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Metals, Volume 5, Issue 3 (September 2015), Pages 1127-1769

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Editorial

Jump to: Research, Review

Open AccessEditorial Advances in Solidification Processing
Metals 2015, 5(3), 1432-1434; doi:10.3390/met5031432
Received: 24 July 2015 / Accepted: 24 July 2015 / Published: 11 August 2015
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Abstract
Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern
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Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern technological societies. As a result, there have been innumerable efforts and full conferences dedicated to this important subject [1–6]. In addition, there are various scientific journals fully devoted to investigating the various aspects which give rise to various solidification microstructures [7–9]. [...] Full article
(This article belongs to the Special Issue Advances in Solidification Processing)
Open AccessEditorial Manganese-based Permanent Magnets
Metals 2015, 5(3), 1435-1436; doi:10.3390/met5031435
Received: 10 August 2015 / Accepted: 10 August 2015 / Published: 11 August 2015
Cited by 1 | PDF Full-text (279 KB) | HTML Full-text | XML Full-text
Abstract
There is a significant gap between the energy product, BH, where B is the magnetic flux density and H is the magnetic field strength, of both the traditional ferrite and AlNiCo permanent magnets of less than 10 MGOe and that of the rare
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There is a significant gap between the energy product, BH, where B is the magnetic flux density and H is the magnetic field strength, of both the traditional ferrite and AlNiCo permanent magnets of less than 10 MGOe and that of the rare earth magnets of greater than 30 MGOe. This is a gap that Mn-based magnets could potentially, inexpensively, fill. This Special Issue presents work on the development of both types of manganese permanent magnets. Some of the challenges involved in the development of these magnets include improving the compounds’ energy product, increasing the thermal stability of these metastable compounds, and producing them in quantity as a bulk material.[...] Full article
(This article belongs to the Special Issue Manganese-based Permanent Magnets)
Open AccessEditorial Titanium Alloys
Metals 2015, 5(3), 1437-1439; doi:10.3390/met5031437
Received: 11 August 2015 / Accepted: 11 August 2015 / Published: 14 August 2015
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Abstract
Although originally discovered in the 18th century [1], the titanium industry did not experience any significant advancement until the middle of the 20th century through the development of the gas turbine engine [2]. Since then, the aerospace sector has dominated worldwide titanium use
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Although originally discovered in the 18th century [1], the titanium industry did not experience any significant advancement until the middle of the 20th century through the development of the gas turbine engine [2]. Since then, the aerospace sector has dominated worldwide titanium use with applications in both engines and airframe structures [3]. The highly desirable combination of properties, which include excellent corrosion resistance, favourable strength to weight ratios, and an impressive resistance to fatigue, has led to an extensive range of applications [4], with only high extraction and processing costs still restricting further implementation. [...] Full article
(This article belongs to the Special Issue Titanium Alloys)

Research

Jump to: Editorial, Review

Open AccessArticle Effect of Yttrium Addition on Glass-Forming Ability and Magnetic Properties of Fe–Co–B–Si–Nb Bulk Metallic Glass
Metals 2015, 5(3), 1127-1135; doi:10.3390/met5031127
Received: 28 April 2015 / Revised: 20 June 2015 / Accepted: 23 June 2015 / Published: 29 June 2015
Cited by 3 | PDF Full-text (662 KB) | HTML Full-text | XML Full-text
Abstract
The glass-forming ability (GFA) and the magnetic properties of the [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4−xYx bulk metallic glasses (BMGs) have been studied. The partial replacement of Nb by Y
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The glass-forming ability (GFA) and the magnetic properties of the [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4−xYx bulk metallic glasses (BMGs) have been studied. The partial replacement of Nb by Y improves the thermal stability of the glass against crystallization. The saturation mass magnetization (σs) exhibits a maximum around 2 at. % Y, and the value of σs of the alloy with 2 at. % Y is 6.5% larger than that of the Y-free alloy. The coercivity shows a tendency to decrease with increasing Y content. These results indicate that the partial replacement of Nb by Y in the Fe–Co–B–Si–Nb BMGs is useful to simultaneous achievement of high GFA, high σs, and good soft magnetic properties. Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
Open AccessArticle Green Nanocomposites from Renewable Plant Oils and Polyhedral Oligomeric Silsesquioxanes
Metals 2015, 5(3), 1136-1147; doi:10.3390/met5031136
Received: 24 March 2015 / Revised: 20 June 2015 / Accepted: 24 June 2015 / Published: 30 June 2015
Cited by 3 | PDF Full-text (457 KB) | HTML Full-text | XML Full-text
Abstract
Green nanocomposites based on renewable plant oils and polyhedral oligomeric silsesquioxanes (POSS) have been developed. An acid-catalyzed curing of epoxidized plant oils with oxirane-containing POSS derivatives produced transparent nanocomposite coatings with high gloss surface, in which the organic and inorganic components were linked
[...] Read more.
Green nanocomposites based on renewable plant oils and polyhedral oligomeric silsesquioxanes (POSS) have been developed. An acid-catalyzed curing of epoxidized plant oils with oxirane-containing POSS derivatives produced transparent nanocomposite coatings with high gloss surface, in which the organic and inorganic components were linked via covalent bonds. The hardness and mechanical strength were improved by the incorporation of the POSS unit into the organic polymer matrix. Nanostructural analyses of the nanocomposites showed the formation of homogeneous structures at the micrometer scale. On the other hand, such improvements of the coating and mechanical properties were not observed in the composite without covalent bonds between the plant oil-based polymer and POSS unit. The study demonstrates the correlation between the nanostructure of composites and macroscopic properties. Full article
Open AccessArticle Influence of Milling on the Fatigue Lifetime of a Ti6Al4V Titanium Alloy
Metals 2015, 5(3), 1148-1162; doi:10.3390/met5031148
Received: 11 February 2015 / Revised: 8 June 2015 / Accepted: 23 June 2015 / Published: 30 June 2015
Cited by 4 | PDF Full-text (9540 KB) | HTML Full-text | XML Full-text
Abstract
The present article focuses on the influence of machining on the fatigue life of a titanium alloy: Ti6Al4V. An experimental design was adopted in order to highlight the effects of machining parameters on surface integrity while generating very different surfaces with a view
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The present article focuses on the influence of machining on the fatigue life of a titanium alloy: Ti6Al4V. An experimental design was adopted in order to highlight the effects of machining parameters on surface integrity while generating very different surfaces with a view to subsequent fatigue testing (four point bending tests). Firstly, the impact of machining parameters on surface integrity was demonstrated. Then, the influence of surface integrity on fatigue lifetime was observed: no influence of the geometric and metallurgical parameters was observed. However, the mechanical parameter (e.g., residual stress) seemed to have a preponderant influence. To conclude, a machining plan of procedure was proposed to significantly improve the fatigue lifetime as compared with a reference industrial plan of procedure. Full article
(This article belongs to the Special Issue Titanium Alloys)
Open AccessArticle The Self-Organized Critical Behavior in Pd-based Bulk Metallic Glass
Metals 2015, 5(3), 1188-1196; doi:10.3390/met5031188
Received: 25 May 2015 / Revised: 19 June 2015 / Accepted: 25 June 2015 / Published: 6 July 2015
Cited by 2 | PDF Full-text (462 KB) | HTML Full-text | XML Full-text
Abstract
Bulk metallic glasses (BMGs) deform irreversibly through shear banding manifested as serrated-flow behavior during compressive tests. The strain-rate-dependent plasticity under uniaxial compression at the strain rates of 2 × 10−2, 2 × 10−3, and 2 × 10−4·s
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Bulk metallic glasses (BMGs) deform irreversibly through shear banding manifested as serrated-flow behavior during compressive tests. The strain-rate-dependent plasticity under uniaxial compression at the strain rates of 2 × 10−2, 2 × 10−3, and 2 × 10−4·s−1 in a Pd-based BMG is investigated. The serrated flow behavior is not observed in the stress-strain curve at the strain rate of 2 × 10−2·s−1. However, the medial state occurs at the strain rates of 2 × 10−3·s−1, and eventually the self-organized critical (SOC) behavior appears at the strain rate of 2 × 10−4·s−1. The distribution of the elastic energy density shows a power-law distribution with the power-law exponent of −2.76, suggesting that the SOC behavior appears. In addition, the cumulative probability is well approximated by a power-law distribution function with the power-law exponent of 0.22 at the strain rate of 2 × 10−4·s−1. The values of the goodness of fit are 0.95 and 0.99 at the strain rates of 2 × 10−3 and 2 × 10−4·s−1, respectively. The transition of the dynamic serrated flows of BMGs is from non-serrated flow to an intermediate state and finally to the SOC state with decreasing the strain rates. Full article
(This article belongs to the Special Issue Serration and Noise Behavior in Advanced Materials)
Open AccessArticle Thermal Stability of Nanoporous Raney Gold Catalyst
Metals 2015, 5(3), 1197-1211; doi:10.3390/met5031197
Received: 17 June 2015 / Revised: 27 June 2015 / Accepted: 1 July 2015 / Published: 7 July 2015
Cited by 3 | PDF Full-text (1175 KB) | HTML Full-text | XML Full-text
Abstract
Nanoporous “Raney gold” sponge was prepared by de-alloying an Au-Al precursor alloy. Catalytic tests using a micro-reactor confirmed that Raney gold can serve as an active heterogeneous catalyst for CO oxidation, reduction of NO to N2, and oxidation of NO to
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Nanoporous “Raney gold” sponge was prepared by de-alloying an Au-Al precursor alloy. Catalytic tests using a micro-reactor confirmed that Raney gold can serve as an active heterogeneous catalyst for CO oxidation, reduction of NO to N2, and oxidation of NO to NO2. In general, the specific surface area of a heterogeneous catalyst has an influence on its catalytic efficacy. Unfortunately, gold sponges coarsen readily, leading to sintering of their structure and reduction in surface area. This potentially places constraints on their upper operating temperature in catalytic reactors. Here we analyzed the behavior of Raney gold when the temperature was raised. We examined the kinetics and mechanism of coarsening of the sponge using a combination of in situ optical measurements and Metropolis Monte Carlo modeling with a Lennard-Jones interatomic potential. Modeling showed that the sponges started with an isotropic “foamy” morphology with negative average “mean curvature” but that subsequent thermally activated coarsening will drive the morphology through a bi-continuous fibrous state and on, eventually, to a sponge consisting of sintered blobs of predominantly positive “mean curvature”. Full article
(This article belongs to the Special Issue Nanoporous Metallic Alloys)
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Open AccessArticle Experimental Simulation of Long Term Weathering in Alkaline Bauxite Residue Tailings
Metals 2015, 5(3), 1241-1261; doi:10.3390/met5031241
Received: 18 June 2015 / Revised: 6 July 2015 / Accepted: 7 July 2015 / Published: 14 July 2015
Cited by 4 | PDF Full-text (1254 KB) | HTML Full-text | XML Full-text
Abstract
Bauxite residue is an alkaline, saline tailings material generated as a byproduct of the Bayer process used for alumina refining. Developing effective plans for the long term management of potential environmental impacts associated with storage of these tailings is dependent on understanding how
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Bauxite residue is an alkaline, saline tailings material generated as a byproduct of the Bayer process used for alumina refining. Developing effective plans for the long term management of potential environmental impacts associated with storage of these tailings is dependent on understanding how the chemical and mineralogical properties of the tailings will change during weathering and transformation into a soil-like material. Hydrothermal treatment of bauxite residue was used to compress geological weathering timescales and examine potential mineral transformations during weathering. Gibbsite was rapidly converted to boehmite; this transformation was examined with in situ synchrotron XRD. Goethite, hematite, and calcite all precipitated over longer weathering timeframes, while tricalcium aluminate dissolved. pH, total alkalinity, and salinity (electrical conductivity) all decreased during weathering despite these experiments being performed under “closed” conditions (i.e., no leaching). This indicates the potential for auto-attenuation of the high alkalinity and salinity that presents challenges for long term environmental management, and suggests that management requirements will decrease during weathering as a result of these mineral transformations. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
Open AccessArticle The Effect of Grinding and Roasting Conditions on the Selective Leaching of Nd and Dy from NdFeB Magnet Scraps
Metals 2015, 5(3), 1306-1314; doi:10.3390/met5031306
Received: 7 June 2015 / Revised: 10 July 2015 / Accepted: 14 July 2015 / Published: 17 July 2015
Cited by 2 | PDF Full-text (570 KB) | HTML Full-text | XML Full-text
Abstract
The pretreatment processes consisting of grinding followed by roasting were investigated to improve the selective leaching of Nd and Dy from neodymium-iron-boron (NdFeB) magnet scraps. The peaks of Nd(OH)3 and Fe were observed in XRD results after grinding with NaOH as the
[...] Read more.
The pretreatment processes consisting of grinding followed by roasting were investigated to improve the selective leaching of Nd and Dy from neodymium-iron-boron (NdFeB) magnet scraps. The peaks of Nd(OH)3 and Fe were observed in XRD results after grinding with NaOH as the amount of water addition increased to 5 cm3. These results indicate that the components of Nd and Fe in NdFeB magnet could be changed successfully into Nd(OH)3 and Fe, respectively. In the roasting tests using the ground product, with increasing roasting temperature to 500 °C, the peaks of Nd(OH)3 and Fe disappeared while those of Nd2O3 and Fe2O3 were shown. The peaks of NdFeO3 in the sample roasted at 600 °C were observed in the XRD pattern. Consequently, 94.2%, 93.1%, 1.0% of Nd, Dy, Fe were leached at 400 rpm and 90 °C in 1 kmol·m−3 acetic acid solution with 1% pulp density using a sample prepared under the following conditions: 15 in stoichiometric molar ratio of NaOH:Nd, 550 rpm in rotational grinding speed, 5 cm3 in water addition, 30 min in grinding time, 400 °C and 2 h in roasting temperature and time. The results indicate that the selective leaching of Nd and Dy from NdFeB magnet could be achieved successfully by grinding and then roasting treatments. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle High Temperature Flow Response Modeling of Ultra-Fine Grained Titanium
Metals 2015, 5(3), 1315-1327; doi:10.3390/met5031315
Received: 14 May 2015 / Revised: 1 July 2015 / Accepted: 14 July 2015 / Published: 22 July 2015
Cited by 5 | PDF Full-text (1674 KB) | HTML Full-text | XML Full-text
Abstract
This work presents the mechanical behavior modeling of commercial purity titanium subjected to severe plastic deformation (SPD) during post-SPD compression, at temperatures of 600-900 °C and at strain rates of 0.001-0.1 s−1. The flow response of the ultra-fine grained microstructure is modeled using
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This work presents the mechanical behavior modeling of commercial purity titanium subjected to severe plastic deformation (SPD) during post-SPD compression, at temperatures of 600-900 °C and at strain rates of 0.001-0.1 s−1. The flow response of the ultra-fine grained microstructure is modeled using the modified Johnson-Cook model as a predictive tool, aiding high temperature forming applications. It was seen that the model was satisfactory at all deformation conditions except for the deformation temperature of 600 °C. In order to improve the predictive capability, the model was extended with a corrective term for predictions at temperatures below 700 °C. The accuracy of the model was displayed with reasonable agreement, resulting in error levels of less than 5% at all deformation temperatures. Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available
Open AccessArticle Copper Recovery from Polluted Soils Using Acidic Washing and Bioelectrochemical Systems
Metals 2015, 5(3), 1328-1348; doi:10.3390/met5031328
Received: 1 July 2015 / Revised: 10 July 2015 / Accepted: 14 July 2015 / Published: 23 July 2015
Cited by 6 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Excavation followed by landfilling is the most common method for treating soils contaminated by metals. However, as this solution is not sustainable, alternative techniques are required. Chemical soil washing is one such alternative. The aim of this experimental lab-scale study is to develop
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Excavation followed by landfilling is the most common method for treating soils contaminated by metals. However, as this solution is not sustainable, alternative techniques are required. Chemical soil washing is one such alternative. The aim of this experimental lab-scale study is to develop a remediation and metal recovery method for Cu contaminated sites. The method is based on the washing of soil or ash (combusted soil/bark) with acidic waste liquids followed by electrolytic Cu recovery by means of bioelectrochemical systems (BES). The results demonstrate that a one- or two-step acidic leaching process followed by water washing removes >80 wt. % of the Cu. Copper with 99.7–99.9 wt. % purity was recovered from the acidic leachates using BES. In all experiments, electrical power was generated during the reduction of Cu. This clearly indicates that Cu can also be recovered from dilute solutions. Additionally, the method has the potential to wash co-pollutants such as polycyclic aromatic hydrocarbons (PAHs) and oxy-PAHs. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
Open AccessArticle Effect of Material and Process Atmosphere in the Preparation of Al-Ti-B Grain Refiner by SHS
Metals 2015, 5(3), 1387-1396; doi:10.3390/met5031387
Received: 4 June 2015 / Revised: 8 July 2015 / Accepted: 16 July 2015 / Published: 30 July 2015
Cited by 3 | PDF Full-text (1140 KB) | HTML Full-text | XML Full-text
Abstract
Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in
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Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in a combustion wave. The advantages of SHS are the low energy requirement, simplicity and product purity. However, the raw material used has to be very pure, with a very small size leading to the necessity of a reactor with a protective gas to produce the reaction. The purpose of this investigation is to fabricate SHS master alloys with commercial standard raw materials, with lower purity and higher grain size without a reactor or protective gas in order to (1) decrease the price and (2) improve the productivity of master alloy manufacturing. The possibility of using cheap borated salts instead of expensive pure boron has been studied. Different compositions of aluminum master alloy have been developed. Bigger TiB2 grain size has been obtained when using bigger commercial raw materials. Larger titanium powder can produce an aluminum master alloy with a maximum of 30% of aluminum without reactor. In comparison, SHS reaction is much more difficult when using finer titanium powder. Full article
(This article belongs to the Special Issue Casting Alloy Design and Modification)
Open AccessArticle Mechanical Properties Analysis of an Al-Mg Alloy Connecting Rod with Submicrometric Structure
Metals 2015, 5(3), 1397-1413; doi:10.3390/met5031397
Received: 22 June 2015 / Revised: 20 July 2015 / Accepted: 27 July 2015 / Published: 31 July 2015
Cited by 1 | PDF Full-text (3033 KB) | HTML Full-text | XML Full-text
Abstract
Over these last few years, there has been a growing interest in developing mechanical components from submicrometric materials due to the significant improvement that these materials present compared to their original state. This present research work deals with the study of the mechanical
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Over these last few years, there has been a growing interest in developing mechanical components from submicrometric materials due to the significant improvement that these materials present compared to their original state. This present research work deals with the study of the mechanical properties of a connecting rod isothermally forged from different starting materials. These materials are as follows: annealed aluminum alloy (AA) 5754, the same alloy previously deformed through equal channel angular pressing (ECAP) and a third case where the previously ECAP-processed material is subjected to a recovery heat treatment. A comparison is made between finite volume (FV) simulations and experimental tests with respect to hardness, plastic strain and forging force. Furthermore, the improvement in the mechanical properties of the connecting rod forged from predeformed material is evaluated in comparison to the connecting rod forged with annealed material. The microstructure of both cases is also compared at the end of the manufacturing process. Full article
Open AccessArticle A Computationally-Efficient Numerical Model to Characterize the Noise Behavior of Metal-Framed Walls
Metals 2015, 5(3), 1414-1431; doi:10.3390/met5031414
Received: 12 June 2015 / Accepted: 3 August 2015 / Published: 7 August 2015
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Abstract
Architects, designers, and engineers are making great efforts to design acoustically-efficient metal-framed walls, minimizing acoustic bridging. Therefore, efficient simulation models to predict the acoustic insulation complying with ISO 10140 are needed at a design stage. In order to achieve this, a numerical model
[...] Read more.
Architects, designers, and engineers are making great efforts to design acoustically-efficient metal-framed walls, minimizing acoustic bridging. Therefore, efficient simulation models to predict the acoustic insulation complying with ISO 10140 are needed at a design stage. In order to achieve this, a numerical model consisting of two fluid-filled reverberation chambers, partitioned using a metal-framed wall, is to be simulated at one-third-octaves. This produces a large simulation model consisting of several millions of nodes and elements. Therefore, efficient meshing procedures are necessary to obtain better solution times and to effectively utilise computational resources. Such models should also demonstrate effective Fluid-Structure Interaction (FSI) along with acoustic-fluid coupling to simulate a realistic scenario. In this contribution, the development of a finite element frequency-dependent mesh model that can characterize the sound insulation of metal-framed walls is presented. Preliminary results on the application of the proposed model to study the geometric contribution of stud frames on the overall acoustic performance of metal-framed walls are also presented. It is considered that the presented numerical model can be used to effectively visualize the noise behaviour of advanced materials and multi-material structures. Full article
(This article belongs to the Special Issue Serration and Noise Behavior in Advanced Materials)
Open AccessArticle Material Properties of Various Cast Aluminum Alloys Made Using a Heated Mold Continuous Casting Technique with and without Ultrasonic Vibration
Metals 2015, 5(3), 1440-1453; doi:10.3390/met5031440
Received: 9 July 2015 / Revised: 30 July 2015 / Accepted: 2 August 2015 / Published: 14 August 2015
Cited by 3 | PDF Full-text (1076 KB) | HTML Full-text | XML Full-text
Abstract
This work was carried out to develop high-quality cast aluminum alloys using a new casting technology. For this purpose, commercial Al alloys were created by heated mold continuous casting (HMC) with ultrasonic vibration (UV). With the HMC process, the grain size and the
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This work was carried out to develop high-quality cast aluminum alloys using a new casting technology. For this purpose, commercial Al alloys were created by heated mold continuous casting (HMC) with ultrasonic vibration (UV). With the HMC process, the grain size and the crystal orientation of the Al alloys were controlled, i.e., fine grains with a uniformly organized lattice formation. In addition, an attempt was made to modify the microstructural formation by cavitation. These microstructural characteristics made excellent mechanical properties. Using UV in the continuous casting process, more fine and spherical grains were slightly disordered, which was detected using electron backscattered diffraction. The mechanical properties of the UV HMC Al alloys were slightly higher than those for the related cast Al alloys without UV. Moreover, the severe vibration caused higher mechanical properties. The lattice and dislocation characteristics of the cast samples made with and without UV processes were analyzed systematically using electron backscattered diffraction. Full article
Open AccessArticle A Straightforward Route to Tetrachloroauric Acid from Gold Metal and Molecular Chlorine for Nanoparticle Synthesis
Metals 2015, 5(3), 1454-1461; doi:10.3390/met5031454
Received: 5 June 2015 / Revised: 12 August 2015 / Accepted: 12 August 2015 / Published: 18 August 2015
Cited by 4 | PDF Full-text (539 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Aqueous solutions of tetrachloroauric acid of high purity and stability were synthesised using the known reaction of gold metal with chlorine gas. The straightforward procedure developed here allows the resulting solution to be used directly for gold nanoparticle synthesis. The procedure involves bubbling
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Aqueous solutions of tetrachloroauric acid of high purity and stability were synthesised using the known reaction of gold metal with chlorine gas. The straightforward procedure developed here allows the resulting solution to be used directly for gold nanoparticle synthesis. The procedure involves bubbling chlorine gas through pure water containing a pellet of gold. The reaction is quantitative and progressed at a satisfactory rate at 50 °C. The gold(III) chloride solutions produced by this method show no evidence of returning to metallic gold over at least twelve months. This procedure also provides a straightforward method to determine the concentration of the resulting solution using the initial mass of gold and volume of water. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Water Impingement Erosion of Deep-Rolled Ti64
Metals 2015, 5(3), 1462-1486; doi:10.3390/met5031462
Received: 10 June 2015 / Revised: 22 July 2015 / Accepted: 13 August 2015 / Published: 18 August 2015
Cited by 9 | PDF Full-text (3836 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the Liquid Impingement Erosion (LIE) performances of deep-rolling (DR) treated and non-treated Ti64 were investigated. Various erosion stages, from the incubation to the terminal erosion stages, could be observed. A full factorial design of experiments was used to study the
[...] Read more.
In this work, the Liquid Impingement Erosion (LIE) performances of deep-rolling (DR) treated and non-treated Ti64 were investigated. Various erosion stages, from the incubation to the terminal erosion stages, could be observed. A full factorial design of experiments was used to study the effect of DR process parameters (Feed Rate, Spindle Velocity, Number of Passes, Pressure) on the residual stress distribution, microhardness and surface roughness of the treated Ti64 specimens. The DR-treated Ti64 specimens exhibited improved surface microhardness, surface roughness, and large magnitude of compressive residual stresses, which were attributed to the amount of cold work induced by the DR process. Although DR improved the mechanical properties of the Ti64, the results showed that the treatment has little or no effect on the LIE performance of Ti64 but different damage modes were observed in these two cases. Evolution of the erosion stages was described based on water-hammer pressure, stress waves, radial wall jetting, and hydraulic penetration modes. The initial erosion stages were mainly influenced by water-hammer pressure and stress waves, whereas the intermediate erosion stages were influenced by the combination of the four modes together. The final erosion stages contain the four modes, however the erosion was greatly driven by the radial jetting and hydraulic penetration modes, where more material was removed. The failure mechanism of the final stages of the LIE test of both DR-treated and non-treated Ti64 was characterized as fatigue fracture. However, a brittle fracture behavior was observed in the initial and intermediate erosion stages of the DR-treated Ti64, whereas a ductile fracture behavior was observed in the non-treated Ti64. This was concluded from the micrographs of the LIE damage through different erosion stages. Full article
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Open AccessArticle A Creep Damage Model for High-Temperature Deformation and Failure of 9Cr-1Mo Steel Weldments
Metals 2015, 5(3), 1487-1506; doi:10.3390/met5031487
Received: 23 July 2015 / Revised: 15 August 2015 / Accepted: 17 August 2015 / Published: 21 August 2015
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Abstract
A dislocation-based creep model combined with a continuum damage formulation was developed and implemented in the finite element method to simulate high temperature deformation behavior in modified 9Cr-1Mo steel welds. The evolution of dislocation structures was considered as the main driving mechanism for
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A dislocation-based creep model combined with a continuum damage formulation was developed and implemented in the finite element method to simulate high temperature deformation behavior in modified 9Cr-1Mo steel welds. The evolution of dislocation structures was considered as the main driving mechanism for creep. The effect of void growth, precipitate coarsening, and solid solution depletion were considered to be the operating damage processes. A semi-implicit numerical integration scheme was developed and implemented in the commercial finite element code ABAQUS-Standard as a user material subroutine. Furthermore, several creep tests of modified 9Cr-1Mo steel welded specimens were conducted at temperatures between 550–700 °C and stresses between 80–200 MPa. The accuracy of the model was verified by comparing the finite element results with experiments. The comparison between the experimental and computational results showed excellent agreement. The model can be used to simulate and predict the creep-damage behavior of Cr-Mo steel components used as structural applications in power plants. Full article
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Open AccessArticle Use of Nanoscale Zero-Valent Iron (NZVI) Particles for Chemical Denitrification under Different Operating Conditions
Metals 2015, 5(3), 1507-1519; doi:10.3390/met5031507
Received: 9 July 2015 / Revised: 7 August 2015 / Accepted: 18 August 2015 / Published: 21 August 2015
Cited by 9 | PDF Full-text (658 KB) | HTML Full-text | XML Full-text
Abstract
The nitrate pollution of waters and groundwaters is an important environmental and health concern. An interesting method to remove the oxidized forms of nitrogen from waters and wastewaters is chemical denitrification by means of metallic iron (Fe0). Particularly advantageous is the
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The nitrate pollution of waters and groundwaters is an important environmental and health concern. An interesting method to remove the oxidized forms of nitrogen from waters and wastewaters is chemical denitrification by means of metallic iron (Fe0). Particularly advantageous is the use of nanoscopic zero-valent iron particles due to the elevated surface area, which allows reaching extremely high reaction rates. In the present paper, the efficiency of nitrate reduction by means of nanoscopic Fe0 has been investigated under several operating conditions. The iron nanoparticles were synthesized by the chemical reduction of ferric ions with sodium borohydride. The effects of Fe0 dosage, initial N–NO3 concentration and pH on chemical denitrification were identified. In particular, the results of the tests carried out showed that it is possible to reach an almost complete nitrate reduction in treating solutions with a nitrate nitrogen concentration higher than 50 mg/L. Moreover, the process performance was satisfactory also under uncontrolled pH. By means of the trends detected during the experiments, the kinetic-type reaction was identified. Furthermore, a relation between the kinetic constant and the process parameters was defined. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Separation and Recycling for Rare Earth Elements by Homogeneous Liquid-Liquid Extraction (HoLLE) Using a pH-Responsive Fluorine-Based Surfactant
Metals 2015, 5(3), 1543-1552; doi:10.3390/met5031543
Received: 27 July 2015 / Accepted: 25 August 2015 / Published: 27 August 2015
Cited by 3 | PDF Full-text (422 KB) | HTML Full-text | XML Full-text
Abstract
A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE) using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga,
[...] Read more.
A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE) using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, In, Ir, La, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Re, Rh, Ru, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Te, Ti, Tl, Tm, V, W, Y, Yb, Zn, and Zr) were examined. By changing pH from a neutral or alkaline solution (pH ≥ 6.5) to that of an acidic solution (pH < 4.0), gallium, zirconium, palladium, silver, platinum, and rare earth elements were extracted at >90% efficiency into a sedimented Zonyl FSA® (CF3(CF2)n(CH2)2S(CH2)2COOH, n = 6–8) liquid phase. Moreover, all rare earth elements were obtained with superior extraction and stripping percentages. In the recycling of rare earth elements, the sedimented phase was maintained using a filter along with a mixed solution of THF and 1 M sodium hydroxide aqueous solution. The Zonyl FSA® was filtrated and the rare earth elements were recovered on the filter as a hydroxide. Furthermore, the filtrated Zonyl FSA was reusable by conditioning the subject pH. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Chalcopyrite Dissolution at 650 mV and 750 mV in the Presence of Pyrite
Metals 2015, 5(3), 1566-1579; doi:10.3390/met5031566
Received: 6 August 2015 / Revised: 21 August 2015 / Accepted: 25 August 2015 / Published: 28 August 2015
Cited by 1 | PDF Full-text (721 KB) | HTML Full-text | XML Full-text
Abstract
The dissolution of chalcopyrite in association with pyrite in mine waste results in the severe environmental issue of acid and metalliferous drainage (AMD). To better understand chalcopyrite dissolution, and the impact of chalcopyrite’s galvanic interaction with pyrite, chalcopyrite dissolution has been examined at
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The dissolution of chalcopyrite in association with pyrite in mine waste results in the severe environmental issue of acid and metalliferous drainage (AMD). To better understand chalcopyrite dissolution, and the impact of chalcopyrite’s galvanic interaction with pyrite, chalcopyrite dissolution has been examined at 75 °C, pH 1.0, in the presence of quartz (as an inert mineral) and pyrite. The presence of pyrite increased the chalcopyrite dissolution rate by more than five times at Eh of 650 mV (SHE) (Cu recovery 2.5 cf. 12% over 132 days) due to galvanic interaction between chalcopyrite and pyrite. Dissolution of Cu and Fe was stoichiometric and no pyrite dissolved. Although the chalcopyrite dissolution rate at 750 mV (SHE) was approximately four-fold greater (Cu recovery of 45% within 132 days) as compared to at 650 mV in the presence of pyrite, the galvanic interaction between chalcopyrite and pyrite was negligible. Approximately all of the sulfur from the leached chalcopyrite was converted to S0 at 750 mV, regardless of the presence of pyrite. At this Eh approximately 60% of the sulfur associated with pyrite dissolution was oxidised to S0 and the remaining 40% was released in soluble forms, e.g., SO42. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Experimental and Numerical Studies on Self-Propagating High-Temperature Synthesis of Ta5Si3 Intermetallics
Metals 2015, 5(3), 1580-1590; doi:10.3390/met5031580
Received: 11 August 2015 / Revised: 21 August 2015 / Accepted: 28 August 2015 / Published: 1 September 2015
Cited by 4 | PDF Full-text (1008 KB) | HTML Full-text | XML Full-text
Abstract
Formation of Ta5Si3 by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion
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Formation of Ta5Si3 by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion wave velocity and reaction temperature. The apparent activation energy, Ea ≈ 108 kJ/mol, was determined for the synthesis reaction. Based upon numerical simulation, the Arrhenius factor of the rate function, K0 = 2.5 × 107 s−1, was obtained for the 5Ta + 3Si combustion system. In addition, the influence of sample density on combustion wave kinetics was correlated with the effective thermal conductivity (keff) of the powder compact. By adopting 0.005 ≤ keff/kbulk ≤ 0.016 in the computation model, the calculated combustion velocity and temperature were in good agreement with experimental data of the samples with compaction densities between 35% and 45% theoretical maximum density (TMD). Full article
(This article belongs to the Special Issue Intermetallics 2016)
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Open AccessArticle Heavy Metal Behavior in Lichen-Mine Waste Interactions at an Abandoned Mine Site in Southwest Japan
Metals 2015, 5(3), 1591-1608; doi:10.3390/met5031591
Received: 13 July 2015 / Revised: 26 August 2015 / Accepted: 28 August 2015 / Published: 2 September 2015
Cited by 3 | PDF Full-text (1324 KB) | HTML Full-text | XML Full-text
Abstract
The lichen, Stereocaulon exutum Nylander, occurring in a contaminated abandoned mine site was investigated to clarify (1) the behavior of heavy metals and As during the slag weathering processes mediated by the lichen; and (2) the distribution of these elements in the lichen
[...] Read more.
The lichen, Stereocaulon exutum Nylander, occurring in a contaminated abandoned mine site was investigated to clarify (1) the behavior of heavy metals and As during the slag weathering processes mediated by the lichen; and (2) the distribution of these elements in the lichen thallus on slag. The heavy metals and As in the slag are dissolved from their original phases during the weathering process by lichen substances (organic acids) and hypha penetration, in addition to non-biological weathering. The dissolved elements are absorbed into the lichen thallus. Some of these dissolved elements are distributed in the cells of the hyphae. The others are distributed on the surface of the hyphae as formless particles and show lateral distribution inside the cortex of the thallus. The Cu and Zn concentrations in the thalli are positively correlated with the concentrations in the corresponding substrata and a positive intercept in the regression curve obtained using a linear function. These chemical characteristics make this lichen a good biomarker for Cu and Zn contamination of the substrata of the lichen. Therefore, the present study supposes that Stereocaulon exutum has a possible practical application in biomonitoring or risk assessment of heavy metal pollution at abandoned mine sites. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Exploring the Possibilities of Biological Fabrication of Gold Nanostructures Using Orange Peel Extract
Metals 2015, 5(3), 1609-1619; doi:10.3390/met5031609
Received: 22 July 2015 / Revised: 3 September 2015 / Accepted: 6 September 2015 / Published: 11 September 2015
Cited by 3 | PDF Full-text (908 KB) | HTML Full-text | XML Full-text
Abstract
Development of nanotechnology requires a constant innovation and improvement in many materials. The exploration of natural resources is a promising eco-friendly alternative for physical and chemical methods. In the present work, colloidal gold nanostructures were prepared using orange peel extract as a stabilizing
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Development of nanotechnology requires a constant innovation and improvement in many materials. The exploration of natural resources is a promising eco-friendly alternative for physical and chemical methods. In the present work, colloidal gold nanostructures were prepared using orange peel extract as a stabilizing and reducing agent. The initial pH value of the solution and the concentration of the gold precursor had an effect on the formation and morphology of nanoparticles. The method developed is environmentally friendly and allows control of nanoparticles. By controlling the pH and, especially, the gold concentration, we are able to synthesize crystalline gold nanowires using orange peel extract in the absence of a surfactant or polymer to direct nanoparticle growth, and without external seeding. UV-VIS spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the nanoparticles obtained by biosynthesis. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Nickel Extraction from Olivine: Effect of Carbonation Pre-Treatment
Metals 2015, 5(3), 1620-1644; doi:10.3390/met5031620
Received: 19 August 2015 / Revised: 2 September 2015 / Accepted: 6 September 2015 / Published: 11 September 2015
Cited by 6 | PDF Full-text (1483 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)2SiO4). The precept is that by altering the morphology and the mineralogy of
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In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)2SiO4). The precept is that by altering the morphology and the mineralogy of the ore via mineral carbonation, the comminution requirements and the acid consumption during hydrometallurgical processing can be reduced. Furthermore, carbonation pre-treatment can lead to mineral liberation and concentration of metals in physically separable phases. In a first processing step, olivine is fully carbonated at high CO2 partial pressures (35 bar) and optimal temperature (200 °C) with the addition of pH buffering agents. This leads to a powdery product containing high carbonate content. The main products of the carbonation reaction include quasi-amorphous colloidal silica, chromium-rich metallic particles, and ferro-magnesite ((Mg1−x,Fex)CO3). Carbonated olivine was subsequently leached using an array of inorganic and organic acids to test their leaching efficiency. Compared to leaching from untreated olivine, the percentage of nickel extracted from carbonated olivine by acid leaching was significantly increased. It is anticipated that the mineral carbonation pre-treatment approach may also be applicable to other ultrabasic and lateritic ores. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Beeswax-Colophony Blend: A Novel Green Organic Coating for Protection of Steel Drinking Water Storage Tanks
Metals 2015, 5(3), 1645-1664; doi:10.3390/met5031645
Received: 30 July 2015 / Revised: 7 September 2015 / Accepted: 9 September 2015 / Published: 15 September 2015
Cited by 1 | PDF Full-text (1749 KB) | HTML Full-text | XML Full-text
Abstract
Beeswax-colophony blend is mainly used as a sealant mixture for preservation applications. The beeswax itself, however, has had a long way in history taking part in conservation processes including mummification. In this research, this blend was used as a protective coating for drinking
[...] Read more.
Beeswax-colophony blend is mainly used as a sealant mixture for preservation applications. The beeswax itself, however, has had a long way in history taking part in conservation processes including mummification. In this research, this blend was used as a protective coating for drinking water distribution tanks. Initially, a layer with 400 μm thickness was applied on a sand blasted mild steel plate. The long-term electrochemical behavior of the coating was investigated by open circuit potential (OCP) and electrochemical microbiological characteristics of the coating, microbial and chemical examinations were performed on drinking water samples that had been in contact with the coating. Furthermore, its behavior in an up-flow anaerobic sludge blanket reactor (UASBR) in a wastewater treatment plant was investigated using the scanning electron microscopy (SEM) technique. Regarding the consistency of experimental results, it was concluded that this proposed recyclable blend could be considered as a novel green organic coating and also a good corrosion barrier even in aggressive environments. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Mechanical Properties of Nanoporous Au: From Empirical Evidence to Phenomenological Modeling
Metals 2015, 5(3), 1665-1694; doi:10.3390/met5031665
Received: 30 June 2015 / Revised: 5 September 2015 / Accepted: 8 September 2015 / Published: 16 September 2015
Cited by 2 | PDF Full-text (1754 KB) | HTML Full-text | XML Full-text
Abstract
The present work focuses on the development of a theoretical model aimed at relating the mechanical properties of nanoporous metals to the bending response of thick ligaments. The model describes the structure of nanoporous metal foams in terms of an idealized regular lattice
[...] Read more.
The present work focuses on the development of a theoretical model aimed at relating the mechanical properties of nanoporous metals to the bending response of thick ligaments. The model describes the structure of nanoporous metal foams in terms of an idealized regular lattice of massive cubic nodes and thick ligaments with square cross-sections. Following a general introduction to the subject, model predictions are compared with Young’s modulus and the yield strength of nanoporous Au foams determined experimentally and available in literature. It is shown that the model provides a quantitative description of the elastic and plastic deformation behavior of nanoporous metals, reproducing to a satisfactory extent the experimental Young’s modulus and yield strength values of nanoporous Au. Full article
(This article belongs to the Special Issue Nanoporous Metallic Alloys)
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Open AccessArticle Effect of Post Heat Treatment on the Microstructure and Microhardness of Friction Stir Processed NiAl Bronze (NAB) Alloy
Metals 2015, 5(3), 1695-1703; doi:10.3390/met5031695
Received: 20 July 2015 / Revised: 21 August 2015 / Accepted: 24 August 2015 / Published: 16 September 2015
Cited by 5 | PDF Full-text (1707 KB) | HTML Full-text | XML Full-text
Abstract
NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of
[...] Read more.
NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of heat treatment on the microstructure and microhardness is studied. The results show that the microstructure of the FSP NAB alloy consists of high density dislocations, retained β phase (β′ phase) and recrystallized grains. When annealed at 675 °C, discontinuous static recrystallization (DSRX) takes place. The content of β′ phase gradually decreases and fine κ phase is precipitated. After annealing for 2 h, both the microhardness of the FSP sample in the stir zone (SZ) and the difference in hardness between the SZ and base metal decrease due to the reduction of the dislocation density and β′ phase, accompanying recrystallized grain coarsening. With further increasing of the annealing time to 4 h, the aforementioned difference in hardness nearly disappears. Full article
(This article belongs to the Special Issue Casting Alloy Design and Modification)
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Open AccessArticle Characterization of Microstructure and Mechanical Properties of Resistance Spot Welded DP600 Steel
Metals 2015, 5(3), 1704-1716; doi:10.3390/met5031704
Received: 9 July 2015 / Revised: 10 September 2015 / Accepted: 13 September 2015 / Published: 17 September 2015
Cited by 9 | PDF Full-text (1712 KB) | HTML Full-text | XML Full-text
Abstract
Resistance spot welding (RSW) as a predominant welding technique used for joining steels in automotive applications needs to be studied carefully in order to improve the mechanical properties of the spot welds. The objectives of the present work are to characterize the resistance
[...] Read more.
Resistance spot welding (RSW) as a predominant welding technique used for joining steels in automotive applications needs to be studied carefully in order to improve the mechanical properties of the spot welds. The objectives of the present work are to characterize the resistance spot weldment of DP600 sheet steels. The mechanical properties of the welded joints were evaluated using tensile-shear and cross-tensile tests. The time-temperature evolution during the welding cycle was measured. The microstructures observed in different sites of the welds were correlated to thermal history recorded by thermocouples in the corresponding areas. It was found that cracks initiated in the periphery region of weld nuggets with a martensitic microstructure and a pull-out failure mode was observed. It was also concluded that tempering during RSW was the main reason for hardness decrease in HAZ. Full article
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Open AccessArticle Constitutive Relationship Modeling and Characterization of Flow Behavior under Hot Working for Fe–Cr–Ni–W–Cu–Co Super-Austenitic Stainless Steel
Metals 2015, 5(3), 1717-1731; doi:10.3390/met5031717
Received: 4 August 2015 / Revised: 9 September 2015 / Accepted: 15 September 2015 / Published: 18 September 2015
Cited by 5 | PDF Full-text (1179 KB) | HTML Full-text | XML Full-text
Abstract
The hot deformation behavior of a Fe–22Cr–25Ni–3.5W–3Cu–1.5Co super-austenitic stainless steel was investigated using isothermal compression tests with a wide range of temperatures (1173–1373 K) and strain rates (0.1–10 s−1). The results showed that all the flow curves gradually turned to balanced stress state
[...] Read more.
The hot deformation behavior of a Fe–22Cr–25Ni–3.5W–3Cu–1.5Co super-austenitic stainless steel was investigated using isothermal compression tests with a wide range of temperatures (1173–1373 K) and strain rates (0.1–10 s−1). The results showed that all the flow curves gradually turned to balanced stress state without notable peak stress characteristics during the entire deformation, which indicated that the dynamic recovery behavior played a main restoration mechanism in the steel. Modeling constitutive equations relating to the temperature, strain rate and flow stress were proposed to determine the materials constants and activation energy necessary for deformation. In order to give the precise predicted values of the flow behavior, the influence of strain was identified using polynomial functions. The relationship of flow stress, temperature and strain rate was represented by the Zener-Hollomon parameter including the Arrhenius term. The predicted results validated that the developed constitutive equations can describe high temperature flow behavior well. Furthermore, a modified Zener-Hollomon parameter map of the studied steel was developed to clarify the restoration mechanism based on the constitutive modeling data and microstructural observation. Full article
Open AccessArticle Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation
Metals 2015, 5(3), 1732-1745; doi:10.3390/met5031732
Received: 13 July 2015 / Revised: 31 August 2015 / Accepted: 15 September 2015 / Published: 18 September 2015
Cited by 3 | PDF Full-text (1350 KB) | HTML Full-text | XML Full-text
Abstract
Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS) because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of
[...] Read more.
Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS) because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior. Full article
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Open AccessArticle Experimental Study of the Mg-Ni-Y System at 673 K Using Diffusion Couples and Key Alloys
Metals 2015, 5(3), 1746-1769; doi:10.3390/met5031746
Received: 1 September 2015 / Revised: 15 September 2015 / Accepted: 16 September 2015 / Published: 22 September 2015
Cited by 4 | PDF Full-text (2338 KB) | HTML Full-text | XML Full-text
Abstract
Three solid-solid and two solid-liquid diffusion couples together with 32 key samples were used to construct the isothermal section of the Mg-Ni-Y system at 673 K. The present investigation revealed 12 ternary intermetallic compounds. Crystal structures of two ternary compounds τ1 (Gd
[...] Read more.
Three solid-solid and two solid-liquid diffusion couples together with 32 key samples were used to construct the isothermal section of the Mg-Ni-Y system at 673 K. The present investigation revealed 12 ternary intermetallic compounds. Crystal structures of two ternary compounds τ1 (Gd4RhIn prototype with lattice parameter of a = 1.3666 nm) and τ2 (Mo2FeB2 prototype with lattice parameters of a = 0.7395 nm and c = 0.3736 nm) were determined. The phase relations and ternary solubility of the binary and ternary compounds at 673 K were determined using scanning electron microscopy (SEM), wave dispersive X-ray spectrometer (WDS) and X-ray diffraction (XRD) analysis. Full article
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Review

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Open AccessReview Dynamics and Geometry of Icosahedral Order in Liquid and Glassy Phases of Metallic Glasses
Metals 2015, 5(3), 1163-1187; doi:10.3390/met5031163
Received: 22 May 2015 / Revised: 24 June 2015 / Accepted: 25 June 2015 / Published: 2 July 2015
Cited by 2 | PDF Full-text (6691 KB) | HTML Full-text | XML Full-text
Abstract
The geometrical properties of the icosahedral ordered structure formed in liquid and glassy phases of metallic glasses are investigated by using molecular dynamics simulations. We investigate the Zr-Cu alloy system as well as a simple model for binary alloys, in which we can
[...] Read more.
The geometrical properties of the icosahedral ordered structure formed in liquid and glassy phases of metallic glasses are investigated by using molecular dynamics simulations. We investigate the Zr-Cu alloy system as well as a simple model for binary alloys, in which we can change the atomic size ratio between alloying components. In both cases, we found the same nature of icosahedral order in liquid and glassy phases. The icosahedral clusters are observed in liquid phases as well as in glassy phases. As the temperature approaches to the glass transition point Tg, the density of the clusters rapidly grows and the icosahedral clusters begin to connect to each other and form a medium-range network structure. By investigating the geometry of connection between clusters in the icosahedral network, we found that the dominant connecting pattern is the one sharing seven atoms which forms a pentagonal bicap with five-fold symmetry. From a geometrical point of view, we can understand the mechanism of the formation and growth of the icosahedral order by using the Regge calculus, which is originally employed to formulate a theory of gravity. The Regge calculus tells us that the distortion energy of the pentagonal bicap could be decreased by introducing an atomic size difference between alloying elements and that the icosahedral network would be stabilized by a considerably large atomic size difference. Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
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Open AccessReview The Promising Features of New Nano Liquid Metals—Liquid Sodium Containing Titanium Nanoparticles (LSnanop)
Metals 2015, 5(3), 1212-1240; doi:10.3390/met5031212
Received: 5 January 2015 / Revised: 15 June 2015 / Accepted: 19 June 2015 / Published: 14 July 2015
Cited by 1 | PDF Full-text (933 KB) | HTML Full-text | XML Full-text
Abstract
A new kind of suspension liquid was developed by dispersing Ti nanoparticles (10 nm) in liquid Na, which was then determined by TEM (transmission electron microscopy) analysis. The volume fraction was estimated to be 0.0088 from the analyzed Ti concentration (2 at. %)
[...] Read more.
A new kind of suspension liquid was developed by dispersing Ti nanoparticles (10 nm) in liquid Na, which was then determined by TEM (transmission electron microscopy) analysis. The volume fraction was estimated to be 0.0088 from the analyzed Ti concentration (2 at. %) and the densities of Ti and Na. This suspension liquid, Liquid Sodium containing nanoparticles of titanium (LSnanop), shows, despite only a small addition of Ti nanoparticles, many striking features, namely a negative deviation of 3.9% from the ideal solution for the atomic volume, an increase of 17% in surface tension, a decrease of 11% for the reaction heat to water, and the suppression of chemical reactivity to water and oxygen. The decrease in reaction heat to water seems to be derived from the existence of excess cohesive energy of LSnanop. The excess cohesive energy was discussed based on simple theoretical analyses, with particular emphasis on the screening effect. The suppression of reactivity is discussed with the relation to the decrease of heat of reaction to water or the excess cohesive energy, surface tension, the action as a plug of Ti oxide, negative adsorption on the surface of LSnanop, and percolation. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessReview Stress-Corrosion Interactions in Zr-Based Bulk Metallic Glasses
Metals 2015, 5(3), 1262-1278; doi:10.3390/met5031262
Received: 7 May 2015 / Revised: 8 July 2015 / Accepted: 10 July 2015 / Published: 15 July 2015
Cited by 1 | PDF Full-text (910 KB) | HTML Full-text | XML Full-text
Abstract
Stress-corrosion interactions in materials may lead to early unpredictable catastrophic failure of structural parts, which can have dramatic effects. In Zr-based bulk metallic glasses, such interactions are particularly important as these have very high yield strength, limited ductility, and are relatively susceptible to
[...] Read more.
Stress-corrosion interactions in materials may lead to early unpredictable catastrophic failure of structural parts, which can have dramatic effects. In Zr-based bulk metallic glasses, such interactions are particularly important as these have very high yield strength, limited ductility, and are relatively susceptible to localized corrosion in halide-containing aqueous environments. Relevant features of the mechanical and corrosion behavior of Zr-based bulk metallic glasses are described, and an account of knowledge regarding corrosion-deformation interactions gathered from ex situ experimental procedures is provided. Subsequently the literature on key phenomena including hydrogen damage, stress corrosion cracking, and corrosion fatigue is reviewed. Critical factors for such phenomena will be highlighted. The review also presents an outlook for the topic. Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
Open AccessReview Toughness of Bulk Metallic Glasses
Metals 2015, 5(3), 1279-1305; doi:10.3390/met5031279
Received: 1 June 2015 / Revised: 6 July 2015 / Accepted: 10 July 2015 / Published: 17 July 2015
Cited by 14 | PDF Full-text (1337 KB) | HTML Full-text | XML Full-text
Abstract
Bulk metallic glasses (BMGs) have desirable properties like high strength and low modulus, but their toughness can show much variation, depending on the kind of test as well as alloy chemistry. This article reviews the type of toughness tests commonly performed and the
[...] Read more.
Bulk metallic glasses (BMGs) have desirable properties like high strength and low modulus, but their toughness can show much variation, depending on the kind of test as well as alloy chemistry. This article reviews the type of toughness tests commonly performed and the factors influencing the data obtained. It appears that even the less-tough metallic glasses are tougher than oxide glasses. The current theories describing the links between toughness and material parameters, including elastic constants and alloy chemistry (ordering in the glass), are discussed. Based on the current literature, a few important issues for further work are identified. Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
Open AccessReview Pyrrolyl Squaraines–Fifty Golden Years
Metals 2015, 5(3), 1349-1370; doi:10.3390/met5031349
Received: 22 June 2015 / Revised: 17 July 2015 / Accepted: 21 July 2015 / Published: 27 July 2015
Cited by 9 | PDF Full-text (409 KB) | HTML Full-text | XML Full-text
Abstract
Pyrrolyl squaraines, both dyes and polymers, were first reported in 1965 and since then a fascinating body of work has been produced investigating the chemistry of these interesting molecules. A major aspect of these molecules that makes them so appealing to those researchers
[...] Read more.
Pyrrolyl squaraines, both dyes and polymers, were first reported in 1965 and since then a fascinating body of work has been produced investigating the chemistry of these interesting molecules. A major aspect of these molecules that makes them so appealing to those researchers who have contributed to this field over the last 50 years is their chemical versatility. In this review, subjects, such as the synthetic history, an understanding of the molecular structure, an overview of the optical properties, a discussion of both the electrical conduction properties, and magnetic properties, plus use of the particles of pyrrolyl squaraines, are presented. Furthermore, previously published results are not just presented; they are in certain cases collated and used to both highlight and explain important aspects of pyrrolyl squaraine chemistry. Full article
(This article belongs to the Special Issue Synthetic Metals)
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Open AccessReview Gas Sensors Based on Electrodeposited Polymers
Metals 2015, 5(3), 1371-1386; doi:10.3390/met5031371
Received: 30 June 2015 / Revised: 21 July 2015 / Accepted: 24 July 2015 / Published: 29 July 2015
Cited by 7 | PDF Full-text (322 KB) | HTML Full-text | XML Full-text
Abstract
Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene) and their derivatives can be used as
[...] Read more.
Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene) and their derivatives can be used as the sensitive layer of conductimetric gas sensors because of their conducting properties. An important advantage of polymer-based gas sensors is their efficiency at room temperature. This characteristic is interesting since most of the commercially-available sensors, usually based on metal oxides, work at high temperatures (300–400 °C). Consequently, polymer-based gas sensors are playing a growing role in the improvement of public health and environment control because they can lead to gas sensors operating with rapid detection, high sensitivity, small size, and specificity in atmospheric conditions. In this review, the recent advances in electrodeposited polymer-based gas sensors are summarized and discussed. It is shown that the sensing characteristics of electrodeposited polymers can be improved by chemical functionalization, nanostructuration, or mixing with other functional materials to form composites or hybrid materials. Full article
(This article belongs to the Special Issue Synthetic Metals)
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Open AccessReview Tannins in Mineral Processing and Extractive Metallurgy
Metals 2015, 5(3), 1520-1542; doi:10.3390/met5031520
Received: 28 July 2015 / Revised: 18 August 2015 / Accepted: 21 August 2015 / Published: 27 August 2015
Cited by 3 | PDF Full-text (811 KB) | HTML Full-text | XML Full-text
Abstract
This study provides an up to date review of tannins, specifically quebracho, in mineral processing and metallurgical processes. Quebracho is a highly useful reagent in many flotation applications, acting as both a depressant and a dispersant. Three different types of quebracho are mentioned
[...] Read more.
This study provides an up to date review of tannins, specifically quebracho, in mineral processing and metallurgical processes. Quebracho is a highly useful reagent in many flotation applications, acting as both a depressant and a dispersant. Three different types of quebracho are mentioned in this study; quebracho “S” or Tupasol ATO, quebracho “O” or Tupafin ATO, and quebracho “A” or Silvafloc. It should be noted that literature often refers simply to “quebracho” without distinguishing a specific type. Quebracho is most commonly used in industry as a method to separate fluorite from calcite, which is traditionally quite challenging as both minerals share a common ion—calcium. Other applications for quebracho in flotation with calcite minerals as the main gangue source include barite and scheelite. In sulfide systems, quebracho is a key reagent in differential flotation of copper, lead, zinc circuits. The use of quebracho in the precipitation of germanium from zinc ores and for the recovery of ultrafine gold is also detailed in this work. This analysis explores the wide range of uses and methodology of quebracho in the extractive metallurgy field and expands on previous research by Iskra and Kitchener at Imperial College entitled, “Quebracho in Mineral Processing”. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessReview New Approaches to Aluminum Integral Foam Production with Casting Methods
Metals 2015, 5(3), 1553-1565; doi:10.3390/met5031553
Received: 25 June 2015 / Revised: 3 August 2015 / Accepted: 21 August 2015 / Published: 28 August 2015
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Abstract
Integral foam has been used in the production of polymer materials for a long time. Metal integral foam casting systems are obtained by transferring and adapting polymer injection technology. Metal integral foam produced by casting has a solid skin at the surface and
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Integral foam has been used in the production of polymer materials for a long time. Metal integral foam casting systems are obtained by transferring and adapting polymer injection technology. Metal integral foam produced by casting has a solid skin at the surface and a foam core. Producing near-net shape reduces production expenses. Insurance companies nowadays want the automotive industry to use metallic foam parts because of their higher impact energy absorption properties. In this paper, manufacturing processes of aluminum integral foam with casting methods will be discussed. Full article
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