Metals

538 KiB

Open AccessArticle

Hot Ductility Loss in a Fe-Ni-Based Superalloy

by Chen-Wei Li, An-Chou Yeh, Chi-San Chen and Woei-Ren Wang

Metals 2015, 5(4), 2428-2434; https://doi.org/10.3390/met5042428 - 21 Dec 2015

Cited by 3 | Viewed by 5347

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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1156 KiB

Open AccessArticle

Direct Aqueous Mineral Carbonation of Waste Slate Using Ammonium Salt Solutions

by Hwanju Jo, Ho Young Jo, Sunwon Rha and Pyeong-Koo Lee

Metals 2015, 5(4), 2413-2427; https://doi.org/10.3390/met5042413 - 18 Dec 2015

Cited by 9 | Viewed by 5010

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)

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852 KiB

Open AccessArticle

Preparation and Characteristics of γ-Fe₂O₃/Polyaniline-Curcumin Composites

by Yongli Li, Chunxia Zhu and Jinqing Kan

Metals 2015, 5(4), 2401-2412; https://doi.org/10.3390/met5042401 - 17 Dec 2015

Cited by 13 | Viewed by 5232

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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119 KiB

Open AccessEditorial

Metallic Glasses

by Kang Cheung Chan and Jordi Sort

Metals 2015, 5(4), 2397-2400; https://doi.org/10.3390/met5042397 - 16 Dec 2015

Cited by 2 | Viewed by 4196

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)

142 KiB

Open AccessEditorial

Ultrafine-Grained Metals

by Heinz Werner Höppel

Metals 2015, 5(4), 2393-2396; https://doi.org/10.3390/met5042393 - 16 Dec 2015

Viewed by 3546

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)

460 KiB

Open AccessArticle

A Simple Up-Scalable Thermal Treatment Method for Synthesis of ZnO Nanoparticles

by Phin Jit Lee, Elias Saion, Naif Mohammed Al-Hada and Nayereh Soltani

Metals 2015, 5(4), 2383-2392; https://doi.org/10.3390/met5042383 - 14 Dec 2015

Cited by 52 | Viewed by 6117

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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650 KiB

Open AccessArticle

Galvanic Corrosion between Alloy 690 and Magnetite in Alkaline Aqueous Solutions

by Soon-Hyeok Jeon, Geun-Dong Song and Do Haeng Hur

Metals 2015, 5(4), 2372-2382; https://doi.org/10.3390/met5042372 - 14 Dec 2015

Cited by 10 | Viewed by 5453

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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161 KiB

Open AccessComment

Comments on Lynch. Pyrrolyl Squaraines—Fifty Golden Years. Metals 2015, 5, 1349–1370

by Daniel E. Lynch

Metals 2015, 5(4), 2370-2371; https://doi.org/10.3390/met5042370 - 14 Dec 2015

Cited by 2 | Viewed by 2938

Abstract

In addition to the papers referenced in the main article [1]; [...] Full article

(This article belongs to the Special Issue Synthetic Metals)

1558 KiB

Open AccessArticle

Damage Analysis of a Ferritic SiMo Ductile Cast Iron Submitted to Tension and Compression Loadings in Temperature

by Isabel Hervas, Anthony Thuault and Eric Hug

Metals 2015, 5(4), 2351-2369; https://doi.org/10.3390/met5042351 - 10 Dec 2015

Cited by 17 | Viewed by 6614

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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902 KiB

Open AccessArticle

Forge-Hardened TiZr Null-Matrix Alloy for Neutron Scattering under Extreme Conditions

by Takuo Okuchi, Akinori Hoshikawa and Toru Ishigaki

Metals 2015, 5(4), 2340-2350; https://doi.org/10.3390/met5042340 - 9 Dec 2015

Cited by 9 | Viewed by 5617

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

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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957 KiB

Open AccessArticle

Modeling of TiAl Alloy Grating by Investment Casting

by Yi Jia, Shulong Xiao, Jing Tian, Lijuan Xu and Yuyong Chen

Metals 2015, 5(4), 2328-2339; https://doi.org/10.3390/met5042328 - 9 Dec 2015

Cited by 7 | Viewed by 5230

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)

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934 KiB

Open AccessArticle

Fatigue Performance of Mg-Zn-Zr Alloy Processed by Hot Severe Plastic Deformation

by Evgeni Vasilev, Mikhail Linderov, Dayan Nugmanov, Oleg Sitdikov, Mikhail Markushev and Alexei Vinogradov

Metals 2015, 5(4), 2316-2327; https://doi.org/10.3390/met5042316 - 8 Dec 2015

Cited by 24 | Viewed by 5052

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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370 KiB

Open AccessArticle

Palladium(II) Recovery from Hydrochloric Acid Solutions by N,N′-Dimethyl-N,N′-Dibutylthiodiglycolamide

by Ana Paula Paiva, Mário E. Martins and Osvaldo Ortet

Metals 2015, 5(4), 2303-2315; https://doi.org/10.3390/met5042303 - 8 Dec 2015

Cited by 23 | Viewed by 5813

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)

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1123 KiB

Open AccessArticle

Corrosion Behavior in 3.5% NaCl Solutions of γ-TiAl Processed by Electron Beam Melting Process

by Asiful Hossain Seikh, Ashfaq Mohammad, El-Sayed M. Sherif and Abdulrahaman Al-Ahmari

Metals 2015, 5(4), 2289-2302; https://doi.org/10.3390/met5042289 - 3 Dec 2015

Cited by 18 | Viewed by 5670

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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770 KiB

Open AccessFeature PaperArticle

Effect of Additions of Ceramic Nanoparticles and Gas-Dynamic Treatment on Al Casting Alloys

by Konstantin Borodianskiy, Vadim Selivorstov, Yuri Dotsenko and Michael Zinigrad

Metals 2015, 5(4), 2277-2288; https://doi.org/10.3390/met5042277 - 3 Dec 2015

Cited by 12 | Viewed by 4538

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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807 KiB

Open AccessArticle

Synthesis and Characterization of 4-Benzyloxybenzaldehyde-4-methyl-3-thiosemicarbazone (Containing Sulphur and Nitrogen Donor Atoms) and Its Cd(II) Complex

by Lakshmi Narayana Suvarapu and Sung-Ok Baek

Metals 2015, 5(4), 2266-2276; https://doi.org/10.3390/met5042266 - 1 Dec 2015

Cited by 6 | Viewed by 5489

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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1160 KiB

Open AccessFeature PaperArticle

In Situ High-Energy X-ray Diffraction during Hot-Forming of a Multiphase TiAl Alloy

by Andreas Stark, Marcus Rackel, Aristide Tchouaha Tankoua, Michael Oehring, Norbert Schell, Lars Lottermoser, Andreas Schreyer and Florian Pyczak

Metals 2015, 5(4), 2252-2265; https://doi.org/10.3390/met5042252 - 30 Nov 2015

Cited by 19 | Viewed by 7364

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

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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1773 KiB

Open AccessFeature PaperArticle

Relationships between Microstructural Parameters and Time-Dependent Mechanical Properties of a New Nickel-Based Superalloy AD730™

by Louis Thébaud, Patrick Villechaise, Jonathan Cormier, Coraline Crozet, Alexandre Devaux, Denis Béchet, Jean-Michel Franchet, Antoine Organista and Florence Hamon

Metals 2015, 5(4), 2236-2251; https://doi.org/10.3390/met5042236 - 27 Nov 2015

Cited by 27 | Viewed by 8449

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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1098 KiB

Open AccessArticle

Effect of Cu Content on Atomic Positions of Ti₅₀Ni₅₀_−xCu_x Shape Memory Alloys Based on Density Functional Theory Calculations

by Liangliang Gou, Yong Liu and Teng Yong Ng

Metals 2015, 5(4), 2222-2235; https://doi.org/10.3390/met5042222 - 26 Nov 2015

Cited by 7 | Viewed by 7052

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 Ti₅₀Ni₅₀_−xCu_x (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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1472 KiB

Open AccessArticle

Effect of Ultrasonic Treatment in the Static and Dynamic Mechanical Behavior of AZ91D Mg Alloy

by Helder Puga, Vitor Carneiro, Joaquim Barbosa and Vanessa Vieira

Metals 2015, 5(4), 2210-2221; https://doi.org/10.3390/met5042210 - 26 Nov 2015

Cited by 26 | Viewed by 4830

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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737 KiB

Open AccessArticle

Effect of Ceramic Content on the Compression Properties of TiB₂-Ti₂AlC/TiAl Composites

by Shili Shu, Cunzhu Tong, Feng Qiu and Qichuan Jiang

Metals 2015, 5(4), 2200-2209; https://doi.org/10.3390/met5042200 - 25 Nov 2015

Cited by 10 | Viewed by 4354

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)

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677 KiB

Open AccessArticle

Study of the Tensile Damage of High-Strength Aluminum Alloy by Acoustic Emission

by Chang Sun, Weidong Zhang, Yibo Ai and Hongbo Que

Metals 2015, 5(4), 2186-2199; https://doi.org/10.3390/met5042186 - 25 Nov 2015

Cited by 4 | Viewed by 4978

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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1496 KiB

Open AccessArticle

Cyclic Oxidation of High Mo, Reduced Density Superalloys

by James L. Smialek, Anita Garg, Timothy P. Gabb and Rebecca A. MacKay

Metals 2015, 5(4), 2165-2185; https://doi.org/10.3390/met5042165 - 24 Nov 2015

Cited by 17 | Viewed by 6846

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

by Maxim Murashkin, Andrey Medvedev, Vil Kazykhanov, Alexander Krokhin, Georgy Raab, Nariman Enikeev and Ruslan Z. Valiev

Metals 2015, 5(4), 2148-2164; https://doi.org/10.3390/met5042148 - 20 Nov 2015

Cited by 62 | Viewed by 8405

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)

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Deformation-Induced Martensitic Transformation in Cu-Zr-Zn Bulk Metallic Glass Composites

by Dianyu Wu, Kaikai Song, Chongde Cao, Ran Li, Gang Wang, Yuan Wu, Feng Wan, Fuli Ding, Yue Shi, Xiaojun Bai, Ivan Kaban and Jürgen Eckert

Metals 2015, 5(4), 2134-2147; https://doi.org/10.3390/met5042134 - 17 Nov 2015

Cited by 19 | Viewed by 5722

Abstract

The microstructures and mechanical properties of (Cu_0.5Zr_0.5)_100−xZn_x (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 (Cu_0.5Zr_0.5)_100−xZn_x (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)

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Open AccessEditorial

Some Issues in Liquid Metals Research

by Maria José Caturla, Jian-Zhong Jiang, Enrique Louis and José Miguel Molina

Metals 2015, 5(4), 2128-2133; https://doi.org/10.3390/met5042128 - 13 Nov 2015

Cited by 5 | Viewed by 5560

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)

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Liquid Phase Separation and the Aging Effect on Mechanical and Electrical Properties of Laser Rapidly Solidified Cu₁₀₀_−xCr_x Alloys

by Song-Hua Si, Hui Zhang, Yi-Zhu He, Ming-Xi Li and Sheng Guo

Metals 2015, 5(4), 2119-2127; https://doi.org/10.3390/met5042119 - 12 Nov 2015

Cited by 18 | Viewed by 5924

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 Cu_100−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 Cu_100−xCr_x (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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Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions

by Soo Yeol Lee, E-Wen Huang, Wanchuck Woo, Cheol Yoon, Hobyung Chae and Soon-Gil Yoon

Metals 2015, 5(4), 2109-2118; https://doi.org/10.3390/met5042109 - 12 Nov 2015

Cited by 30 | Viewed by 5915

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

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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Detecting Structural Features in Metallic Glass via Synchrotron Radiation Experiments Combined with Simulations

by Gu-Qing Guo, Shi-Yang Wu, Sheng Luo and Liang Yang

Metals 2015, 5(4), 2093-2108; https://doi.org/10.3390/met5042093 - 9 Nov 2015

Cited by 19 | Viewed by 7129

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

(This article belongs to the Special Issue Metals Challenged by Neutron and Synchrotron Radiation)

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Open AccessReview

Iron, Aging, and Neurodegeneration

by Dafina M. Angelova and David R. Brown

Metals 2015, 5(4), 2070-2092; https://doi.org/10.3390/met5042070 - 6 Nov 2015

Cited by 18 | Viewed by 7456

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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Metals, Volume 5, Issue 4 (December 2015) – 50 articles , Pages 1770-2434

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