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Metals, Volume 4, Issue 4 (December 2014), Pages 465-646

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Research

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Open AccessArticle Production of Liquid Metal Spheres by Molding
Metals 2014, 4(4), 465-476; doi:10.3390/met4040465
Received: 1 August 2014 / Revised: 18 September 2014 / Accepted: 8 October 2014 / Published: 15 October 2014
Cited by 12 | PDF Full-text (958 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper demonstrates a molding technique for producing spheres composed of eutectic gallium-indium (EGaIn) with diameters ranging from hundreds of microns to a couple millimeters. The technique starts by spreading EGaIn across an elastomeric sheet featuring cylindrical reservoirs defined by replica molding. The
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This paper demonstrates a molding technique for producing spheres composed of eutectic gallium-indium (EGaIn) with diameters ranging from hundreds of microns to a couple millimeters. The technique starts by spreading EGaIn across an elastomeric sheet featuring cylindrical reservoirs defined by replica molding. The metal flows into these features during spreading. The spontaneous formation of a thin oxide layer on the liquid metal keeps the metal flush inside these reservoirs. Subsequent exposure to acid removes the oxide and causes the metal to bead up into a sphere with a size dictated by the volume of the reservoirs. This technique allows for the production and patterning of droplets with a wide range of volumes, from tens of nanoliters up to a few microliters. EGaIn spheres can be embedded or encased subsequently in polymer matrices using this technique. These spheres may be useful as solder bumps, electrodes, thermal contacts or components in microfluidic devices (valves, switches, pumps). The ease of parallel-processing and the ability to control the location of the droplets during their formation distinguishes this technique. Full article
(This article belongs to the Special Issue Liquid Metals)
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Open AccessArticle Correlation vs. Causation: The Effects of Ultrasonic Melt Treatment on Cast Metal Grain Size
Metals 2014, 4(4), 477-489; doi:10.3390/met4040477
Received: 11 July 2014 / Revised: 16 September 2014 / Accepted: 22 October 2014 / Published: 29 October 2014
Cited by 5 | PDF Full-text (795 KB) | HTML Full-text | XML Full-text
Abstract
Interest in ultrasonic treatment of liquid metal has waxed and waned for nearly 80 years. A review of several experiments representative of ultrasonic cavitation treatment of Al and Mg alloys shows that the theoretical mechanisms thought to be responsible for grain refinement are
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Interest in ultrasonic treatment of liquid metal has waxed and waned for nearly 80 years. A review of several experiments representative of ultrasonic cavitation treatment of Al and Mg alloys shows that the theoretical mechanisms thought to be responsible for grain refinement are (1) cavitation-induced increase in melting temperature predicted by the Clausius-Clapeyron equation and (2) cavitation-induced wetting of otherwise unwetted insoluble particles. Neither of these theoretical mechanisms can be directly confirmed by experiment, and though they remain speculative, the available literature generally assumes that one or the other or both mechanisms are active. However, grain size is known to depend on temperature of the liquid, temperature of the mold, and cooling rate of the entire system. From the reviewed experiments, it is difficult to isolate temperature and cooling rate effects on grain size from the theoretical effects. Ultrasonic treatments of Al-A356 were carried out to isolate such effects, and though it was found that ultrasound produced significant grain refinement, the treatments also significantly chilled the liquid and thereby reduced the pouring temperature. The grain sizes attained closely correlated with pouring temperature suggesting that ultrasonic grain refinement is predominantly a result of heat removal by the horn and ultrasonic stirring. Full article
Open AccessArticle Laser Driven Compression to Investigate Shock-Induced Melting of Metals
Metals 2014, 4(4), 490-502; doi:10.3390/met4040490
Received: 19 September 2014 / Revised: 11 October 2014 / Accepted: 22 October 2014 / Published: 30 October 2014
Cited by 4 | PDF Full-text (2184 KB) | HTML Full-text | XML Full-text
Abstract
High pressure shock compression induces a large temperature increase due to the dissipation within the shock front. Hence, a solid sample subjected to intense shock loading can melt, partially or fully, either on compression or upon release from the shocked state. In particular,
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High pressure shock compression induces a large temperature increase due to the dissipation within the shock front. Hence, a solid sample subjected to intense shock loading can melt, partially or fully, either on compression or upon release from the shocked state. In particular, such melting is expected to be associated with specific damage and fragmentation processes following shock propagation. In this paper, we show that laser driven shock experiments can provide a procedure to investigate high pressure melting of metals at high strain rates, which is an issue of key interest for various engineering applications as well as for geophysics. After a short description of experimental and analytical tools, we briefly review some former results reported for tin, then we present more recent observations for aluminum and iron. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessArticle Design of a Nickel-Based Bond-Coat Alloy for Thermal Barrier Coatings on Copper Substrates
Metals 2014, 4(4), 503-518; doi:10.3390/met4040503
Received: 15 September 2014 / Revised: 22 October 2014 / Accepted: 23 October 2014 / Published: 6 November 2014
Cited by 3 | PDF Full-text (5429 KB) | HTML Full-text | XML Full-text
Abstract
To increase the lifetime of rocket combustion chambers, thermal barrier coatings (TBC) may be applied on the copper chamber wall. Since standard TBC systems used in gas turbines are not suitable for rocket-engine application and fail at the interface between the substrate and
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To increase the lifetime of rocket combustion chambers, thermal barrier coatings (TBC) may be applied on the copper chamber wall. Since standard TBC systems used in gas turbines are not suitable for rocket-engine application and fail at the interface between the substrate and bond coat, a new bond-coat material has to be designed. This bond-coat material has to be chemically compatible to the copper substrate to improve the adhesion and needs a coefficient of thermal expansion close to that of copper to reduce thermal stresses. One approach to achieve this is to modify the standard NiCrAlY alloy used in gas turbines by adding copper. In this work, the influence of copper on the microstructure of NiCrAlY-alloys is investigated with thermodynamical calculations, optical microscopy, SEM, EDX and calorimetry. Adding copper leads to the formation of a significant amount of \(\beta\) and \(\alpha\) Reducing the aluminum and chromium content leads furthermore to a two-phase fcc microstructure. Full article
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Open AccessArticle Predicting Composition Dependence of Glass Forming Ability in Ternary Al-Cu-Y System by Thermodynamic Calculation
Metals 2014, 4(4), 519-529; doi:10.3390/met4040519
Received: 22 September 2014 / Revised: 14 October 2014 / Accepted: 10 November 2014 / Published: 21 November 2014
Cited by 3 | PDF Full-text (808 KB) | HTML Full-text | XML Full-text
Abstract
The composition dependence of glass forming ability in the ternary Al-Cu-Y system is predicted by thermodynamic calculations based on the Miedema’s model and Alonso’s method. By comparing the relative energetic status of the amorphous phase versus the solid solution phase, a hexagonal composition
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The composition dependence of glass forming ability in the ternary Al-Cu-Y system is predicted by thermodynamic calculations based on the Miedema’s model and Alonso’s method. By comparing the relative energetic status of the amorphous phase versus the solid solution phase, a hexagonal composition region that energetically favoring the metallic glass formation is predicted. The glass formation driving force and crystallization resistance are further calculated and the composition of Al72Cu10Y18 is pinpointed with the largest glass forming ability in the Al-Cu-Y system. The calculation results are well supported by the experimental observations reported in the literature. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessArticle Dynamic and Thermal Properties of Aluminum Alloy A356/Silicon Carbide Hollow Particle Syntactic Foams
Metals 2014, 4(4), 530-548; doi:10.3390/met4040530
Received: 8 August 2014 / Revised: 27 November 2014 / Accepted: 27 November 2014 / Published: 2 December 2014
Cited by 13 | PDF Full-text (2096 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum alloy A356 matrix syntactic foams filled with SiC hollow particles (SiCHP) are studied in the present work. Two compositions of syntactic foams are studied for quasi-static and high strain rate compression. In addition, dynamic mechanical analysis is conducted to study
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Aluminum alloy A356 matrix syntactic foams filled with SiC hollow particles (SiCHP) are studied in the present work. Two compositions of syntactic foams are studied for quasi-static and high strain rate compression. In addition, dynamic mechanical analysis is conducted to study the temperature dependent energy dissipation and damping capabilities of these materials. The thermal characterization includes study of the coefficient of thermal expansion (CTE). A356/SiCHP syntactic foams are not strain rate sensitive as the compressive strength displayed little variation between the tested strain rates of 0.001–2100 s−1. Microscopic analysis of the high strain rate compression tested specimens showed that the fracture is initiated by the failure of hollow particles at the onset of the plastic deformation region. This is followed by plastic deformation of the matrix material and further crushing of particles. The syntactic foams showed decrease in storage modulus with increasing temperature and the trend was nearly linear up to 500 °C. The alloy shows a similar behavior at low temperature but the decrease in storage modulus increases sharply over 375 °C. The loss modulus is very small for the tested materials because of lack of viscoelasticity in metallic materials. The trend in the loss modulus is opposite, where the matrix alloy has lower loss modulus than syntactic foams at low temperature. However, over 250 °C the matrix loss modulus starts to increase rapidly and attains a peak around 460 °C. Syntactic foams have higher damping parameter at low temperatures than the matrix alloy. Incorporation of SiCHP helps in decreasing CTE. Compared to the CTE of the matrix alloy, 23.4 × 10−6 °C−1, syntactic foams showed CTE values as low as 11.67 × 10−6 °C−1. Full article
Open AccessArticle Estimating the Energy State of Liquids
Metals 2014, 4(4), 570-585; doi:10.3390/met4040570
Received: 23 October 2014 / Revised: 26 November 2014 / Accepted: 2 December 2014 / Published: 8 December 2014
Cited by 2 | PDF Full-text (678 KB) | HTML Full-text | XML Full-text
Abstract
In contrast to the gaseous and the solid states, the liquid state does not have a simple model that could be developed into a quantitative theory. A central issue in the understanding of liquids is to estimate the energy state of liquids. Here,
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In contrast to the gaseous and the solid states, the liquid state does not have a simple model that could be developed into a quantitative theory. A central issue in the understanding of liquids is to estimate the energy state of liquids. Here, on the basis of our recent studies on crystal melting, we show that the energy sate of liquids may be reasonably approximated by the energy and volume of a vacancy. Consequently, estimation of the liquid state energy is significantly simplified comparing with previous methods that inevitably invoke many-body interactions. Accordingly, a possible equation for the state for liquids is proposed. On this basis, it seems that a simple model for liquids is in sight. Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessArticle Grain Refinement and High-Performance of Equal-Channel Angular Pressed Cu-Mg Alloy for Electrical Contact Wire
Metals 2014, 4(4), 586-596; doi:10.3390/met4040586
Received: 29 October 2014 / Revised: 25 November 2014 / Accepted: 3 December 2014 / Published: 9 December 2014
Cited by 4 | PDF Full-text (1227 KB) | HTML Full-text | XML Full-text
Abstract
Multi-pass equal-channel angular pressing (EACP) was applied to produce ultrafine-grained (UFG) Cu-0.2wt%Mg alloy contact wire with high mechanical/electric performance, aim to overcome the catenary barrier of high-speed trains by maximizing the tension and improving the power delivery. Microstructure evolution and overall properties of
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Multi-pass equal-channel angular pressing (EACP) was applied to produce ultrafine-grained (UFG) Cu-0.2wt%Mg alloy contact wire with high mechanical/electric performance, aim to overcome the catenary barrier of high-speed trains by maximizing the tension and improving the power delivery. Microstructure evolution and overall properties of the Cu-Mg alloy after different severe-plastic-deformation (SPD) routes were investigated by microscopic observation, tensile and electric tests. The results show that the Cu-Mg alloy after multi-pass ECAP at 473 K obtains ultrafine grains, higher strength and desired conductivity. More passes of ECAP leads to finer grains and higher strength, but increasing ECAP temperature significantly lower the strength increment of the UFG alloy. Grain refinement via continuous SPD processing can endow the Cu-Mg alloy superior strength and good conductivity characteristics, which are advantageous to high-speed electrification railway systems. Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available
Open AccessArticle Corrosion and Serration Behaviors of TiZr0.5NbCr0.5VxMoy High Entropy Alloys in Aqueous Environments
Metals 2014, 4(4), 597-608; doi:10.3390/met4040597
Received: 4 November 2014 / Revised: 2 December 2014 / Accepted: 11 December 2014 / Published: 15 December 2014
Cited by 11 | PDF Full-text (1793 KB) | HTML Full-text | XML Full-text
Abstract
The corrosion and serration behaviors of TiZr0.5NbCr0.5, TiZr0.5NbCr0.5V and TiZr0.5NbCr0.5Mo high entropy alloys (HEAs) in NaCl and H2SO4 solutions were studied by potentiodynamic polarizations (PP) and immersion tests.
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The corrosion and serration behaviors of TiZr0.5NbCr0.5, TiZr0.5NbCr0.5V and TiZr0.5NbCr0.5Mo high entropy alloys (HEAs) in NaCl and H2SO4 solutions were studied by potentiodynamic polarizations (PP) and immersion tests. The results show that all the alloys display excellent corrosion resistance no matter in NaCl solution or in H2SO4 solution. The additions of V and Mo increase the pitting corrosion resistance for the three alloys in NaCl solution slightly and greatly improve the corrosion resistance in H2SO4 solution. The corrosion behaviors of TiZr0.5NbCr0.5 and TiZr0.5NbCr0.5Mo alloys are more sensitive to temperature than that of TiZr0.5NbCr0.5V alloy. After immersion, the surface of TiZr0.5NbCr0.5 alloy appears some pitting holes, this may be related to the electrochemical noise and serration behavior on PP curves; localized corrosion initiates mainly on the boundaries of the BCC and Cr2Zr Laves phase for TiZr0.5NbCr0.5V alloy; while for the TiZr0.5NbCr0.5Mo alloy, the dendrites with Mo element rich region exhibit poor corrosion resistance. Full article
Open AccessArticle Magnetic Field-Induced Reverse Martensitic Transformation and Thermal Transformation Arrest Phenomenon of Ni41Co9Mn39Sb11 Alloy
Metals 2014, 4(4), 609-622; doi:10.3390/met4040609
Received: 11 November 2014 / Revised: 1 December 2014 / Accepted: 3 December 2014 / Published: 18 December 2014
Cited by 4 | PDF Full-text (1107 KB) | HTML Full-text | XML Full-text
Abstract
In order to investigate behavior of magnetic field-induced reverse martensitic transformation for Ni-Co-Mn-Sb, magnetization experiments up to a static magnetic field of 18 T and a pulsed magnetic field of 40 T were carried out. In the thermomagnetization curves for Ni41Co
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In order to investigate behavior of magnetic field-induced reverse martensitic transformation for Ni-Co-Mn-Sb, magnetization experiments up to a static magnetic field of 18 T and a pulsed magnetic field of 40 T were carried out. In the thermomagnetization curves for Ni41Co9Mn39Sb11 alloy, the equilibrium transformation temperature T0 was observed to decrease with increasing applied magnetic field, μ0H, at a rate of dT0/dμ0H = 4.6 K/T. The estimated value of entropy change evaluated from the Clausius-Clapeyron relation was about 14.1 J/(K·kg), which was in good agreement with the value obtained by differential scanning calorimetric measurements. For the isothermal magnetization curves, metamagnetic behavior associated with the magnetic field-induced martensitic transformation was observed. The equilibrium magnetic field, μ0H0 = (μ0HAf + μ0HMs)/2, of the martensitic transformation tended to be saturated at lower temperature; that is, transformation arrest phenomenon was confirmed for the Ni-Co-Mn-Sb system, analogous with the Ni(Co)-Mn-Z (Z = In, Sn, Ga, Al) alloys. Temperature dependence of the magnetic field hysteresis, μ0Hhys = μ0HAf − μ0HMs, was analyzed based on the model for the plastic deformation introduced by the dislocations. The behavior can be explained by the model and the difference of the sweeping rate of the applied magnetic field was well reflected by the experimental results. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2014)
Open AccessArticle Vaporization and Poor Wettability as the Main Challenges in Fabrication of TiB2-Cu Cermets Studied by SPS
Metals 2014, 4(4), 623-638; doi:10.3390/met4040623
Received: 31 October 2014 / Revised: 9 December 2014 / Accepted: 11 December 2014 / Published: 19 December 2014
PDF Full-text (1767 KB) | HTML Full-text | XML Full-text
Abstract
TiB2-Cu cermets with various volume fractions of copper (from 3 to 30 vol. %) were produced via liquid phase sintering at the temperature range 1100–1200 °C in vacuum using spark plasma sintering (SPS) technique. Full densification could not be achieved as
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TiB2-Cu cermets with various volume fractions of copper (from 3 to 30 vol. %) were produced via liquid phase sintering at the temperature range 1100–1200 °C in vacuum using spark plasma sintering (SPS) technique. Full densification could not be achieved as the consequence of poor wettability and vaporizing Cu. The quantitative Rietveld analysis indicated that insignificant reduction in Cu content occurred only in sample with initially 3 vol. % of Cu, but then densification was negligible. The relative density improved along with increasing volume content of Cu (10–20 vol. %), but then predominant amount of Cu introduced was reduced as the effect of vaporization or swelling, which caused that pellet with intended 20 or 30 vol. % of Cu contained respectively only 6 or 17 vol. % after sintering. Moreover, Cu droplets were released from the die at the temperature of 1000–1030 °C near the Cu melting point. The effect of vaporization was successfully reduced by increased heating rate and when isothermal annealing process was skipped, however, it could not be entirely eliminated. The experimental results on Cu vaporization are confronted with parameters that are commonly considered in the production of cermets, such as oxidation, wettability, contact angle and viscosity as well as their impact on densification. Full article
(This article belongs to the Special Issue Advances in Cermets)
Open AccessArticle Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium
Metals 2014, 4(4), 639-646; doi:10.3390/met4040639
Received: 8 October 2014 / Revised: 29 October 2014 / Accepted: 16 December 2014 / Published: 22 December 2014
Cited by 3 | PDF Full-text (906 KB) | HTML Full-text | XML Full-text
Abstract
This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al) in comparison to an anodizing process (NaTESi process). The
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This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al) in comparison to an anodizing process (NaTESi process). The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO) as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process. Full article
(This article belongs to the Special Issue Titanium Alloys)

Review

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Open AccessReview Titanium Implant Osseointegration Problems with Alternate Solutions Using Epoxy/Carbon-Fiber-Reinforced Composite
Metals 2014, 4(4), 549-569; doi:10.3390/met4040549
Received: 29 October 2014 / Revised: 19 November 2014 / Accepted: 24 November 2014 / Published: 5 December 2014
Cited by 7 | PDF Full-text (1466 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with
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The aim of the article is to present recent developments in material research with bisphenyl-polymer/carbon-fiber-reinforced composite that have produced highly influential results toward improving upon current titanium bone implant clinical osseointegration success. Titanium is now the standard intra-oral tooth root/bone implant material with biocompatible interface relationships that confer potential osseointegration. Titanium produces a TiO2 oxide surface layer reactively that can provide chemical bonding through various electron interactions as a possible explanation for biocompatibility. Nevertheless, titanium alloy implants produce corrosion particles and fail by mechanisms generally related to surface interaction on bone to promote an inflammation with fibrous aseptic loosening or infection that can require implant removal. Further, lowered oxygen concentrations from poor vasculature at a foreign metal surface interface promote a build-up of host-cell-related electrons as free radicals and proton acid that can encourage infection and inflammation to greatly influence implant failure. To provide improved osseointegration many different coating processes and alternate polymer matrix composite (PMC) solutions have been considered that supply new designing potential to possibly overcome problems with titanium bone implants. Now for important consideration, PMCs have decisive biofunctional fabrication possibilities while maintaining mechanical properties from addition of high-strengthening varied fiber-reinforcement and complex fillers/additives to include hydroxyapatite or antimicrobial incorporation through thermoset polymers that cure at low temperatures. Topics/issues reviewed in this manuscript include titanium corrosion, implant infection, coatings and the new epoxy/carbon-fiber implant results discussing osseointegration with biocompatibility related to nonpolar molecular attractions with secondary bonding, carbon fiber in vivo properties, electrical semiconductors, stress transfer, additives with low thermal PMC processing and new coating possibilities. Full article
(This article belongs to the Special Issue Titanium Alloys)
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