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Metals, Volume 5, Issue 4 (December 2015) , Pages 1770-2434

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Open AccessArticle Hot Ductility Loss in a Fe-Ni-Based Superalloy
Metals 2015, 5(4), 2428-2434; https://doi.org/10.3390/met5042428
Received: 31 October 2015 / Revised: 29 November 2015 / Accepted: 15 December 2015 / Published: 21 December 2015
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Abstract
High temperature tensile tests have been conducted on samples of a Fe-Ni based superalloy, Incoloy A-286, and significant ductility loss has been observed at 1220 °C. Titanium-rich, thin-film-like phase has been found on the inter-granular facets of fracture surfaces. It appears that sulfur [...] Read more.
High temperature tensile tests have been conducted on samples of a Fe-Ni based superalloy, Incoloy A-286, and significant ductility loss has been observed at 1220 °C. Titanium-rich, thin-film-like phase has been found on the inter-granular facets of fracture surfaces. It appears that sulfur content of Ti-rich phase was higher than that of the matrix. At 1220 °C, liquation of Ti-rich phases has resulted in thin-film-like morphology along the grain boundary and caused the ductility loss during tensile deformation. Full article
(This article belongs to the Special Issue Superalloys)
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Open AccessArticle Direct Aqueous Mineral Carbonation of Waste Slate Using Ammonium Salt Solutions
Metals 2015, 5(4), 2413-2427; https://doi.org/10.3390/met5042413
Received: 18 October 2015 / Revised: 9 December 2015 / Accepted: 15 December 2015 / Published: 18 December 2015
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Abstract
The carbonation of asbestos-containing waste slate using a direct aqueous mineral carbonation method was evaluated. Leaching and carbonation tests were conducted on asbestos-containing waste slate using ammonium salt (CH3COONH4, NH4NO3, and NH4HSO4) solutions at various concentrations. The CH3COONH4 solution had the highest Ca-leaching [...] Read more.
The carbonation of asbestos-containing waste slate using a direct aqueous mineral carbonation method was evaluated. Leaching and carbonation tests were conducted on asbestos-containing waste slate using ammonium salt (CH3COONH4, NH4NO3, and NH4HSO4) solutions at various concentrations. The CH3COONH4 solution had the highest Ca-leaching efficiency (17%–35%) and the NH4HSO4 solution had the highest Mg-leaching efficiency (7%–24%) at various solid dosages and solvent concentrations. The CaCO3 content of the reacted materials based on thermogravimetric analysis (TGA) was approximately 10%–17% higher than that of the as-received material for the 1 M CH3COONH4 and the 1 M NH4HSO4 solutions. The carbonates were precipitated on the surface of chrysotile, which was contained in the waste slate reacted with CO2. These results imply that CO2 can be sequestered by a direct aqueous mineral carbonation using waste slate. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Preparation and Characteristics of γ-Fe2O3/Polyaniline-Curcumin Composites
Metals 2015, 5(4), 2401-2412; https://doi.org/10.3390/met5042401
Received: 18 November 2015 / Revised: 7 December 2015 / Accepted: 11 December 2015 / Published: 17 December 2015
Cited by 6 | Viewed by 1584 | PDF Full-text (852 KB) | HTML Full-text | XML Full-text
Abstract
Superparamagnetic nanomaterials are showing great prospects in medical treatments with targeting medicines. A new conductive superparamagnetic nanocomposite, γ-Fe2O3/polyaniline-curcumin (γ-Fe2O3/PANI-curcumin), was prepared by using the interaction between an amino group in polyaniline and a ketone group [...] Read more.
Superparamagnetic nanomaterials are showing great prospects in medical treatments with targeting medicines. A new conductive superparamagnetic nanocomposite, γ-Fe2O3/polyaniline-curcumin (γ-Fe2O3/PANI-curcumin), was prepared by using the interaction between an amino group in polyaniline and a ketone group in curcumin. The γ-Fe2O3/PANI-curcumin nanocomposite showed superparamagnetism (30 emu·g−1) and electrochemical activity, based on the results of magnetization curve and cyclic voltammetry (CV). Transmission electron microscope (TEM) indicated that the particle size of γ-Fe2O3/PANI-curcumin was between 10 and 50 nm. Fourier transform infrared spectra (FT-IR) and X-ray diffraction (XRD) were used to characterize the γ-Fe2O3/PANI-curcumin nanocomposite, confirming that curcumin was immobilized into the γ-Fe2O3/PANI chain. This study provided an academic foundation for developing a new material for immobilizing an anticancer drug. Full article
(This article belongs to the Special Issue Synthetic Metals)
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Open AccessEditorial Metallic Glasses
Metals 2015, 5(4), 2397-2400; https://doi.org/10.3390/met5042397
Received: 15 December 2015 / Accepted: 15 December 2015 / Published: 16 December 2015
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Abstract
Metallic glasses are a fascinating class of metallic materials that do not display long-range atomic order. [...] Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
Open AccessEditorial Ultrafine-Grained Metals
Metals 2015, 5(4), 2393-2396; https://doi.org/10.3390/met5042393
Received: 10 December 2015 / Accepted: 10 December 2015 / Published: 16 December 2015
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Abstract
Ultrafine-grained (UFG) metallic materials are at the cutting edge of modern materials science as they exhibit outstanding properties which make them very interesting for prospective structural or functional engineering applications. [...] Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available
Open AccessArticle A Simple Up-Scalable Thermal Treatment Method for Synthesis of ZnO Nanoparticles
Metals 2015, 5(4), 2383-2392; https://doi.org/10.3390/met5042383
Received: 9 October 2015 / Revised: 3 December 2015 / Accepted: 8 December 2015 / Published: 14 December 2015
Cited by 21 | Viewed by 1832 | PDF Full-text (460 KB) | HTML Full-text | XML Full-text
Abstract
A simple thermal treatment method, utilizing only zinc nitrate, polyvinyl pyrrolidone (PVP), and deionized water, was used to synthesize ZnO nanoparticles, and their characteristics were investigated by various techniques. The TGA measurement demonstrated that the bulk of the capping agent PVP can be [...] Read more.
A simple thermal treatment method, utilizing only zinc nitrate, polyvinyl pyrrolidone (PVP), and deionized water, was used to synthesize ZnO nanoparticles, and their characteristics were investigated by various techniques. The TGA measurement demonstrated that the bulk of the capping agent PVP can be removed at temperatures higher than 500 °C and is consistent with the absence of the majority of PVP absorption peaks in the FT-IR spectra. The formation of almost pure ZnO nanoparticles was established by the presence of single absorption peak in the FT-IR spectra due to being only Zn–O bonds at calcination temperatures of 500 °C and above. The TEM images revealed that the nanoparticles have a spherical shape and the particle size increased from 60.1–83.1 nm with an increase in calcination temperatures from 500–600 °C. The XRD diffraction patterns indicated that the particles are of a wurzite lattice structure. The optical properties were determined by UV-Vis spectrophotometer, and it was found that the band gap of ZnO nanoparticles decreased from 3.249–3.239 eV with an increase in calcination temperature from 500–600 °C. Full article
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Open AccessArticle Galvanic Corrosion between Alloy 690 and Magnetite in Alkaline Aqueous Solutions
Metals 2015, 5(4), 2372-2382; https://doi.org/10.3390/met5042372
Received: 15 October 2015 / Revised: 18 November 2015 / Accepted: 9 December 2015 / Published: 14 December 2015
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Abstract
The galvanic corrosion behavior of Alloy 690 coupled with magnetite has been investigated in an alkaline solution at 30 °C and 60 °C using a potentiodynamic polarization method and a zero resistance ammeter. The positive current values were recorded in the galvanic couple [...] Read more.
The galvanic corrosion behavior of Alloy 690 coupled with magnetite has been investigated in an alkaline solution at 30 °C and 60 °C using a potentiodynamic polarization method and a zero resistance ammeter. The positive current values were recorded in the galvanic couple and the corrosion potential of Alloy 690 was relatively lower. These results indicate that Alloy 690 behaves as the anode of the pair. The galvanic coupling between Alloy 690 and magnetite increased the corrosion rate of Alloy 690. The temperature increase led to an increase in the extent of galvanic effect and a decrease in the stability of passive film. Galvanic effect between Alloy 690 and magnetite is proposed as an additional factor accelerating the corrosion rate of Alloy 690 steam generator tubing in secondary water. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessComment Comments on Lynch. Pyrrolyl Squaraines—Fifty Golden Years. Metals 2015, 5, 1349–1370
Metals 2015, 5(4), 2370-2371; https://doi.org/10.3390/met5042370
Received: 7 December 2015 / Accepted: 9 December 2015 / Published: 14 December 2015
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Abstract
In addition to the papers referenced in the main article [1]; [...] Full article
(This article belongs to the Special Issue Synthetic Metals)
Open AccessArticle Damage Analysis of a Ferritic SiMo Ductile Cast Iron Submitted to Tension and Compression Loadings in Temperature
Metals 2015, 5(4), 2351-2369; https://doi.org/10.3390/met5042351
Received: 9 November 2015 / Revised: 30 November 2015 / Accepted: 4 December 2015 / Published: 10 December 2015
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Abstract
Tensile and compression tests were carried out on a ductile cast iron for temperatures up to 1073 K. The damage caused inside and around graphite nodules was evaluated as a function of the local equivalent plastic strain by using microstructural quantifications. The mechanical [...] Read more.
Tensile and compression tests were carried out on a ductile cast iron for temperatures up to 1073 K. The damage caused inside and around graphite nodules was evaluated as a function of the local equivalent plastic strain by using microstructural quantifications. The mechanical properties are strongly dependent on a temperature above 773 K. Concerning tensile behavior, an evolutional law issued from the Gurson model representing the void growth as a function of the deformation and temperature was successfully employed. It is demonstrated that the strain state and the temperature have a strong influence on the void growth function. In the case of compression tests, the temperature has a weak influence on the nodule deformation for temperatures lower than 773 K, and the mechanical behavior is driven by the viscoplastic properties of the ferrite. For higher temperatures, the mechanical properties in compression are progressively modified, since graphite nodules tend to remain spherical, and ferrite grains are severely deformed. A synthesis of the damage mechanisms is proposed in the studied range of temperature and plastic strain. It appears that the graphite nodule aspect ratio can be used as an indicator of the deformation under compression loading for temperatures ranging from room temperature to 673 K. Full article
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Open AccessArticle Forge-Hardened TiZr Null-Matrix Alloy for Neutron Scattering under Extreme Conditions
Metals 2015, 5(4), 2340-2350; https://doi.org/10.3390/met5042340
Received: 8 October 2015 / Revised: 2 December 2015 / Accepted: 7 December 2015 / Published: 9 December 2015
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Abstract
For neutron scattering research that is performed under extreme conditions, such as high static pressures, high-strength metals that are transparent to the neutron beam are required. The diffraction of the neutron beam by the metal, which follows Bragg’s law, can be completely removed [...] Read more.
For neutron scattering research that is performed under extreme conditions, such as high static pressures, high-strength metals that are transparent to the neutron beam are required. The diffraction of the neutron beam by the metal, which follows Bragg’s law, can be completely removed by alloying two metallic elements that have coherent scattering lengths with opposite signs. An alloy of Ti and Zr, which is known as a TiZr null-matrix alloy, is an ideal combination for such purposes. In this study, we increased the hardness of a TiZr null-matrix alloy via extensive mechanical deformation at high temperatures. We successfully used the resulting product in a high-pressure cell designed for high-static-pressure neutron scattering. This hardened TiZr null-matrix alloy may play a complementary role to normal TiZr alloy in future neutron scattering research under extreme conditions. Full article
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Open AccessArticle Modeling of TiAl Alloy Grating by Investment Casting
Metals 2015, 5(4), 2328-2339; https://doi.org/10.3390/met5042328
Received: 19 October 2015 / Revised: 3 December 2015 / Accepted: 4 December 2015 / Published: 9 December 2015
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Abstract
The investment casting of TiAl alloys has become the most promising cost-effective technique for manufacturing TiAl components. This study aimed to investigate a series of problems associated with the investment casting of TiAl alloys. The mold filling and solidification of this casting model [...] Read more.
The investment casting of TiAl alloys has become the most promising cost-effective technique for manufacturing TiAl components. This study aimed to investigate a series of problems associated with the investment casting of TiAl alloys. The mold filling and solidification of this casting model were numerically simulated using ProCAST. Shrinkage porosity was quantitatively predicted by a built-in feeding criterion. The results obtained from the numerical simulations were compared with experiments, which were carried out on Vacuum Skull Furnace using an investment block mold. The investment casting of TiAl grating was conducted for verifying the correctness and feasibility of the proposed method. The tensile test results indicated that, at room temperature, the tensile strength and elongation were approximately 675 MPa and 1.7%, respectively. The microstructure and mechanical property of the investment cast TiAl alloy were discussed. Full article
(This article belongs to the Special Issue Intermetallics 2016) Printed Edition available
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Open AccessArticle Fatigue Performance of Mg-Zn-Zr Alloy Processed by Hot Severe Plastic Deformation
Metals 2015, 5(4), 2316-2327; https://doi.org/10.3390/met5042316
Received: 9 November 2015 / Revised: 27 November 2015 / Accepted: 4 December 2015 / Published: 8 December 2015
Cited by 10 | Viewed by 1595 | PDF Full-text (934 KB) | HTML Full-text | XML Full-text
Abstract
Fatigue properties under axisymmetric push-pull loading of a magnesium alloy Mg-6Zn-0.5Zr (ZK60) after processing by multiaxial isothermal forging (MIF) to a total strain of 4.2 at 400 °C were investigated. The strong influence of the microstructure on the mechanical behavior is demonstrated. Hot [...] Read more.
Fatigue properties under axisymmetric push-pull loading of a magnesium alloy Mg-6Zn-0.5Zr (ZK60) after processing by multiaxial isothermal forging (MIF) to a total strain of 4.2 at 400 °C were investigated. The strong influence of the microstructure on the mechanical behavior is demonstrated. Hot severe plastic deformation was shown effective in improving the fatigue life in both the high- and low-cyclic regimes. Full article
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Open AccessArticle Palladium(II) Recovery from Hydrochloric Acid Solutions by N,N′-Dimethyl-N,N′-Dibutylthiodiglycolamide
Metals 2015, 5(4), 2303-2315; https://doi.org/10.3390/met5042303
Received: 27 October 2015 / Revised: 24 November 2015 / Accepted: 30 November 2015 / Published: 8 December 2015
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Abstract
N,N′-dimethyl-N,N′-dibutylthiodiglycolamide (DMDBTDGA) has been synthesized, characterized, and is investigated in this work as a potential liquid-liquid extractant for palladium(II), platinum(IV), and rhodium(III) from hydrochloric acid solutions. Pd(II) is the only ion which is efficiently removed by [...] Read more.
N,N′-dimethyl-N,N′-dibutylthiodiglycolamide (DMDBTDGA) has been synthesized, characterized, and is investigated in this work as a potential liquid-liquid extractant for palladium(II), platinum(IV), and rhodium(III) from hydrochloric acid solutions. Pd(II) is the only ion which is efficiently removed by DMDBTDGA in toluene from 1.5 M to 4.5 M HCl, but it is not extracted from 7.5 M HCl. Pd(II) stripping is quantitatively achieved by an acidic thiourea solution. Pd(II) extraction kinetics are highly favored (2–5 min). Distribution data points to a DMDBTDGA:Pd(II) species with a 1:1 molar ratio. Pd(II) can selectively be recovered by DMDBTDGA from 4.0 M HCl complex mixtures containing equivalent concentrations of Pt(IV) and Rh(III). When five-fold Fe(III) and Al(III) concentrations are present, only Pt(IV) in the presence of Fe(III), and Fe(III) itself, are extensively co-extracted together with Pd(II). However, Fe(III) can easily be eliminated through an intermediate scrubbing step with water. Full article
(This article belongs to the Special Issue Hydrometallurgy) Printed Edition available
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Open AccessArticle Corrosion Behavior in 3.5% NaCl Solutions of γ-TiAl Processed by Electron Beam Melting Process
Metals 2015, 5(4), 2289-2302; https://doi.org/10.3390/met5042289
Received: 19 October 2015 / Revised: 22 November 2015 / Accepted: 27 November 2015 / Published: 3 December 2015
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Abstract
In this work, the corrosion behavior of γ-TiAl alloy produced by electron beam melting (EBM) process in 3.5% NaCl solution was reported. The study has been performed using potentiodynamic polarization resistance and electrochemical impedance spectroscopy techniques and complemented by scanning electron microscopy investigations. [...] Read more.
In this work, the corrosion behavior of γ-TiAl alloy produced by electron beam melting (EBM) process in 3.5% NaCl solution was reported. The study has been performed using potentiodynamic polarization resistance and electrochemical impedance spectroscopy techniques and complemented by scanning electron microscopy investigations. All measurements were carried out after different periods of alloy exposure in the chloride solutions and at different temperatures. The results showed that the EBM produced γ-TiAl alloy has excellent corrosion resistance confirmed by the high values of polarization resistance and the low values of corrosion current and corrosion rate. With increase in immersion time, the corrosion potential moved to a higher positive value with a decrease in corrosion current and corrosion rate, which suggests an improvement in corrosion resistance. On the other hand, the increase of temperature was found to significantly increase the corrosion of the processed γ-TiAl alloy. Full article
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Open AccessFeature PaperArticle Effect of Additions of Ceramic Nanoparticles and Gas-Dynamic Treatment on Al Casting Alloys
Metals 2015, 5(4), 2277-2288; https://doi.org/10.3390/met5042277
Received: 18 October 2015 / Revised: 24 November 2015 / Accepted: 27 November 2015 / Published: 3 December 2015
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Abstract
In recent years, improving the mechanical properties of metals has become the main challenge in the modern materials and metallurgical industry. An alloying process is usually used to achieve advanced performance of metals. This paper, however, describes an alternative approach. Modification with ceramic [...] Read more.
In recent years, improving the mechanical properties of metals has become the main challenge in the modern materials and metallurgical industry. An alloying process is usually used to achieve advanced performance of metals. This paper, however, describes an alternative approach. Modification with ceramic nanoparticles, gas-dynamic treatment (GDT) and a combined treatment were investigated on a hypoeutectic Al-Si A356 alloy. Microstructural studies revealed the refinement of coarse α-Al grains and the formation of distributed eutectic Si particles. Subsequent testing of the mechanical properties revealed improvement after applying each of the treatments. The best results were obtained after modification with TiCN nanoparticles followed by GDT; the tensile strength and elongation of the A356 alloys increased by 18% and 19%, respectively. Full article
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Open AccessArticle Synthesis and Characterization of 4-Benzyloxybenzaldehyde-4-methyl-3-thiosemicarbazone (Containing Sulphur and Nitrogen Donor Atoms) and Its Cd(II) Complex
Metals 2015, 5(4), 2266-2276; https://doi.org/10.3390/met5042266
Received: 5 September 2015 / Revised: 12 November 2015 / Accepted: 23 November 2015 / Published: 1 December 2015
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Abstract
A chelating agent, 4-benzyloxybenzaldehyde-4-methyl-3-thiosemicarbazone (BBMTSC), containing sulphur and nitrogen donor atoms was synthesized and applied as a ligand for the chelation of Cd(II). Both the BBMTSC and its Cd(II) complex were characterized by elemental analysis, UV-Vis absorption spectra, Fourier transform infrared spectroscopy (FT-IR), [...] Read more.
A chelating agent, 4-benzyloxybenzaldehyde-4-methyl-3-thiosemicarbazone (BBMTSC), containing sulphur and nitrogen donor atoms was synthesized and applied as a ligand for the chelation of Cd(II). Both the BBMTSC and its Cd(II) complex were characterized by elemental analysis, UV-Vis absorption spectra, Fourier transform infrared spectroscopy (FT-IR), mass spectra, nuclear magnetic resonance spectroscopy (NMR), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FESEM). The FTIR spectra confirmed the formation of both BBMTSC and its Cd(II) complex. XRD revealed the polycrystalline nature of the synthesized compounds. BBMTSC exhibited a flake-like micro-rod morphology, whereas the Cd(II) complex had a flower-like nanorod structure. Full article
(This article belongs to the Special Issue Synthetic Metals)
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Open AccessFeature PaperArticle In Situ High-Energy X-ray Diffraction during Hot-Forming of a Multiphase TiAl Alloy
Metals 2015, 5(4), 2252-2265; https://doi.org/10.3390/met5042252
Received: 28 September 2015 / Revised: 19 November 2015 / Accepted: 23 November 2015 / Published: 30 November 2015
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Abstract
Intermetallic γ-TiAl based alloys exhibit excellent high-temperature strength combined with low density. This makes them ideal candidates for replacing the twice as dense Ni base super-alloys, currently used in the medium temperature range (~700 °C) of industrial and aviation gas turbines. An important [...] Read more.
Intermetallic γ-TiAl based alloys exhibit excellent high-temperature strength combined with low density. This makes them ideal candidates for replacing the twice as dense Ni base super-alloys, currently used in the medium temperature range (~700 °C) of industrial and aviation gas turbines. An important step towards the serial production of TiAl parts is the development of suitable hot-forming processes. Thermo-mechanical treatments often result in mechanical anisotropy due to the formation of crystallographic textures. However, with conventional texture analysis techniques, their formation can only be studied after processing. In this study, in situ high-energy X-ray diffraction measurements with synchrotron radiation were performed during hot-forming. Thus, it was possible to record the evolution of the phase constitution as well as the formation of crystallographic texture of different phases directly during processing. Several process temperatures (1100 °C to 1300 °C) and deformation rates were investigated. Based on these experiments, a process window can be recommended which results in the formation of an optimal reduced texture. Full article
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Open AccessFeature PaperArticle Relationships between Microstructural Parameters and Time-Dependent Mechanical Properties of a New Nickel-Based Superalloy AD730™
Metals 2015, 5(4), 2236-2251; https://doi.org/10.3390/met5042236
Received: 5 November 2015 / Revised: 20 November 2015 / Accepted: 23 November 2015 / Published: 27 November 2015
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Abstract
High temperature creep and dwell-fatigue properties of the new nickel-based superalloy AD730™ have been investigated. Three microstructures have been studied in creep (850 °C and 700 °C) and dwell-fatigue (700 °C stress control with trapezoidal signals, and dwell times ranging from 1 s [...] Read more.
High temperature creep and dwell-fatigue properties of the new nickel-based superalloy AD730™ have been investigated. Three microstructures have been studied in creep (850 °C and 700 °C) and dwell-fatigue (700 °C stress control with trapezoidal signals, and dwell times ranging from 1 s to 3600 s): a coarse grains microstructure, a fine grains one, and single crystalline samples. The aim of this study is to assess the influence of the grain size on creep and creep-fatigue properties. It is demonstrated that fine and coarse grains microstructures perform similarly in creep at 700 °C, showing that the creep properties at this temperature are controlled by the intragranular precipitation. Moreover, both the coarse grains and the fine grains microstructures show changes in creep deformation mechanisms depending on the applied stress in creep at 700 °C. At higher creep temperatures, the coarse grains microstructure performs better and almost no effect is observed by suppressing grain boundaries. During dwell-fatigue tests at 700 °C, a clear effect of the mechanical cycling has been evidenced on the time to failure on both the coarse and the fine grains microstructures. At high applied stresses, a beneficial effect of the cyclic unloading to the lifetime has been observed whereas at lower applied stresses, mechanical cycling is detrimental compared to the pure creep lifetime due to the development of a fatigue damage. Complex creep-fatigue interactions are hence clearly evidenced and they depend on the pure creep behavior reference. Full article
(This article belongs to the Special Issue Superalloys)
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Open AccessArticle Effect of Cu Content on Atomic Positions of Ti50Ni50xCux Shape Memory Alloys Based on Density Functional Theory Calculations
Metals 2015, 5(4), 2222-2235; https://doi.org/10.3390/met5042222
Received: 11 August 2015 / Revised: 16 November 2015 / Accepted: 23 November 2015 / Published: 26 November 2015
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Abstract
The study of crystal structures in shape memory alloys is of fundamental importance for understanding the shape memory effect. In order to investigate the mechanism of how Cu content affects martensite crystal structures of TiNiCu alloys, the present research examines the atomic displacement [...] Read more.
The study of crystal structures in shape memory alloys is of fundamental importance for understanding the shape memory effect. In order to investigate the mechanism of how Cu content affects martensite crystal structures of TiNiCu alloys, the present research examines the atomic displacement of Ti50Ni50xCux (x = 0, 5, 12.5, 15, 18.75, 20, 25) shape memory alloys using density functional theory (DFT). By the introduction of Cu atoms into TiNi martensite crystal to replace Ni, the displacements of Ti and Ni/Cu atoms along the x-axis are obvious, but they are minimal along the y- and z-axes. It is found that along the x-axis, the two Ti atoms in the unit cell move in opposite directions, and the same occurred with the two Ni/Cu atoms. With increasing Cu content, the distance between the two Ni/Cu atoms increases while the Ti atoms draw closer along the x-axis, leading to a rotation of the (100) plane, which is responsible for the decrease in the monoclinic angle. It is also found that the displacements of both Ti atoms and Ni/Cu atoms along the x-axis are progressive, which results in a gradual change of monoclinic angle and a transition to B19 martensite crystal structure. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2014)
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Open AccessArticle Effect of Ultrasonic Treatment in the Static and Dynamic Mechanical Behavior of AZ91D Mg Alloy
Metals 2015, 5(4), 2210-2221; https://doi.org/10.3390/met5042210
Received: 10 November 2015 / Revised: 18 November 2015 / Accepted: 23 November 2015 / Published: 26 November 2015
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Abstract
The present study evaluates the effect of high-intensity ultrasound (US) in the static and dynamic mechanical behavior of AZ91D by microstructural modification. The characterization of samples revealed that US treatment promoted the refinement of dendrite cell size, reduced the thickness, and changed the [...] Read more.
The present study evaluates the effect of high-intensity ultrasound (US) in the static and dynamic mechanical behavior of AZ91D by microstructural modification. The characterization of samples revealed that US treatment promoted the refinement of dendrite cell size, reduced the thickness, and changed the β-Mg17Al12 intermetallic phase to a globular shape, promoted its uniform distribution along the grain boundaries and reduced the level of porosity. In addition to microstructure refinement, US treatment improved the alloy mechanical properties, namely the ultimate tensile strength (40.7%) and extension (150%) by comparison with values obtained for castings produced without US vibration. Moreover, it is suggested that the internal friction, enhanced by the reduction of grain size, is compensated by the homogenization of the secondary phase and reduction of porosity. It seems that by the use of US treatment, it is possible to enhance static mechanical properties without compromising the damping properties in AZ91D alloys. Full article
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Open AccessArticle Effect of Ceramic Content on the Compression Properties of TiB2-Ti2AlC/TiAl Composites
Metals 2015, 5(4), 2200-2209; https://doi.org/10.3390/met5042200
Received: 29 September 2015 / Revised: 1 November 2015 / Accepted: 6 November 2015 / Published: 25 November 2015
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Abstract
In situ synthesized TiB2-reinforced TiAl composites usually possess high strength. However, it is very expensive to use B powder to synthesize TiB2 particles. Moreover, the strength enhancement of TiB2/TiAl composite is generally at the cost of plasticity. In [...] Read more.
In situ synthesized TiB2-reinforced TiAl composites usually possess high strength. However, it is very expensive to use B powder to synthesize TiB2 particles. Moreover, the strength enhancement of TiB2/TiAl composite is generally at the cost of plasticity. In this study, in situ dual reinforcement TiB2-Ti2AlC/TiAl composites were fabricated by using B4C powder as the B and C source, which greatly reduces the potential production cost. The 6 vol. % TiB2-Ti2AlC/TiAl composite fabricated by using the Ti-Al-B4C system shows greatly improved compressive properties, i.e., 316 MPa and 234 MPa higher than those of TiAl alloy and with no sacrifice in plasticity. Full article
(This article belongs to the Special Issue Intermetallics 2016) Printed Edition available
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Open AccessArticle Study of the Tensile Damage of High-Strength Aluminum Alloy by Acoustic Emission
Metals 2015, 5(4), 2186-2199; https://doi.org/10.3390/met5042186
Received: 11 October 2015 / Revised: 16 November 2015 / Accepted: 18 November 2015 / Published: 25 November 2015
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Abstract
The key material of high-speed train gearbox shells is high-strength aluminum alloy. Material damage is inevitable in the process of servicing. It is of great importance to study material damage for in-service gearboxes of high-speed train. Structural health monitoring methods have been widely [...] Read more.
The key material of high-speed train gearbox shells is high-strength aluminum alloy. Material damage is inevitable in the process of servicing. It is of great importance to study material damage for in-service gearboxes of high-speed train. Structural health monitoring methods have been widely used to study material damage in recent years. This study focuses on the application of an acoustic emission (AE) method to quantify tensile damage evolution of high-strength aluminum alloy. First, a characteristic parameter was developed to connect AE signals with tensile damage. Second, a tensile damage quantification model was presented based on the relationship between AE counts and tensile behavior to study elastic deformation of tensile damage. Then tensile tests with AE monitoring were employed to collect AE signals and tensile damage data of nine samples. The experimental data were used to quantify tensile damage of high-strength aluminum alloy A356 to demonstrate the effectiveness of the proposed method. Full article
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Open AccessArticle Cyclic Oxidation of High Mo, Reduced Density Superalloys
Metals 2015, 5(4), 2165-2185; https://doi.org/10.3390/met5042165
Received: 31 October 2015 / Revised: 13 November 2015 / Accepted: 18 November 2015 / Published: 24 November 2015
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Abstract
Cyclic oxidation was characterized as part of a statistically designed, 12-alloy compositional study of 2nd generation single crystal superalloys as part of a broader study to co-optimize density, creep strength, and cyclic oxidation. The primary modification was a replacement of 5 wt. % [...] Read more.
Cyclic oxidation was characterized as part of a statistically designed, 12-alloy compositional study of 2nd generation single crystal superalloys as part of a broader study to co-optimize density, creep strength, and cyclic oxidation. The primary modification was a replacement of 5 wt. % W by 7% or 12% Mo for density reductions of 2%–7%. Compositions at two levels of Mo, Cr, Co, and Re were produced, along with a midpoint composition. Initially, polycrystalline vacuum induction samples were screened in 1100 °C cyclic furnace tests using 1 h cycles for 200 h. The behavior was primarily delimited by Cr content, producing final weight changes of −40 mg/cm2 to −10 mg/cm2 for 0% Cr alloys and −2 mg/cm2 to +1 mg/cm2 for 5% Cr alloys. Accordingly, a multiple linear regression fit yielded an equation showing a strong positive Cr effect and lesser negative effects of Co and Mo. The results for 5% Cr alloys compare well to −1 mg/cm2, and +0.5 mg/cm2 for Rene′ N4 and Rene′ N5 (or Rene′ N6), respectively. Scale phases commonly identified were Al2O3, NiAl2O4, NiTa2O6, and NiO, with (Ni,Co)MoO4 found only on the least resistant alloys having 0% Cr and 12% Mo. Scale microstructures were complex and reflected variations in the regional spallation history. Large faceted NiO grains and fine NiTa2O6 particles distributed along NiAl2O4 grain boundaries were typical distinctive features. NiMoO4 formation, decomposition, and volatility occurred for a few high Mo compositions. A creep, density, phase stability, and oxidation balanced 5% Cr, 10% Co, 7% Mo, and 3% Re alloy was selected to be taken forward for more extensive evaluations in single crystal form. Full article
(This article belongs to the Special Issue Superalloys)
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Open AccessArticle Enhanced Mechanical Properties and Electrical Conductivity in Ultrafine-Grained Al 6101 Alloy Processed via ECAP-Conform
Metals 2015, 5(4), 2148-2164; https://doi.org/10.3390/met5042148
Received: 17 September 2015 / Accepted: 17 November 2015 / Published: 20 November 2015
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Abstract
This paper studies the effect of equal channel angular pressing-Conform (ECAP-C) and further artificial aging (AA) on microstructure, mechanical, and electrical properties of Al 6101 alloy. As is shown, ECAP-C at 130 °C with six cycles resulted in the formation of an ultrafine-grained [...] Read more.
This paper studies the effect of equal channel angular pressing-Conform (ECAP-C) and further artificial aging (AA) on microstructure, mechanical, and electrical properties of Al 6101 alloy. As is shown, ECAP-C at 130 °C with six cycles resulted in the formation of an ultrafine-grained (UFG) structure with a grain size of 400–600 nm containing nanoscale spherical metastable β′ and stable β second-phase precipitates. As a result, processed wire rods demonstrated the ultimate tensile strength (UTS) of 308 MPa and electrical conductivity of 53.1% IACS. Electrical conductivity can be increased without any notable degradation in mechanical strength of the UFG alloy by further AA at 170 °C and considerably enhanced by additional decomposition of solid solution accompanied by the formation of rod-shaped metastable β′ precipitates mainly in the ultrafine grain interior and by the decrease of the alloying element content in the Al matrix. It is demonstrated that ECAP-C can be used to process Al-Mg-Si wire rods with the specified UFG microstructure. The mechanical strength and electrical conductivity in this case are shown to be much higher than those in the industrial semi-finished products made of similar material processed by the conventional T6 or T81 treatment. Full article
(This article belongs to the Special Issue Ultrafine-grained Metals) Printed Edition available
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Open AccessArticle Deformation-Induced Martensitic Transformation in Cu-Zr-Zn Bulk Metallic Glass Composites
Metals 2015, 5(4), 2134-2147; https://doi.org/10.3390/met5042134
Received: 23 October 2015 / Revised: 7 November 2015 / Accepted: 11 November 2015 / Published: 17 November 2015
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Abstract
The microstructures and mechanical properties of (Cu0.5Zr0.5)100−xZnx (x = 0, 1.5, 2.5, 4.5, 7, 10, and 14 at. %) bulk metallic glass (BMG) composites were studied. CuZr martensitic crystals together with minor B2 CuZr [...] Read more.
The microstructures and mechanical properties of (Cu0.5Zr0.5)100−xZnx (x = 0, 1.5, 2.5, 4.5, 7, 10, and 14 at. %) bulk metallic glass (BMG) composites were studied. CuZr martensitic crystals together with minor B2 CuZr and amorphous phases dominate the microstructures of the as-quenched samples with low Zn additions (x = 0, 1.5, and 2.5 at. %), while B2 CuZr and amorphous phases being accompanied with minor martensitic crystals form at a higher Zn content (x = 4.5, 7, 10, and 14 at. %). The fabricated Cu-Zr-Zn BMG composites exhibit macroscopically appreciable compressive plastic strain and obvious work-hardening due to the formation of multiple shear bands and the deformation-induced martensitic transformation (MT) within B2 crystals. The present BMG composites could be a good candidate as high-performance structural materials. Full article
(This article belongs to the Special Issue Metallic Glasses) Printed Edition available
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Open AccessEditorial Some Issues in Liquid Metals Research
Metals 2015, 5(4), 2128-2133; https://doi.org/10.3390/met5042128
Received: 10 November 2015 / Accepted: 10 November 2015 / Published: 13 November 2015
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Abstract
The ten articles [1–10] included in this Special Issue on “Liquid Metals” do not intend to comprehensively cover this extensive field, but, rather, to highlight recent discoveries that have greatly broadened the scope of technological applications of these materials. Improvements in understanding the [...] Read more.
The ten articles [1–10] included in this Special Issue on “Liquid Metals” do not intend to comprehensively cover this extensive field, but, rather, to highlight recent discoveries that have greatly broadened the scope of technological applications of these materials. Improvements in understanding the physics of liquid metals are, to a large extent, due to the powerful theoretical tools in the hands of scientists, either semi-empirical [1,5,6] or ab initio (molecular dynamics, see [7]). Surface tension and wetting at metal/ceramic interfaces is an everlasting field of fundamental research with important technological implications. The review of [2] is broad enough, as the work carried out at Grenoble covers almost all interesting matters in the field. Some issues of interest in geophysics and astrophysics are discussed in [3]. The recently discovered liquid–liquid transition in several metals is dealt with in [4]. The fifth contribution [5] discusses the role of icosahedral superclusters in crystallization. In [6], thermodynamic calculations are carried out to identify the regions of the ternary phase diagram of Al-Cu-Y, where the formation of amorphous alloys is most probable. Experimental data and ab initio calculations are presented in [7] to show that an optimal microstructure is obtained if Mg is added to the Al-Si melt before than the modifier AlP alloy. Shock-induced melting of metals by means of laser driven compression is discussed in [8]. With respect to recent discoveries, one of the most outstanding developments is that of gallium alloys that are liquid at room temperature [9], and that, due to the oxide layer that readily cover their surface, maintain some “stiffness”. This has opened the possibility of 3D printing with liquid metals. The last article in this Special Issue [10] describes nano-liquid metals, a suspension of liquid metal and its alloy containing nanometer-sized particles. A room-temperature nano-liquid metal and its alloys were first introduced in the area of cooling high heat flux devices, which now is a commercial reality. However, their applications are not only in chip cooling, and can also be extended to waste heat recovery, kinetic energy harvesting, thermal interface material, etc. This is mainly due to properties such as low melting point, high thermal and electrical conductivity, as well as other additional physical or chemical properties. These articles are summarized in more detail hereafter [...] Full article
(This article belongs to the Special Issue Liquid Metals)
Open AccessArticle Liquid Phase Separation and the Aging Effect on Mechanical and Electrical Properties of Laser Rapidly Solidified Cu100xCrx Alloys
Metals 2015, 5(4), 2119-2127; https://doi.org/10.3390/met5042119
Received: 18 September 2015 / Revised: 3 November 2015 / Accepted: 6 November 2015 / Published: 12 November 2015
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Abstract
Duplex structure Cu-Cr alloys are widely used as contact materials. They are generally designed by increasing the Cr content for the hardness improvement, which, however, leads to the unfavorable rapid increase of the electrical resistivity. The solidification behavior of Cu100−xCr [...] Read more.
Duplex structure Cu-Cr alloys are widely used as contact materials. They are generally designed by increasing the Cr content for the hardness improvement, which, however, leads to the unfavorable rapid increase of the electrical resistivity. The solidification behavior of Cu100−xCrx (x = 4.2, 25 and 50 in wt.%) alloys prepared by laser rapid solidification is studied here, and their hardness and electrical conductivity after aging are measured. The results show that the Cu-4.2%Cr alloy has the most desirable combination of hardness and conductive properties after aging in comparison with Cu-25%Cr and Cu-50%Cr alloys. Very importantly, a 50% improvement in hardness is achieved with a simultaneous 70% reduction in electrical resistivity. The reason is mainly attributed to the liquid phase separation occurring in the Cu-4.2%Cr alloy, which introduces a large a Full article
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Open AccessArticle Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions
Metals 2015, 5(4), 2109-2118; https://doi.org/10.3390/met5042109
Received: 2 September 2015 / Revised: 26 October 2015 / Accepted: 4 November 2015 / Published: 12 November 2015
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Abstract
We investigated the evolution of the strain fields around a fatigued crack tip between the steady- and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, [...] Read more.
We investigated the evolution of the strain fields around a fatigued crack tip between the steady- and overloaded-fatigue conditions using a nondestructive neutron diffraction technique. The two fatigued compact-tension specimens, with a different fatigue history but an identical applied stress intensity factor range, were used for the direct comparison of the crack tip stress/strain distributions during in situ loading. While strains behind the crack tip in the steady-fatigued specimen are irrelevant to increasing applied load, the strains behind the crack tip in the overloaded-fatigued specimen evolve significantly under loading, leading to a lower driving force of fatigue crack growth. The results reveal the overload retardation mechanism and the correlation between crack tip stress distribution and fatigue crack growth rate. Full article
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Open AccessArticle Detecting Structural Features in Metallic Glass via Synchrotron Radiation Experiments Combined with Simulations
Metals 2015, 5(4), 2093-2108; https://doi.org/10.3390/met5042093
Received: 23 September 2015 / Revised: 29 October 2015 / Accepted: 3 November 2015 / Published: 9 November 2015
Cited by 8 | Viewed by 2015 | PDF Full-text (900 KB) | HTML Full-text | XML Full-text
Abstract
Revealing the essential structural features of metallic glasses (MGs) will enhance the understanding of glass-forming mechanisms. In this work, a feasible scheme is provided where we performed the state-of-the-art synchrotron-radiation based experiments combined with simulations to investigate the microstructures of ZrCu amorphous compositions. [...] Read more.
Revealing the essential structural features of metallic glasses (MGs) will enhance the understanding of glass-forming mechanisms. In this work, a feasible scheme is provided where we performed the state-of-the-art synchrotron-radiation based experiments combined with simulations to investigate the microstructures of ZrCu amorphous compositions. It is revealed that in order to stabilize the amorphous state and optimize the topological and chemical distribution, besides the icosahedral or icosahedral-like clusters, other types of clusters also participate in the formation of the microstructure in MGs. This cluster-level co-existing feature may be popular in this class of glassy materials. Full article
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Open AccessReview Iron, Aging, and Neurodegeneration
Metals 2015, 5(4), 2070-2092; https://doi.org/10.3390/met5042070
Received: 5 October 2015 / Revised: 30 October 2015 / Accepted: 2 November 2015 / Published: 6 November 2015
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Abstract
Iron is a trace element of considerable interest to both chemistry and biology. In a biological context its chemistry is vital to the roles it performs. However, that same chemistry can contribute to a more deleterious role in a variety of diseases. The [...] Read more.
Iron is a trace element of considerable interest to both chemistry and biology. In a biological context its chemistry is vital to the roles it performs. However, that same chemistry can contribute to a more deleterious role in a variety of diseases. The brain is a very sensitive organ due to the irreplaceable nature of neurons. In this regard regulation of brain iron chemistry is essential to maintaining neuronal viability. During the course of normal aging, the brain changes the way it deals with iron and this can contribute to its susceptibility to disease. Additionally, many of the known neurodegenerative diseases have been shown to be influenced by changes in brain iron. This review examines the role of iron in the brain and neurodegenerative diseases and the potential role of changes in brain iron caused by aging. Full article
(This article belongs to the Special Issue Metallomics)
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