 2D dislocation structures are analyzed first, and the calculated fractal dimension ( n 2 ) is found to be consistent with experimental results gleaned from transmission electron microscopy images. The value of n 2 is found to be close to unity for sizes smaller than 300 nm, and increases to a saturation value of ≈1.8 for sizes above approximately 10 microns. It is discovered that reducing the sample size leads to a decrease in the fractal dimension because of the decrease in the likelihood of forming strong tangles at small scales. Dislocation ensembles are found to exist in a more isolated way at the nano- and micro-scales. Fractal analysis is carried out on 3D dislocation structures and the 3D fractal dimension ( n 3 ) is determined. The analysis here shows that ( n 3 ) is significantly smaller than ( n 2 + 1 ) of 2D projected dislocations in all considered sizes. Full article
(This article belongs to the Special Issue Dislocation Mechanics of Metal Plasticity and Fracturing)
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Open AccessArticle
Influence of Intergranular Mechanical Interactions on Orientation Stabilities during Rolling of Pure Aluminum
Metals 2019, 9(4), 477; https://doi.org/10.3390/met9040477
Received: 22 February 2019 / Revised: 22 April 2019 / Accepted: 23 April 2019 / Published: 25 April 2019
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Abstract
Taylor strain principles are widely accepted in current predominant crystallographic deformation theories and models for reaching the necessary stress and strain equilibria in polycrystalline metals. However, to date, these principles have obtained neither extensive experimental support nor sufficient theoretical explanation and understanding. Therefore, [...] Read more.
Taylor strain principles are widely accepted in current predominant crystallographic deformation theories and models for reaching the necessary stress and strain equilibria in polycrystalline metals. However, to date, these principles have obtained neither extensive experimental support nor sufficient theoretical explanation and understanding. Therefore, the validity and necessity of Taylor strain principles is questionable. The present work attempts to calculate the elastic energy of grains and their orientation stabilities after deformation, whereas the stress and strain equilibria are reached naturally, simply and reasonably based on the proposed reaction stress (RS) model without strain prescription. The RS model is modified by integrating normal RS in the transverse direction of rolling sheets into the model. The work hardening effect, which is represented by an effective dislocation distance, is connected with the engineering strength level of metals. Crystallographic rolling texture development in roughly elastic isotropic pure aluminum is simulated based on the modified RS model, whereas orientation positions and peak densities of main texture components, i.e., brass, copper and S texture, can be predicted accurately. RS σ12 commonly accumulates to a high level and features a strong influence on texture formation, whereas RS σ23 and σ31 hardly accumulate and can only promote random texture. Cube orientations can obtain certain stability under the effects of RSs including σ22. A portion of elastic strain energy remains around the grains. This phenomenon is orientation-dependent and connected to RSs during deformation. The grain stability induced by elastic strain energy may influence grain behavior in subsequent recovery or recrystallization. Full article
(This article belongs to the Special Issue Multiscale Modeling of Materials and Processes)
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Open AccessArticle
Quantitative Analysis of Inclusion Engineering on the Fatigue Property Improvement of Bearing Steel
Metals 2019, 9(4), 476; https://doi.org/10.3390/met9040476
Received: 1 April 2019 / Revised: 13 April 2019 / Accepted: 20 April 2019 / Published: 24 April 2019
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Abstract
The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the [...] Read more.
The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design. Full article
(This article belongs to the Special Issue Bearing Steels)
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Open AccessArticle
Material Flow in Ultrasonic Orbital Microforming
Metals 2019, 9(4), 475; https://doi.org/10.3390/met9040475
Received: 18 March 2019 / Revised: 18 April 2019 / Accepted: 22 April 2019 / Published: 24 April 2019
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Abstract
Ultrasonic orbital microforming—UOM—uses the broadly understood idea of orbital forging but uses very different laws of physics. The only shaping force in this process is the inertia force resulting from the acceleration in the rotary motion of the workpiece. Micro specimen blanked from [...] Read more.
Ultrasonic orbital microforming—UOM—uses the broadly understood idea of orbital forging but uses very different laws of physics. The only shaping force in this process is the inertia force resulting from the acceleration in the rotary motion of the workpiece. Micro specimen blanked from cold rolled aluminum sheet metal was used in the applied UOM process. Only the upper and lower part of the sample is deformed that gives about 70% of volume. The rest—the middle part—remains undeformed. The final shape of the product is influenced by the shape of the inside of the die in which the UMO process is carried out. However, this effect is not a direct one. The product shape does not repeat the shape of the interior of the die. The preliminary experiments with modular micro-die have been performed on the way of controlling the shape of deformed micro-objects. The microstructure analysis has been done as well as micro-hardness distribution. Full article
(This article belongs to the Special Issue Metal Micro-forming)
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Open AccessArticle
Characterization of Microstructure and Mechanical Properties of Stellite 6 Part Fabricated by Wire Arc Additive Manufacturing
Metals 2019, 9(4), 474; https://doi.org/10.3390/met9040474
Received: 22 March 2019 / Revised: 15 April 2019 / Accepted: 20 April 2019 / Published: 24 April 2019
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Abstract
Stellite 6 alloy has excellent wear resistance, corrosion resistance, and oxidation resistance, however the difficulties in traditional processing limit its wide application. Additive manufacturing technology that has emerged in recent years is expected to provide a new way for the processing of stellite [...] Read more.
Stellite 6 alloy has excellent wear resistance, corrosion resistance, and oxidation resistance, however the difficulties in traditional processing limit its wide application. Additive manufacturing technology that has emerged in recent years is expected to provide a new way for the processing of stellite 6 alloy. In this study, two square thin-walled stellite 6 parts were fabricated through the wire arc additive manufacturing technology. At the same time, the effect of stress relief annealing on the mechanical performance of the fabricated stellite 6 part was studied and compared with the corresponding casting part. The results indicate that the additive manufacturing stellite 6 components exhibit satisfactory quality and appearance. Moreover, the microstructure of the additive manufacturing part is much finer than that of the casting part. From the substrate to the top region of the additive manufacturing part, the morphology of the dendrites changes from columnar to equiaxed, and the hardness increases firstly and then decreases gradually. In addition, the average hardness of the additive manufacturing part is ~7–8 HRC higher than the casting part. The ultimate tensile strength and yield strength is ~150MPa higher than the casting part, while the elongation is almost the same. The stress relief annealing has no significant effect on the hardness of the AM part, but it can slightly improve the strength. Full article
(This article belongs to the Special Issue Arc-based Additive Manufacturing)
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Open AccessArticle
Determination of Johnson–Cook Constitutive Parameters for Cutting Simulations
Metals 2019, 9(4), 473; https://doi.org/10.3390/met9040473
Received: 29 March 2019 / Revised: 12 April 2019 / Accepted: 19 April 2019 / Published: 23 April 2019
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Abstract
The Johnson–Cook constitutive equation is very widely used for simulating cutting processes. Different methods are applied for establishing parameters of the constitutive equation. Based on the methods analysed in this study, two algorithms were worked out to determine the constitutive parameters for the [...] Read more.
The Johnson–Cook constitutive equation is very widely used for simulating cutting processes. Different methods are applied for establishing parameters of the constitutive equation. Based on the methods analysed in this study, two algorithms were worked out to determine the constitutive parameters for the prevailing conditions during cutting processes. In the first algorithm, all constitutive parameters were established simultaneously with standardized test methods. In the second algorithm, the constitutive parameters were established separately in accordance with the cutting conditions prevailing in machining processes. The developed methodology was verified with AISI 1045 heat-treatable steel and Ti10V2Fe3Al (Ti-1023) titanium alloy. The two materials were examined in standardized tensile and compression tests with varying strain rates and temperatures. In addition, the kinetic characteristics of the orthogonal cutting process were established. Based on the results obtained by experiment and the algorithms developed, the constitutive parameters for the cutting conditions were calculated. The parameters were used to determine the material model for simulating the orthogonal cutting process. The algorithms developed were verified by comparing the simulated and experimentally determined kinetic cutting characteristics, which confirmed their good quality. Full article
(This article belongs to the Special Issue Constitutive Modelling for Metals)
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Open AccessArticle
Modified Leach Residues from Processing Deep-Sea Nodules as Effective Heavy Metals Adsorbents
Metals 2019, 9(4), 472; https://doi.org/10.3390/met9040472
Received: 14 March 2019 / Revised: 13 April 2019 / Accepted: 18 April 2019 / Published: 23 April 2019
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Abstract
The possible use of leaching residue from leaching deep-sea nodules in SO2/H2SO4/H2O medium as a low-cost adsorbent of heavy metals (Pb(II), Cd(II), Cu(II), Ni(II), Co(II), As(V)) was studied. The leaching residue was found to be [...] Read more.
The possible use of leaching residue from leaching deep-sea nodules in SO2/H2SO4/H2O medium as a low-cost adsorbent of heavy metals (Pb(II), Cd(II), Cu(II), Ni(II), Co(II), As(V)) was studied. The leaching residue was found to be an effective adsorbent for all of the tested elements; however, it was inactive in the solution containing As(V). The chemical activation of adsorbent in 10 vol. % HCl resulted in the greatest improvement of adsorption properties, while the activation in 10 vol. % HNO3 and heat treatment at 250 °C did not significantly affect the sorption characteristics of treated adsorbents compared with the original leaching residue. After HCl activation, the maximal adsorption capacities for lead (12.0 mg/g at pH 5.0 after 1 h), nickel (3.1 mg/g at pH 5.5 after 4 h) and cobalt (2.0 mg/g at pH 5.0 after 2 h) were achieved. Additional mechanical treatment connected with HCl activation provided the highest adsorption capacities for cadmium (11.5 mg/g at pH 4.0) and copper (5.7 mg/g at pH 4.5). Coprecipitation of Fe/Al-based particles on the surface of the leaching residue increased As(V) removal of the adsorbent. Surface coating based on AlIII was extremely effective, causing the increase of the adsorption capacity from 0 with the original leaching residue, to 28.1 mg/g (pH 7.0, 24 min). Kinetics studies showed the rapid progress of adsorption for Pb(II), Cd(II), and As(V) in tens of minutes, while the adsorption of Cu(II), Ni(II) and Co(II) approached a steady state after 2 h. Full article
(This article belongs to the Special Issue Metal Removal and Recycling)
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Open AccessFeature PaperReview
Electromagnetic Forces in Continuous Casting of Steel Slabs
Metals 2019, 9(4), 471; https://doi.org/10.3390/met9040471
Received: 23 March 2019 / Revised: 14 April 2019 / Accepted: 20 April 2019 / Published: 23 April 2019
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Abstract
This paper reviews the current state of the art in the application of electromagnetic forces to control fluid flow to improve quality in continuous casting of steel slabs. Many product defects are controlled by flow-related phenomena in the mold region, such as slag [...] Read more.
This paper reviews the current state of the art in the application of electromagnetic forces to control fluid flow to improve quality in continuous casting of steel slabs. Many product defects are controlled by flow-related phenomena in the mold region, such as slag entrapment due to excessive surface velocity and level fluctuations, meniscus hook defects due to insufficient transport of flow and superheat to the meniscus region, and particle entrapment into the solidification front, which depends on transverse flow across the dendritic interface. Fluid flow also affects heat transfer, solidification, and solute transport, which greatly affect grain structure and internal quality of final steel products. Various electromagnetic systems can affect flow, including static magnetic fields and traveling fields which actively accelerate, slow down, or stir the flow in the mold or strand regions. Optimal electromagnetic effects to control flow depends greatly on the caster geometry and other operating conditions. Previous works on how to operate electromagnetic systems to reduce defects are discussed based on results from plant experiments, validated computational models, and lab scale model experiments. Full article
(This article belongs to the Special Issue Continuous Casting)
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Open AccessArticle
Isothermal Kinetic Mechanism of Coke Dissolving in Hot Metal
Metals 2019, 9(4), 470; https://doi.org/10.3390/met9040470
Received: 31 March 2019 / Revised: 17 April 2019 / Accepted: 18 April 2019 / Published: 22 April 2019
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Abstract
The carburization of molten iron is close to saturation in the blast furnace process, while that in the flash ironmaking process is uncertain because there is no pressure from solid charge and no carburization reactions occurring between the deadman and hot metal. Some [...] Read more.
The carburization of molten iron is close to saturation in the blast furnace process, while that in the flash ironmaking process is uncertain because there is no pressure from solid charge and no carburization reactions occurring between the deadman and hot metal. Some experiments were conducted to reveal the kinetic mechanism of coke dissolving in carbon-iron melts. Reduced iron powder, electrolytic iron as well as chemical pure graphite were used as experiment materials. With high-purity argon injected as the protective gas, the specimens were heated up to 1873 K in a tubular resistance furnace to study the isothermal mechanism. The results show that the composition of the ferrous sample affects the dissolution rate. When the FeO content of the iron-bearing material rises from 0% to 4.76%, the apparent dissolution rate constant, kt, falls from 7.98 × 10−6 m/s to 5.48 × 10−6 m/s. There are some differences amongst the dissolution rate coefficients of different cokes despite interacting with similar carbon-iron melts, with coke 1 of 7.98 × 10−6 m/s, coke 2 of 5.17 × 10−6 m/s, and coke 3 of 3.77 × 10−6 m/s. Besides, this index decreases with the increase of the dissolution time and solely depends on the procedure of the mass transfer. A negative correlation is demonstrated between kt and the sulfur content in the iron bath as well. The content of silicon dioxide in the coke has a significant influence on kt. Additionally, the dissolution rate coefficient increases with the increase of the graphitization degree of coke. Full article
(This article belongs to the Special Issue Selected Papers from 8th ICSTI 2018)
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Open AccessArticle
Investigation of the Dynamic Recrystallization of FeMnSiCrNi Shape Memory Alloy under Hot Compression Based on Cellular Automaton
Metals 2019, 9(4), 469; https://doi.org/10.3390/met9040469
Received: 29 March 2019 / Revised: 16 April 2019 / Accepted: 19 April 2019 / Published: 22 April 2019
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Abstract
Dynamic recrystallization (DRX) takes place when FeMnSiCrNi shape memory alloy (SMA) is subjected to compression deformation at high temperatures. Cellular automaton (CA) simulation was used for revealing the DRX mechanism of FeMnSiCrNi SMA by predicting microstructures, grain size, flow stress, and dislocation density. [...] Read more.
Dynamic recrystallization (DRX) takes place when FeMnSiCrNi shape memory alloy (SMA) is subjected to compression deformation at high temperatures. Cellular automaton (CA) simulation was used for revealing the DRX mechanism of FeMnSiCrNi SMA by predicting microstructures, grain size, flow stress, and dislocation density. The DRX of FeMnSiCrNi SMA has a characteristic of repeated nucleation and finite growth. The size of recrystallized grains increases with increasing deformation temperatures, but it decreases with increasing strain rates. The increase of deformation temperature leads to the decrease of the flow stress, whereas the increase in strain rate results in the increase of the flow stress. The dislocation density exhibits the same situation as the flow stress. The simulated results were supported by the experimental ones very well. Dislocation density is a crucial factor during DRX of FeMnSiCrNi SMA. It affects not only the nucleation but also the growth of the recrystallized grains. Occurrence of DRX depends on a critical dislocation density. The difference between the dislocation densities of the recrystallized and original grains becomes the driving force for the growth of the recrystallized grains, which lays a solid foundation for the recrystallized grains growing repeatedly. Full article
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Open AccessArticle
Effect of Fe Addition on Heat-Resistant Aluminum Alloys Produced by Selective Laser Melting
Metals 2019, 9(4), 468; https://doi.org/10.3390/met9040468
Received: 26 March 2019 / Revised: 13 April 2019 / Accepted: 20 April 2019 / Published: 22 April 2019
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Abstract
The effect of Fe addition on the high-temperature mechanical properties of heat-resistant aluminum alloys produced by selective laser melting (SLM) was investigated in relation to the alloy microstructures. Fe is generally detrimental to the properties of cast aluminum alloys; however, we found that [...] Read more.
The effect of Fe addition on the high-temperature mechanical properties of heat-resistant aluminum alloys produced by selective laser melting (SLM) was investigated in relation to the alloy microstructures. Fe is generally detrimental to the properties of cast aluminum alloys; however, we found that Fe-containing alloys produced by SLM had improved high-temperature strength and good ductility. Microstructural observations revealed that the increase in the high-temperature strength of the alloys was due to the dispersion of fine rod-shaped Fe-Si-Ni particles unique to the SLM material instead of the cell-like structure of eutectic Si. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals)
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Open AccessArticle
Kinetics of Phosphorus Transfer during Industrial Electroslag Remelting of G20CrNi2Mo Bearing Steel
Metals 2019, 9(4), 467; https://doi.org/10.3390/met9040467
Received: 13 March 2019 / Revised: 16 April 2019 / Accepted: 19 April 2019 / Published: 22 April 2019
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Abstract
Phosphorus is undesirable in steel for it greatly decreases ductility and causes embrittlement in most cases. The kinetic behavior of phosphorus transfer was investigated during electroslag remelting (ESR) of G20CrNi2Mo bearing steel. Four heat treatments were carried out using an industrial furnace with [...] Read more.
Phosphorus is undesirable in steel for it greatly decreases ductility and causes embrittlement in most cases. The kinetic behavior of phosphorus transfer was investigated during electroslag remelting (ESR) of G20CrNi2Mo bearing steel. Four heat treatments were carried out using an industrial furnace with a capacity to refine 2400 kg ingot. It was found the P content in the four ingots were all higher than that in the electrodes, indicating rephosphorization occurs during ESR. A kinetic model based on film and penetration theory was developed to elucidate the variation of phosphorus from metal film to droplet and metal pool. The model indicates that the rate-determining step of phosphorus transfer is at the slag side. Rephosphorization mainly occurs in the metal film and falling droplet. In addition, the effect of P in the slag and electrode, as well as the temperature of the slag pool on the P content in the metal pool were discussed. In order to achieve a low-P ingot of no more than 0.015%, the corresponding maximum P content in slag under the condition of a certain P content in the electrode was proposed. Full article
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Open AccessArticle
Influence of a Diamond-Like Carbon-Coated Mechanical Part on the Operation of an Orbital Hydraulic Motor in Water
Metals 2019, 9(4), 466; https://doi.org/10.3390/met9040466
Received: 21 March 2019 / Revised: 13 April 2019 / Accepted: 17 April 2019 / Published: 22 April 2019
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Abstract
The increasing focus on reducing the environmental impact of hydraulic applications has driven efforts to apply new surface-engineering technologies and replace classic lubricants with alternative solutions. In particular, water has gained increasing attention in recent years. However, water has very poor lubrication properties [...] Read more.
The increasing focus on reducing the environmental impact of hydraulic applications has driven efforts to apply new surface-engineering technologies and replace classic lubricants with alternative solutions. In particular, water has gained increasing attention in recent years. However, water has very poor lubrication properties and, especially in combination with steel/steel contact, it leads to severe tribological behavior. A literature review and preliminary research showed that appropriate surface engineering regarding diamond-like carbon (DLC) coatings represents a promising solution to overcome the limitation of steel/steel contacts in water. Basic tribological ball-on-disc tests were performed. The result of the tribological investigation showed that there was very low friction and wear in the steel/DLC contact in water. This was our motivation for using DLC coating in a real hydraulic application. The DLC was deployed on the floating outer ring, so steel/DLC contacts between the floating outer ring and three other important parts were created. It was proven that the poor lubrication properties of the water were overcome with appropriate surface engineering. In such a case, the hydraulic motor operated satisfactorily when the water was applied as a working fluid. Full article
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Open AccessArticle
Leaching Kinetics of Sulfides from Refractory Gold Concentrates by Nitric Acid
Metals 2019, 9(4), 465; https://doi.org/10.3390/met9040465
Received: 5 April 2019 / Revised: 19 April 2019 / Accepted: 19 April 2019 / Published: 22 April 2019
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Abstract
The processing of refractory gold-containing concentrates by hydrometallurgical methods is becoming increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of [...] Read more.
The processing of refractory gold-containing concentrates by hydrometallurgical methods is becoming increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of arsenic in the ores. This paper describes the investigation of the kinetics of HNO3 leaching of sulfide gold-containing concentrates of the Yenisei ridge (Yakutia, Russia). The effect of temperature (70–85 °C), the initial concentration of HNO3 (10–40%) and the content of sulfur in the concentrate (8.22–22.44%) on the iron recovery into the solution was studied. It has been shown that increasing the content of S in the concentrate from 8.22 to 22.44% leads to an average of 45% increase in the iron recovery across the entire range temperatures and concentrations of HNO3 per one hour of leaching. The leaching kinetics of the studied types of concentrates correlates well with the new shrinking core model, which indicates that the reaction is regulated by interfacial diffusion and diffusion through the product layer. Elemental S is found on the surface of the solid leach residue, as confirmed by XRD and SEM/EDS analysis. The apparent activation energy is 60.276 kJ/mol. The semi-empirical expression describing the reaction rate under the studied conditions can be written as follows: 1/3ln(1 − X) + [(1 − X)−1/3 − 1] = 87.811(HNO3)0.837(S)2.948e−60276/RT·t. Full article
(This article belongs to the Special Issue Leaching Kinetics of Valuable Metals)
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Open AccessArticle
Microstructure of a V-Containing Cobalt Based Alloy Prepared by Mechanical Alloying and Hot Pressed Sintering
Metals 2019, 9(4), 464; https://doi.org/10.3390/met9040464
Received: 8 March 2019 / Revised: 12 April 2019 / Accepted: 16 April 2019 / Published: 22 April 2019
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Abstract
In this paper, a bulk V-containing cobalt-based alloy with high chromium and tungsten contents was prepared by mechanical alloying and hot pressed sintering using Co, Cr, W, Ni, V and C pure element powders. XRD, SEM, TEM and Vickers hardness tests were employed [...] Read more.
In this paper, a bulk V-containing cobalt-based alloy with high chromium and tungsten contents was prepared by mechanical alloying and hot pressed sintering using Co, Cr, W, Ni, V and C pure element powders. XRD, SEM, TEM and Vickers hardness tests were employed to characterize the microstructure and mechanical properties of the mechanical alloyed powders and hot pressed bulk cobalt-based alloy. The results show that all elements can be mixed uniformly and that the Co, Cr, and Ni elements were made into an amorphous state after 10 h ball milling in a high energy ball miller. The microstructure of the prepared bulk alloy was composed of a γ-Co matrix with a large number of nano-twins and fine M23C6 and M12C carbide particles well-distributed in the alloy. The V element was mainly distributed in M23C6-type carbide and no V-rich MC-type carbide was found in the microstructure. The prepared alloy had a high hardness of 960 ± 9.2 HV and good a fracture toughness KIc of about 10.5 ± 0.46 MPa·m1/2. The microstructure formation and strengthening mechanisms of the prepared cobalt-based alloy are discussed. Full article
(This article belongs to the Special Issue Metals Powders: Synthesis and Processing)
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Open AccessArticle
Microstructure Formation of Low-Carbon Ferritic Stainless Steel during High Temperature Plastic Deformation
Metals 2019, 9(4), 463; https://doi.org/10.3390/met9040463
Received: 11 March 2019 / Revised: 16 April 2019 / Accepted: 18 April 2019 / Published: 20 April 2019
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Abstract
In this paper, the effects of the deformation temperature, the deformation reduction and the deformation rate on the microstructural formation, ferritic and martensitic phase transformation, stress–strain behaviors and micro-hardness in low-carbon ferritic stainless steel were investigated. The increase in deformation temperature promotes the [...] Read more.
In this paper, the effects of the deformation temperature, the deformation reduction and the deformation rate on the microstructural formation, ferritic and martensitic phase transformation, stress–strain behaviors and micro-hardness in low-carbon ferritic stainless steel were investigated. The increase in deformation temperature promotes the formation of the fine equiaxed dynamic strain-induced transformation ferrite and suppresses the martensitic transformation. The higher deformation temperature results in a lower starting temperature for martensitic transformation. The increase in deformation can effectively promote the transformation of DSIT ferrite, and decrease the martensitic transformation rate, which is caused by the work hardening effect on the metastable austenite. The increase in the deformation rate leads to an increase in the ferrite fraction, because a high density of dislocation remains that can provide sufficient nucleation sites for ferrite transformation. The slow deformation rate results in dynamic recovery according to the stress–strain curve. Full article
(This article belongs to the Special Issue Thermomechanical Processing of Steels)
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Open AccessArticle
Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys
Metals 2019, 9(4), 462; https://doi.org/10.3390/met9040462
Received: 9 April 2019 / Revised: 16 April 2019 / Accepted: 18 April 2019 / Published: 20 April 2019
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Abstract
Ag microalloyed Sn58Bi has been investigated in this study as a Pb-free solder candidate to be used in modern electronics industry in order to cope with the increasing demands for low temperature soldering. Microstructural and mechanical properties of the eutectic Sn58Bi and microalloyed [...] Read more.
Ag microalloyed Sn58Bi has been investigated in this study as a Pb-free solder candidate to be used in modern electronics industry in order to cope with the increasing demands for low temperature soldering. Microstructural and mechanical properties of the eutectic Sn58Bi and microalloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag microalloy, the tensile strength was improved, and this was attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility was slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag microalloyed Sn58Bi solder joints produced utilizing a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results revealed that microalloyed Sn57.6Bi0.4Ag had a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn–Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure. Full article
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Open AccessArticle
Effects of a Post-Weld Heat Treatment on the Mechanical Properties and Microstructure of a Friction-Stir-Welded Beryllium-Copper Alloy
Metals 2019, 9(4), 461; https://doi.org/10.3390/met9040461
Received: 11 March 2019 / Revised: 16 April 2019 / Accepted: 17 April 2019 / Published: 19 April 2019
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Abstract
This paper investigated the microstructure and mechanical properties of a friction-stir-welded beryllium-copper alloy, which is difficult to weld with conventional fusion welding processes. Friction stir welding (FSW) was successfully conducted with a tungsten-carbide (WC) tool. Sound joints without defects were obtained with a [...] Read more.
This paper investigated the microstructure and mechanical properties of a friction-stir-welded beryllium-copper alloy, which is difficult to weld with conventional fusion welding processes. Friction stir welding (FSW) was successfully conducted with a tungsten-carbide (WC) tool. Sound joints without defects were obtained with a tool rotational speed of 700 RPM and tool travel speed of 60 mm/min. A post-weld heat treatment (PWHT) of the FSW joints was performed to analyze the evolution of the microstructure at 315 °C for a half, one, two, three, four, five and eight hours, respectively. The microstructures of the joints were observed using an optical microscope (OM), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Observed softening of microstructure is suggested to be due to the dissolution of the strengthening precipitates during the FSW process, whereas the strength of the joints was recovered via the formation of the CuBe (γ′) phase during the post-weld heat treatment. However, the strength was decreased upon an excessive post-weld heat treatment exceeding three hours. It is considered that the formation of the γ phase and the coarse γ′ phase contributed to the reduction in the strength. Full article
(This article belongs to the Special Issue Characterization of Welded Joints)
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Open AccessArticle
Effect of Manganese on Microstructure and Corrosion Behavior of the Mg-3Al Alloys
Metals 2019, 9(4), 460; https://doi.org/10.3390/met9040460
Received: 25 March 2019 / Revised: 12 April 2019 / Accepted: 16 April 2019 / Published: 19 April 2019
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Abstract
Microstructure and corrosion behavior of the Mg-3Al-xMn (x = 0, 0.12, 0.21, 0.36, 0.45) (hereafter in wt.%) alloys were experimentally investigated by electron probe microanalysis (EPMA), scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), electrochemical, [...] Read more.
Microstructure and corrosion behavior of the Mg-3Al-xMn (x = 0, 0.12, 0.21, 0.36, 0.45) (hereafter in wt.%) alloys were experimentally investigated by electron probe microanalysis (EPMA), scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), electrochemical, and hydrogen evolution tests. A new self-constructed Mg-Al-Mn-Fe thermodynamic database was used to predict the solidification paths of the alloys. The addition of Mn showed no grain refinement in the cast Mg-3Al alloys. According to the microstructure observation, Al-Fe phases were observed in the non-Mn-added alloy, while Al8Mn5(LT) (Al8Mn5 in low temperature) became the main intermetallic phase in the Mn-added alloys, and the amount increased gradually with the Mn addition. The τ–Al0.89Mn1.11 phase with lower Al/(Fe + Mn) ratio was observed in the alloys with 0.36 and 0.45 wt.% Mn content. According to the electrochemical tests, all five alloys showed localized corrosion characteristics in 3.5 wt.% NaCl solution. Compared with the Mg-3Al alloy, the corrosion resistance of Mn-added alloys were significantly improved and increased gradually with the Mn addition, which was due to the variation of Al-containing intermetallic compounds. The present experimental investigations and thermodynamic calculations confirmed the mechanism that the increasing amount of Al8Mn5(LT) with Mn addition could encapsulate the B2-Al(Mn,Fe) phase with higher Fe. Therefore, it could prevent this detrimental phase from contacting magnesium matrix, thus suppressing micro-galvanic corrosion and improving corrosion resistance gradually. Full article
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Open AccessArticle
Microbiologically Influenced Corrosion of a Pipeline in a Petrochemical Plant
Metals 2019, 9(4), 459; https://doi.org/10.3390/met9040459
Received: 1 March 2019 / Revised: 13 April 2019 / Accepted: 16 April 2019 / Published: 19 April 2019
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Abstract
This paper investigates a severe microbiologically influenced failure in the elbows of a buried amine pipeline in a petrochemical plant. Pipelines can experience different corrosion mechanisms, including microbiologically influenced corrosion (MIC). MIC, a form of biodeterioration initiated by microorganisms, can have a devastating [...] Read more.
This paper investigates a severe microbiologically influenced failure in the elbows of a buried amine pipeline in a petrochemical plant. Pipelines can experience different corrosion mechanisms, including microbiologically influenced corrosion (MIC). MIC, a form of biodeterioration initiated by microorganisms, can have a devastating impact on the reliability and lifetime of buried installations. This paper provides a systematic investigation of a severe MIC-related failure in a buried amine pipeline and includes a detailed microstructural analysis, corrosion products/biofilm analyses, and monitoring of the presence of causative microorganisms. Conclusions were drawn based on experimental data, obtained from visual observations, optical/electron microscopy, and Energy-dispersive X-ray spectroscopy (EDS)/X-Ray Diffraction (XRD) analyses. Additionally, monitoring the presence of causative microorganisms, especially sulfate-reducing bacteria which play the main role in corrosion, was performed. The results confirmed that the failure, in this case, is attributable to sulfate-reducing bacteria (SRB), which is a long-known key group of microorganisms when it comes to microbial corrosion. Full article
(This article belongs to the Special Issue Microbes Meet Metals)
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Open AccessArticle
Mold-Level Prediction for Continuous Casting Using VMD–SVR
Metals 2019, 9(4), 458; https://doi.org/10.3390/met9040458
Received: 5 March 2019 / Revised: 17 April 2019 / Accepted: 17 April 2019 / Published: 18 April 2019
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Abstract
In the continuous-casting process, mold-level control is one of the most important factors that ensures the quality of high-efficiency continuous casting slabs. In traditional mold-level prediction control, the mold-level prediction accuracy is low, and the calculation cost is high. In order to improve [...] Read more.
In the continuous-casting process, mold-level control is one of the most important factors that ensures the quality of high-efficiency continuous casting slabs. In traditional mold-level prediction control, the mold-level prediction accuracy is low, and the calculation cost is high. In order to improve the prediction accuracy for mold-level prediction, an adaptive hybrid prediction algorithm is proposed. This new algorithm is the combination of empirical mode decomposition (EMD), variational mode decomposition (VMD), and support vector regression (SVR), and it effectively overcomes the impact of noise on the original signal. Firstly, the intrinsic mode functions (IMFs) of the mold-level signal are obtained by the adaptive EMD, and the key parameter of the VMD is obtained by the correlation analysis between the IMFs. VMD is performed based on the key parameter to obtain several IMFs, and the noise IMFs are denoised by wavelet threshold denoising (WTD). Then, SVR is used to predict each denoised component to obtain the predicted IMF. Finally, the predicted mold-level signal is reconstructed by the predicted IMFs. In addition, compared with WTD–SVR and EMD–SVR, VMD–SVR has a competitive advantage against the above three methods in terms of robustness. This new method provides a new idea for mold-level prediction. Full article
(This article belongs to the Special Issue Continuous Casting)
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Open AccessArticle
Effect of Normalizing Annealing Temperature on Precipitates and Texture of Nb-Cr-Bearing Decarburized Grain-Oriented Silicon Steels
Metals 2019, 9(4), 457; https://doi.org/10.3390/met9040457
Received: 25 March 2019 / Revised: 8 April 2019 / Accepted: 13 April 2019 / Published: 18 April 2019
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Abstract
The evolution of precipitates and texture was investigated in Nb-Cr-bearing decarburized specimens after normalizing at different temperatures. Enough inhibitors, including Nb(C,N), were obtained, of 20~40 nm in size. Increasing normalizing annealing temperature leads to the number density of the precipitates decreasing and that [...] Read more.
The evolution of precipitates and texture was investigated in Nb-Cr-bearing decarburized specimens after normalizing at different temperatures. Enough inhibitors, including Nb(C,N), were obtained, of 20~40 nm in size. Increasing normalizing annealing temperature leads to the number density of the precipitates decreasing and that of mean size increasing. The Goss texture content in the decarburized specimens decreases in different degrees compared with the normalized ones. The minimum Goss texture and maximum ∑9 grain boundaries were obtained in the decarburized specimen normalizing at 950 °C and in this specimen, enough fine dispersed inhibitors, weak but relative stable Goss texture and uniform grain size will be beneficial for Goss grains growth in secondary recrystallization, according to the coincidence site lattice theory. Full article
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Open AccessFeature PaperArticle
Influence of Material Property Variation on Computationally Calculated Melt Pool Temperature during Laser Melting Process
Metals 2019, 9(4), 456; https://doi.org/10.3390/met9040456
Received: 18 March 2019 / Revised: 3 April 2019 / Accepted: 17 April 2019 / Published: 18 April 2019
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Abstract
Selective Laser Melting (SLM) is a popular additive manufacturing (AM) method where a laser beam selectively melts powder layer by layer based on the building geometry. The melt pool peak temperature during build process is an important parameter to determine build quality of [...] Read more.
Selective Laser Melting (SLM) is a popular additive manufacturing (AM) method where a laser beam selectively melts powder layer by layer based on the building geometry. The melt pool peak temperature during build process is an important parameter to determine build quality of a fabricated component by SLM process. The melt pool temperature depends on process parameters including laser power, scanning speed, and hatch space as well as the properties of the build material. In this paper, the sensitivity of melt pool peak temperature during the build process to temperature dependent material properties including density, specific heat, and thermal conductivity are investigated for a range of laser powers and laser scanning speeds. It is observed that the melt pool temperature is most sensitive to melt pool thermal conductivity of the processed material for a set of specific process parameters (e.g., laser power and scan speed). Variations in the other mechanical–physical properties of powder and melt pool such as density and specific heat are found to have minimal effect on melt pool temperature. Full article
(This article belongs to the Special Issue Advances in Selective Laser Melting)
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Open AccessFeature PaperArticle
On the Evaluation of Surface Fatigue Strength of a Stainless-Steel Aeronautical Component
Metals 2019, 9(4), 455; https://doi.org/10.3390/met9040455
Received: 8 March 2019 / Revised: 2 April 2019 / Accepted: 15 April 2019 / Published: 17 April 2019
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Abstract
In this paper, a novel method for the evaluation of the surface fatigue strength of a stainless-steel component is proposed. The use of stainless steel is necessary indeed, whenever a component has to work in a particularly aggressive environment that may cause an [...] Read more.
In this paper, a novel method for the evaluation of the surface fatigue strength of a stainless-steel component is proposed. The use of stainless steel is necessary indeed, whenever a component has to work in a particularly aggressive environment that may cause an oxidation of the component itself. One of the major problems that affect stainless-steel components is the possible wear of the antioxidant film that reduces the antioxidant properties of the component itself. One of the main causes that can lead to wear is related to the surface corrosion that occurs every time two evolving bodies are forced to work against each other. If the antioxidant film is affected by surface fatigue problems, such as pitting or spalling, the antioxidant capacities of this type of steel may be lost. In this context, it is, therefore, necessary to verify, at least, by calculation that no corrosion problems exist. The method proposed in this activity is a hybrid method, numerical-theoretical, which allows to estimate the surface fatigue strength in a very short time without having to resort to finite element models that often are so complex to be in contrast with industrial purposes. Full article
(This article belongs to the Special Issue Manufacturing and Application of Stainless Steels)
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Open AccessArticle
Close Range Explosive Loading on Steel Column in the Framework of Anisotropic Viscoplasticity
Metals 2019, 9(4), 454; https://doi.org/10.3390/met9040454
Received: 12 March 2019 / Revised: 7 April 2019 / Accepted: 11 April 2019 / Published: 17 April 2019
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Abstract
The research was based on data obtained from experimental studies and aims in the challenge of mapping these results by a mathematical (phenomenological) model. The field experiments were performed on an H-section steel column supported by a reinforced concrete foundation and subjected to [...] Read more.
The research was based on data obtained from experimental studies and aims in the challenge of mapping these results by a mathematical (phenomenological) model. The field experiments were performed on an H-section steel column supported by a reinforced concrete foundation and subjected to a close-in explosion. Numerical studies were carried out using Abaqus/Explicit code. The user subroutine VUMAT for metallic obstacle was also implemented, together with a coupled Eulerian–Lagrangian approach. The steel column failure recorded during real field tests versus computational results was examined and compared. It was crucial that, from the computational point of view, the obstacle reflected the generalized thermo-elasto-viscoplastic (GTEV) behavior of Perzyna’s type, including an anisotropic measure of damage. Full article
(This article belongs to the Special Issue Metallic Materials under Dynamic Loading)
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Open AccessArticle
Investigation of Bipolar Plate Forming with Various Die Configurations by Magnetic Pulse Method
Metals 2019, 9(4), 453; https://doi.org/10.3390/met9040453
Received: 22 March 2019 / Revised: 12 April 2019 / Accepted: 15 April 2019 / Published: 17 April 2019
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Abstract
Bipolar plates are a major part of fuel cells, which are a clean and recyclable energy source. This study was carried out with two dies for a bipolar plate forming investigation with the magnetic pulse method: a bipolar plate die and a 10-channel [...] Read more.
Bipolar plates are a major part of fuel cells, which are a clean and recyclable energy source. This study was carried out with two dies for a bipolar plate forming investigation with the magnetic pulse method: a bipolar plate die and a 10-channel die. With the bipolar plate die, the forming of bipolar plates with a Cu110 sheet and a Grade 2 Ti sheet indicated that the bipolar plate die needed optimization for a full replication. The obtained maximum average depth percentage was 86% for a Cu110 sheet, while it was 54% for a Grade 2 Ti sheet in this study. A further increase of the depth percentage is possible but requires a much higher capacitor bank energy. The increase of the capacitor bank energy would result in severe tearing, while the depth percentage increase was little. The primary current and flyer velocity were measured at various capacitor bank energies. With the 10-channel die, the die parameters’ effect on metal sheet forming was investigated with a Cu110 sheet and an SS201 sheet. The draft angle had a significant effect on the replication of the die surface. The full replication was achieved for channels with proper parameters with both a Cu110 sheet and an SS201 sheet. Therefore, the bipolar plate die could be optimized based on the 10-channel die results. Full article
(This article belongs to the Special Issue Forming and Heat Treatment of Modern Metallic Materials)
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Open AccessArticle
Numerical Simulation of Solidification Behavior and Solute Transport in Slab Continuous Casting with S-EMS
Metals 2019, 9(4), 452; https://doi.org/10.3390/met9040452
Received: 28 March 2019 / Revised: 12 April 2019 / Accepted: 15 April 2019 / Published: 17 April 2019
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Abstract
A 3D numerical model was built to investigate the transport phenomena in slab continuous casting process with secondary electromagnetic stirring (S-EMS). In the model, the columnar grain grew from strand surface and it should be treated as a porous media. While for the [...] Read more.
A 3D numerical model was built to investigate the transport phenomena in slab continuous casting process with secondary electromagnetic stirring (S-EMS). In the model, the columnar grain grew from strand surface and it should be treated as a porous media. While for the equiaxed zone, the nucleated grain moves with fluid flow in the earlier stage and it was regarded as a slurry. The model was validated by measured strand surface temperature and magnetic induction intensity. The results show that the solidification end near the 1/4 width of slab was postponed, due to the liquid flow from a submerged entry nozzle injected to the strand’s narrow face. As the linear stirring in the same direction is applied, liquid moves from side B to side A and then penetrates deep downward with higher temperature. In the later stage, the solidification end near the side A is postponed and the solute element is concentrated. When linear stirring in the opposite direction is used, the solidification end near the side A moves backward, while that near the side B moves forward. Moreover, it is found that the solute segregation in the side B is deteriorated, but that in the side A is reduced. As rotational stirring mode is applied, the evenness of solidification end profile is improved and the centerline segregation is reduced, especially with higher current intensity. Therefore, it is concluded that the linear stirring mode is not appropriated for slab casting, while the rotational stirring mode is more suitable. Full article
(This article belongs to the Special Issue Advanced Simulation Technologies of Metallurgical Processing)
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