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Volume 6
Issue 9
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Metals, Volume 6, Issue 9 (September 2016) – 34 articles

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7385 KiB  
Article
Microstructure and Dry-Sliding Wear Behavior of B4C Ceramic Particulate Reinforced Al 5083 Matrix Composite
by Qian Zhao, Yunhong Liang, Zhihui Zhang, Xiujuan Li and Luquan Ren
Metals 2016, 6(9), 227; https://doi.org/10.3390/met6090227 - 21 Sep 2016
Cited by 22 | Viewed by 5341
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 [...] Read more.
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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1383 KiB  
Article
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
by Nebojša Pantelić, Bojana B. Zmejkovski, Dragana D. Marković, Jelena M. Vujić, Tatjana P. Stanojković, Tibor J. Sabo and Goran N. Kaluđerović
Metals 2016, 6(9), 226; https://doi.org/10.3390/met6090226 - 20 Sep 2016
Cited by 10 | Viewed by 5511
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 ( [...] Read more.
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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3284 KiB  
Article
Glass-Forming Ability and Early Crystallization Kinetics of Novel Cu-Zr-Al-Co Bulk Metallic Glasses
by Xiaoliang Han, Yusheng Qin, Kai Qin, Xuelian Li, Shenghai Wang, Jun Mi, Kaikai Song and Li Wang
Metals 2016, 6(9), 225; https://doi.org/10.3390/met6090225 - 15 Sep 2016
Cited by 13 | Viewed by 5907
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 [...] Read more.
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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5179 KiB  
Article
Utilization of a Porous Cu Interlayer for the Enhancement of Pb-Free Sn-3.0Ag-0.5Cu Solder Joint
by Nashrah Hani Jamadon, Ai Wen Tan, Farazila Yusof, Tadashi Ariga, Yukio Miyashita and Mohd Hamdi
Metals 2016, 6(9), 220; https://doi.org/10.3390/met6090220 - 15 Sep 2016
Cited by 9 | Viewed by 6307
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. [...] Read more.
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)
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4092 KiB  
Article
Influence of Milling Atmosphere on the Controlled Formation of Ultrafine Dispersoids in Al-Based MMCs
by Eduardo S. Caballero, Jesús Cintas, Francisco G. Cuevas, Juan Manuel Montes and Fátima Ternero
Metals 2016, 6(9), 224; https://doi.org/10.3390/met6090224 - 12 Sep 2016
Cited by 6 | Viewed by 4214
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 [...] Read more.
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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13777 KiB  
Article
Deformation Characteristic and Constitutive Modeling of 2707 Hyper Duplex Stainless Steel under Hot Compression
by Huabing Li, Weichao Jiao, Hao Feng, Xinxu Li, Zhouhua Jiang, Guoping Li, Lixin Wang, Guangwei Fan and Peide Han
Metals 2016, 6(9), 223; https://doi.org/10.3390/met6090223 - 12 Sep 2016
Cited by 16 | Viewed by 6841
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 [...] Read more.
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
(This article belongs to the Special Issue Process-Structure-Property Relationships in Metals)
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3401 KiB  
Article
Influence of Annealing on the Microstructures and Oxidation Behaviors of Al8(CoCrFeNi)92, Al15(CoCrFeNi)85, and Al30(CoCrFeNi)70 High-Entropy Alloys
by Todd M. Butler and Mark L. Weaver
Metals 2016, 6(9), 222; https://doi.org/10.3390/met6090222 - 12 Sep 2016
Cited by 42 | Viewed by 6872
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 [...] Read more.
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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8144 KiB  
Article
Nanocrystalline β-Ta Coating Enhances the Longevity and Bioactivity of Medical Titanium Alloys
by Linlin Liu, Jiang Xu and Shuyun Jiang
Metals 2016, 6(9), 221; https://doi.org/10.3390/met6090221 - 10 Sep 2016
Cited by 10 | Viewed by 7102
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 [...] Read more.
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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3161 KiB  
Article
The Unified Creep-Fatigue Equation for Stainless Steel 316
by Dan Liu, Dirk John Pons and Ee-hua Wong
Metals 2016, 6(9), 219; https://doi.org/10.3390/met6090219 - 10 Sep 2016
Cited by 13 | Viewed by 7891
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 [...] Read more.
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)
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9820 KiB  
Article
Aging Behaviour and Mechanical Performance of 18-Ni 300 Steel Processed by Selective Laser Melting
by Riccardo Casati, Jannis N. Lemke, Ausonio Tuissi and Maurizio Vedani
Metals 2016, 6(9), 218; https://doi.org/10.3390/met6090218 - 8 Sep 2016
Cited by 224 | Viewed by 15230
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 [...] Read more.
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)
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6029 KiB  
Article
Numerical Modeling of Cyclic Deformation in Bulk Metallic Glasses
by Yunpeng Jiang
Metals 2016, 6(9), 217; https://doi.org/10.3390/met6090217 - 7 Sep 2016
Cited by 8 | Viewed by 5850
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 [...] Read more.
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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12800 KiB  
Article
The Effect of Ag Addition on the Enhancement of the Thermal and Mechanical Properties of CuZrAl Bulk Metallic Glasses
by Tsan-Man Chung, Sheng-Rui Jian and Pei-Ju Hsieh
Metals 2016, 6(9), 216; https://doi.org/10.3390/met6090216 - 7 Sep 2016
Cited by 8 | Viewed by 5893
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), [...] Read more.
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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6012 KiB  
Article
The Effect of Creep Aging on the Fatigue Fracture Behavior of 2524 Aluminum Alloy
by Wenke Li, Lihua Zhan, Lingfeng Liu and Yongqian Xu
Metals 2016, 6(9), 215; https://doi.org/10.3390/met6090215 - 7 Sep 2016
Cited by 4 | Viewed by 5731
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 [...] Read more.
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)
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7482 KiB  
Article
Welding Distortion Prediction in 5A06 Aluminum Alloy Complex Structure via Inherent Strain Method
by Zhi Zeng, Xiaoyong Wu, Mao Yang and Bei Peng
Metals 2016, 6(9), 214; https://doi.org/10.3390/met6090214 - 6 Sep 2016
Cited by 8 | Viewed by 7391
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 [...] Read more.
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)
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5693 KiB  
Article
Sintering Behaviors of Carbon Nanotubes—Aluminum Composite Powders
by Biao Chen and Katsuyoshi Kondoh
Metals 2016, 6(9), 213; https://doi.org/10.3390/met6090213 - 6 Sep 2016
Cited by 23 | Viewed by 6546
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 [...] Read more.
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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1021 KiB  
Communication
Kinetic Study of Copper(II) Simultaneous Extraction/Stripping from Aqueous Solutions by Bulk Liquid Membranes Using Coupled Transport Mechanisms
by Loreto León, Gerardo León, Javier Senent and María Amelia Guzmán
Metals 2016, 6(9), 212; https://doi.org/10.3390/met6090212 - 2 Sep 2016
Cited by 12 | Viewed by 4668
Abstract
Heavy metals removal/recovery from industrial wastewater has become a prime concern for both economic and environmental reasons. This paper describes a comparative kinetic study of the removal/recovery of copper(II) from aqueous solutions by bulk liquid membrane using two types of coupled facilitated transport [...] Read more.
Heavy metals removal/recovery from industrial wastewater has become a prime concern for both economic and environmental reasons. This paper describes a comparative kinetic study of the removal/recovery of copper(II) from aqueous solutions by bulk liquid membrane using two types of coupled facilitated transport mechanisms and three carriers of different chemical nature: benzoylacetone, 8-hydroxyquinoline, and tri-n-octylamine. The results are analyzed by means of a kinetic model involving two consecutive irreversible first-order reactions (extraction and stripping). Rate constants and efficiencies of the extraction (k1, EE) and the stripping (k2, SE) reactions, and maximum fluxes through the membrane, were determined for the three carriers to compare their efficiency in the Cu(II) removal/recovery process. Counter-facilitated transport mechanism using benzoylacetone as carrier and protons as counterions led to higher maximum flux and higher extraction and stripping efficiencies due to the higher values of both the extraction and the stripping rate constants. Acceptable linear relationships between EE and k1, and between SE and k2, were found. Full article
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3264 KiB  
Article
Study of the Isothermal Oxidation Process and Phase Transformations in B2-(Ni,Pt)Al/RENE-N5 System
by Luis Alberto Cáceres-Díaz, Juan Manuel Alvarado-Orozco, Haidee Ruiz-Luna, John Edison García-Herrera, Alma Gabriela Mora-García, Gerardo Trápaga-Martínez, Raymundo Arroyave and Juan Muñoz-Saldaña
Metals 2016, 6(9), 208; https://doi.org/10.3390/met6090208 - 1 Sep 2016
Cited by 5 | Viewed by 5453
Abstract
Changes in composition, crystal structure and phase transformations of B2-(Ni,Pt)Al coatings upon isothermal oxidation experiments (natural and scale free oxidation) at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are [...] Read more.
Changes in composition, crystal structure and phase transformations of B2-(Ni,Pt)Al coatings upon isothermal oxidation experiments (natural and scale free oxidation) at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are performed to identify changes in the B2-(Ni,Pt)Al phase upon the chemically-driven L10-(Ni,Pt)Al and L12-(Ni,Pt)3Al transformations. The B2-(Ni,Pt)Al phase was found to disorder and transform the martensite during the heat treatments for both oxidation experiments at approximately 36.3 and 40.9 at. % of Al, 47.7 and 42.9 at. % of Ni, 6.2 and 8.5 at. % of Pt, 4.2 and 2.9 at. % of Cr and 4.4 and 3.8 at. % of Co. The lattice constant and the long-range order parameter of the B2-(Ni,Pt)Al phase decreased linearly as a function of the elemental content irrespective of the nature of the oxidation experiments. Full article
(This article belongs to the Special Issue Intermetallics 2016)
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3981 KiB  
Article
Decrease in Hydrogen Embrittlement Susceptibility of 10B21 Screws by Bake Aging
by Kuan-Jen Chen, Fei-Yi Hung, Truan-Sheng Lui and Chien-Hao Tseng
Metals 2016, 6(9), 211; https://doi.org/10.3390/met6090211 - 31 Aug 2016
Cited by 4 | Viewed by 6825
Abstract
The effects of baking on the mechanical properties and fracture characteristics of low-carbon boron (10B21) steel screws were investigated. Fracture torque tests and hydrogen content analysis were performed on baked screws to evaluate hydrogen embrittlement (HE) susceptibility. The diffusible hydrogen content within 10B21 [...] Read more.
The effects of baking on the mechanical properties and fracture characteristics of low-carbon boron (10B21) steel screws were investigated. Fracture torque tests and hydrogen content analysis were performed on baked screws to evaluate hydrogen embrittlement (HE) susceptibility. The diffusible hydrogen content within 10B21 steel dominated the fracture behavior of the screws. The fracture torque of 10B21 screws baked for a long duration was affected by released hydrogen. Secondary ion mass spectroscopy (SIMS) result showed that hydrogen content decreased with increasing baking duration, and thus the HE susceptibility of 10B21 screws improved. Diffusible hydrogen promoted crack propagation in high-stress region. The HE of 10B21 screws can be prevented by long-duration baking. Full article
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3425 KiB  
Article
Hot Tensile and Fracture Behavior of 35CrMo Steel at Elevated Temperature and Strain Rate
by Zhengbing Xiao, Yuanchun Huang, Hui Liu and Sanxing Wang
Metals 2016, 6(9), 210; https://doi.org/10.3390/met6090210 - 31 Aug 2016
Cited by 23 | Viewed by 5981
Abstract
To better understand the tensile deformation and fracture behavior of 35CrMo steel during hot processing, uniaxial tensile tests at elevated temperatures and strain rates were performed. Effects of deformation condition on the flow behavior, strain rate sensitivity, microstructure transformation, and fracture characteristic were [...] Read more.
To better understand the tensile deformation and fracture behavior of 35CrMo steel during hot processing, uniaxial tensile tests at elevated temperatures and strain rates were performed. Effects of deformation condition on the flow behavior, strain rate sensitivity, microstructure transformation, and fracture characteristic were characterized and discussed. The results indicated that the flow stress was sensitive to the deformation condition, and fracture occurs immediately after the peak stress level is reached, especially when the temperature is low or the strain rate is high. The strain rate sensitivity increases with the deformation temperature, which indicates that formability could improve at high temperatures. Photographs showing both the fracture surfaces and the matrix near the fracture section indicated the ductile nature of the material. However, the fracture mechanisms varied according to the deformation condition, which influences the dynamic recrystallization (DRX) condition, and the DRX was accompanied by the formation of voids. For samples deformed at high temperatures or low strain rates, coalescence of numerous voids formed in the recrystallized grains is responsible for fracture, while at high strain rates or low temperatures, the grains rupture mainly by splitting because of cracks formed around the inclusions. Full article
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12025 KiB  
Article
Simulation Study on Thermo-Mechanical Controlled Process of 800 MPa-Grade Steel for Hydropower Penstocks
by Qingfeng Ding, Yuefeng Wang, Qingfeng Wang and Tiansheng Wang
Metals 2016, 6(9), 209; https://doi.org/10.3390/met6090209 - 31 Aug 2016
Cited by 2 | Viewed by 4794
Abstract
The thermo-mechanical controlled process (TMCP) of 800-MPa-grade non-quenched tempered steel used for penstocks was simulated on a Gleeble-3500 thermo-mechanical simulator. The effect of the finish cooling temperature (FCT) which ranged from 350–550 °C on the microstructure and mechanical properties was studied. The microstructure [...] Read more.
The thermo-mechanical controlled process (TMCP) of 800-MPa-grade non-quenched tempered steel used for penstocks was simulated on a Gleeble-3500 thermo-mechanical simulator. The effect of the finish cooling temperature (FCT) which ranged from 350–550 °C on the microstructure and mechanical properties was studied. The microstructure of TMCP specimens is primarily composed of lath bainite (LB) and granular bainite (GB). The decreased FCT can induce the increase of LB and the decrease of GB in the volume fraction, and the decrease in the amount and the size of Martensite/Austenite (M/A) constituents with a more dispersive distribution. The LB has higher strength and hardness than GB, and the GB with fine and dispersive M/A constituents has excellent impact toughness. The minimum values of the yield strength, tensile strength and hardness, and the maximum value of the impact absorbed energy are obtained for the FCT of 450 °C. For the FCT over 450 °C, the yield strength, tensile strength and hardness are increased slightly, but the impact absorbed energy is rapidly decreased, which is mainly attributed to the formation of block M/A constituents. When the FCT is around 400 °C, the optimal combination of yield strength and impact toughness is obtained, which meets the technical requirements of 800-MPa-grade hydropower penstock steel. Full article
(This article belongs to the Special Issue Process-Structure-Property Relationships in Metals)
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4589 KiB  
Article
The Electrochemical Investigation of the Corrosion Rates of Welded Pipe ASTM A106 Grade B
by Trinet Yingsamphancharoen, Nakarin Srisuwan and Aphichart Rodchanarowan
Metals 2016, 6(9), 207; https://doi.org/10.3390/met6090207 - 31 Aug 2016
Cited by 15 | Viewed by 7860
Abstract
The aim of this work was to investigate the corrosion rate of welded carbon steel pipe (ASTM (American Society for Testing and Materials) A106 Grade B) by GTAW under the currents of 60, 70, and 80 A. All welded pipes satisfied weld procedure [...] Read more.
The aim of this work was to investigate the corrosion rate of welded carbon steel pipe (ASTM (American Society for Testing and Materials) A106 Grade B) by GTAW under the currents of 60, 70, and 80 A. All welded pipes satisfied weld procedure specifications and were verified by a procedure qualification record. The property of used materials was in agreement with the ASME standard: section IX. The welded pipe was used for schematic model corrosion measurements applied in 3.5 wt % NaCl at various flow rates and analyzed by using the electrochemical technique with Tafel’s equation. The results showed the correlation between the flow rate and the corrosion rate of the pipe; the greater the flow rate, the higher corrosion rate. Moreover, the welded pipe from the welding current of 70 A exhibited higher tensile strength and corrosion resistance than those from currents of 60 and 80 A. It indicated that the welding current of 70 A produced optimum heat for the welding of A106 pipe grade B. In addition, the microstructure of the welded pipe was observed by SEM. The phase transformation and crystallite size were analyzed by XRD and Sherrer’s equation. The results suggested that the welding current could change the microstructure and phase of the welded pipe causing change in the corrosion rate. Full article
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1446 KiB  
Article
Study on the Leaching of Mercuric Oxide with Thiosulfate Solutions
by Chao Han, Wei Wang and Feng Xie
Metals 2016, 6(9), 206; https://doi.org/10.3390/met6090206 - 30 Aug 2016
Cited by 15 | Viewed by 5811
Abstract
Mercury is receiving more concern due to its high mobility and high toxicity to human health and the environment. Restrictive legislations and world-wide efforts have been made on mercury control, especially the release and disposal of mercury-contaminated wastes. This paper describes a novel [...] Read more.
Mercury is receiving more concern due to its high mobility and high toxicity to human health and the environment. Restrictive legislations and world-wide efforts have been made on mercury control, especially the release and disposal of mercury-contaminated wastes. This paper describes a novel technology for detoxifying mercury-containing solid wastes with thiosulfate salts. Various parameters which may potentially influence mercury extraction from mercuric oxide with the thiosulfate leaching system—including reagent concentration, solution pH, and temperature—have been examined. The experimental results show that virtually all mercuric oxide can rapidly dissolve into the thiosulfate leaching system under optimized experimental conditions, indicating that thiosulfate is an effective lixivant for recovering mercury from mercury-containing solid waste. Full article
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29637 KiB  
Article
Improvement in the Design of Welded Joints of EN 235JR Low Carbon Steel by Multiple Response Surface Methodology
by Ruben Lostado Lorza, Ruben Escribano García, María Ángeles Martínez Calvo and Rodolfo Múgica Vidal
Metals 2016, 6(9), 205; https://doi.org/10.3390/met6090205 - 30 Aug 2016
Cited by 30 | Viewed by 7462
Abstract
Gas metal arc welding (GMAW) is a joining process that is controlled by several inputs or welding parameters. However, speed, current and voltage are the parameters that are most frequently used in setting this process. Cord area, yield stress, tensile strength, residual stresses, [...] Read more.
Gas metal arc welding (GMAW) is a joining process that is controlled by several inputs or welding parameters. However, speed, current and voltage are the parameters that are most frequently used in setting this process. Cord area, yield stress, tensile strength, residual stresses, hardness and roughness are considered to be outputs or welded joints parameters. They are widely used when the design requirements are based on the cost, manufacturing speed, strength and surface finish. This paper seeks to determine the relationship between the welding parameters and the welded joint parameters of speed, current and voltage in butt joints (X-groove) of EN 235JR by the response surface method (RSM). The optimal joints when considering the design requirements of cost, manufacturing speed, strength and surface finish were achieved by using the multi-response surface (MRS). The optimal welding parameters reached when considering the design requirements of cost were 140.593 amps, 8.192 mm/s and 29.999 volts, respectively, whereas the design requirements of manufacturing speed were 149.88 amps, 9.261 mm/s and 29.999 volts. Finally, the welding parameters for the design requirements of joint strength and surface finish were 149.086 amps, 7.139 mm/s and 28.541 volts and 150.372 amps, 8.561 mm/s and 29.877 volts, respectively. Full article
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10902 KiB  
Article
Devising Strain Hardening Models Using Kocks–Mecking Plots—A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel
by Markus Bambach, Irina Sizova, Sebastian Bolz and Sabine Weiß
Metals 2016, 6(9), 204; https://doi.org/10.3390/met6090204 - 29 Aug 2016
Cited by 22 | Viewed by 9234
Abstract
The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a [...] Read more.
The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B) alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening) initially and exhibits neither a plateau (stage IV hardening) nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys. Full article
(This article belongs to the Special Issue Intermetallics 2016)
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672 KiB  
Article
Cold Agglomeration of Ultrafine Oxidized Dust (UOD) from Ferromanganese and Silicomanganese Industrial Process
by María Ordiales, Juan Iglesias, Daniel Fernández-González, José Sancho-Gorostiaga, Alberto Fuentes and Luis Felipe Verdeja
Metals 2016, 6(9), 203; https://doi.org/10.3390/met6090203 - 27 Aug 2016
Cited by 14 | Viewed by 4755
Abstract
Different wastes are generated in ferromanganese and silicomanganese alloy production. One of them is the ultrafine oxidized dust (UOD) produced in the collection and control of flying dusts in the ferroalloy industry. This waste has fairly high manganese content (20%–40% Mn), making it [...] Read more.
Different wastes are generated in ferromanganese and silicomanganese alloy production. One of them is the ultrafine oxidized dust (UOD) produced in the collection and control of flying dusts in the ferroalloy industry. This waste has fairly high manganese content (20%–40% Mn), making it suitable to be a secondary raw material for the ferromanganese industry. This research proposes a method for the transformation of UOD into a useable raw material. Cold agglomeration is the best option, due to its low energy consumption. Portland cement and refractory cement are compared as suitable candidates in the management of the UOD for their reuse in the electric arc furnace feed. Full article
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4910 KiB  
Article
Influences of Laser Spot Welding on Magnetic Property of a Sintered NdFeB Magnet
by Baohua Chang, Dong Du, Chenhui Yi, Bin Xing and Yihong Li
Metals 2016, 6(9), 202; https://doi.org/10.3390/met6090202 - 26 Aug 2016
Cited by 8 | Viewed by 6721
Abstract
Laser welding has been considered as a promising method to join sintered NdFeB permanent magnets thanks to its high precision and productivity. However, the influences of laser welding on the magnetic property of NdFeB are still not clear. In the present paper, the [...] Read more.
Laser welding has been considered as a promising method to join sintered NdFeB permanent magnets thanks to its high precision and productivity. However, the influences of laser welding on the magnetic property of NdFeB are still not clear. In the present paper, the effects of laser power on the remanence (Br) were experimentally investigated in laser spot welding of a NdFeB magnet (N48H). Results show that the Br decreased with the increase of laser power. For the same welding parameters, the Br of magnets, that were magnetized before welding, were much lower than that of magnets that were magnetized after welding. The decrease in Br of magnets after laser welding resulted from the changes in microstructures and, in turn, the deterioration of magnetic properties in the nugget and the heat affected zone (HAZ) in a laser weld. It is recommended that the dimensions of nuggets and HAZ in laser welds of a NdFeB permanent magnet should be as small as possible, and the magnets should be welded before being magnetized in order to achieve a better magnetic performance in practical engineering applications. Full article
(This article belongs to the Special Issue Advances in Welding Metal Alloys, Dissimilar Metals and Additively Manufactured Parts)
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4010 KiB  
Article
The Influence of Different External Fields on Aging Kinetics of 2219 Aluminum Alloy
by Lihua Zhan, Wenke Li, Qiangqiang Ma and Lingfeng Liu
Metals 2016, 6(9), 201; https://doi.org/10.3390/met6090201 - 26 Aug 2016
Cited by 9 | Viewed by 4614
Abstract
By undertakig an aging experiment on 2219 aluminum alloy under different external field and by the method of hardness test, a comparative study on the kinetics of aging generated under different external fields was conducted. Furthermore, the time-temperature-transformation curves (TTT curve) were obtained, [...] Read more.
By undertakig an aging experiment on 2219 aluminum alloy under different external field and by the method of hardness test, a comparative study on the kinetics of aging generated under different external fields was conducted. Furthermore, the time-temperature-transformation curves (TTT curve) were obtained, and the microstructure and mechanical property of the alloy under the effect of different external fields were tested. Results indicated that the effect of magnetic field postponed the alloy’s aging precipitation process, and slightly reduced its mechanical property; the effects of electric field accelerated the alloy’s aging precipitation, increased its mechanical property and made the precipitated phase of alloy smaller and diffused. In addition, through analysis, it was concluded that the performance of the specimen was even more balanced under the effect of electromagnetic field. Full article
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961 KiB  
Review
An Insight into Evolution of Light Weight High Entropy Alloys: A Review
by Amit Kumar and Manoj Gupta
Metals 2016, 6(9), 199; https://doi.org/10.3390/met6090199 - 26 Aug 2016
Cited by 139 | Viewed by 14263
Abstract
High Entropy Alloys (HEAs) are the most recently developed new class of materials, which are known for their unique structural properties. Lightweight materials are currently in excessive demand for transportation and energy saving applications. In this review, efforts have been made to summarize [...] Read more.
High Entropy Alloys (HEAs) are the most recently developed new class of materials, which are known for their unique structural properties. Lightweight materials are currently in excessive demand for transportation and energy saving applications. In this review, efforts have been made to summarize the work done towards the development of HEAs targeting lightweight applications. Some new synthesis techniques are suggested for the fabrication of lightweight HEAs (LWHEAs). The concept of porous structure fabrication, microwave sintering of green compact, casting by disintegration melt deposition and advanced manufacturing using additive manufacturing are discussed as future directions of LWHEAs synthesis. LWHEAs for potential biomedical applications have also been addressed. Full article
(This article belongs to the Special Issue High-Entropy Alloys (HEAs))
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2863 KiB  
Article
Microstructure, Hardness Evolution, and Thermal Stability Mechanism of Mechanical Alloyed Cu-Nb Alloy during Heat Treatment
by Ruoshan Lei, Mingpu Wang, Shiqing Xu, Huanping Wang and Guangrun Chen
Metals 2016, 6(9), 194; https://doi.org/10.3390/met6090194 - 26 Aug 2016
Cited by 10 | Viewed by 5267
Abstract
The microstructure, hardness evolution, and thermal stability of mechanically alloyed (MA-ed) nanocrystalline Cu–10 wt %Nb solid solution during heat treatment were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) observations, and microhardness measurement. It is [...] Read more.
The microstructure, hardness evolution, and thermal stability of mechanically alloyed (MA-ed) nanocrystalline Cu–10 wt %Nb solid solution during heat treatment were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) observations, and microhardness measurement. It is found that the pronounced precipitation of Nb from the Cu-Nb supersaturated solid solution occurs at temperatures up to 700 °C, and the annealed alloy shows a bi-nanostructure with Nb nanoparticles dispersed in the nanocrystalline Cu matrix. The bi-nanostructure remains stable with Cu crystalline grain size below 100 nm and Nb particle size around 10 nm even after annealing at 900 °C for 3 h. The microhardness of the annealed sample shows a small increase after annealing at 400 °C, and then it shows a slow decreasing trend with further increasing temperatures. With the help of the kinetics analyses, it is found that the coarsening of the stable Nb nanoparticles is controlled by volume diffusion. The enhanced stability of the nanocrystalline Cu microstructure is mainly attributed to the solute drag and precipitate pinning effects. Full article
(This article belongs to the Special Issue Mechanical Alloying)
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3590 KiB  
Article
Molecular Docking and Aberration-Corrected STEM of Palladium Nanoparticles on Viral Templates
by Liliana Carreño-Fuentes, Daniel Bahena, Laura A. Palomares, Octavio T. Ramírez, Miguel José-Yacamán and Germán Plascencia-Villa
Metals 2016, 6(9), 200; https://doi.org/10.3390/met6090200 - 25 Aug 2016
Cited by 7 | Viewed by 7236
Abstract
Viral templates are highly versatile biotemplates used for the synthesis of nanostructured materials. Rotavirus VP6 self-assembles into nanotubular hollow structures with well-defined diameters and variable lengths, serving as a nucleic acid-free biotemplate to synthesize metal nanoparticles of controlled size, shape, and orientation. Molecular [...] Read more.
Viral templates are highly versatile biotemplates used for the synthesis of nanostructured materials. Rotavirus VP6 self-assembles into nanotubular hollow structures with well-defined diameters and variable lengths, serving as a nucleic acid-free biotemplate to synthesize metal nanoparticles of controlled size, shape, and orientation. Molecular docking simulations show that exposed residues (H173-S240-D242 and N200-N310) of VP6 have the ability to specifically bind Pd(II) ions, which serve as nucleation sites for the growth and stabilization of palladium nanoclusters. Using VP6 nanotubes as biotemplates allows for obtaining small Pd particles of 1–5 nm in diameter. Advanced electron microscopy imaging and characterization through ultra-high-resolution field-emission scanning electron microscopy (UHR-FE-SEM) and spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM) at a low voltage dose (80 kV) reveals, with high spatial resolution, the structure of Pd nanoparticles attached to the macromolecular biotemplates. Full article
(This article belongs to the Special Issue Metallomics)
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