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Metals, Volume 5, Issue 1 (March 2015), Pages 1-483

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Editorial

Jump to: Research, Review

Open AccessEditorial Acknowledgement to Reviewers of Metals in 2014
Metals 2015, 5(1), 52-53; doi:10.3390/met5010052
Received: 7 January 2015 / Accepted: 7 January 2015 / Published: 7 January 2015
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Abstract
The editors of Metals would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle The Effect of Mg Adding Order on the Liquid Structure and Solidified Microstructure of the Al-Si-Mg-P Alloy: An Experiment and ab Initio Study
Metals 2015, 5(1), 40-51; doi:10.3390/met5010040
Received: 1 October 2014 / Accepted: 19 December 2014 / Published: 26 December 2014
Cited by 3 | PDF Full-text (1798 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the relationship between the liquid structure and the corresponding solidified microstructure of an Al-Si-Mg-P alloy was studied. Experimental results show that Mg can reduce the phosphorous-modification effect if it was added after adding Al-P alloy. However, when it is added
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In this paper, the relationship between the liquid structure and the corresponding solidified microstructure of an Al-Si-Mg-P alloy was studied. Experimental results show that Mg can reduce the phosphorous-modification effect if it was added after adding Al-P alloy. However, when it is added before adding Al-P alloy, Mg has no effect on the phosphorous-modification. It is considered that the difference in liquid structure induced by changing the adding order of Mg should be responsible for the above phenomenon, and was investigated by ab initio molecular dynamics simulation (AIMD). It was believed that the high-active Mg atoms could bond P atoms to form P-Mg clusters and then reduce the modification effect of AlP, when pure Mg was added into the prepared Al-Si-P melt. When the pure Mg was added into Al-Si melt before adding Al-P alloy, the Mg atoms would be first occupied by Si atoms to form Mg-Si clusters, and thus lose the ability to eliminate P-Al clusters which dissolve into melt later, leading to a good phosphorous-modification effect. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessArticle Titanium Matrix Composite Ti/TiN Produced by Diode Laser Gas Nitriding
Metals 2015, 5(1), 54-69; doi:10.3390/met5010054
Received: 11 November 2014 / Accepted: 4 January 2015 / Published: 9 January 2015
Cited by 31 | PDF Full-text (3082 KB) | HTML Full-text | XML Full-text
Abstract
A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808–940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers
[...] Read more.
A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808–940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer beads at different heat inputs, different scanning speeds, and different powers of laser beam. The influence of laser nitriding parameters on the quality, shape, and morphology of the surface layers was investigated. It was found that the nitrided surface layers consist of titanium nitride precipitations mainly in the form of dendrites embedded in the titanium alloy matrix. The titanium nitrides are produced as a result of the reaction between molten Ti and gaseous nitrogen. Solidification and subsequent growth of the TiN dendrites takes place to a large extent at the interface of the molten Ti and the nitrogen gas atmosphere. The direction of TiN dendrites growth is perpendicular to the surface of molten Ti. The roughness of the surface layers depends strongly on the heat input of laser nitriding and can be precisely controlled. In spite of high microhardness up to 2400 HV0.2, the surface layers are crack free. Full article
(This article belongs to the Special Issue Titanium Alloys)
Open AccessArticle Microstructure and Properties of Spark Plasma Sintered Aluminum Containing 1 wt.% SiC Nanoparticles
Metals 2015, 5(1), 70-83; doi:10.3390/met5010070
Received: 19 November 2014 / Accepted: 6 January 2015 / Published: 12 January 2015
Cited by 3 | PDF Full-text (2274 KB) | HTML Full-text | XML Full-text
Abstract
The low hardness and strength of aluminum, which limits its use in many industrial applications, could be increased through the addition of nanoparticles. However, the appropriate processing method and parameters should be carefully selected in order to achieve the desired improvement in properties.
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The low hardness and strength of aluminum, which limits its use in many industrial applications, could be increased through the addition of nanoparticles. However, the appropriate processing method and parameters should be carefully selected in order to achieve the desired improvement in properties. In this work, aluminum was reinforced with low weight fraction (1 wt.%) of SiC nanoparticles and consolidated through spark plasma sintering. The effect of processing parameters on the densification, microstructure, and properties of the processed material was investigated. Field Emission Scanning Electron Microscope (FE-SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) facility was used to characterize the microstructure and analyze the reinforcement’s distribution in sintered samples. Phases present were characterized through X-ray diffraction (XRD). A densimeter and a digital microhardness tester were used to measure the density and hardness, respectively. Compressive tests were performed using universal testing machine. A fully dense Al-1 wt.% SiC sample was obtained. Analysis of density and hardness values showed that the influence of applied pressure was more pronounced than heating rate while the influence of sintering temperature was more significant than sintering time. Within the range of parameters used, the highest values of the characterized properties were obtained at a sintering temperature of 600 °C, sintering time of 10 min, pressure of 50 MPa, and heating rate of 200 °C/min. Full article
Open AccessArticle Experimental Investigation of the Mg-Nd-Zn Isothermal Section at 300 °C
Metals 2015, 5(1), 84-101; doi:10.3390/met5010084
Received: 8 December 2014 / Accepted: 26 December 2014 / Published: 12 January 2015
Cited by 6 | PDF Full-text (1755 KB) | HTML Full-text | XML Full-text
Abstract
The Mg-Nd-Zn isothermal section at 300 °C was established in the full composition range using diffusion couples and equilibrated key alloys. Microstructural characterization was carried out using WDS, XRD, and metallographic methods. The homogeneity ranges of the binary and ternary compounds were determined
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The Mg-Nd-Zn isothermal section at 300 °C was established in the full composition range using diffusion couples and equilibrated key alloys. Microstructural characterization was carried out using WDS, XRD, and metallographic methods. The homogeneity ranges of the binary and ternary compounds were determined by WDS analysis. Six ternary compounds were observed in the Mg-Nd-Zn system at 300 °C. These are: τ1 (Nd5Mg21+xZn45x; 0 ≤ x ≤ 4), τ2 (Nd5Mg3+yZn25y; 0 ≤ y ≤ 1), τ3 (NdMg1+zZn2z; 0 ≤ z ≤ 0.44), τ4 (Mg40Nd5Zn55), τ5 (Mg22–23.5Nd15.5–17.5Zn59.1–61.8), and τ6 (Nd2(Mg,Zn)23). τ5 was found to have a homogeneity range of 22.0–23.5 atom % Mg, 15.5–17.6 atom % Nd and 59.1–61.8 atom % Zn and τ6 was found to have 54.1–61.3 atom % Mg at a constant Nd of 8.0 atom %. The ternary solubility of Zn in Mg-Nd compounds was found to increase with the decrease in Mg concentration. Accordingly, (Mg41Nd5) was found to have an extended solubility of 3.1 atom % Zn, whereas (Mg3Nd) was found to have 30.0 atom % Zn. MgNd was found to have a complete substitution of Mg by Zn. The maximum solid solubility of Zn in α-Mg was measured as 4.8 atom % Zn. Full article
Open AccessArticle The Effect of Indium Content on the Atomic Environment and Cluster Stability of GeSe4Inx=10,15 Glasses
Metals 2015, 5(1), 102-118; doi:10.3390/met5010102
Received: 27 October 2014 / Accepted: 8 January 2015 / Published: 14 January 2015
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Abstract
The atomic environments of two chalcogenide glasses, with compositions GeSe4In10 and GeSe4In15, were studied via Reverse Monte Carlo and Density Functional Theory. Indium content demoted Ge–Se bonding in favor of Se-In while the contribution of Se–Se
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The atomic environments of two chalcogenide glasses, with compositions GeSe4In10 and GeSe4In15, were studied via Reverse Monte Carlo and Density Functional Theory. Indium content demoted Ge–Se bonding in favor of Se-In while the contribution of Se–Se in the first coordination shell order was faint. Upon transition to the richer In glass, there was formation of rich Ge-centered clusters at radial distances further than 4 Å from the RMC box center, which was taken to signify a reduction of Ge–Se interactions. Cluster coordination by Se promoted stability while, very conclusively, In coordination lowered cluster stability by intervening in the Ge–Se and Se–Se networks. Full article
Open AccessArticle Experimental Investigations on the Influence of Adhesive Oxides on the Metal-Ceramic Bond
Metals 2015, 5(1), 119-130; doi:10.3390/met5010119
Received: 23 September 2014 / Revised: 22 December 2014 / Accepted: 12 January 2015 / Published: 21 January 2015
Cited by 2 | PDF Full-text (678 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to test the influence of selected base metals, which act as oxide formers, on the metal-ceramic bond of dental veneer systems. Using ion implantation techniques, ions of Al, In and Cu were introduced into near-surface layers of
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The objective of this study was to test the influence of selected base metals, which act as oxide formers, on the metal-ceramic bond of dental veneer systems. Using ion implantation techniques, ions of Al, In and Cu were introduced into near-surface layers of a noble metal alloy containing no base metals. A noble metal alloy with base metals added for oxide formation was used as a reference. Both alloys were coated with a low-temperature fusing dental ceramic. Specimens without ion implantation or with Al2O3 air abrasion were used as controls. The test procedures comprised the Schwickerath shear bond strength test (ISO 9693-1), profile height (surface roughness) measurements (ISO 4287; ISO 4288; ISO 25178), scanning electron microscopy (SEM) imaging, auger electron spectroscopy (AES) and energy dispersive X-ray analysis (EDX). Ion implantation resulted in no increase in bond strength. The highest shear bond strengths were achieved after oxidation in air and air abrasion with Al2O3 (41.5 MPa and 47.8 MPa respectively). There was a positive correlation between shear bond strength and profile height. After air abrasion, a pronounced structuring of the surface occurred compared to ion implantation. The established concentration shifts in alloy and ceramic could be reproduced. However, their positive effects on shear bond strength were not confirmed. The mechanical bond appears to be of greater importance for metal-ceramic bonding. Full article
(This article belongs to the Special Issue Advances in Cermets)
Open AccessArticle Effect of Heat Treatment on Microstructure and Hardness of Grade 91 Steel
Metals 2015, 5(1), 131-149; doi:10.3390/met5010131
Received: 4 December 2014 / Accepted: 12 January 2015 / Published: 21 January 2015
Cited by 14 | PDF Full-text (2357 KB) | HTML Full-text | XML Full-text
Abstract
Grade 91 steel (modified 9Cr-1Mo steel) is considered a prospective material for the Next Generation Nuclear Power Plant for application in reactor pressure vessels at temperatures of up to 650 °C. In this study, heat treatment of Grade 91 steel was performed by
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Grade 91 steel (modified 9Cr-1Mo steel) is considered a prospective material for the Next Generation Nuclear Power Plant for application in reactor pressure vessels at temperatures of up to 650 °C. In this study, heat treatment of Grade 91 steel was performed by normalizing and tempering the steel at various temperatures for different periods of time. Optical microscopy, scanning and transmission electron microscopy in conjunction with microhardness profiles and calorimetric plots were used to understand the microstructural evolution including precipitate structures and were correlated with mechanical behavior of the steel. Thermo-Calc™ calculations were used to support the experimental work. Furthermore, carbon isopleth and temperature dependencies of the volume fraction of different precipitates were constructed. Full article
Open AccessArticle Effects of Silicon on Mechanical Properties and Fracture Toughness of Heavy-Section Ductile Cast Iron
Metals 2015, 5(1), 150-161; doi:10.3390/met5010150
Received: 3 December 2014 / Accepted: 8 January 2015 / Published: 21 January 2015
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Abstract
The effects of silicon (Si) on the mechanical properties and fracture toughness of heavy-section ductile cast iron were investigated to develop material for spent-nuclear-fuel containers. Two castings with different Si contents of 1.78 wt.% and 2.74 wt.% were prepared. Four positions in the
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The effects of silicon (Si) on the mechanical properties and fracture toughness of heavy-section ductile cast iron were investigated to develop material for spent-nuclear-fuel containers. Two castings with different Si contents of 1.78 wt.% and 2.74 wt.% were prepared. Four positions in the castings from the edge to the center, with different solidification cooling rates, were chosen for microstructure observation and mechanical properties’ testing. Results show that the tensile strength, elongation, impact toughness and fracture toughness at different positions of the two castings decrease with the decrease in cooling rate. With an increase in Si content, the graphite morphology and the mechanical properties at the same position deteriorate. Decreasing cooling rate changes the impact fracture morphology from a mixed ductile-brittle fracture to a brittle fracture. The fracture morphology of fracture toughness is changed from ductile to brittle fracture. When the Si content exceeds 1.78 wt.%, the impact and fracture toughness fracture morphology transforms from ductile to brittle fracture. The in-situ scanning electronic microscope (SEM) tensile experiments were first used to observe the dynamic tensile process. The influence of the vermicular and temper graphite on fracture formation of heavy section ductile iron was investigated. Full article
(This article belongs to the Special Issue Advances in Solidification Processing)
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Open AccessArticle A New Ni-Based Metallic Glass with High Thermal Stability and Hardness
Metals 2015, 5(1), 162-171; doi:10.3390/met5010162
Received: 20 October 2014 / Revised: 9 January 2015 / Accepted: 27 January 2015 / Published: 2 February 2015
Cited by 1 | PDF Full-text (780 KB) | HTML Full-text | XML Full-text
Abstract
Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5) metallic glasses have been investigated. For each alloy, thin sheets of samples having thickness of 20 µm and 100 µm
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Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5) metallic glasses have been investigated. For each alloy, thin sheets of samples having thickness of 20 µm and 100 µm were synthesized by piston and anvil method in a vacuum arc furnace. Also, 400 µm thick samples of the alloys were synthesized by suction casting method. The samples were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). Crystallization temperature of the base alloy, Ni51W31.6B17.4, is found to be 996 K and 5 at.% copper substitution for nickel increases the crystallization temperature to 1063 K, which is the highest value reported for Ni-based metallic glasses up to the present. In addition, critical casting thickness of alloy Ni51W31.6B17.4 is 100 µm and copper substitution does not have any effect on critical casting thickness of the alloys. Also, microhardness of the alloys are found to be around 1200 Hv, which is one of the highest microhardness values reported for a Ni-based metallic glass until now. Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
Open AccessArticle Effect of Strain Localization on Pitting Corrosion of an AlMgSi0.5 Alloy
Metals 2015, 5(1), 172-191; doi:10.3390/met5010172
Received: 8 December 2014 / Revised: 12 January 2015 / Accepted: 29 January 2015 / Published: 3 February 2015
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Abstract
The corrosion susceptibility of an age-hardened aluminum alloy in different processing conditions, especially after a single pass of equal-channel angular pressing (ECAP), is examined. The main question addressed is how corrosive attack is changed by strain localization. For that purpose, an AlMgSi0.5 alloy
[...] Read more.
The corrosion susceptibility of an age-hardened aluminum alloy in different processing conditions, especially after a single pass of equal-channel angular pressing (ECAP), is examined. The main question addressed is how corrosive attack is changed by strain localization. For that purpose, an AlMgSi0.5 alloy with a strain localized microstructure containing alternating shear bands was subjected to potentiodynamic polarization on a macro-scale and micro-scale using the micro-capillary technique. Pitting potentials and the corrosion appearance (pit depth, corroded area fractions and volumes) are discussed with respect to microstructural evolution due to casting, extrusion and ECAP. Size, shape and orientation of grains, constituent particle fragmentation, cell size and microstrain were analyzed. Stable pitting of shear bands results in less positive potentials compared to adjacent microstructure. More pits emerge in the shear bands, but the pit depth is reduced significantly. This is attributed to higher microstrains influencing the stability of the passivation layer and the reduced size of grains and constituent particles. The size of the crystallographic pits is associated with the deformation-induced cell size of the aluminum alloy. Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available
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Open AccessArticle Vacuum Die Casting Process and Simulation for Manufacturing 0.8 mm-Thick Aluminum Plate with Four Maze Shapes
Metals 2015, 5(1), 192-205; doi:10.3390/met5010192
Received: 3 December 2014 / Revised: 20 January 2015 / Accepted: 26 January 2015 / Published: 4 February 2015
Cited by 3 | PDF Full-text (1901 KB) | HTML Full-text | XML Full-text
Abstract
Using vacuum die casting, 0.8 mm-thick plates in complicated shapes are manufactured with the highly castable aluminum alloy Silafont-36 (AlSi9MgMn). The sizes and shapes of the cavities, made of thin plates, feature four different mazes. To investigate formability and mechanical properties by shot
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Using vacuum die casting, 0.8 mm-thick plates in complicated shapes are manufactured with the highly castable aluminum alloy Silafont-36 (AlSi9MgMn). The sizes and shapes of the cavities, made of thin plates, feature four different mazes. To investigate formability and mechanical properties by shot condition, a total of six parameters (melt temperatures of 730 °C and 710 °C; plunger speeds of 3.0 m/s and 2.5 m/s; vacuum pressure of 250 mbar and no vacuum) are varied in experiments, and corresponding simulations are performed. Simulation results obtained through MAGMA software show similar tendencies to those of the experiments. When the melt pouring temperature is set to 730 °C rather than 710 °C, formability and mechanical properties are superior, and when the plunger speed is set to 3.0 m/s rather than to 2.5 m/s, a fine, even structure is obtained with better mechanical properties. The non-vacuumed sample is half unfilled. The tensile strength and elongation of the sample fabricated under a melt temperature of 730 °C, plunger speed of 3.0 m/s, and vacuum pressure of 250 mbar are 265 MPa and 8.5%, respectively. Full article
(This article belongs to the Special Issue Casting Alloy Design and Modification)
Open AccessArticle Nanocrystalline Ti Produced by Cryomilling and Consolidation by Severe Plastic Deformation
Metals 2015, 5(1), 206-215; doi:10.3390/met5010206
Received: 18 December 2014 / Revised: 12 January 2015 / Accepted: 30 January 2015 / Published: 5 February 2015
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Abstract
We report on a study of the nanocrystalline structure in Ti, which was produced by cryogenic milling followed by subsequent consolidation via severe plastic deformation using high pressure torsion. The mechanisms that are believed to be responsible for the formation of grains smaller
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We report on a study of the nanocrystalline structure in Ti, which was produced by cryogenic milling followed by subsequent consolidation via severe plastic deformation using high pressure torsion. The mechanisms that are believed to be responsible for the formation of grains smaller than 40 nm are discussed and the influence of structural characteristics, such as nanometric grains and oxide nanoparticles, on Ti hardening is established. Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available
Open AccessArticle Hot Deformation Behavior of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe Alloy in α + β Field
Metals 2015, 5(1), 216-227; doi:10.3390/met5010216
Received: 10 January 2015 / Revised: 22 January 2015 / Accepted: 3 February 2015 / Published: 13 February 2015
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Abstract
The deformation behavior of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe high strength β titanium alloy is systematically investigated by isothermal compression in α + β field with the deformation temperatures ranging from 1003 K to 1078 K, the strain rates ranging from 0.001 s−1 to 1 s
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The deformation behavior of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe high strength β titanium alloy is systematically investigated by isothermal compression in α + β field with the deformation temperatures ranging from 1003 K to 1078 K, the strain rates ranging from 0.001 s−1 to 1 s−1 and the height reduction is around 50%. Essentially, the flow stress-strain curve of isothermal compression in α + β field exhibits a flow softening feature when the strain rate is higher than 0.1 s−1 as while it exhibits a steady-state feature as the strain rate is lower than 0.1 s−1. The peak stress increases with a decrease in deformation temperature and the increase of strain rate. The activation energy for deformation in α + β field was calculated and the average activation energy of 271.1 kJ/mol. The microstructure observation reveals that the isothermal deformation in the α + β field of the alloy is mainly controlled by the dynamic recovery mechanism accompanied with the secondary dynamic recrystallizitation of β phase. The α phase shows an obvious pinning effect for the movement of dislocations. During deformation, the α phase was elongated and fragmented. Full article
(This article belongs to the Special Issue Titanium Alloys)
Open AccessArticle Investigation of Material Performance Degradation for High-Strength Aluminum Alloy Using Acoustic Emission Method
Metals 2015, 5(1), 228-238; doi:10.3390/met5010228
Received: 10 December 2014 / Accepted: 28 January 2015 / Published: 13 February 2015
Cited by 2 | PDF Full-text (780 KB) | HTML Full-text | XML Full-text
Abstract
Structural materials damages are always in the form of micro-defects or cracks. Traditional or conventional methods such as micro and macro examination, tensile, bend, impact and hardness tests can be used to detect the micro damage or defects. However, these tests are destructive
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Structural materials damages are always in the form of micro-defects or cracks. Traditional or conventional methods such as micro and macro examination, tensile, bend, impact and hardness tests can be used to detect the micro damage or defects. However, these tests are destructive in nature and not in real-time, thus a non-destructive and real-time monitoring and characterization of the material damage is needed. This study is focused on the application of a non-destructive and real-time acoustic emission (AE) method to study material performance degradation of a high-strength aluminum alloy of high-speed train gearbox shell. By applying data relative analysis and interpretation of AE signals, the characteristic parameters of materials performance were achieved and the failure criteria of the characteristic parameters for the material tensile damage process were established. The results show that the AE method and signal analysis can be used to accomplish the non-destructive and real-time detection of the material performance degradation process of the high-strength aluminum alloy. This technique can be extended to other engineering materials. Full article
Open AccessArticle Graphite and Solid Fraction Evolutions during Solidification of Nodular Cast Irons
Metals 2015, 5(1), 239-255; doi:10.3390/met5010239
Received: 8 January 2015 / Revised: 9 February 2015 / Accepted: 14 February 2015 / Published: 25 February 2015
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Abstract
Ductile iron casting production is strongly affected by austenite and graphite distribution obtained after the solidification process. At the same time it is accepted that solidification behavior can be considered as hypo-, hyper- or eutectic depending on the chemical composition; there is still
[...] Read more.
Ductile iron casting production is strongly affected by austenite and graphite distribution obtained after the solidification process. At the same time it is accepted that solidification behavior can be considered as hypo-, hyper- or eutectic depending on the chemical composition; there is still some misconception about the growth evolution of graphite nodules and about solid fraction progression. Quenching experiments were performed on two different carbon equivalent compositions using inoculated and non-inoculated thermal analysis standard samples with the aim of freezing the existing phases at different solid fractions for each alloy. As a result of these experiments, it was possible to study the structural features found at different locations of each sample and at different stages of solidification. Additionally nodule evolution during the liquid-solid transformation was also analyzed and discussed regarding the chemical and processing characteristics of the prepared alloys. Full article
(This article belongs to the Special Issue Advances in Solidification Processing)
Open AccessArticle Role of Alloying Additions in the Solidification Kinetics and Resultant Chilling Tendency and Chill of Cast Iron
Metals 2015, 5(1), 256-288; doi:10.3390/met5010256
Received: 10 January 2015 / Revised: 17 February 2015 / Accepted: 25 February 2015 / Published: 4 March 2015
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Abstract
The present work describes the effect of the solidification processing and alloy chemistry on the chilling tendency index, CT, and the chill, w, of wedge-shaped castings made of cast iron. In this work, theoretical predictions were experimentally verified for the role of elements,
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The present work describes the effect of the solidification processing and alloy chemistry on the chilling tendency index, CT, and the chill, w, of wedge-shaped castings made of cast iron. In this work, theoretical predictions were experimentally verified for the role of elements, such as C, Si, Mn, P and S, on the cast iron CT. In addition, inoculation and fading effects were considered in the experimental outcome. Accordingly, the graphite nucleation coefficients, Ns, b, the eutectic cell growth coefficient, μ, and the critical cooling rate, Qcr, for the development of eutectic cementite (chill) were all determined as a function of the cast iron chemistry and time after inoculation. In particular, it was found that increasing the Mn and S contents, as well as the time after inoculation lowers the critical cooling rate, thus increasing the chilling tendency of the cast iron. In contrast, C, Si and P increase the critical cooling rate, and as a result, they reduce the cast iron CT and chill. Full article
(This article belongs to the Special Issue Advances in Solidification Processing)
Open AccessArticle Canonical Models of Geophysical and Astrophysical Flows: Turbulent Convection Experiments in Liquid Metals
Metals 2015, 5(1), 289-335; doi:10.3390/met5010289
Received: 25 July 2014 / Revised: 2 September 2014 / Accepted: 9 February 2015 / Published: 9 March 2015
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Abstract
Planets and stars are often capable of generating their own magnetic fields. This occurs through dynamo processes occurring via turbulent convective stirring of their respective molten metal-rich cores and plasma-based convection zones. Present-day numerical models of planetary and stellar dynamo action are not
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Planets and stars are often capable of generating their own magnetic fields. This occurs through dynamo processes occurring via turbulent convective stirring of their respective molten metal-rich cores and plasma-based convection zones. Present-day numerical models of planetary and stellar dynamo action are not carried out using fluids properties that mimic the essential properties of liquid metals and plasmas (e.g., using fluids with thermal Prandtl numbers Pr < 1 and magnetic Prandtl numbers Pm ≪ 1). Metal dynamo simulations should become possible, though, within the next decade. In order then to understand the turbulent convection phenomena occurring in geophysical or astrophysical fluids and next-generation numerical models thereof, we present here canonical, end-member examples of thermally-driven convection in liquid gallium, first with no magnetic field or rotation present, then with the inclusion of a background magnetic field and then in a rotating system (without an imposed magnetic field). In doing so, we demonstrate the essential behaviors of convecting liquid metals that are necessary for building, as well as benchmarking, accurate, robust models of magnetohydrodynamic processes in Pm ≪ Pr < 1 geophysical and astrophysical systems. Our study results also show strong agreement between laboratory and numerical experiments, demonstrating that high resolution numerical simulations can be made capable of modeling the liquid metal convective turbulence needed in accurate next-generation dynamo models. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessArticle Measurement and Determination of Friction Characteristic of Air Flow through Porous Media
Metals 2015, 5(1), 336-349; doi:10.3390/met5010336
Received: 8 January 2015 / Revised: 10 February 2015 / Accepted: 2 March 2015 / Published: 9 March 2015
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Abstract
Sintered metal porous media currently plays an important role in air bearing systems. When flowing through porous media, the flow properties are generally represented by incompressible Darcy-Forchheimer regime or Ergun regime. In this study, a modified Ergun equation, which includes air compressibility effects,
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Sintered metal porous media currently plays an important role in air bearing systems. When flowing through porous media, the flow properties are generally represented by incompressible Darcy-Forchheimer regime or Ergun regime. In this study, a modified Ergun equation, which includes air compressibility effects, is developed to describe friction characteristic. Experimental and theoretical investigations on friction characteristic are conducted with a series of metal-sintered porous media. Re = 10 is selected as the boundary for a viscous drag region and a form drag region. Experimental data are first used to determine the coefficient α in the viscous drag region, and then the coefficient β in the form drag region, rather than both simultaneously. Also, the theoretical mass flow rate in terms of the modified Ergun equation provides close approximations to the experimental data. Finally, it is also known that both the air compressibility and inertial effects can obviously enhance the pressure drop. Full article
(This article belongs to the Special Issue Nanoporous Metallic Alloys)
Open AccessArticle Formulation of the Effect of Different Alloying Elements on the Tensile Strength of the in situ Al-Mg2Si Composites
Metals 2015, 5(1), 371-382; doi:10.3390/met5010371
Received: 25 December 2014 / Revised: 2 March 2015 / Accepted: 5 March 2015 / Published: 11 March 2015
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Abstract
In this paper, the effect of different alloying elements on the ultimate tensile strength of Al-Mg2Si composites is theoretically studied. The feed forward back propagation neural network with sigmoid function is used. The extensive experimental results taken from literature are modeled
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In this paper, the effect of different alloying elements on the ultimate tensile strength of Al-Mg2Si composites is theoretically studied. The feed forward back propagation neural network with sigmoid function is used. The extensive experimental results taken from literature are modeled and mathematical formula is presented in explicit form. In addition, it is observed that magnesium and copper have a stronger effect on the ultimate tensile strength of Al-Mg2Si composites comparison to other alloying elements. The proposed model shows good agreement with test results and can be used to find the ultimate tensile strength of Al-Mg2Si composites. Full article
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Open AccessArticle Effects of Rare Earth on the Microstructure and Impact Toughness of H13 Steel
Metals 2015, 5(1), 383-394; doi:10.3390/met5010383
Received: 19 January 2015 / Revised: 15 February 2015 / Accepted: 16 February 2015 / Published: 11 March 2015
Cited by 5 | PDF Full-text (1779 KB) | HTML Full-text | XML Full-text
Abstract
Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM) can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM
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Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM) can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM additions. In this present work, the microstructure evolution and mechanical properties of H13 steel with rare earth additions (0, 0.015, 0.025 and 0.1 wt.%) were investigated. The grain size, inclusions and fracture morphology were systematically studied by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that REM addition of 0.015 wt.% can result in good improvement of performance compared to the REM additions of 0.025 wt.% and 0.1 wt.%. It is found that the impact toughness is significantly enhanced with the addition of 0.015% REM, which can be improved 90% from 10 J to 19 J. Such an addition of REM can result in a huge volume fraction of finer and more dispersive inclusions which are extremely good to toughness. Full article
(This article belongs to the Special Issue Casting Alloy Design and Modification)
Open AccessArticle “High-Throughput” Evaluation of Polymer-Supported Triazolic Appendages for Metallic Cations Extraction
Metals 2015, 5(1), 418-427; doi:10.3390/met5010418
Received: 25 February 2015 / Revised: 5 March 2015 / Accepted: 7 March 2015 / Published: 12 March 2015
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Abstract
The aim of this work was to find and use a low-cost high-throughput method for a quick primary evaluation of several metal extraction by substituted piperazines appendages as chelatants grafted onto Merrifield polymer using click-chemistry by the copper (I)-catalyzed Huisgen’s reaction (CuAAC) The
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The aim of this work was to find and use a low-cost high-throughput method for a quick primary evaluation of several metal extraction by substituted piperazines appendages as chelatants grafted onto Merrifield polymer using click-chemistry by the copper (I)-catalyzed Huisgen’s reaction (CuAAC) The polymers were tested for their efficiency to remove various metal ions from neutral aqueous solutions (13 cations studied: Li+, Na+, K+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Cd2+, Ba2+, Ce3+, Hg+ and Pb2+) using the simple conductimetric measurement method. The polymers were found to extract all metals with low efficiencies ≤40%), except for Fe3+ and Hg+, and sometimes Pb2+. Some polymers exhibited a selectively for K+, Cd2+ and Ba2+, with good efficiencies. The values obtained here using less polymer, and a faster method, are in fair correspondence (average difference ±16%) with another published evaluation by atomic absorption spectroscopy (AAS). Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
Open AccessCommunication Channel Structures Formed in Copper Ingots upon Melting and Evaporation by a High-Power Electron Beam
Metals 2015, 5(1), 428-438; doi:10.3390/met5010428
Received: 5 November 2014 / Revised: 12 February 2015 / Accepted: 5 March 2015 / Published: 12 March 2015
PDF Full-text (1277 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A new phenomenon is described in this paper: the formation of macroscopic channel structures on the bottom of copper ingots which were used as the target for the synthesis of copper nanoparticles by high-power electron beam evaporation and condensation. In the synthesis experiment,
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A new phenomenon is described in this paper: the formation of macroscopic channel structures on the bottom of copper ingots which were used as the target for the synthesis of copper nanoparticles by high-power electron beam evaporation and condensation. In the synthesis experiment, the cylindrical copper ingot is melted and partially evaporated in a graphite crucible. The channel structures were originally observed after a series of nanoparticle synthesis experiments in varying conditions. In the present work, various process conditions are varied in order to recreate the structures and identify their mechanism of formation. Conditions in which the channel structures form and do not form are identified and interesting microstructures are observed near the channel structures. Full article
Open AccessArticle A Study of Calcareous Deposits on Cathodically Protected Mild Steel in Artificial Seawater
Metals 2015, 5(1), 439-456; doi:10.3390/met5010439
Received: 18 December 2014 / Revised: 15 January 2015 / Accepted: 15 February 2015 / Published: 12 March 2015
Cited by 3 | PDF Full-text (933 KB) | HTML Full-text | XML Full-text
Abstract
Calcareous deposits were formed on steel under conditions of cathodic protection in artificial seawater at applied constant current densities ranging from 50 to 400 mA·m2. The calcareous layers were characterized using a Field Emission Gun Scanning Electron Microscope (FEG SEM)
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Calcareous deposits were formed on steel under conditions of cathodic protection in artificial seawater at applied constant current densities ranging from 50 to 400 mA·m2. The calcareous layers were characterized using a Field Emission Gun Scanning Electron Microscope (FEG SEM) in conjunction with Energy Dispersive X-Ray Analysis (EDX), and Electrochemical Impedance Spectroscopy (EIS). At cathodic current densities of 50–100 mA·m2 where corrosion was still occurring, a clear correlation existed between the iron containing corrosion product and the overlying magnesium hydroxide layer. This revealed that the mapping of magnesium rich areas on a steel surface can be used in the identification of local corrosion sites. At current densities of 150–200 mA·m2, a layered deposit was shown to occur consisting of an inner magnesium-containing layer and an outer calcium-containing layer. At current densities of 300–400 mA·m2, intense hydrogen bubbling through macroscopic pores in the deposits gave rise to cracking of the deposited film. Under such conditions deposits do not have a well-defined double layer structure. There is also preferential formation of magnesium-rich compounds near the steel surface at the early stages of polarisation and within the developing pores and cracks of calcareous deposits later on. Based on SEM/EDX investigation of calcareous depositions the impedance model was proposed and used to monitor in situ variations in steel corrosion resistance, and to calculate the thickness of formed deposits using the length of oxygen diffusion paths. Full article
Open AccessArticle A Comparative Characterization of the Microstructures and Tensile Properties of As-Cast and Thixoforged in situ AM60B-10 vol% Mg2Sip Composite and Thixoforged AM60B
Metals 2015, 5(1), 457-470; doi:10.3390/met5010457
Received: 30 December 2014 / Revised: 28 February 2015 / Accepted: 5 March 2015 / Published: 13 March 2015
Cited by 8 | PDF Full-text (1989 KB) | HTML Full-text | XML Full-text
Abstract
The microstructure and tensile properties of the thixoforged in situ Mg2Sip/AM60B composite were characterized in comparison with the as-cast composite and thixoforged AM60B. The results indicate that the morphology of α-Mg phases, the distribution and amount of β phases
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The microstructure and tensile properties of the thixoforged in situ Mg2Sip/AM60B composite were characterized in comparison with the as-cast composite and thixoforged AM60B. The results indicate that the morphology of α-Mg phases, the distribution and amount of β phases and the distribution and morphology of Mg2Si particles in thixoforged composite are completely different from those in as-cast composite. The Mg2Si particles block heat transfer and prevent the α-Mg particles from rotation or migration during reheating. Both the thixoforged composite and thixoforged AM60B alloy exhibit virtually no porosity in the microstructure. The thixoforged composite has the highest comprehensive tensile properties (ultimate tensile strength (UTS)) of 209 MPa and an elongation of 10.2%. The strengthening mechanism of the Mg2Si particle is the additive or synergetic effect of combining the load transfer mechanism, the Orowan looping mechanism and the dislocation strengthening mechanism. Among them, the load transfer mechanism is the main mechanism, and the latter two are minor. The particle splitting and interfacial debonding are the main damage patterns of the composite. Full article
(This article belongs to the Special Issue Casting Alloy Design and Modification)
Open AccessArticle Experimental Investigation of the Equal Channel Forward Extrusion Process
Metals 2015, 5(1), 471-483; doi:10.3390/met5010471
Received: 3 February 2015 / Revised: 3 March 2015 / Accepted: 3 March 2015 / Published: 16 March 2015
Cited by 2 | PDF Full-text (939 KB) | HTML Full-text | XML Full-text
Abstract
Among all recognized severe plastic deformation techniques, a new method, called the equal channel forward extrusion process, has been experimentally studied. It has been shown that this method has similar characteristics to other severe plastic deformation methods, and the potential of this new
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Among all recognized severe plastic deformation techniques, a new method, called the equal channel forward extrusion process, has been experimentally studied. It has been shown that this method has similar characteristics to other severe plastic deformation methods, and the potential of this new method was examined on the mechanical properties of commercial pure aluminum. The results indicate that approximate 121%, 56%, and 84% enhancements, at the yield strength, ultimate tensile strength, and Vickers micro-hardness measurement are, respectively, achieved after the fourth pass, in comparison with the annealed condition. The results of drop weight impact test showed that the increment of 26% at the impact force, and also decreases of 32%, 15%, and 4% at the deflection, impulse, and absorbed energy, are respectively attained for the fourth pass when compared to the annealed condition. Furthermore, the electron backscatter diffraction examination revealed that the average grain size of the final pass is about 480 nm. Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available

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Open AccessReview Mechanical Properties of Magnesium-Rare Earth Alloy Systems: A Review
Metals 2015, 5(1), 1-39; doi:10.3390/met5010001
Received: 4 November 2014 / Accepted: 15 December 2014 / Published: 23 December 2014
Cited by 19 | PDF Full-text (1420 KB) | HTML Full-text | XML Full-text
Abstract
Magnesium-rare earth based alloys are increasingly being investigated due to the formation of highly stable strengthening phases, activation of additional deformation modes and improvement in mechanical properties. Several investigations have been done to study the effect of rare earths when they are alloyed
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Magnesium-rare earth based alloys are increasingly being investigated due to the formation of highly stable strengthening phases, activation of additional deformation modes and improvement in mechanical properties. Several investigations have been done to study the effect of rare earths when they are alloyed to pure magnesium and other Mg alloys. In this review, the mechanical properties of the previously investigated different magnesium-rare earth based binary alloys, ternary alloys and other higher alloys with more than three alloying elements are presented. Full article
Open AccessReview Wetting by Liquid Metals—Application in Materials Processing: The Contribution of the Grenoble Group
Metals 2015, 5(1), 350-370; doi:10.3390/met5010350
Received: 4 February 2015 / Revised: 24 February 2015 / Accepted: 1 March 2015 / Published: 10 March 2015
Cited by 14 | PDF Full-text (1236 KB) | HTML Full-text | XML Full-text
Abstract
The wettability of ceramics by liquid metals is discussed from both the fundamental point of view and the point of view of applications. The role of interfacial reactions (simple dissolution of the solid in the liquid or formation of a layer of a
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The wettability of ceramics by liquid metals is discussed from both the fundamental point of view and the point of view of applications. The role of interfacial reactions (simple dissolution of the solid in the liquid or formation of a layer of a new compound) is illustrated and analysed. Several results are presented in order to illustrate the role of wettability in materials processing, namely infiltration processing, joining dissimilar materials by brazing and selecting crucibles for crystallising liquid metals and semiconductors. The review includes results obtained during the last 15 years mainly, but not only, by the Grenoble group. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessReview Temperature-Induced Liquid-Liquid Transition in Metallic Melts: A Brief Review on the New Physical Phenomenon
Metals 2015, 5(1), 395-417; doi:10.3390/met5010395
Received: 30 November 2014 / Revised: 17 February 2015 / Accepted: 1 March 2015 / Published: 11 March 2015
Cited by 9 | PDF Full-text (1664 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Understanding the nature of liquid structures and properties remains an open problem for many fundamental and applied fields. It is well known that there is no other defined phase line above liquidus (TL) in phase diagrams of ordinary alloys. However,
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Understanding the nature of liquid structures and properties remains an open problem for many fundamental and applied fields. It is well known that there is no other defined phase line above liquidus (TL) in phase diagrams of ordinary alloys. However, via resorts of internal friction, electric resistivity, thermal analysis, X-ray diffraction, solidification, etc., the results of our research on lots of single- and multiple-component melts show a novel physical image: temperature induced liquid-liquid structure transition (TI-LLST) can occur above TL. Moreover, the solidification behaviors and structures out of the melts that experienced TI-LLST are distinct from those out of the melts before TI-LLST. In this paper, some typical examples of TI-LLST and characteristic aspects of the TI-LLST are briefly reviewed, in which the main contents are limited in our own achievements, although other groups have also observed similar phenomena using different methods. In the sense of phenomenology, TI-LLST reported here is quite different from other recognized liquid transitions, i.e., there are only a few convincing cases of liquid P, Si, C, H2O, Al2O3-Y2O3, etc. in which the transition occurs, either induced by pressure or at a supercooled state and near liquidus. Full article
(This article belongs to the Special Issue Liquid Metals)

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