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Volume 7
Issue 9
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Metals, Volume 7, Issue 9 (September 2017) – 62 articles

Cover Story (view full-size image): Magnesium based materials are gaining significant attention in numerous engineering and biomedical sectors due to their high specific mechanical properties, biocompatibility and recyclability. Judicious development of materials is crucial for finding applications in automobile, aerospace and biomedical sector to realize desired properties as well as to help in maintaining the ecological balance with the environment. In search of such lightweight and high performance materials, magnesium nanocomposites containing Sm2O3 rare earth oxide (REO) nanoparticles were developed using powder metallurgy in absence of any protective inert atmosphere. The nanocomposites exhibited an excellent combination of strength, ductility, ignition resistance, and damping behaviour that is attributed to the presence of Sm2O3 nanoparticles. This study opens the door for new series of nanocomposites based on Mg/REO formulations [...] Read more.
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25470 KiB  
Article
Numerical and Experimental Investigation of the Influence of Growth Restriction on Grain Size in Binary Cu Alloys
by Andreas Cziegler, Olga Geraseva and Peter Schumacher
Metals 2017, 7(9), 383; https://doi.org/10.3390/met7090383 - 20 Sep 2017
Cited by 4 | Viewed by 4474
Abstract
Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several [...] Read more.
Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the growth restriction factor Q, grain size modelling was performed. The results obtained by the grain size model were compared to variations in the grain size of binary Cu alloys with increasing solute content under defined cooling conditions of the TP-1 grain refiner test of the Aluminium Association©. It was found that the experimental results differed significantly from the predicted grain size values for several alloying elements. A decreasing grain size with increasing alloy concentration was observed independently of the growth restriction potency of the alloying elements. Furthermore, excessive grain coarsening was found for several solutes beyond a transition point. It is assumed that contradictory variations in grain size result from a change in the nucleating particle density of the melt. Significant decreases in grain size are supposed to be due to the in-situ formation of potent nucleation sites. Excessive grain coarsening with increasing solute content may occur due to the removal of nucleating particles. The model shows that the difference in the actual number of particles before and beyond the transition point must be in the range of several orders of magnitude. Full article
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12194 KiB  
Article
Study of the Heat-Treatments Effect on High Strength Ductile Cast Iron Welded Joints
by Ronny M. Gouveia, Francisco J. G. Silva, Olga C. Paiva, Maria F. Andrade, Luiz Silva, Paulo C. Moselli and Konrad J. M. Papis
Metals 2017, 7(9), 382; https://doi.org/10.3390/met7090382 - 19 Sep 2017
Cited by 15 | Viewed by 5734
Abstract
Nowadays, ultimate tensile strengths above 400 MPa become usual for ductile irons, thus allowing the implementation of new design paradigms. Large concentrations of carbon and other influencing elements can negatively interfere with the welding process of ductile cast irons. Efforts made by researchers [...] Read more.
Nowadays, ultimate tensile strengths above 400 MPa become usual for ductile irons, thus allowing the implementation of new design paradigms. Large concentrations of carbon and other influencing elements can negatively interfere with the welding process of ductile cast irons. Efforts made by researchers have led to the discovery of solutions which enable good enough operational results to consider welding as a viable repairing or joining method. Although these alloys have been available for quite some time, researchers have mainly focused on issues relating to microstructural phenomena tied to casting and similar processes, leaving much to explore in terms of their weldability. Thus, this work intends to investigate the effect of different heat-treatments on the weldability of a high strength ductile cast iron by assessing the mechanical properties of welded joints as well as structural modifications induced by thermal cycles imposed before and after welding. Successful weld joints were achieved showing a clear heat affected zone (HAZ) close to the joint area. This area is coincident with the fracture area of the welded samples when loaded on a tensile test bench, having obtained promising results regarding mechanical strength and strain. The hardness of the welded zone was also carefully investigated, showing clear changes throughout the joint. Full article
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9304 KiB  
Article
Study of the Microstructure Evolution and Properties Response of a Friction-Stir-Welded Copper-Chromium-Zirconium Alloy
by Ruilin Lai, Diqiu He, Guoai He, Junyuan Lin and Youqing Sun
Metals 2017, 7(9), 381; https://doi.org/10.3390/met7090381 - 19 Sep 2017
Cited by 20 | Viewed by 8386
Abstract
In this article, the copper-chromium-zirconium (CuCrZr) alloys plates with 21 mm in thickness were butt joined together by means of FSW (friction stir welding). The properties of the FSW joints are studied. The microstructure variations during the process of FSW were investigated by [...] Read more.
In this article, the copper-chromium-zirconium (CuCrZr) alloys plates with 21 mm in thickness were butt joined together by means of FSW (friction stir welding). The properties of the FSW joints are studied. The microstructure variations during the process of FSW were investigated by optical microscopy (OM), electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM). The results show that the grains size in the nugget zone (NZ) are significantly refined, which can be attributed to the dynamic recrystallization (DRX). The microstructure distribution in the NZ is inhomogeneous and the size of equiaxed grains are decreased gradually along the thickness direction from the top to bottom area of the welds. Meanwhile, it is found that the micro-hardness and tensile strength of the welds are slightly increased along the thickness direction from the top to the bottom area of the welds. All the nano-strengthening precipitates in the BM are dissolved into the Cu matrix in the NZ. Therefore, the decreases in hardness, tensile strength, and electrical conductivity can be attributed to the comprehensive effect of dissolution of nano-strengthening precipitates into the supersaturation matrix and severe DRX in the welded NZ. Full article
(This article belongs to the Special Issue Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys)
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5129 KiB  
Article
Effect of Computational Parameters on Springback Prediction by Numerical Simulation
by Tomasz Trzepiecinski and Hirpa G. Lemu
Metals 2017, 7(9), 380; https://doi.org/10.3390/met7090380 - 19 Sep 2017
Cited by 50 | Viewed by 8317
Abstract
Elastic recovery of the material, called springback, is one of the problems in sheet metal forming of drawpieces, especially with a complex shape. The springback can be influenced by various technological, geometrical, and material parameters. In this paper the results of experimental testing [...] Read more.
Elastic recovery of the material, called springback, is one of the problems in sheet metal forming of drawpieces, especially with a complex shape. The springback can be influenced by various technological, geometrical, and material parameters. In this paper the results of experimental testing and numerical study are presented. The experiments are conducted on DC04 steel sheets, commonly used in the automotive industry. The numerical analysis of V-die air bending tests is carried out with the finite element method (FEM)-based ABAQUS/Standard 2016 program. A quadratic Hill anisotropic yield criterion is compared with an isotropic material described by the von Mises yield criterion. The effect of a number of integration points and integration rules on the springback amount and computation time is also considered. Two integration rules available in ABAQUS: the Gauss’ integration rule and Simpson’s integration rule are considered. The effect of sample orientation according to the sheet rolling direction and friction contact behaviour on the prediction of springback is also analysed. It is observed that the width of the sample bend in the V-bending test influences the stress-state in the cross-section of the sample. Different stress-states in the sample bend of the V-shaped die cause that the sheet undergoes springback in different planes. Friction contact phenomena slightly influences the springback behaviour. Full article
(This article belongs to the Special Issue Advances in Plastic Forming of Metals)
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3014 KiB  
Article
Physical-Mechanism Exploration of the Low-Cycle Unified Creep-Fatigue Formulation
by Dan Liu and Dirk John Pons
Metals 2017, 7(9), 379; https://doi.org/10.3390/met7090379 - 18 Sep 2017
Cited by 4 | Viewed by 4996
Abstract
Background—Creep-fatigue behavior is identified as the incorporated effects of fatigue and creep. One class of constitutive-based models attempts to evaluate creep and fatigue separately, but the interaction of fatigue and creep is neglected. Other models treat the damage as a single component, but [...] Read more.
Background—Creep-fatigue behavior is identified as the incorporated effects of fatigue and creep. One class of constitutive-based models attempts to evaluate creep and fatigue separately, but the interaction of fatigue and creep is neglected. Other models treat the damage as a single component, but the complex numerical structures that result are inconvenient for engineering application. The models derived through a curve-fitting method avoid these problems. However, the method of curving fitting cannot translate the numerical formulation to underlying physical mechanisms. Need—Therefore, there is a need to develop a new creep-fatigue formulation for metal that accommodates all relevant variables and where the relationships between them are consistent with physical mechanisms of fatigue and creep. Method—In the present work, the main dependencies and relationships for the unified creep-fatigue equation were presented through exploring what the literature says about the mechanisms. Outcomes—This shows that temperature, cyclic time and grain size have significant influences on creep-fatigue behavior, and the relationships between them (such as linear relation, logarithmical relation and power-law relation) are consistent with phenomena of diffusion creep and crack growth. Significantly, the numerical form of “1 − x” is presented to show the consumption of creep effect on fatigue capacity, and the introduction of the reference condition gives the threshold of creep effect. Originality—By this means, the unified creep-fatigue equation is linked to physical phenomena, where the influence of different dependencies on creep fatigue was explored and relationships shown in this equation were investigated in a microstructural level. Particularly, a physical explanation of the grain-size exponent via consideration of crack-growth planes was proposed. Full article
(This article belongs to the Special Issue Fatigue Damage)
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3027 KiB  
Article
Ceramic Materials in a Ti–C–Co–Ca3(PO4)2–Ag–Mg System Obtained by MA SHS for the Deposition of Biomedical Coatings
by Artem Potanin, Yury Pogozhev, Alexander Novikov and Evgeny Levashov
Metals 2017, 7(9), 378; https://doi.org/10.3390/met7090378 - 15 Sep 2017
Cited by 3 | Viewed by 4463
Abstract
This study aimed to obtain biocompatible ceramic materials in a Ti–C–Co–Ca3(PO4)2–Ag–Mg system by the combustion mode of mechanically activated (MA) reaction mixtures. The influence of the MA time on the reaction ability capability of the mixtures, on [...] Read more.
This study aimed to obtain biocompatible ceramic materials in a Ti–C–Co–Ca3(PO4)2–Ag–Mg system by the combustion mode of mechanically activated (MA) reaction mixtures. The influence of the MA time on the reaction ability capability of the mixtures, on their structural and chemical homogeneity, on the combustion parameters and structural-phase conversions in the combustion wave, as well as on the structure and phase composition of the electrode materials has been researched. It was found that the intense treatment of powder mixtures causes plastic deformation of components, the formation of lamellar composite granules, a reduction in the sizes of coherent scattering regions, and also the formation of minor amounts of products. The influence of the activation duration of the ignition temperature and heat release during the combustion of the reaction mixtures was studied. By the method of quenching the combustion front, it was demonstrated that in a combustion wave, chemical transformations occur within the lamellar structures formed during the process of mechanoactivation. It was shown that in the combustion wave, parallel chemical reactions of Ti with C as well as Ti with Co and Ca3(PO4)2 occur, with a Ti–Co-based melt forming the reaction surface. Ceramic electrodes with different contents of Ag and Mg were synthesized by force self-propagating high-temperature synthesis (SHS)-pressing technology using the MA mixtures. The microstructure of the materials consisted of round-shaped grains of nonstoichiometric titanium carbide TiCx grains, intermetallic matrix (TiCo, TiCo2, CoTiP), inclusions of Ca and Mg oxides, and grains of the Ag-based solid solution. An increased content of Ag and Mg in the composition of the electrodes, as well as an increased MA duration, leads to an enlargement of the inclusions of the Ag-containing phase size and deterioration in the uniformity of their distribution. Full article
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5515 KiB  
Article
The Influence of La and Ce Addition on Inclusion Modification in Cast Niobium Microalloyed Steels
by Hadi Torkamani, Shahram Raygan, Carlos Garcia Mateo, Jafar Rassizadehghani, Javier Vivas, Yahya Palizdar and David San-Martin
Metals 2017, 7(9), 377; https://doi.org/10.3390/met7090377 - 15 Sep 2017
Cited by 39 | Viewed by 6391
Abstract
The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In [...] Read more.
The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE > 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al2O3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix–MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 °C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix. Full article
(This article belongs to the Special Issue Advances in Microalloyed Steels)
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11115 KiB  
Article
A Numerical Study on Contact Condition and Wear of Roller in Cold Rolling
by Qichao Jin, Wenhu Wang, Ruisong Jiang, Louis Ngai Sum Chiu, Di Liu and Wenyi Yan
Metals 2017, 7(9), 376; https://doi.org/10.3390/met7090376 - 15 Sep 2017
Cited by 12 | Viewed by 8413
Abstract
An accurate determination of the contact pressure and local sliding in a cold rolling process is an essential step towards the prediction of the roller’s life due to wear damage. This investigation utilized finite element analysis to quantify the local contact pressure and [...] Read more.
An accurate determination of the contact pressure and local sliding in a cold rolling process is an essential step towards the prediction of the roller’s life due to wear damage. This investigation utilized finite element analysis to quantify the local contact pressure and local sliding over the rolling bite in a plate cold rolling process. It was the first study to quantify the local sliding distance in a rolling process using the Finite Element Analysis (FEA). The numerical results indicate that the local contact pressure over the rolling bite demonstrates a hill profile, and the peak coincides with the neutral plane. The local sliding distance over the rolling bite demonstrates a double-peak profile with the two peaks appearing at the forward slip and backward slip zones respectively. The amplitude of sliding distance in the backward slip zone is larger than that in the forward slip zone. A stick zone was confirmed between the forward slip and backward slip zones. According to a parametric study, the local contact pressure and sliding distance decrease when the thickness reduction is reduced or the diameter of the roller is decreased. The location of the neutral plane always presents at the rolling exit side of the rolling bite’s center. The size of the stick zone enlarges and the sizes of slip zones shrink significantly when the friction coefficient is increased. Finally, a novel concept of wear intensity was defined to examine the wear of the roller based on the local contact pressure and local sliding distance. The results show that a two-peak wear response exists in the backward and forward slip zones. The magnitude of the wear in the backward slip zone is larger than that in the forward slip zone. For a given roller and blank material combination, using a smaller thickness reduction, a smaller diameter roller and a higher friction coefficient condition can reduce the wear of the roller for a single rolling cycle. The current paper develops an understanding of rolling contact responses to the wear of the roller in rolling process. The research method can also be applied to study other rolling or sliding wear problems. Full article
(This article belongs to the Special Issue Researches and Simulations in Steel Rolling)
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7047 KiB  
Article
Torsional Fatigue Strength of Newly Developed Case Hardening TRIP-Aided Steel
by Koh-ichi Sugimoto, Tomohiko Hojo and Yuta Mizuno
Metals 2017, 7(9), 375; https://doi.org/10.3390/met7090375 - 15 Sep 2017
Cited by 11 | Viewed by 7213
Abstract
The torsional fatigue strength of newly developed case hardening steel, i.e., transformation-induced plasticity-aided martensitic steel subjected to vacuum carburizing followed by fine particle peening, was investigated for the fabrication of downsized precision gears with high torque capacity and wear resistance. The surface-hardened layer [...] Read more.
The torsional fatigue strength of newly developed case hardening steel, i.e., transformation-induced plasticity-aided martensitic steel subjected to vacuum carburizing followed by fine particle peening, was investigated for the fabrication of downsized precision gears with high torque capacity and wear resistance. The surface-hardened layer properties—i.e., high Vickers hardness, high compressive residual stress, and a large amount of retained austenite—considerably increased the torsional fatigue limits of vacuum-carburized and fine particle peened TM and JIS-SNCM420 steels, although the notch-sensitivity to fatigue was increased. The relation between torsional and rotational bending fatigue limits for the smooth specimens was found to be between the maximum principal stress and the minimum shear strain energy criterions. On the other hand, this relation for the notched specimens was represented through the maximum principal stress criterion. Full article
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4578 KiB  
Article
Investigation of the Frozen Bath Layer under Cold Anodes
by Donald Picard, Jayson Tessier, Guillaume Gauvin, Donald Ziegler, Houshang Alamdari and Mario Fafard
Metals 2017, 7(9), 374; https://doi.org/10.3390/met7090374 - 15 Sep 2017
Cited by 5 | Viewed by 3726
Abstract
Hall-Héroult cell stability is highly affected by anode changing operations. Upon the insertion of a cold anode in the cell, a layer of molten cryolite freezes under the anode. The thickness, microstructure, and chemical composition of this layer vary as a function of [...] Read more.
Hall-Héroult cell stability is highly affected by anode changing operations. Upon the insertion of a cold anode in the cell, a layer of molten cryolite freezes under the anode. The thickness, microstructure, and chemical composition of this layer vary as a function of time and its location in the cell. To better understand the evolution of the frozen layer, mandatory for the validation of numerical models, a measurement campaign was conducted on the anodes having a few hours of operation in the cell. The macrostructure of the selected frozen bath samples has been investigated using computed tomography while scanning electron microscope (SEM) has been used to qualify its microstructure. An energy-dispersive X-ray spectroscope (EDS) coupled to the SEM has revealed the chemical content. The results showed not only very different macrostructures between samples, but also significantly heterogeneous structure within the same sample. Nevertheless, for all samples, there is a clear distinction between the frozen cryolite and alumina/dusting phases, with the latter surrounding the cryolite matrix. Full article
(This article belongs to the Special Issue Selected Papers from the International Committee for Study of Bauxite, Alumina & Aluminium 2016)
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6053 KiB  
Article
Fretting Wear Behaviors of Aluminum Cable Steel Reinforced (ACSR) Conductors in High-Voltage Transmission Line
by Xingchi Ma, Lei Gao, Junxi Zhang and Lai-Chang Zhang
Metals 2017, 7(9), 373; https://doi.org/10.3390/met7090373 - 14 Sep 2017
Cited by 17 | Viewed by 5828
Abstract
This work reports the fretting wear behavior of aluminum cable steel reinforced (ACSR) conductors for use in high-voltage transmission line. Fretting wear tests of Al wires were conducted on a servo-controlled fatigue testing machine with self-made assistant apparatus, and their fretting process characteristics, [...] Read more.
This work reports the fretting wear behavior of aluminum cable steel reinforced (ACSR) conductors for use in high-voltage transmission line. Fretting wear tests of Al wires were conducted on a servo-controlled fatigue testing machine with self-made assistant apparatus, and their fretting process characteristics, friction force, wear damage, and wear surface morphology were detailed analyzed. The results show that the running regime of Al wires changes from a gross slip regime to a mixed regime more quickly as increasing contact load. With increasing amplitudes, gross slip regimes are more dominant under contact loads of lower than 30 N. The maximum friction force is relatively smaller in the NaCl solution than in a dry friction environment. The primary wear mechanisms in dry friction environments are abrasive wear and adhesive wear whereas abrasive wear and fatigue damage are dominant in NaCl solution. Full article
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4107 KiB  
Article
The Fabrication of All-Solid-State Lithium-Ion Batteries via Spark Plasma Sintering
by Xialu Wei, Jack Rechtin and Eugene A. Olevsky
Metals 2017, 7(9), 372; https://doi.org/10.3390/met7090372 - 14 Sep 2017
Cited by 29 | Viewed by 6936
Abstract
Spark plasma sintering (SPS) has been successfully used to produce all-solid-state lithium-ion batteries (ASSLibs). Both regular and functionally graded electrodes are implemented into novel three-layer and five-layer battery designs together with solid-state composite electrolyte. The electrical capacities and the conductivities of the SPS-processed [...] Read more.
Spark plasma sintering (SPS) has been successfully used to produce all-solid-state lithium-ion batteries (ASSLibs). Both regular and functionally graded electrodes are implemented into novel three-layer and five-layer battery designs together with solid-state composite electrolyte. The electrical capacities and the conductivities of the SPS-processed ASSLibs are evaluated using the galvanostatic charge-discharge test. Experimental results have shown that, compared to the three-layer battery, the five-layer battery is able to improve energy and power densities. Scanning electron microscopy (SEM) is employed to examine the microstructures of the batteries especially at the electrode–electrolyte interfaces. It reveals that the functionally graded structure can eliminate the delamination effect at the electrode–electrolyte interface and, therefore, retains better performance. Full article
(This article belongs to the Special Issue Powder Synthesis and Processing)
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6365 KiB  
Article
Isothermal Austenite–Ferrite Phase Transformations and Microstructural Evolution during Annealing in Super Duplex Stainless Steels
by Andrea Francesco Ciuffini, Silvia Barella, Cosmo Di Cecca, Andrea Gruttadauria, Carlo Mapelli and Davide Mombelli
Metals 2017, 7(9), 368; https://doi.org/10.3390/met7090368 - 14 Sep 2017
Cited by 25 | Viewed by 5887
Abstract
Super Duplex Stainless Steels (SDSSs) are composed of α-ferrite and γ-austenite grains, the simultaneous presence of which forms an optimal microstructure to achieve the best combination of mechanical and corrosion resistance properties. Moreover, international quality standards are strict about the phase fraction ratio. [...] Read more.
Super Duplex Stainless Steels (SDSSs) are composed of α-ferrite and γ-austenite grains, the simultaneous presence of which forms an optimal microstructure to achieve the best combination of mechanical and corrosion resistance properties. Moreover, international quality standards are strict about the phase fraction ratio. The purpose of this work is the achievement of a better description of the phase ratio evolution taking place during annealing at 1080 °C in the super duplex stainless steels F53–S32750 and F55–S32760. The experimental results show a damped sinusoidal trend in the α/γ phase ratio evolution with the increase of the soaking time of thermal treatment. This can be described by coupling both the competitive coarsening growth regime and the concept of the local equilibrium phase transformations, pointing out a good correspondence with the experimental data. Further, recrystallization phenomena also play a major role. Finally, the additivity character of the observed processes has been proven. Full article
(This article belongs to the Special Issue Microstructure based Modeling of Metallic Materials)
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3206 KiB  
Article
An Eco-Friendly Neutralization Process by Carbon Mineralization for Ca-Rich Alkaline Wastewater Generated from Concrete Sludge
by Jongchan Yoo, Heeyoung Shin and Sangwoo Ji
Metals 2017, 7(9), 371; https://doi.org/10.3390/met7090371 - 13 Sep 2017
Cited by 22 | Viewed by 7016
Abstract
Waste-concrete recycling processes using wet-based crushing methods inevitably generate a large amount of alkaline concrete sludge, as well as wastewater, which contains abundant Ca ions. The Ca-rich alkaline wastewater must then be neutralized for reuse in the waste-concrete recycling process. In this study, [...] Read more.
Waste-concrete recycling processes using wet-based crushing methods inevitably generate a large amount of alkaline concrete sludge, as well as wastewater, which contains abundant Ca ions. The Ca-rich alkaline wastewater must then be neutralized for reuse in the waste-concrete recycling process. In this study, the feasibility of a carbon mineralization process for the neutralization of alkaline wastewater was considered from both environmental and economic perspectives. The optimal reaction time, efficiency of Ca removal and CO2 sequestration as a function of the CO2 gas flow rate were assessed. The carbon mineralization process resulted in sequestering CO2 (85–100% efficiency) and removing Ca from the solution (84–99%) by precipitating pure CaCO3. Increasing the gas flow rate reduced the reaction time (65.0 down to 3.4 min for 2.5 L of solution), but decreased CO2 sequestration (from 463.3 down to 7.3 mg CO2 for 2.5 L of solution). Optimization of the gas flow rate is essential for efficient CO2 sequestration, Ca removal, CaCO3 production and, therefore, successful wastewater neutralization following the wet-based crushing process. The method presented here is an eco-friendly and economically viable substitute for dealing with alkaline wastewater. It may also provide a practical guide for the design of carbon mineralization processes for the neutralization of alkaline solutions containing large amounts of Ca. Full article
(This article belongs to the Special Issue Valuable Metal Recycling)
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6551 KiB  
Article
Effects of Post-Sinter Processing on an Al–Zn–Mg–Cu Powder Metallurgy Alloy
by Matthew David Harding, Ian William Donaldson, Rich Lester Hexemer Junior and Donald Paul Bishop
Metals 2017, 7(9), 370; https://doi.org/10.3390/met7090370 - 13 Sep 2017
Cited by 8 | Viewed by 4870
Abstract
The objective of this work was to study the effects of several post-sinter processing operations (heat-treatment, sizing, shot peening) on a press-and-sinter 7xxx series aluminum powder metallurgy (PM) alloy. The characterization of the products was completed through a combination of non-contact surface profiling, [...] Read more.
The objective of this work was to study the effects of several post-sinter processing operations (heat-treatment, sizing, shot peening) on a press-and-sinter 7xxx series aluminum powder metallurgy (PM) alloy. The characterization of the products was completed through a combination of non-contact surface profiling, hardness measurements, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X-ray diffraction (XRD), tensile, and three-point bend fatigue testing. It was determined that sizing in the as-quenched state imparted appreciable reductions in surface hardness (78 HRB) and fatigue strength (168 MPa) relative to counterpart specimens that were sized prior to solutionizing (85 HRB and 228 MPa). These declines in performance were ascribed to the annihilation of quenched in vacancies that subsequently altered the nature of precipitates within the finished product. The system responded well to shot peening, as this process increased fatigue strength to 294 MPa. However, thermal exposure at 353 K (80 °C) and 433 K (160 °C) then reduced fatigue performance to 260 MPa and 173 MPa, respectively, as a result of residual stress relaxation and in-situ over-aging. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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6961 KiB  
Article
Electrical Resistivity Measurement of Carbon Anodes Using the Van der Pauw Method
by Geoffroy Rouget, Hicham Chaouki, Donald Picard, Donald Ziegler and Houshang Alamdari
Metals 2017, 7(9), 369; https://doi.org/10.3390/met7090369 - 13 Sep 2017
Cited by 1 | Viewed by 6758
Abstract
The electrical resistivity of carbon anodes is an important parameter in the overall efficiency of the aluminum smelting process. The aim of this work is to explore the Van der Pauw (VdP) method as an alternative technique to the standard method, which is [...] Read more.
The electrical resistivity of carbon anodes is an important parameter in the overall efficiency of the aluminum smelting process. The aim of this work is to explore the Van der Pauw (VdP) method as an alternative technique to the standard method, which is commonly used in the aluminum industry, in order to characterize the electrical resistivity of carbon anodes and to assess the accuracy of the method. For this purpose, a cylindrical core is extracted from the top of the anodes. The electrical resistivity of the core samples is measured according to the ISO 11713 standard method. This method consists of applying a 1 A current along the revolution axis of the sample, and then measuring the voltage drop on its side, along the same direction. Theoretically, this technique appears to be satisfying, but cracks in the sample that are generated either during the anode production or while coring the sample may induce high variations in the measured signal. The VdP method, as presented in 1958 by L.J. Van der Pauw, enables the electrical resistivity of any plain sample with an arbitrary shape and low thickness to be measured, even in the presence of cracks. In this work, measurements were performed using both the standard method and the Van der Pauw method, on both flawless and cracked samples. Results provided by the VdP method appeared to be more reliable and repeatable. Furthermore, numerical simulations using the finite element method (FEM) were performed in order to assess the effect of the presence of cracks and their thicknesses on the accuracy of the VdP method. Full article
(This article belongs to the Special Issue Selected Papers from the International Committee for Study of Bauxite, Alumina & Aluminium 2016)
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10364 KiB  
Article
Influence of Powder Surface Contamination in the Ni-Based Superalloy Alloy718 Fabricated by Selective Laser Melting and Hot Isostatic Pressing
by Yen-Ling Kuo and Koji Kakehi
Metals 2017, 7(9), 367; https://doi.org/10.3390/met7090367 - 13 Sep 2017
Cited by 35 | Viewed by 7253
Abstract
The aim of this study was to gain a deep understanding of the microstructure-mechanical relationship between solid-state sintering and full-melting processes. The IN718 superalloy was fabricated by hot isostatic pressing (HIP) and selective laser melting (SLM). Continuous precipitates were clearly localized along the [...] Read more.
The aim of this study was to gain a deep understanding of the microstructure-mechanical relationship between solid-state sintering and full-melting processes. The IN718 superalloy was fabricated by hot isostatic pressing (HIP) and selective laser melting (SLM). Continuous precipitates were clearly localized along the prior particle boundary (PPB) in the HIP materials, while SLM materials showed a microstructure free of PPB. The mechanical properties of specimens that underwent SLM + solution treatment and aging were comparable to those of conventional wrought specimens both at room temperature and 650 °C. However, a drop was observed in the ductility of HIP material at 650 °C. The brittle particles along the PPB were found to affect the HIP materials’ creep life and ductility during solid-state sintering. Full article
(This article belongs to the Special Issue Powder Synthesis and Processing)
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2608 KiB  
Article
DFT Modelling of Cu Segregation in Al-Cu Alloys Covered by an Ultrathin Oxide Film and Possible Links with Passivity
by Pauline Cornette, Dominique Costa and Philippe Marcus
Metals 2017, 7(9), 366; https://doi.org/10.3390/met7090366 - 12 Sep 2017
Cited by 10 | Viewed by 6040
Abstract
We modelled with Density Functional Theory (DFT) an Al-Cu alloy covered with a passive film, with several Cu concentrations (from the limit of the isolated atom to the monolayer) at the interface with the oxide, as well as Guinier-Preston 1 (GP1) zones. At [...] Read more.
We modelled with Density Functional Theory (DFT) an Al-Cu alloy covered with a passive film, with several Cu concentrations (from the limit of the isolated atom to the monolayer) at the interface with the oxide, as well as Guinier-Preston 1 (GP1) zones. At low (respectively high) concentration, Cu segregates in the first (respectively second) metal layer underneath the passive film. The Cu monolayer is the most stable configuration (−0.37 eV/Cu atom). GP1 zones were modelled, with a three-copper atom cluster in the alloy. The GP1 zone is slightly favoured with respect to the Cu monolayer under the oxide film. A low (respectively high) Cu concentration induces an electronic workfunction increase (respectively decrease) by 0.3 eV (respectively −0.4 to −0.6 eV) as compared to pure Al. In contrast, without oxide, Cu segregation at the Al surface induces no workfunction change at low concentration and an increase of 0.3 eV of the workfunction at high concentration. Thus, the presence of oxide modifies the expected tendency of workfunction increase by adding a more noble metal. For the studied models, no spontaneous electron transfer occurs to the O2 molecule. Full article
(This article belongs to the Special Issue Corrosion Inhibition)
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5046 KiB  
Article
Effects of the Preparation Solvent on the Catalytic Properties of Cobalt–Boron Alloy for the Hydrolysis of Alkaline Sodium Borohydride
by Yongjin Zou, Yubo Gao, Pengru Huang, Cuili Xiang, Hailiang Chu, Shujun Qiu, Erhu Yan, Fen Xu and Lixian Sun
Metals 2017, 7(9), 365; https://doi.org/10.3390/met7090365 - 12 Sep 2017
Cited by 19 | Viewed by 4441
Abstract
In this study, the effects of the solvent used to prepare Co–B alloy on its catalytic properties were investigated. The solvent effects on the morphology, composition, and specific surface area of the alloy particles were also examined. The morphology of the alloy particles [...] Read more.
In this study, the effects of the solvent used to prepare Co–B alloy on its catalytic properties were investigated. The solvent effects on the morphology, composition, and specific surface area of the alloy particles were also examined. The morphology of the alloy particles was found to be dependent on the solvent. The particles were granular in water, methanol, and acetone, although the particle diameters differed, whereas they were nanoflake-like in acetonitrile. Acetonitrile produced the largest surface area of the alloy particles, but the lowest catalytic activity for the hydrolysis of NaBH4 owing to the ready oxidation of the particles in air. The Co–B in acetone exhibited the highest catalytic activity, represented by a hydrogen generation rate of 5733 mL·min−1·g−1 during the hydrolysis of 1.5 wt % NaBH4 at 298 K. This hydrogen generation rate is more than twice that produced by the Co–B in water. Full article
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1977 KiB  
Article
High Field X-ray Diffraction Study for Ni46.4Mn38.8In12.8Co2.0 Metamagnetic Shape Memory Film
by Yoshifuru Mitsui, Keiichi Koyama, Makoto Ohtsuka, Rie Y. Umetsu, Ryosuke Kainuma and Kazuo Watanabe
Metals 2017, 7(9), 364; https://doi.org/10.3390/met7090364 - 12 Sep 2017
Cited by 1 | Viewed by 4733
Abstract
The transformation behaviors on metamagnetic shape memory Ni46.4Mn38.8In12.8Co2.0 film were investigated by X-ray diffraction experiments in the temperature up to 473 K and magnetic fields µ0H up to 5 T. The prepared film showed [...] Read more.
The transformation behaviors on metamagnetic shape memory Ni46.4Mn38.8In12.8Co2.0 film were investigated by X-ray diffraction experiments in the temperature up to 473 K and magnetic fields µ0H up to 5 T. The prepared film showed the parent phase with L21 structure at 473 K, and with preferred orientation along the 111 plane. The magnetic field induced reverse transformation was directly observed at T = 366 K, which was just around the reverse transformation starting temperature. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
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6923 KiB  
Article
Mushy Zone Morphology Calculation with Application of CALPHAD Technique
by Piotr Mikolajczak, Amber Genau and Lorenz Ratke
Metals 2017, 7(9), 363; https://doi.org/10.3390/met7090363 - 12 Sep 2017
Cited by 5 | Viewed by 5994
Abstract
Mushy zone morphology in AlSiMn alloys was studied using directional solidification, and the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique was applied for thermodynamic calculations. The specimens solidified with forced convection presented segregation across the sample diameter, and the measured compositions [...] Read more.
Mushy zone morphology in AlSiMn alloys was studied using directional solidification, and the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique was applied for thermodynamic calculations. The specimens solidified with forced convection presented segregation across the sample diameter, and the measured compositions were located on the Al-Si-Mn phase diagram. Scheil-Gulliver calculations for measured compositions were used to determine various solidification paths that may occur in specimens. Property diagrams and solidification paths presented the segregation effect on the characteristic temperatures, mushy zone length and the sequence of occurring phases whilst 2D maps enabled visualization of the mushy zone during directional solidification. Melt stirring was found to change solidification range, as well as mushy zone length and shape, and the dendrite tips formed a rough profile across the specimens. The study revealed mushy zones with dense dendritic structure and liquid channels empty of Mn phases, where intermetallics had no possibility to flow in the liquid, whilst in other samples with channels filled with Al15Si2Mn4, Mn-precipitates also flowed above the α-Al. The melt flow may lead to a mainly dendritic mushy zone or to a mushy zone with dendrites reaching only lower half of mushy length with intermetallics forming and freely flowing above dendrites in the liquid upper half. Full article
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4030 KiB  
Article
Dynamic Strain Aging Behaviour in AISI 316L Austenitic Stainless Steel under As-Received and As-Welded Conditions
by Guma Alnaji Muhamed, Süleyman Gündüz, Mehmet Akif Erden and Demet Taştemur
Metals 2017, 7(9), 362; https://doi.org/10.3390/met7090362 - 12 Sep 2017
Cited by 14 | Viewed by 6512
Abstract
In the current study, dynamic strain ageing (DSA) phenomena in 316L austenitic stainless steel was investigated under as-received and as-welded conditions. A tensile test was carried out on as-received and as-welded samples for the temperatures of 25–800 °C at a strain rate of [...] Read more.
In the current study, dynamic strain ageing (DSA) phenomena in 316L austenitic stainless steel was investigated under as-received and as-welded conditions. A tensile test was carried out on as-received and as-welded samples for the temperatures of 25–800 °C at a strain rate of 1 × 10−3 s−1. Microstructure and fracture surfaces were investigated by optic and scanning electron microscopes (SEM). 316L austenitic stainless steel showed different DSA behavior under as-received and as-welded conditions, which are discussed in terms of microstructure and mechanical properties. Full article
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30190 KiB  
Article
Microstructure and Mechanical Properties of Ultrasonic Welded Joint of 1060 Aluminum Alloy and T2 Pure Copper
by Guanpeng Liu, Xiaowu Hu, Yanshu Fu and Yulong Li
Metals 2017, 7(9), 361; https://doi.org/10.3390/met7090361 - 11 Sep 2017
Cited by 24 | Viewed by 7148
Abstract
The microstructure and mechanical properties of Al/Cu ultrasonic welding joints were investigated. Results show that: (i) the joint strength increased when the welding time increased within a certain range, and a maximal resistant force of 163.04 N was obtained when the welding duration [...] Read more.
The microstructure and mechanical properties of Al/Cu ultrasonic welding joints were investigated. Results show that: (i) the joint strength increased when the welding time increased within a certain range, and a maximal resistant force of 163.04 N was obtained when the welding duration and welding static pressure were 200 ms and 7.2 MPa, respectively; (ii) with a further increase of welding time, the bonding interface was gradually occupied by a thick strip layer of brittle Al2Cu (θ2) phase, thus decreasing the strength; (iii) the maximum temperature in the welding region was 360 °C during the welding process, and a recrystallization phenomenon was identified near the welding interface; (iv) the average nanohardness of Cu, the Cu-Al interfacial reaction layer and Al were 1.04 GPa, 1.34 GPa, and 0.53 GPa, respectively, which is consistent with the formation of the intermetallic compound identified by energy-dispersive X-ray spectroscopy (EDS) and XRD analysis. Full article
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8599 KiB  
Article
Preparation of Vanadium Nitride Using a Thermally Processed Precursor with Coating Structure
by Jingli Han, Yimin Zhang, Tao Liu, Jing Huang, Nannan Xue and Pengcheng Hu
Metals 2017, 7(9), 360; https://doi.org/10.3390/met7090360 - 11 Sep 2017
Cited by 15 | Viewed by 4716
Abstract
A new effective method is proposed to prepare vanadium nitride (VN) via carbothermal reduction–nitridation (CRN) of the precursor, obtained by adding carbon black (C) to the stripping solution during the vanadium recovery from black shale. VN was successfully prepared at a low temperature [...] Read more.
A new effective method is proposed to prepare vanadium nitride (VN) via carbothermal reduction–nitridation (CRN) of the precursor, obtained by adding carbon black (C) to the stripping solution during the vanadium recovery from black shale. VN was successfully prepared at a low temperature of 1150 °C for only 1 h with a C/V2O5 mass ratio of 0.30 in N2 atmosphere, but a temperature of 1300–1500 °C is required for several hours in the traditional CRN method. The low synthesis temperature and short period for the preparation of VN was due to the vanadium-coated carbon structure of the precursor, which enlarged the contact area between reactants significantly and provided more homogeneous chemical composition. In addition, the simultaneous direct reduction and indirect reduction of the interphase caused by the coating structure obviously accelerated the reaction. The phase evolution of the precursor was as follows: (NH4)2V6O16·1.5H2O → V2O5 → V6O13 → VO2 → V4O7 → V2O3 → VC → VN. The precursor converted to V6O13 and VO2 completely after being calcined at 550 °C, indicating that the pre-reduction of V2O5 in the traditional CRN method can be omitted. This method combined the synthesis of VN with the vanadium extraction creatively, having the advantages of simple reaction conditions, low cost and short processing time. Full article
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3589 KiB  
Article
Effect of Al2O3 Nanoparticles as Reinforcement on the Tensile Behavior of Al-12Si Composites
by Pan Ma, Yandong Jia, Prashanth Konda Gokuldoss, Zhishui Yu, Shanglei Yang, Jian Zhao and Chonggui Li
Metals 2017, 7(9), 359; https://doi.org/10.3390/met7090359 - 10 Sep 2017
Cited by 51 | Viewed by 6995
Abstract
Al2O3 nanoparticle-reinforced Al-12Si matrix composites were successfully fabricated by hot pressing and subsequent hot extrusion. The influence of weight fraction of Al2O3 particles on the microstructure, mechanical properties, and the corresponding strengthening mechanisms were investigated in detail. [...] Read more.
Al2O3 nanoparticle-reinforced Al-12Si matrix composites were successfully fabricated by hot pressing and subsequent hot extrusion. The influence of weight fraction of Al2O3 particles on the microstructure, mechanical properties, and the corresponding strengthening mechanisms were investigated in detail. The Al2O3 particles are uniformly distributed in the matrix, when 2 and 5 wt. % of Al2O3 particles were added to the Al-12Si matrix. Significant agglomeration can be found in composites with 10 wt. % addition of Al2O3 nanoparticles. The maximum hardness, the yield strength, and tensile strength were obtained for the composite with 5 wt. % Al2O3 addition, which showed an increase of about ~11%, 23%, and 26%, respectively, compared with the Al-12Si matrix. Meanwhile, the elongation increased to about ~30%. The contribution of different mechanisms including Orowan strengthening, thermal mismatch strengthening, and load transfer strengthening were analyzed. It was shown that the thermal mismatch strengthening has a more significant contribution to strengthening these composites than the Orowan and load transfer strengthening mechanisms. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Properties of Structural Metals and Alloys)
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4419 KiB  
Article
In Vitro Corrosion Properties of Mg Matrix In Situ Composites Fabricated by Spark Plasma Sintering
by Nguyen Q. Cao, Dinh N. Pham, Narita Kai, Hai V. Dinh, Sachiko Hiromoto and Equo Kobayashi
Metals 2017, 7(9), 358; https://doi.org/10.3390/met7090358 - 9 Sep 2017
Cited by 25 | Viewed by 4561
Abstract
Mg matrix in situ composites were fabricated from Mg and ZnO powder by a spark plasma sintering method. The composition and microstructure of the sintered samples were characterized. Corrosion properties of fabricated composites were evaluated by immersion and by electrochemical tests using Hanks’ [...] Read more.
Mg matrix in situ composites were fabricated from Mg and ZnO powder by a spark plasma sintering method. The composition and microstructure of the sintered samples were characterized. Corrosion properties of fabricated composites were evaluated by immersion and by electrochemical tests using Hanks’ solution. The results showed that the formation of in situ products improved significantly the corrosion resistance of the fabricated composites compared with pure Mg; Mg-10 wt % ZnO composites especially exhibited the lowest corrosion rate. In addition, an energy-dispersive X-ray (EDX) analysis showed that calcium phosphate formed as a corrosion product on the surface of Mg-10 wt % ZnO composites, while Mg(OH)2 appeared as a corrosion product on the surface of Mg-20 wt % ZnO composite. The findings suggested Mg-10 wt % ZnO composite as a potential candidate for temporary implant application. Full article
(This article belongs to the Special Issue Spark Plasma Sintering-A Key Technology towards the Development of New Materials)
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2523 KiB  
Article
Significantly Enhancing the Ignition/Compression/Damping Response of Monolithic Magnesium by Addition of Sm2O3 Nanoparticles
by Milli Suchita Kujur, Ashis Mallick, Vyasaraj Manakari, Gururaj Parande, Khin Sandar Tun and Manoj Gupta
Metals 2017, 7(9), 357; https://doi.org/10.3390/met7090357 - 9 Sep 2017
Cited by 56 | Viewed by 6774
Abstract
The present study reports the development of Mg–Sm2O3 nanocomposites as light-weight materials for weight critical applications targeted to reduce CO2 emissions, particularly in the transportation sector. Mg-0.5, 1.0, and 1.5 vol % Sm2O3 nanocomposites are synthesized [...] Read more.
The present study reports the development of Mg–Sm2O3 nanocomposites as light-weight materials for weight critical applications targeted to reduce CO2 emissions, particularly in the transportation sector. Mg-0.5, 1.0, and 1.5 vol % Sm2O3 nanocomposites are synthesized using a powder metallurgy method incorporating hybrid microwave sintering and hot extrusion. The microstructural studies showed dispersed Sm2O3 nanoparticles (NPs), refinement of grain size due to the presence of Sm2O3 NPs, and presence of limited porosity. Microhardness and dimensional stability of pure Mg increased with the progressive addition of Sm2O3 NPs. The addition of 1.5 vol % of Sm2O3 NPs to the Mg matrix enhanced the ignition temperature by ~69 °C. The ability of pure Mg to absorb vibration also progressively enhanced with the addition of Sm2O3 NPs. The room temperature compressive strengths (CYS and UCS) of Mg–Sm2O3 nanocomposites were found to be higher without having any adverse effect on ductility, leading to a significant increase in energy absorbed prior to compressive failure. Further, microstructural characteristics are correlated with the enhancement of various properties exhibited by nanocomposites. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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6283 KiB  
Article
A Combined Experimental-Numerical Approach for Investigating Texture Evolution of NiTi Shape Memory Alloy under Uniaxial Compression
by Li Hu, Shuyong Jiang and Yanqiu Zhang
Metals 2017, 7(9), 356; https://doi.org/10.3390/met7090356 - 9 Sep 2017
Cited by 8 | Viewed by 5084
Abstract
Texture evolution of NiTi shape memory alloy was investigated during uniaxial compression deformation at 673 K (400 °C) by combining crystal plasticity finite element method with electron back-scattered diffraction experiment and transmission electron microscope experiment. Transmission electron microscope observation indicates that dislocation slip [...] Read more.
Texture evolution of NiTi shape memory alloy was investigated during uniaxial compression deformation at 673 K (400 °C) by combining crystal plasticity finite element method with electron back-scattered diffraction experiment and transmission electron microscope experiment. Transmission electron microscope observation indicates that dislocation slip rather than deformation twinning plays a dominant role in plastic deformation of B2 austenite NiTi shape memory alloy at 673 K (400 °C). Electron back-scattered diffraction experiment illustrates heterogeneous microstructure evolution resulting from dislocation slip in NiTi shape memory alloy at 673 K (400 °C). {110}<100>, {010}<100> and {110}<111> slip systems are introduced into a crystal plasticity constitutive model. Based on the constructed representative volume element model and the extracted crystallographic orientations, particle swarm optimization algorithm is used to identify crystal plasticity parameters from experimental results of NiTi shape memory alloy. Using the fitted material parameters, a crystal plasticity finite element method is used to predict texture evolution of NiTi shape memory alloy during uniaxial compression deformation. The simulation results agree well with the experimental ones. With the progression of plastic deformation, a crystallographic plane of NiTi shape memory alloy gradually rotates to be vertical to the loading direction, which lays the foundation for forming the <111> fiber texture. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
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10180 KiB  
Article
Mechanical Characterization of Composite Coatings Formed by Reactive Detonation Spraying of Titanium
by Sergey Panin, Ilya Vlasov, Dina Dudina, Vladimir Ulianitsky, Roman Stankevich, Igor Batraev and Filippo Berto
Metals 2017, 7(9), 355; https://doi.org/10.3390/met7090355 - 8 Sep 2017
Cited by 4 | Viewed by 4006
Abstract
The structure and mechanical properties of the coatings formed by reactive detonation spraying of titanium in a wide range of spraying conditions were studied. The variable deposition parameters were the nature of the carrier gas, the spraying distance, the O2/C2 [...] Read more.
The structure and mechanical properties of the coatings formed by reactive detonation spraying of titanium in a wide range of spraying conditions were studied. The variable deposition parameters were the nature of the carrier gas, the spraying distance, the O2/C2H2 ratio, and the volume of the explosive mixture. The phase composition of the coatings and the influence of the spraying parameters on the mechanical properties of the coatings were investigated. In addition, nanohardness of the individual phases contained in the coatings was evaluated. It was found that the composition of the strengthening phases in the coatings depends on the O2/C2H2 ratio and the nature of the carrier gas. Detonation spraying conditions ensuring the formation of composite coatings with a set of improved mechanical properties are discussed. The strength of the coatings was determined through the microhardness measurements and local characterization of the phases via nanoindentation. Three-point bending tests were employed in order to evaluate the crack resistance of the coatings. The strengthening mechanisms of the coatings by oxide or carbonitride phases were discussed. Full article
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16239 KiB  
Article
Characterisation of Calcium- and Phosphorus-Enriched Porous Coatings on CP Titanium Grade 2 Fabricated by Plasma Electrolytic Oxidation
by Krzysztof Rokosz, Tadeusz Hryniewicz, Sofia Gaiaschi, Patrick Chapon, Steinar Raaen, Kornel Pietrzak and Winfried Malorny
Metals 2017, 7(9), 354; https://doi.org/10.3390/met7090354 - 8 Sep 2017
Cited by 18 | Viewed by 5256
Abstract
In the paper, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), and Glow Discharge Optical Emission Spectroscopy (GDOES) analyses of calcium- and phosphorus-enriched coatings obtained on commercial purity (CP) Titanium Grade 2 by plasma electrolytic oxidation (PEO), known also [...] Read more.
In the paper, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), and Glow Discharge Optical Emission Spectroscopy (GDOES) analyses of calcium- and phosphorus-enriched coatings obtained on commercial purity (CP) Titanium Grade 2 by plasma electrolytic oxidation (PEO), known also as micro arc oxidation (MAO), in electrolytes based on concentrated phosphoric acid with calcium nitrate tetrahydrate, are presented. The preliminary studies were performed in electrolytes containing 10, 300, and 600 g/L of calcium nitrate tetrahydrate, whereas for the main research the solution contained 500 g/L of the same hydrated salt. It was found that non-porous coatings, with very small amounts of calcium and phosphorus in them, were formed in the solution with 10 g/L Ca(NO3)2·4H2O, whereas the other coatings, fabricated in the consecutive electrolytes containing from 300 up to 650 g/L Ca(NO3)2·4H2O, were porous. Based on the GDOES data, it was also found that the obtained porous PEO coating may be divided into three sub-layers: the first, top, porous layer was the thinnest; the second, semi-porous layer was about 12 times thicker than the first; and the third, transition sub-layer was about 10 times thicker than the first. Based on the recorded XPS spectra, it was possible to state that the top 10-nm layer of porous PEO coatings included chemical compounds containing titanium (Ti4+), calcium (Ca2+), as well as phosphorus and oxygen (PO43− and/or HPO42− and/or H2PO4−, and/or P2O74−). Full article
(This article belongs to the Special Issue Plasma Electrolytic Oxidation)
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