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Metals, Volume 7, Issue 5 (May 2017)

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Cover Story (view full-size image) The pine-like dendrites produced by a galvanostatic electrodeposition at a current density of 13.05 [...] Read more.
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Open AccessArticle Laser Beam Welding of a Ti–6Al–4V Support Flange for Buy-to-Fly Reduction
Metals 2017, 7(5), 183; https://doi.org/10.3390/met7050183
Received: 12 April 2017 / Revised: 5 May 2017 / Accepted: 16 May 2017 / Published: 20 May 2017
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Abstract
Titanium and its alloys are increasingly being used in aerospace, although a number of issues must be addressed. Namely, in the framework of welding to produce complex parts, the same mechanical strength and a reduced buy-to-fly ratio are desired in comparison with the
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Titanium and its alloys are increasingly being used in aerospace, although a number of issues must be addressed. Namely, in the framework of welding to produce complex parts, the same mechanical strength and a reduced buy-to-fly ratio are desired in comparison with the same components resulting from machining. To give grounds to actual application of autogenous laser beam welding, Ti–6Al–4V L- and T-joints have been investigated in this paper, as they are a common occurrence in general complex components. Discussions in terms of possible imperfections, microstructure, and microhardness have been conducted. Then, a real part consisting of a support flange for aerospace application has been chosen as a valuable test-article to be compared with its machined counterpart both in terms of strength and buy-to-fly. The feasibility and the effectiveness of the process are shown. Full article
(This article belongs to the Special Issue Laser Welding)
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Open AccessArticle Corrosion Behavior of Pipeline Carbon Steel under Different Iron Oxide Deposits in the District Heating System
Metals 2017, 7(5), 182; https://doi.org/10.3390/met7050182
Received: 21 April 2017 / Revised: 11 May 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
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Abstract
The corrosion behavior of pipeline steel covered by iron oxides (α-FeOOH; Fe3O4 and Fe2O3) was investigated in simulated district heating water. In potentiodynamic polarization tests; the corrosion rate of pipeline steel is increased under the iron
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The corrosion behavior of pipeline steel covered by iron oxides (α-FeOOH; Fe3O4 and Fe2O3) was investigated in simulated district heating water. In potentiodynamic polarization tests; the corrosion rate of pipeline steel is increased under the iron oxide but the increaseing rate is different due to the differnet chemical reactions of the covered iron oxides. Pitting corrosion was only observed on the α-FeOOH-covered specimen; which is caused by the crevice corrosion under the α-FeOOH. From Mott-Schottky and X-ray diffraction results; the surface reaction and oxide layer were dependent on the kind of iron oxides. The iron oxides deposit increases the failure risk of the pipeline and localized corrosion can be occurred under the α-FeOOH-covered region of the pipeline. Thus, prevention methods for the iron oxide deposit in the district pipeline system such as filtering or periodic chemical cleaning are needed. Full article
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Open AccessArticle Effect of Calcium Oxide on the Crushing Strength, Reduction, and Smelting Performance of High-Chromium Vanadium–Titanium Magnetite Pellets
Metals 2017, 7(5), 181; https://doi.org/10.3390/met7050181
Received: 18 March 2017 / Revised: 16 May 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
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Abstract
The effect of calcium oxide on the crushing strength, reduction, and smelting performance of high-chromium vanadium–titanium magnetite pellets (HCVTMP) was studied in this work. The main characterization methods of an electronic universal testing machine (EUTM), X-ray fluorescent (XRF), inductively-coupled plasma-atomic emission spectroscopy (ICP-AES),
[...] Read more.
The effect of calcium oxide on the crushing strength, reduction, and smelting performance of high-chromium vanadium–titanium magnetite pellets (HCVTMP) was studied in this work. The main characterization methods of an electronic universal testing machine (EUTM), X-ray fluorescent (XRF), inductively-coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), and scanning electron microscope-energy disperse spectroscopy (SEM-EDS) were employed. The crushing strength was affected by the mineral phases generated during oxidative baking and the subsequently-formed pellet microstructures owing to CaO addition. The reduction and smelting properties of HCVTMP with different CaO additives were measured and characterized with different softening-melting-dripping indices. Although HCVTMP showed the highest crushing strength with CaO addition of ca. 2 wt %, more CaO addition may be needed to achieve high permeability of the furnace burdens and a good separation condition of the slag and melted iron. In the formation process of the slag and melted iron, it can be determined that CaO could have a relationship with the transformation behavior of Cr, V, and Ti to some extent, with respect to the predominant chemical composition analysis of ICP-AES and XRF. With the microscopic examination, the restraining formation of Ti(C,N) and the promoting formation of CaTiO3 are in accordance with the improved melting-dripping indices, including the decrease of the maximum external static load and gas permeability, and the increase of the melting-dripping zone and dripping difficulty. Full article
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Open AccessArticle A Phase Field Model for Rate-Dependent Ductile Fracture
Metals 2017, 7(5), 180; https://doi.org/10.3390/met7050180
Received: 17 April 2017 / Revised: 29 April 2017 / Accepted: 5 May 2017 / Published: 17 May 2017
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Abstract
In this study, a phase field viscoplastic model is proposed to model the influence of the loading rate on the ductile fracture, as one of the main causes of metallic alloys’ failure. To this aim, the effects of the phase field are incorporated
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In this study, a phase field viscoplastic model is proposed to model the influence of the loading rate on the ductile fracture, as one of the main causes of metallic alloys’ failure. To this aim, the effects of the phase field are incorporated in the Peric’s viscoplastic model; the model can efficiently be converted to a standard rate-independent model. The novel aspects of this work include: Describing a coupling between rate-dependent plasticity and phase field formulation by defining an energy function that contains the energy dissipation caused by plastic deformation as well as the fracture process and elastic energy. In addition, the equations required to develop the numerical solution are presented. The governing equations are determined by a minimization principle that results in balance laws for the coupled displacement-phase field problem. Furthermore, an implicit integration algorithm for a viscoplasticity model coupled with a phase field is presented for a three-dimensional stress state. The proposed algorithm can be utilized for different constitutive models of rate-dependent and rate-independent plasticity models coupled with fracture by changing the definition of the plastic multiplier. In addition, to control the influence of the plastic deformation and its work on the crack propagation, a threshold variable is defined in the model. Finally, using the proposed model, the influence of the loading rate on the responses of the different specimens in one-dimensional and multi-dimensional cases is investigated and the accuracy of the results was verified by comparing them with existing experimental and numerical results. The obtained result proves that the model can simulate the impact of the loading rate on the material response, and the gradual change of the fracture phase from ductile to brittle, caused by increasing the loading rate. Full article
(This article belongs to the Special Issue Microstructure based Modeling of Metallic Materials)
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Open AccessArticle Effect of Deep Cryogenic Treatment on the Microstructure and the Corrosion Resistance of AZ61 Magnesium Alloy Welded Joint
Metals 2017, 7(5), 179; https://doi.org/10.3390/met7050179
Received: 28 March 2017 / Revised: 30 April 2017 / Accepted: 12 May 2017 / Published: 17 May 2017
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Abstract
The effect of deep cryogenic treatment on the microstructure and corrosion resistance of an AZ61 magnesium alloy metal inert-gas (MIG) welded joint was investigated. The welded joints were deep-cryogenically treated using different parameters, and were analyzed by metallographic observations, X-ray diffraction, microhardness, and
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The effect of deep cryogenic treatment on the microstructure and corrosion resistance of an AZ61 magnesium alloy metal inert-gas (MIG) welded joint was investigated. The welded joints were deep-cryogenically treated using different parameters, and were analyzed by metallographic observations, X-ray diffraction, microhardness, and NaCl immersion test. The results show that the treatment changes the microstructure of the entire joint by causing grain refinement and increase in the β-phase. The crystal structure, chemical composition, and electrode potentials are different for the α and the β-phases. Therefore, any change in content, status, and distribution of the β phase has important implications on the corrosion resistance of the samples. With an increase in the holding time, the microhardness value of the whole joint increases, and the difference between the three regions of the joint decreases. The results of the NaCl immersion test show that there is an improvement in the corrosion resistance of the treated joints. Compared with the untreated samples, the corrosion potential of the samples treated by deep cryogenic treatment for 4 h at −180 °C is about 0.017 V higher, and the corrosion current density decreased by one order of magnitude (from about 2.769 × 10−5 A·cm−2 to 1.578 × l0−6 A·cm−2). Full article
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Open AccessArticle Flat-Top Cylinder Indenter Examination of Duplex Stainless Steel 2205 after Different Heat Treatments
Metals 2017, 7(5), 178; https://doi.org/10.3390/met7050178
Received: 5 April 2017 / Revised: 10 May 2017 / Accepted: 12 May 2017 / Published: 17 May 2017
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Abstract
The duplex stainless steel 2205 was heat treated at 750 °C, 850 °C, and 900 °C for increasing durations of up to 10 h. The samples were investigated through light microscopy (LM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to characterize the
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The duplex stainless steel 2205 was heat treated at 750 °C, 850 °C, and 900 °C for increasing durations of up to 10 h. The samples were investigated through light microscopy (LM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to characterize the volume fraction and morphology of the precipitated secondary phases. The samples were then tested via flat-top cylinder indenter for mechanical characterization (FIMEC) testing to determine the yield stresses that were found to be significantly affected by the different heat treatments. The yield stress evolution with heat treatments resulted in being correlated to both the relative volumes of the secondary phases and the morphology of the σ phase. The FIMEC test proved to be capable of detecting the effects of small amounts of secondary phases on yield stress in DSS 2205 and seems to be a promising technique for industrial applications. Full article
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Open AccessArticle Mechanical Behavior and Sliding Wear Studies on Iron Aluminide Coatings Reinforced with Titanium Carbide
Metals 2017, 7(5), 177; https://doi.org/10.3390/met7050177
Received: 11 April 2017 / Revised: 5 May 2017 / Accepted: 8 May 2017 / Published: 16 May 2017
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Abstract
Wear-resistant iron aluminide-based composites were coated on steel substrates with the High-Velocity Oxy-Fuel (HVOF) technique using ball milled Fe3Al and TiC powders as feedstock. The phase composition, microstructure, microhardness, elastic modulus and dry sliding wear performance of unreinforced Fe3Al
[...] Read more.
Wear-resistant iron aluminide-based composites were coated on steel substrates with the High-Velocity Oxy-Fuel (HVOF) technique using ball milled Fe3Al and TiC powders as feedstock. The phase composition, microstructure, microhardness, elastic modulus and dry sliding wear performance of unreinforced Fe3Al and Fe3Al–TiC composite coatings (reinforced with 30 and 50 vol. % TiC particles) were evaluated in order to reveal the relationship between the mechanical and tribological behaviors. Compared to the unreinforced coatings, the composite coating with 30 vol. % TiC particles exhibited much greater hardness and higher elastic modulus. The increase of the elastic modulus of the composite coatings did not result in deterioration of sliding wear behavior. The addition of 50 vol. % TiC resulted in a further increase in hardness, however, both composite coatings showed the same elastic modulus. The fractured cross sectional surface of the unreinforced coating showed a weakly bonded microstructure promoting delamination in wear tests, whereas the composite fractured surface showed strong mechanical bonding between the matrix and carbide particles, leading to better cohesion. The Fe3Al–TiC coatings showed almost three orders of magnitude higher wear resistance under the dry sliding wear test compared to the unreinforced coatings. Full article
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Open AccessArticle Transparent Conducting Film Fabricated by Metal Mesh Method with Ag and Cu@Ag Mixture Nanoparticle Pastes
Metals 2017, 7(5), 176; https://doi.org/10.3390/met7050176
Received: 7 March 2017 / Revised: 18 April 2017 / Accepted: 11 May 2017 / Published: 16 May 2017
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Abstract
Transparent conducting electrode film is highly desirable for application in touch screen panels (TSPs), flexible and wearable displays, sensors, and actuators. A sputtered film of indium tin oxide (ITO) shows high transmittance (90%) at low sheet resistance (50 Ω/cm2). However, ITO
[...] Read more.
Transparent conducting electrode film is highly desirable for application in touch screen panels (TSPs), flexible and wearable displays, sensors, and actuators. A sputtered film of indium tin oxide (ITO) shows high transmittance (90%) at low sheet resistance (50 Ω/cm2). However, ITO films lack mechanical flexibility, especially under bending stress, and have limitation in application to large-area TSPs (over 15 inches) due to the trade-off in high transmittance and low sheet resistance properties. One promising solution is to use metal mesh-type transparent conducting film, especially for touch panel application. In this work, we investigated such inter-related issues as UV imprinting process to make a trench layer pattern, the synthesis of core-shell-type Ag and Cu@Ag composite nanoparticles and their paste formulation, the filling of Ag and Cu@Ag mixture nanoparticle paste to the trench layer, and touch panel fabrication processes. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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Open AccessArticle Variable-Frequency Ultrasonic Treatment on Microstructure and Mechanical Properties of ZK60 Alloy during Large Diameter Semi-Continuous Casting
Metals 2017, 7(5), 173; https://doi.org/10.3390/met7050173
Received: 7 April 2017 / Revised: 4 May 2017 / Accepted: 4 May 2017 / Published: 16 May 2017
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Abstract
Traditional fixed-frequency ultrasonic technology and a variable-frequency ultrasonic technology were applied to refine the as-cast microstructure and improve the mechanical properties of a ZK60 (Mg–Zn–Zr) alloy during large diameter semi-continuous casting. The acoustic field propagation was obtained by numerical simulation. The microstructure of
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Traditional fixed-frequency ultrasonic technology and a variable-frequency ultrasonic technology were applied to refine the as-cast microstructure and improve the mechanical properties of a ZK60 (Mg–Zn–Zr) alloy during large diameter semi-continuous casting. The acoustic field propagation was obtained by numerical simulation. The microstructure of the as-cast samples was characterized by optical and scanning electron microscopy. The variable-frequency ultrasonic technology shows its outstanding ability in grain refinement compared with traditional fixed-ultrasonic technology. The variable-frequency acoustic field promoted the formation of small α-Mg globular grains and changed the distribution and morphology of β-phases throughout the castings. Ultimate tensile strength and elongation are increased to 280 MPa and 8.9%, respectively, which are 19.1% and 45.9% higher than the values obtained from billets without ultrasonic treatment and are 11.6% and 18.7% higher than fixed-frequency ultrasound treated billets. Different refinement efficiencies appear in different districts of billets attributed to the sound attenuation in melt. The variable-frequency acoustic field improves the refinement effect by enhancing cavitation-enhanced heterogeneous nucleation and dendrite fragmentation effects. Full article
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Open AccessArticle Microstructure and Properties of the Interface Area in the Laser Cladded Ni Based Coatings on the 1Cr10Mo1NiWVNbN Steel
Metals 2017, 7(5), 175; https://doi.org/10.3390/met7050175
Received: 21 January 2017 / Revised: 14 April 2017 / Accepted: 10 May 2017 / Published: 15 May 2017
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Abstract
The Ni-based coatings were deposited on the 1Cr10Mo1NiWVNbN steel by using laser cladding process. The microstructure and properties of the coatings interface area were investigated by OM (Optical Microscopy), SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction) microhardness test and EDS (Energy Spectrum Analysis)
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The Ni-based coatings were deposited on the 1Cr10Mo1NiWVNbN steel by using laser cladding process. The microstructure and properties of the coatings interface area were investigated by OM (Optical Microscopy), SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction) microhardness test and EDS (Energy Spectrum Analysis) analysis. The results show that the bonding condition of the coatings interface is different in the monolayer and the trilayer. The monolayer coatings have a small dilution area. The dilution rate in a coating layer increases by layers. The scale of ferrite (α) phase increases with the layer increases. The surface cladding quality of a monolayer is better than that of the trilayer coatings. The width of the interface increases with the increase of the layer. The width of the interface region in the trilayer coatings increases significantly. The microhardness of the interface zone is much higher than that in the coatings zone and the substrate zone. The microhardness of trilayer coatings is higher than that of the monolayer. Full article
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Open AccessArticle Leaching Process of Rare Earth Elements, Gallium and Niobium in a Coal-Bearing Strata-Hosted Rare Metal Deposit—A Case Study from the Late Permian Tuff in the Zhongliangshan Mine, Chongqing
Metals 2017, 7(5), 174; https://doi.org/10.3390/met7050174
Received: 15 February 2017 / Revised: 7 May 2017 / Accepted: 11 May 2017 / Published: 15 May 2017
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Abstract
The tuff, a part of coal-bearing strata, in the Zhongliangshan coal mine, Chongqing, southwestern China, hosts a rare metal deposit enriched in rare earth elements (REE), Ga and Nb. However, the extraction techniques directly related to the recovery of rare metals in coal-bearing
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The tuff, a part of coal-bearing strata, in the Zhongliangshan coal mine, Chongqing, southwestern China, hosts a rare metal deposit enriched in rare earth elements (REE), Ga and Nb. However, the extraction techniques directly related to the recovery of rare metals in coal-bearing strata have been little-studied in the literature. The purpose of this paper is to investigate the extractability of REE, Ga and Nb in the tuff in the Zhongliangshan mine using the alkaline sintering-water immersion-acid leaching (ASWIAL) method. The results show that ASWIAL can separate and extract REE, Ga and Nb effectively under the optimized conditions of calcining at 860 °C for 0.5 h with a sample to sintering agent ratio of 1:1.5, immersing at 90 °C for 2 h with 150 mL hot water dosage, and leaching using 4 mol/L HCl at 40 °C for 2 h with a liquid-solid ratio of 20:1 (mL:g). The final leaching efficiencies of REE and Ga are up to 85.81% and 93.37%, respectively, whereas the leaching efficiency of Nb is less than 1%, suggesting the high concentration of Nb in the leaching residue, which needs further extraction. Full article
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Open AccessArticle Grain Refinement Mechanism of the As-Cast and As-Extruded Mg–14Li Alloys with Al or Sn Addition
Metals 2017, 7(5), 172; https://doi.org/10.3390/met7050172
Received: 13 April 2017 / Revised: 8 May 2017 / Accepted: 9 May 2017 / Published: 13 May 2017
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Abstract
The microstructures of the as-cast and as-extruded Mg–14 wt. % Li–1 wt. % Al (LA141) and Mg–14 wt. % Li–2 wt. % Sn (LT142) were observed by optical and scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The effects
[...] Read more.
The microstructures of the as-cast and as-extruded Mg–14 wt. % Li–1 wt. % Al (LA141) and Mg–14 wt. % Li–2 wt. % Sn (LT142) were observed by optical and scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The effects of Al and Sn on the grain refinement on the Mg–14Li alloy were investigated. In addition, the mechanism of grain refinement on the as-cast and as-extruded alloys was discussed from the view of the solute effect and heterogeneous nucleation effect via edge-to-edge matching model. The results showed that the average grain sizes of the as-cast LA141 and LT142 alloys were similar due to the close solute effect of 1.1 wt. % Al and 1.8 wt. % Sn, while, in the as-extruded alloys, the average grain size of LT142 was over two times finer than that of LA141. This was attributed to the reason that Li2MgSn particles can serve as heterogeneous nucleation sites for the β-Li matrix during the process of dynamic recrystallization (DRX), but LiMgAl2 cannot serve the same way. Therefore, Sn can act as a more effective grain refiner for the Mg–14Li alloy compared to Al. Full article
(This article belongs to the Special Issue Microstructure based Modeling of Metallic Materials)
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Open AccessArticle Mechanical and Corrosion Behavior of Al-Zn-Cr Family Alloys
Metals 2017, 7(5), 171; https://doi.org/10.3390/met7050171
Received: 9 February 2017 / Revised: 29 April 2017 / Accepted: 3 May 2017 / Published: 12 May 2017
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Abstract
Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and powder metallurgy techniques. Cr additions ranged between 5 to 10 wt. %, while Zn was added in an amount between 0 and 20 wt. %. Heat treatment processes were
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Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and powder metallurgy techniques. Cr additions ranged between 5 to 10 wt. %, while Zn was added in an amount between 0 and 20 wt. %. Heat treatment processes were performed during powder metallurgy process, at different temperatures, followed by water quenching. Similar alloys were extruded with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the alloys investigated. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys, containing 10 wt. % Cr and heat treated at 500 °C for one hour followed by water quenching, exhibited the highest wear resistance and better mechanical properties. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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Open AccessArticle Characteristics of Cold and Hot Pressed Iron Aluminum Powder Metallurgical Alloys
Metals 2017, 7(5), 170; https://doi.org/10.3390/met7050170
Received: 4 March 2017 / Revised: 29 April 2017 / Accepted: 3 May 2017 / Published: 12 May 2017
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Abstract
Iron powders having average particle sizes of ~40 µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt. %, with an average particle size of ~10 µm. Two different powder metallurgy (PM) techniques, cold and hot pressing, are
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Iron powders having average particle sizes of ~40 µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt. %, with an average particle size of ~10 µm. Two different powder metallurgy (PM) techniques, cold and hot pressing, are used to study the effect of the additive element powder on the mechanical properties, wear properties, and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature reaching up to 500 °C at 445.6 MPa. The cold pressing technique was performed at 909 MPa at room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the Brinell hardness number was decreased from 780 to 690 and the radial strength from 380 to 228 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to five times was achieved, compared to the alloy without Al addition for different wear parameters: wear time and sliding speed. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
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Open AccessArticle Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange
Metals 2017, 7(5), 169; https://doi.org/10.3390/met7050169
Received: 23 February 2017 / Revised: 4 May 2017 / Accepted: 8 May 2017 / Published: 12 May 2017
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Abstract
This work shows the physicochemical behavior of two different diatoms from the country of Mexico (State of Jalisco and Hidalgo) with similar compositions. These were used to eliminate toxic cations from a synthetic solution containing 5.270 mg As3+/L; 4.280 mg Ag
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This work shows the physicochemical behavior of two different diatoms from the country of Mexico (State of Jalisco and Hidalgo) with similar compositions. These were used to eliminate toxic cations from a synthetic solution containing 5.270 mg As3+/L; 4.280 mg Ag+/L; 3.950 mgNi2+/L; 4.090 mg Cr6+/L; and 4.081 mg Pb2+/L. These diatoms were used as filters, and the quantity of cations remaining in the solution after filtering was measured. According to the most important results found, for the recovery of metals, both minerals achieved arsenic, silver, lead, and nickel recoveries up to 95%, and lower than 10% for chromium. This could be due to the absence of an environment to reduce Cr6+ to Cr3+. On the other hand, it was observed that there was no selectivity during the recovery of the other cations present in the solution. According to efficiency of interchange, the mineral from Hidalgo is slightly better than the mineral from Jalisco for the removal of arsenic, lead, and silver. For nickel, and particularly Cr6+, the efficiency is higher for the sample from Jalisco. Full article
(This article belongs to the Special Issue Heavy Metal Determination and Removal)
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