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Metals, Volume 6, Issue 9 (September 2016)

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Open AccessArticle Microstructure and Dry-Sliding Wear Behavior of B4C Ceramic Particulate Reinforced Al 5083 Matrix Composite
Metals 2016, 6(9), 227; https://doi.org/10.3390/met6090227
Received: 17 August 2016 / Revised: 14 September 2016 / Accepted: 14 September 2016 / Published: 21 September 2016
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Abstract
B4C ceramic particulate–reinforced Al 5083 matrix composite with various B4C content was fabricated successfully via hot-press sintering under Argon atmosphere. B4C particles presented relative high wettability, bonding strength and symmetrical distribution in the Al 5083 matrix. The
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B4C ceramic particulate–reinforced Al 5083 matrix composite with various B4C content was fabricated successfully via hot-press sintering under Argon atmosphere. B4C particles presented relative high wettability, bonding strength and symmetrical distribution in the Al 5083 matrix. The hardness value, friction coefficient and wear resistance of the composite were higher than those of the Al 5083 matrix. The augment of the B4C content resulted in the increase of the friction coefficient and decrease of the wear mass loss, respectively. The 30 wt % B4C/Al 5083 composite exhibited the highest wear resistance. At a low load of 50 N, the dominant wear mechanisms of the B4C/Al 5083 composite were micro-cutting and abrasive wear. At a high load of 200 N, the dominant wear mechanisms were micro-cutting and adhesion wear associated with the formation of the delamination layer which protected the composite from further wear and enhanced the wear resistance under the condition of high load. Full article
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Open AccessFeature PaperArticle Synthesis, Characterization, and Cytotoxicity of a Novel Gold(III) Complex with O,O′-Diethyl Ester of Ethylenediamine-N,N′-Di-2-(4-Methyl)Pentanoic Acid
Metals 2016, 6(9), 226; https://doi.org/10.3390/met6090226
Received: 16 June 2016 / Revised: 12 September 2016 / Accepted: 14 September 2016 / Published: 20 September 2016
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Abstract
A novel gold(III) complex, [AuCl2{(S,S)-Et2eddl}]PF6, ((S,S)-Et2eddl = O,O′-diethyl ester of ethylenediamine-N,N′-di-2-(4-methyl)pentanoic acid) was synthesized and characterized by IR, 1D (
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A novel gold(III) complex, [AuCl2{(S,S)-Et2eddl}]PF6, ((S,S)-Et2eddl = O,O′-diethyl ester of ethylenediamine-N,N′-di-2-(4-methyl)pentanoic acid) was synthesized and characterized by IR, 1D (1H and 13C), and 2D (H,H-COSY and H,H-NOESY) NMR spectroscopy, mass spectrometry, and elemental analysis. Density functional theory calculations confirmed that (R,R)-N,N′ diastereoisomer was energetically the most stable isomer. In vitro antitumor action of ligand precursor [(S,S)-H2Et2eddl]Cl2 and corresponding gold(III) complex was determined against tumor cell lines: human adenocarcinoma (HeLa), human colon carcinoma (LS174), human breast cancer (MCF7), non-small cell lung carcinoma cell line (A549), and non-cancerous cell line human embryonic lung fibroblast (MRC-5) using microculture tetrazolium test (MTT) assay. The results indicate that both ligand precursor and gold(III) complex have showed very good to moderate cytotoxic activity against all tested malignant cell lines. The highest activity was expressed by [AuCl2{(S,S)-Et2eddl}]PF6 against the LS174 cells, with IC50 value of 7.4 ± 1.2 µM. Full article
(This article belongs to the Special Issue Metallomics)
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Open AccessArticle Glass-Forming Ability and Early Crystallization Kinetics of Novel Cu-Zr-Al-Co Bulk Metallic Glasses
Metals 2016, 6(9), 225; https://doi.org/10.3390/met6090225
Received: 11 July 2016 / Revised: 12 September 2016 / Accepted: 13 September 2016 / Published: 15 September 2016
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Abstract
In recent years, CuZr-based bulk metallic glass (BMG) composites ductilized by a shape memory B2 CuZr phase have attracted great attention owing to their outstanding mechanical properties. However, the B2 CuZr phase for most CuZr-based glass-forming compositions is only stable at very high
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In recent years, CuZr-based bulk metallic glass (BMG) composites ductilized by a shape memory B2 CuZr phase have attracted great attention owing to their outstanding mechanical properties. However, the B2 CuZr phase for most CuZr-based glass-forming compositions is only stable at very high temperatures, leading to the uncontrollable formation of B2 crystals during quenching. In this work, by introducing Co (i.e., 4, 5, and 6 at. %) and 10 at. % Al into CuZr-based alloys, the relatively good glass-forming ability (GFA) of CuZr-based alloys still can be achieved. Meanwhile, the B2 phase can be successfully stabilized to lower temperatures than the final temperatures of crystallization upon heating CuZr-based BMGs. Unlike previous reported CuZr-based BMGs, the primary crystallization products upon heating are mainly B2 CuZr crystals but not CuZr2 and Cu10Zr7 crystals. Furthermore, the primary precipitates during solidification are still dominated by B2 crystals, whose percolation threshold is detected to lie between 10 ± 2 vol. % and 31 ± 2 vol. %. The crystallization kinetics underlying the precipitation of B2 crystals was also investigated. Our results show that the present glass-forming composites are promising candidates for the fabrication of ductile CuZr-based BMG composites. Full article
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Open AccessArticle Utilization of a Porous Cu Interlayer for the Enhancement of Pb-Free Sn-3.0Ag-0.5Cu Solder Joint
Metals 2016, 6(9), 220; https://doi.org/10.3390/met6090220
Received: 29 June 2016 / Revised: 1 September 2016 / Accepted: 5 September 2016 / Published: 15 September 2016
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Abstract
The joining of lead-free Sn-3.0Ag-0.5Cu (SAC305) solder alloy to metal substrate with the addition of a porous Cu interlayer was investigated. Two types of porous Cu interlayers, namely 15 ppi—pore per inch (P15) and 25 ppi (P25) were sandwiched in between SAC305/Cu substrate.
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The joining of lead-free Sn-3.0Ag-0.5Cu (SAC305) solder alloy to metal substrate with the addition of a porous Cu interlayer was investigated. Two types of porous Cu interlayers, namely 15 ppi—pore per inch (P15) and 25 ppi (P25) were sandwiched in between SAC305/Cu substrate. The soldering process was carried out at soldering time of 60, 180, and 300 s at three temperature levels of 267, 287, and 307 °C. The joint strength was evaluated by tensile testing. The highest strength for solder joints with addition of P25 and P15 porous Cu was 51 MPa (at 180 s and 307 °C) and 54 MPa (at 300 s and 307 °C ), respectively. The fractography of the solder joint was analyzed by optical microscope (OM) and scanning electron microscopy (SEM). The results showed that the propagation of fracture during tensile tests for solder with a porous Cu interlayer occurred in three regions: (i) SAC305/Cu interface; (ii) inside SAC305 solder alloy; and (iii) inside porous Cu. Energy dispersive X-ray spectroscopy (EDX) was used to identify intermetallic phases. Cu6Sn5 phase with scallop-liked morphology was observed at the interface of the SAC305/Cu substrate. In contrast, the scallop-liked intermetallic phase together with more uniform but a less defined scallop-liked phase was observed at the interface of porous Cu and solder alloy. Full article
(This article belongs to the Special Issue Intermetallics 2016) Printed Edition available
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Open AccessArticle Influence of Milling Atmosphere on the Controlled Formation of Ultrafine Dispersoids in Al-Based MMCs
Metals 2016, 6(9), 224; https://doi.org/10.3390/met6090224
Received: 27 July 2016 / Revised: 31 August 2016 / Accepted: 8 September 2016 / Published: 12 September 2016
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Abstract
Properties of compacts made from aluminium powder, milled under different atmospheres, were evaluated. The duration of all the milling processes was 10 h, although different atmospheres were tested: vacuum, confined ammonia, and vacuum combined with a short-time ammonia gas flow (5 min). Milled
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Properties of compacts made from aluminium powder, milled under different atmospheres, were evaluated. The duration of all the milling processes was 10 h, although different atmospheres were tested: vacuum, confined ammonia, and vacuum combined with a short-time ammonia gas flow (5 min). Milled powders were consolidated by cold uniaxial pressing and vacuum sintering. Full article
(This article belongs to the Special Issue Mechanical Alloying)
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Open AccessArticle Deformation Characteristic and Constitutive Modeling of 2707 Hyper Duplex Stainless Steel under Hot Compression
Metals 2016, 6(9), 223; https://doi.org/10.3390/met6090223
Received: 18 August 2016 / Revised: 2 September 2016 / Accepted: 5 September 2016 / Published: 12 September 2016
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Abstract
Hot deformation behavior and microstructure evolution of 2707 hyper duplex stainless steel (HDSS) were investigated through hot compression tests in the temperature range of 900–1250 °C and strain rate range of 0.01–10 s−1. The results showed that the flow behavior strongly
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Hot deformation behavior and microstructure evolution of 2707 hyper duplex stainless steel (HDSS) were investigated through hot compression tests in the temperature range of 900–1250 °C and strain rate range of 0.01–10 s−1. The results showed that the flow behavior strongly depended on strain rate and temperature, and flow stress increased with increasing strain rate and decreasing temperature. At lower temperatures, many precipitates appeared in ferrite and distributed along the deformation direction, which could restrain processing of discontinuous dynamic recrystallization (DRX) because of pinning grain boundaries. When the temperature increased to 1150 °C, the leading softening behaviors were dynamic recovery (DRV) in ferrite and discontinuous DRX in austenite. When the temperature reached 1250 °C, softening behavior was mainly DRV in ferrite. The increase of strain rate was conducive to the occurrence of discontinuous DRX in austenite. A constitutive equation at peak strain was established and the results indicated that 2707 HDSS had a higher Q value (569.279 kJ·mol−1) than other traditional duplex stainless steels due to higher content of Cr, Mo, Ni, and N. Constitutive modeling considering strain was developed to model the hot deformation behavior of 2707 HDSS more accurately, and the correlation coefficient and average absolute relative error were 0.992 and 5.22%, respectively. Full article
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Open AccessArticle Influence of Annealing on the Microstructures and Oxidation Behaviors of Al8(CoCrFeNi)92, Al15(CoCrFeNi)85, and Al30(CoCrFeNi)70 High-Entropy Alloys
Metals 2016, 6(9), 222; https://doi.org/10.3390/met6090222
Received: 28 July 2016 / Revised: 2 September 2016 / Accepted: 5 September 2016 / Published: 12 September 2016
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Abstract
The understanding of the oxidation behaviors of as-cast and annealed high-entropy alloys (HEAs) is currently limited. This work systematically investigates the influence of annealing on the microstructures and oxidation behaviors of AlCoCrFeNi-based HEAs. Annealing was found to alter the distribution of Al-rich phases
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The understanding of the oxidation behaviors of as-cast and annealed high-entropy alloys (HEAs) is currently limited. This work systematically investigates the influence of annealing on the microstructures and oxidation behaviors of AlCoCrFeNi-based HEAs. Annealing was found to alter the distribution of Al-rich phases which caused a change in the oxidation mechanisms. In general, all three of the investigated HEAs displayed some degree of transient oxidation at 1050 °C that was later followed by protective, parabolic oxide growth. The respective oxidation behaviors are discussed relative to existing oxide formation models for Ni–Cr–Al alloys. Full article
(This article belongs to the Special Issue High-Entropy Alloys (HEAs))
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Open AccessArticle Nanocrystalline β-Ta Coating Enhances the Longevity and Bioactivity of Medical Titanium Alloys
Metals 2016, 6(9), 221; https://doi.org/10.3390/met6090221
Received: 4 July 2016 / Revised: 24 August 2016 / Accepted: 24 August 2016 / Published: 10 September 2016
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Abstract
A β-Ta nanocrystalline coating was engineered onto a Ti-6Al-4V substrate using a double cathode glow discharge technique to improve the corrosion resistance and bioactivity of this biomedical alloy. The new coating has a thickness of ~40 μm and exhibits a compact and homogeneous
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A β-Ta nanocrystalline coating was engineered onto a Ti-6Al-4V substrate using a double cathode glow discharge technique to improve the corrosion resistance and bioactivity of this biomedical alloy. The new coating has a thickness of ~40 μm and exhibits a compact and homogeneous structure composed of equiaxed β-Ta grains with an average grain size of ~22 nm, which is well adhered on the substrate. Nanoindentation and scratch tests indicated that the β-Ta coating exhibited high hardness combined with good resistance to contact damage. The electrochemical behavior of the new coating was systematically investigated in Hank’s physiological solution at 37 °C. The results showed that the β-Ta coating exhibited a superior corrosion resistance as compared to uncoated Ti-6Al-4V and commercially pure tantalum, which was attributed to a stable passive film formed on the β-Ta coating. The in vitro bioactivity was studied by evaluating the apatite-forming capability of the coating after seven days of immersion in Hank’s physiological solution. The β-Ta coating showed a higher apatite-forming ability than both uncoated Ti-6Al-4V and commercially pure Ta, suggesting that the β-Ta coating has the potential to enhance functionality and increase longevity of orthopaedic implants. Full article
(This article belongs to the Special Issue Metallic Biomaterials)
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Open AccessArticle The Unified Creep-Fatigue Equation for Stainless Steel 316
Metals 2016, 6(9), 219; https://doi.org/10.3390/met6090219
Received: 1 August 2016 / Revised: 23 August 2016 / Accepted: 2 September 2016 / Published: 10 September 2016
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Abstract
Background—The creep-fatigue properties of stainless steel 316 are of interest because of the wide use of this material in demanding service environments, such as the nuclear industry. Need—A number of models exist to describe creep-fatigue behaviours, but they are limited by the need
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Background—The creep-fatigue properties of stainless steel 316 are of interest because of the wide use of this material in demanding service environments, such as the nuclear industry. Need—A number of models exist to describe creep-fatigue behaviours, but they are limited by the need to obtain specialized coefficients from a large number of experiments, which are time-consuming and expensive. Also, they do not generalise to other situations of temperature and frequency. There is a need for improved formulations for creep-fatigue, with coefficients that determinable directly from the existing and simple creep-fatigue tests and creep rupture tests. Outcomes—A unified creep-fatigue equation is proposed, based on an extension of the Coffin-Manson equation, to introduce dependencies on temperature and frequency. The equation may be formulated for strain as ε p = C 0 c ( T , t , ε p ) N β 0 , or as a power-law ε p = C 0 c ( T , t ) N β 0 b ( T , t ) . These were then validated against existing experimental data. The equations provide an excellent fit to data (r2 = 0.97 or better). Originality—This work develops a novel formulation for creep-fatigue that accommodates temperature and frequency. The coefficients can be obtained with minimum experimental effort, being based on standard rather than specialized tests. Full article
(This article belongs to the Special Issue Fatigue Damage) Printed Edition available
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Open AccessArticle Aging Behaviour and Mechanical Performance of 18-Ni 300 Steel Processed by Selective Laser Melting
Metals 2016, 6(9), 218; https://doi.org/10.3390/met6090218
Received: 2 August 2016 / Revised: 31 August 2016 / Accepted: 5 September 2016 / Published: 8 September 2016
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Abstract
An 18-Ni 300 grade maraging steel was processed by selective laser melting and an investigation was carried out on microstructural and mechanical behaviour as a function of aging condition. Owing to the rapid cooling rate, the as-built alloy featured a full potential for
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An 18-Ni 300 grade maraging steel was processed by selective laser melting and an investigation was carried out on microstructural and mechanical behaviour as a function of aging condition. Owing to the rapid cooling rate, the as-built alloy featured a full potential for precipitate strengthening, without the need of a solution treatment prior to aging. The amount of reversed austenite found in the microstructure increased after aging and revealed to depend on aging temperature and time. Similarly to the corresponding wrought counterpart, also in the selective laser-melted 18-Ni 300 alloy, aging promoted a dramatic increase in strength with respect to the as-built condition and a drop in tensile ductility. No systematic changes were found in tensile properties as a function of measured amount of austenite. It is proposed that the submicrometric structure and the phase distribution inherited by the rapid solidification condition brought by selective laser melting are such that changes in tensile strength and ductility are mainly governed by the effects brought by the strengthening precipitates, whereas the concurrent reversion of the γ-Fe phase in different amounts seems to play a minor role. Full article
(This article belongs to the Special Issue 3D Printing of Metals) Printed Edition available
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Open AccessArticle Numerical Modeling of Cyclic Deformation in Bulk Metallic Glasses
Metals 2016, 6(9), 217; https://doi.org/10.3390/met6090217
Received: 24 July 2016 / Revised: 12 August 2016 / Accepted: 27 August 2016 / Published: 7 September 2016
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Abstract
In this paper, a systematic numerical simulation was performed to elucidate the damage mechanisms in bulk metallic glasses (BMGs) subjected to the tension-compression cyclic loading, and then the relation between fatigue life, applied strain, and cycling frequency was therefore presented. The free volume
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In this paper, a systematic numerical simulation was performed to elucidate the damage mechanisms in bulk metallic glasses (BMGs) subjected to the tension-compression cyclic loading, and then the relation between fatigue life, applied strain, and cycling frequency was therefore presented. The free volume was selected as an internal state variable to depict the shear-band nucleation, growth, and coalescence with the help of free volume theory, which was incorporated into the ABAQUS code via a user material subroutine UMAT. Under cyclic loading, the shear banding initiation mainly stems from the microstructure inhomogeneity in BMGs and, further, the effect of applied strain amplitude and cycling frequency was discussed. The present simulations will shed some light on the fatigue damage mechanisms and fatigue life evaluation of BMG structures. Full article
(This article belongs to the Special Issue Amorphous Alloys and Related Transitions)
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Open AccessArticle The Effect of Ag Addition on the Enhancement of the Thermal and Mechanical Properties of CuZrAl Bulk Metallic Glasses
Metals 2016, 6(9), 216; https://doi.org/10.3390/met6090216
Received: 3 July 2016 / Revised: 29 August 2016 / Accepted: 1 September 2016 / Published: 7 September 2016
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Abstract
In this study, the thermal and mechanical properties of Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6) bulk metallic glasses (BMGs) are investigated by using an X-ray diffractometer (XRD), a differential scanning calorimeter (DSC),
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In this study, the thermal and mechanical properties of Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6) bulk metallic glasses (BMGs) are investigated by using an X-ray diffractometer (XRD), a differential scanning calorimeter (DSC), differential thermal analysis (DTA), a Vickers hardness tester, a material test system (MTS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6) BMGs were made by arc-melting and an injection casting process. The results revealed that the glass transition temperature (Tg) and the crystallization temperature (Tx) of CuZrAl alloy decreased with the Ag addition. Hence, the supercooled liquid region and γ of Cu45Zr43Al7Ag5 alloy increased to 76 K and 0.42, respectively. The thermal stability and glass forming ability of CuZrAlAg BMG alloys were enhanced by the microalloyed Ag content. The room temperature compressive fracture strength and strain measured of Cu47Zr43Al7Ag3 were about 2200 MPa and 2.1%, respectively. The distribution of vein patterns and the formation of nanocrystalline phases on the fracture surface of Cu47Zr43Al7Ag3 alloy can be observed by SEM and TEM to be significant, indicating a typical ductile fracture behavior and an improved plasticity of alloys with the addition of microalloyed Ag from 0 to 6 atom %. Full article
(This article belongs to the Special Issue Amorphous Alloys and Related Transitions)
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Open AccessArticle The Effect of Creep Aging on the Fatigue Fracture Behavior of 2524 Aluminum Alloy
Metals 2016, 6(9), 215; https://doi.org/10.3390/met6090215
Received: 26 July 2016 / Revised: 23 August 2016 / Accepted: 31 August 2016 / Published: 7 September 2016
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Abstract
Normal temperature tensile and fatigue tests were adopted to test the mechanical performance and fatigue life of 2524 aluminum alloy under the three states of T3, artificial aging, and creep aging, and scanning electron microscope and transmission electron microscope were also used to
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Normal temperature tensile and fatigue tests were adopted to test the mechanical performance and fatigue life of 2524 aluminum alloy under the three states of T3, artificial aging, and creep aging, and scanning electron microscope and transmission electron microscope were also used to observe the fatigue fracture morphology and aging precipitation features of the alloy under the above three states. Results showed that the alloy treated by creep aging can obtain higher fatigue life, but that treated by artificial aging is lower than T3; T3 alloy is mainly dominated by GPB region. Meanwhile, the crystal boundary displays continuously distributed fine precipitated phases; after artificial aging and creep aging treatment, a large amount of needle-shaped S′ phases precipitate inside the alloy, while there are wide precipitated phases at the crystal boundary. Wide precipitation free zones appear at the crystal boundary of artificial-aging samples, but precipitation free zones at the alloy crystal boundary of creep aging become narrower and even disappear. It can be seen that creep aging can change the precipitation features of the alloy and improve its fatigue life. Full article
(This article belongs to the Special Issue Aluminum Alloys) Printed Edition available
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Open AccessArticle Welding Distortion Prediction in 5A06 Aluminum Alloy Complex Structure via Inherent Strain Method
Metals 2016, 6(9), 214; https://doi.org/10.3390/met6090214
Received: 9 June 2016 / Revised: 27 July 2016 / Accepted: 11 August 2016 / Published: 6 September 2016
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Abstract
Finite element (FE) simulation with inherent deformation is an ideal and practical computational approach for predicting welding stress and distortion in the production of complex aluminum alloy structures. In this study, based on the thermal elasto-plastic analysis, FE models of multi-pass butt welds
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Finite element (FE) simulation with inherent deformation is an ideal and practical computational approach for predicting welding stress and distortion in the production of complex aluminum alloy structures. In this study, based on the thermal elasto-plastic analysis, FE models of multi-pass butt welds and T-type fillet welds were investigated to obtain the inherent strain distribution in a 5A06 aluminum alloy cylindrical structure. The angular distortion of the T-type joint was used to investigate the corresponding inherent strain mechanism. Moreover, a custom-designed experimental system was applied to clarify the magnitude of inherent deformation. With the mechanism investigation of welding-induced buckling by FE analysis using inherent deformation, an application for predicting and mitigating the welding buckling in fabrication of complex aluminum alloy structure was developed. Full article
(This article belongs to the Special Issue Aluminum Alloys) Printed Edition available
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Open AccessFeature PaperArticle Sintering Behaviors of Carbon Nanotubes—Aluminum Composite Powders
Metals 2016, 6(9), 213; https://doi.org/10.3390/met6090213
Received: 8 July 2016 / Revised: 27 August 2016 / Accepted: 31 August 2016 / Published: 6 September 2016
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Abstract
Carbon nanotubes (CNTs) are promising reinforcements for fabricating aluminum (Al) matrix composites with outstanding properties. The understanding of the consolidation process of CNT–Al composite powders plays a significant role in achieving high performances of bulk composites. In this study, an advanced consolidation technique
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Carbon nanotubes (CNTs) are promising reinforcements for fabricating aluminum (Al) matrix composites with outstanding properties. The understanding of the consolidation process of CNT–Al composite powders plays a significant role in achieving high performances of bulk composites. In this study, an advanced consolidation technique of spark plasma sintering (SPS) was used to fabricate CNT–Al composites with homogeneously dispersed CNTs. The sintering kinetics of pure Al powders and those powders coated with 1 wt % CNTs were studied. By combining the electrical conductivity and relative density results, it was found that the sintering process consisted of two stages with distinct densification rates. The second stage with a much lower rate was governed by the breaking down of alumina films at primary particle boundaries. The activation energy of the controlling second stage increased by 55% in CNT–Al composite powders compared to that of pure Al powder. As a result, CNT addition led to the overall decrease of sintering ability, which raised a challenge in the processing of CNT–Al composites. Full article
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