Next Issue
Previous Issue

Table of Contents

Metals, Volume 6, Issue 4 (April 2016)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-24
Export citation of selected articles as:

Research

Open AccessArticle Structural Origin of the Enhanced Glass-Forming Ability Induced by Microalloying Y in the ZrCuAl Alloy
Metals 2016, 6(4), 67; doi:10.3390/met6040067
Received: 16 January 2016 / Revised: 16 March 2016 / Accepted: 17 March 2016 / Published: 23 March 2016
PDF Full-text (1927 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the structural origin of the enhanced glass-forming ability induced by microalloying Y in a ZrCuAl multicomponent system is studied by performing synchrotron radiation experiments combined with simulations. It is revealed that the addition of Y leads to the optimization of
[...] Read more.
In this work, the structural origin of the enhanced glass-forming ability induced by microalloying Y in a ZrCuAl multicomponent system is studied by performing synchrotron radiation experiments combined with simulations. It is revealed that the addition of Y leads to the optimization of local structures, including: (1) more Zr-centered and Y-centered icosahedral-like clusters occur in the microstructure; (2) the atomic packing efficiency inside clusters and the regularity of clusters are both enhanced. These structural optimizations help to stabilize the amorphous structure in the ZrCuAlY system, and lead to a high glass-forming ability (GFA). The present work provides an understanding of GFAs in multicomponent alloys and will shed light on the development of more metallic glasses with high GFAs. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Corrosion Behavior of Pure Ti under a Solid NaCl Deposit in a Wet Oxygen Flow at 600 °C
Metals 2016, 6(4), 72; doi:10.3390/met6040072
Received: 27 January 2016 / Revised: 12 March 2016 / Accepted: 17 March 2016 / Published: 24 March 2016
PDF Full-text (5605 KB) | HTML Full-text | XML Full-text
Abstract
The corrosion behavior of pure Ti under a solid NaCl deposit in a wet O2 flow at 600 °C has been studied. The results showed that the corrosion rate was greatly accelerated by solid NaCl, which destroyed the compact and protective TiO
[...] Read more.
The corrosion behavior of pure Ti under a solid NaCl deposit in a wet O2 flow at 600 °C has been studied. The results showed that the corrosion rate was greatly accelerated by solid NaCl, which destroyed the compact and protective TiO2 scale to yield non-protective N4Ti5O12 and other products. Detailed scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDX), and X-ray diffraction (XRD) analysis showed that, during the corrosion process, the metal (Ti) diffused outward rapidly and reacted with the wet O2 to form a thick and porous corrosion products scale. The electrochemical reaction was also observed during the whole corrosion process at 600 °C, which further accelerated the corrosion rate. A possible mechanism has been proposed for pure Ti covered with a solid NaCl deposit in wet O2 at 600 °C, based on the experimental results. Full article
Figures

Open AccessArticle Effects of Cr2N Precipitation on the Antibacterial Properties of AISI 430 Stainless Steel
Metals 2016, 6(4), 73; doi:10.3390/met6040073
Received: 12 February 2016 / Revised: 8 March 2016 / Accepted: 17 March 2016 / Published: 24 March 2016
PDF Full-text (4176 KB) | HTML Full-text | XML Full-text
Abstract
Based on their mechanical properties and good corrosion resistance, some commercial Ni-Cr stainless steels have been widely applied as biomaterials, including the austenitic 304 stainless steel, the austenitic 316 stainless steel, the duplex 2205 stainless steel, and the ferritic 430 stainless steel. In
[...] Read more.
Based on their mechanical properties and good corrosion resistance, some commercial Ni-Cr stainless steels have been widely applied as biomaterials, including the austenitic 304 stainless steel, the austenitic 316 stainless steel, the duplex 2205 stainless steel, and the ferritic 430 stainless steel. In order to reduce the occurrence of infections resulting from biomaterial implants, instruments, and medical devices, Cu2+ and Ag2+ ions have been added onto biomaterials for increasing the antibacterial properties, but they are known to damage biofilm. The occurrence of nanoparticles can also improve the antibacterial properties of biomaterials through various methods. In this study, we used Escherichia coli and analyzed the microstructures of American Iron and Steel Institute (AISI) 430 stainless steel with a 0.18 mass % N alloy element. During a lower temperature aging, the microstructure of the as-quenched specimen is essentially a ferrite and martensite duplex matrix with some Cr2N precipitates formed. Additionally, the antibacterial properties of the alloy for E. coli ranged from 3% to 60%, consistent with the presence of Cr2N precipitates. When aged at a lower temperature, which resulted in nano-Cr2N precipitation, the specimen possessed the highest antibacterial activity. Full article
(This article belongs to the Special Issue Metallic Biomaterials)
Figures

Open AccessArticle Preparation of Property-Controlled Bi-Based Solder Powders by a Ball-Milling Process
Metals 2016, 6(4), 74; doi:10.3390/met6040074
Received: 28 January 2016 / Revised: 23 February 2016 / Accepted: 4 March 2016 / Published: 25 March 2016
Cited by 5 | PDF Full-text (2899 KB) | HTML Full-text | XML Full-text
Abstract
Three kinds of Bi-based solder powders with different chemical compositions of binary Bi–Sn, ternary Bi–Sn–In, and quaternary Bi–Sn–In–Ga were prepared using a gas atomization process and subsequently ball-milled for smaller-size fabrication. In particular, only the quaternary Bi–Sn–In–Ga solder powders were severely broken to
[...] Read more.
Three kinds of Bi-based solder powders with different chemical compositions of binary Bi–Sn, ternary Bi–Sn–In, and quaternary Bi–Sn–In–Ga were prepared using a gas atomization process and subsequently ball-milled for smaller-size fabrication. In particular, only the quaternary Bi–Sn–In–Ga solder powders were severely broken to the size of less than 10 μm in a polyhedral shape due to the presence of the constitutional element, the degree of overall oxidation, and the formation of solid solution, which had affected the fractured extent of the Ga-containing solder powders. Furthermore, a melting point also decreased by the addition of In and/or Ga into the binary Bi–Sn solder system, resulting in a melting point of 60.3 °C for the Bi–Sn–In–Ga solder powders. Thus, it was possible that fractured Bi–Sn–In–Ga solder powders were appropriate for the adhesion of more compact solder bump arrays, enabling reflowing at the low temperature of 110 °C on a flexible polyethylene terephthalate (PET) substrate. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Figures

Open AccessArticle Influence of Post-Weld Heat Treatment on the Microstructure, Microhardness, and Toughness of a Weld Metal for Hot Bend
Metals 2016, 6(4), 75; doi:10.3390/met6040075
Received: 31 December 2015 / Revised: 13 March 2016 / Accepted: 18 March 2016 / Published: 25 March 2016
Cited by 3 | PDF Full-text (21514 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a weld metal in K65 pipeline steel pipe has been processed through self-designed post-weld heat treatments including reheating and tempering associated with hot bending. The microstructures and the corresponding toughness and microhardness of the weld metal subjected to the post-weld
[...] Read more.
In this work, a weld metal in K65 pipeline steel pipe has been processed through self-designed post-weld heat treatments including reheating and tempering associated with hot bending. The microstructures and the corresponding toughness and microhardness of the weld metal subjected to the post-weld heat treatments have been investigated. Results show that with the increase in reheating temperature, austenite grain size increases and the main microstructures transition from fine polygonal ferrite (PF) to granular bainitic ferrite (GB). The density of the high angle boundary decreases at higher reheating temperature, leading to a loss of impact toughness. Lots of martensite/austenite (M/A) constituents are observed after reheating, and to a large extent transform into cementite after further tempering. At high reheating temperatures, the increased hardenability promotes the formation of large quantities of M/A constituents. After tempering, the cementite particles become denser and coarser, which considerably deteriorates the impact toughness. Additionally, microhardness has a good linear relation with the mean equivalent diameter of ferrite grain with a low boundary tolerance angle (2°−8°), which shows that the hardness is controlled by low misorientation grain boundaries for the weld metal. Full article
Figures

Open AccessFeature PaperArticle Electrochemical Surface Treatment of a β-titanium Alloy to Realize an Antibacterial Property and Bioactivity
Metals 2016, 6(4), 76; doi:10.3390/met6040076
Received: 18 February 2016 / Revised: 20 March 2016 / Accepted: 24 March 2016 / Published: 28 March 2016
Cited by 3 | PDF Full-text (3622 KB) | HTML Full-text | XML Full-text
Abstract
In this study, micro-arc oxidation (MAO) was performed on a β-type titanium alloy, namely, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), to improve not only its antibacterial property but also bioactivity in body fluids. The surface oxide layer formed on TNTZ by MAO treatment in a mixture
[...] Read more.
In this study, micro-arc oxidation (MAO) was performed on a β-type titanium alloy, namely, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), to improve not only its antibacterial property but also bioactivity in body fluids. The surface oxide layer formed on TNTZ by MAO treatment in a mixture of calcium glycerophosphate, calcium acetate, and silver nitrate was characterized using surface analyses. The resulting porous oxide layer was mainly composed of titanium oxide, and it also contained calcium, phosphorus, and a small amount of silver, all of which were incorporated from the electrolyte during the treatment. The MAO-treated TNTZ showed a strong inhibition effect on anaerobic Gram-negative bacteria when the electrolyte contained more than 0.5 mM silver ions. The formation of calcium phosphate on the surface of the specimens after immersion in Hanks’ solution was evaluated to determine the bioactivity of TNTZ with sufficient antibacterial property. As a result, thick calcium phosphate layers formed on the TNTZ specimen that underwent MAO treatment, whereas no precipitate was observed on TNTZ without treatment. Thus, the MAO treatment of titanium-based alloys is confirmed to be effective in realizing both antibacterial and bioactive properties. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Figures

Open AccessArticle Finite-Element Thermal Analysis and Grain Growth Behavior of HAZ on Argon Tungsten-Arc Welding of 443 Stainless Steel
Metals 2016, 6(4), 77; doi:10.3390/met6040077
Received: 26 February 2016 / Revised: 14 March 2016 / Accepted: 24 March 2016 / Published: 29 March 2016
Cited by 2 | PDF Full-text (3794 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a numerical and infrared experimental study of thermal and grain growth behavior during argon tungsten arc welding of 443 stainless steel. A 3D finite element model was proposed to simulate the welding process. The simulations were carried out via the
[...] Read more.
This paper presents a numerical and infrared experimental study of thermal and grain growth behavior during argon tungsten arc welding of 443 stainless steel. A 3D finite element model was proposed to simulate the welding process. The simulations were carried out via the Ansys Parametric Design Language (APDL) available in the finite-element code, ANSYS. To validate the simulation accuracy, a series of experiments using a fully-automated welding process was conducted. The results of the numerical analysis show that the simulation weld bead size and the experiment results have good agreement. The grain growth in the heat-affected zone of 443 stainless steel is influenced via three factors: (1) the thermal cycle experienced; (2) grain boundary migration; and (3) particle precipitation. Grain boundary migration is the main factor. The modified coefficient k of the grain growth index is calculated. The value is 1.16. Moreover, the microhardness of the weld bead softened slightly compared to the base metal. Full article
Figures

Open AccessArticle First-Principles Study of Chemical and Topological Short-Range Orders in the Mg–Si Liquid Alloys
Metals 2016, 6(4), 78; doi:10.3390/met6040078
Received: 21 January 2016 / Revised: 20 March 2016 / Accepted: 23 March 2016 / Published: 30 March 2016
Cited by 1 | PDF Full-text (2418 KB) | HTML Full-text | XML Full-text
Abstract
The structures of a series of Mg–Si liquid alloys were investigated by means of ab initio molecular dynamic simulation. The pair distribution function analysis manifests a tendency of aggregating for the Si–Si pairs in the Mg90Si10 liquid alloy. Chemical short-range
[...] Read more.
The structures of a series of Mg–Si liquid alloys were investigated by means of ab initio molecular dynamic simulation. The pair distribution function analysis manifests a tendency of aggregating for the Si–Si pairs in the Mg90Si10 liquid alloy. Chemical short-range orders are observed around Si atoms between unlike atoms, and the maximum is observed for the eutectic Mg47Si53 alloy. Furthermore, the topological environment changed abruptly near the eutectic Mg47Si53 alloy according to Voronoi polyhedra analysis. The variation of diffusion coefficients of Mg and Si suggests that the dynamical properties of Mg–Si liquid alloys are more sensitive to temperature than to compositions. Full article
Figures

Open AccessArticle Effect of Heat Treatment on the In-Plane Anisotropy of As-Rolled 7050 Aluminum Alloy
Metals 2016, 6(4), 79; doi:10.3390/met6040079
Received: 22 January 2016 / Revised: 28 March 2016 / Accepted: 29 March 2016 / Published: 2 April 2016
Cited by 1 | PDF Full-text (4393 KB) | HTML Full-text | XML Full-text
Abstract
Tensile tests were conducted on both as-quenched and over-aged 7050 aluminum alloy to investigate the effect of heat treatment on the in-plane anisotropy of as-rolled 7050 aluminum alloy. The results showed that the tensile direction has limited effect on mechanical properties of the
[...] Read more.
Tensile tests were conducted on both as-quenched and over-aged 7050 aluminum alloy to investigate the effect of heat treatment on the in-plane anisotropy of as-rolled 7050 aluminum alloy. The results showed that the tensile direction has limited effect on mechanical properties of the as-quenched 7050 aluminum alloy. The in-plane anisotropy factors (IPA factor) of tensile strength, yield strength, and elongation in as-rolled 7050 aluminum alloy fluctuate in the vicinity of 5%. The anisotropy of the as-quenched 7050 aluminum alloy is mainly affected by the texture according to single crystal analysis based on the Schmid factor method. Besides, the IPA factor of the elongation in the over-aged 7050 aluminum alloy reaches 11.6%, illustrating that the anisotropy of the over-aged 7050 aluminum alloy is more prominent than that of the as-quenched. The occurrence of the anisotropy in the over-aged 7050 aluminum alloy is mainly attributed to the microstructures. which are characterized by visible precipitate free zones (PFZs) and coarse precipitates in (sub)grain boundaries. Full article
(This article belongs to the Special Issue Aluminum Alloys)
Figures

Open AccessArticle Detecting Milling Deformation in 7075 Aluminum Alloy Aeronautical Monolithic Components Using the Quasi-Symmetric Machining Method
Metals 2016, 6(4), 80; doi:10.3390/met6040080
Received: 25 February 2016 / Revised: 28 March 2016 / Accepted: 29 March 2016 / Published: 7 April 2016
Cited by 2 | PDF Full-text (4959 KB) | HTML Full-text | XML Full-text
Abstract
The deformation of aeronautical monolithic components due to CNC machining is a bottle-neck issue in the aviation industry. The residual stress releases and redistributes in the process of material removal, and the distortion of the monolithic component is generated. The traditional one-side machining
[...] Read more.
The deformation of aeronautical monolithic components due to CNC machining is a bottle-neck issue in the aviation industry. The residual stress releases and redistributes in the process of material removal, and the distortion of the monolithic component is generated. The traditional one-side machining method will produce oversize deformation. Based on the three-stage CNC machining method, the quasi-symmetric machining method is developed in this study to reduce deformation by symmetry material removal using the M-symmetry distribution law of residual stress. The mechanism of milling deformation due to residual stress is investigated. A deformation experiment was conducted using traditional one-side machining method and quasi-symmetric machining method to compare with finite element method (FEM). The deformation parameters are validated by comparative results. Most of the errors are within 10%. The reason for these errors is determined to improve the reliability of the method. Moreover, the maximum deformation value of using quasi-symmetric machining method is within 20% of that of using the traditional one-side machining method. This result shows the quasi-symmetric machining method is effective in reducing deformation caused by residual stress. Thus, this research introduces an effective method for reducing the deformation of monolithic thin-walled components in the CNC milling process. Full article
(This article belongs to the Special Issue Aluminum Alloys)
Figures

Open AccessFeature PaperArticle On the Relationship between Structural Quality Index and Fatigue Life Distributions in Aluminum Aerospace Castings
Metals 2016, 6(4), 81; doi:10.3390/met6040081
Received: 4 March 2016 / Revised: 29 March 2016 / Accepted: 1 April 2016 / Published: 7 April 2016
Cited by 3 | PDF Full-text (2168 KB) | HTML Full-text | XML Full-text
Abstract
Tensile and fatigue testing results of D357 and B201 aluminum alloy aerospace castings reported in the literature have been reanalyzed. Yield strength–elongation bivariate data have been used as a measure of the structural quality of castings, and converted into quality index. These results
[...] Read more.
Tensile and fatigue testing results of D357 and B201 aluminum alloy aerospace castings reported in the literature have been reanalyzed. Yield strength–elongation bivariate data have been used as a measure of the structural quality of castings, and converted into quality index. These results as well as fatigue data have been analyzed by using Weibull statistics. A distinct relationship has been observed between expected fatigue life and quality index. Moreover, probability of survival in fatigue life was found to be directly linked to the proportions of the quality index distributions in two different regions, providing further evidence about the strong relationship between elongation, i.e., structural quality and fatigue performance. Full article
(This article belongs to the Special Issue Aluminum Alloys)
Figures

Open AccessArticle Reaction Behavior of Phosphorus in Coal-Based Reduction of an Oolitic Hematite Ore and Pre-Dephosphorization of Reduced Iron
Metals 2016, 6(4), 82; doi:10.3390/met6040082
Received: 8 January 2016 / Revised: 29 March 2016 / Accepted: 1 April 2016 / Published: 8 April 2016
Cited by 2 | PDF Full-text (3665 KB) | HTML Full-text | XML Full-text
Abstract
Coal-based reduction followed by magnetic separation is an effective way to recover iron from high phosphorus-containing oolitic hematite ore. Given that high quantities of dephosphorization agent are needed to obtain low phosphorus reduced iron, a novel approach is proposed by the authors. Without
[...] Read more.
Coal-based reduction followed by magnetic separation is an effective way to recover iron from high phosphorus-containing oolitic hematite ore. Given that high quantities of dephosphorization agent are needed to obtain low phosphorus reduced iron, a novel approach is proposed by the authors. Without prior phosphorus removal, the phosphorus was enriched in the reduced iron during a reduction process, then high-phosphorus reduced iron was refined to low phosphorus molten iron and high phosphorus dephosphorization slag to be used as a phosphate fertilizer. The influences of various parameters, including the reduction temperature, the reduction time, and the C/O molar ratio, on the reaction behavior of phosphorus during reduction process were studied. Experimental results indicate that a higher reduction temperature, a longer reduction time, or a higher C/O molar ratio was favorable for the reduction of apatite to phosphorus and the enrichment of phosphorus in reduced iron. X-ray diffraction (XRD) analysis demonstrated that the apatite was reduced to phosphorus and Ca2SiO4 (or Ca(Al2Si2O8)) in the presence of SiO2 and Al2O3, whilst the phosphorus enriched in reduced iron formed Fe3P. The migration behavior of phosphorus was investigated using line scanning analysis of reduction products at different reduction times. The results show that the phosphorus primarily existed in the slag phase 10 min before reduction, and a large amount of phosphorus migrated into iron phase from slag phase with a reduction time of 40 min. The phosphorus content in the iron phase only slightly changed after 50 min. The pre-dephosphorization of reduced iron was performed at 1873 K, indicating a higher basicity or FetO content of CaO-based slag was beneficial to dephosphorization of the reduced iron. Full article
(This article belongs to the Special Issue Recycling of Metals)
Open AccessArticle Influencing Factors for the Microstructure and Mechanical Properties of Micro Porous Titanium Manufactured by Metal Injection Molding
Metals 2016, 6(4), 83; doi:10.3390/met6040083
Received: 16 March 2016 / Revised: 30 March 2016 / Accepted: 31 March 2016 / Published: 9 April 2016
PDF Full-text (18288 KB) | HTML Full-text | XML Full-text
Abstract
Porous titanium is a new structural and functional material. It is widely used in many fields since it integrates the properties of biomaterials with those of metallic foam. A new technology that combines both the preparation and forming of porous materials has been
[...] Read more.
Porous titanium is a new structural and functional material. It is widely used in many fields since it integrates the properties of biomaterials with those of metallic foam. A new technology that combines both the preparation and forming of porous materials has been proposed in this paper. Moreover, a new solder was developed that could be employed in the joining of porous materials. Influencing factors for microstructure and mechanical properties of the parent material and joint interface are identified. Metal injection molding (MIM) technology was used for fabricating porous materials. The feedstock for injection molding of porous titanium powders was prepared from titanium powders and a polymer-based binder system. In addition, the proportion of powder loading and binders was optimized. Through MIM technology, a porous titanium filter cartridge was prepared. For the purpose of investigating the thermal debinding technology of the filter cartridge, effects of the sintering temperature on the porosity, morphology of micropores and mechanical properties were analyzed. It could be found that when the sintering temperature increased, the relative density, bending and compression strength of the components also increased. Moreover, the porosity reached 32.28% when the sintering temperature was 1000 °C. The microstructure morphology indicated that micropores connected with each other. Meanwhile, the strength of the components was relatively high, i.e., the bending and compression strength was 65 and 60 MPa, respectively. By investigating the joining technology of porous filter cartridges, the ideal components of the solder and pressure were determined. Further research revealed that the micropore structure of the joint interface is the same as that of the parent material, and that the bending strength of the joint interface is 40 MPa. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
Figures

Open AccessArticle Effect of BaO Addition on Densification and Mechanical Properties of Al2O3-MgO-CaO Refractories
Metals 2016, 6(4), 84; doi:10.3390/met6040084
Received: 31 December 2015 / Revised: 5 April 2016 / Accepted: 7 April 2016 / Published: 11 April 2016
Cited by 3 | PDF Full-text (4827 KB) | HTML Full-text | XML Full-text
Abstract
Considering the requirement for a reduction of refractory consumption, the present work investigated the fabrication of Al2O3-MgO-CaO-based refractory with BaO addition by means of solid-state reaction sintering. The effect of BaO addition on densification and the properties of the
[...] Read more.
Considering the requirement for a reduction of refractory consumption, the present work investigated the fabrication of Al2O3-MgO-CaO-based refractory with BaO addition by means of solid-state reaction sintering. The effect of BaO addition on densification and the properties of the refractory were also discussed. Results indicated that the formation of calcium hexaluminate (CaO·6Al2O3, or CA6) grains with a high aspect ratio in the alumina-rich zone depressed the densification of the sample without BaO addition, resulting in a higher apparent porosity of 21.2%. When 6 wt. % BaO was added, a new phase of Ba2Mg6Al28O50 (BAM) with a lower aspect ratio was formed and the densification of the sample with an apparent porosity of 5.52% was promoted. In addition, mechanical performance was significantly improved due to an increase in compactness and modification of the microstructure. The cold compressive strength increased from 348 MPa to 569 MPa and the flexural strength increased from 178 MPa to 243 MPa by addition of 6 wt. % BaO. Meanwhile, the breadth of the widest crack after the thermal shock test decreased from 7 μm to 1 μm in the refractory. Full article
(This article belongs to the Special Issue Refractory Metals and Alloys)
Figures

Open AccessArticle Corrosion Resistance of the Superhydrophobic Mg(OH)2/Mg-Al Layered Double Hydroxide Coatings on Magnesium Alloys
Metals 2016, 6(4), 85; doi:10.3390/met6040085
Received: 18 January 2016 / Revised: 18 March 2016 / Accepted: 6 April 2016 / Published: 13 April 2016
Cited by 3 | PDF Full-text (5719 KB) | HTML Full-text | XML Full-text
Abstract
Coatings of the Mg(OH)2/Mg-Al layered double hydroxide (LDH) composite were formed by a combined co-precipitation method and hydrothermal process on the AZ31 alloy substrate in alkaline condition. Subsequently, a superhydrophobic surface was successfully constructed to modify the composite coatings on the
[...] Read more.
Coatings of the Mg(OH)2/Mg-Al layered double hydroxide (LDH) composite were formed by a combined co-precipitation method and hydrothermal process on the AZ31 alloy substrate in alkaline condition. Subsequently, a superhydrophobic surface was successfully constructed to modify the composite coatings on the AZ31 alloy substrate using stearic acid. The characteristics of the composite coatings were investigated by means of X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electronic microscope (SEM) and contact angle (CA). The corrosion resistance of the coatings was assessed by potentiodynamic polarization, the electrochemical impedance spectrum (EIS), the test of hydrogen evolution and the immersion test. The results showed that the superhydrophobic coatings considerably improved the corrosion resistant performance of the LDH coatings on the AZ31 alloy substrate. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Open AccessArticle Improving Beneficiation of Copper and Iron from Copper Slag by Modifying the Molten Copper Slag
Metals 2016, 6(4), 86; doi:10.3390/met6040086
Received: 26 February 2016 / Revised: 4 April 2016 / Accepted: 7 April 2016 / Published: 14 April 2016
Cited by 9 | PDF Full-text (5600 KB) | HTML Full-text | XML Full-text
Abstract
In the paper, a new technology was developed to improve the beneficiation of copper and iron components from copper slag, by modifying the molten slag to promote the mineralization of valuable minerals and to induce the growth of mineral grains. Various parameters, including
[...] Read more.
In the paper, a new technology was developed to improve the beneficiation of copper and iron components from copper slag, by modifying the molten slag to promote the mineralization of valuable minerals and to induce the growth of mineral grains. Various parameters, including binary basicity, dosage of compound additive, modification temperature, cooling rate and the end point temperature of slow cooling were investigated. Meanwhile, optical microscope, scanning electron microscope and energy dispersive spectrometer (SEM-EDS) was employed to determine the mineralogy of the modified and unmodified slag, as well as to reveal the mechanisms of enhancing beneficiation. The results show that under the proper conditions, the copper grade of rougher copper concentrate was increased from 6.43% to 11.04%, iron recovery of magnetic separation was increased significantly from 32.40% to 63.26%, and other evaluation indexes were changed slightly, in comparison with unmodified copper slag. Moreover, matte and magnetite grains in the modified slag aggregated together and grew obviously to the mean size of over 50 μm, resulting in an improvement of beneficiation of copper and iron. Full article
Open AccessArticle Effect of Welding Speed on Defect Features and Mechanical Performance of Friction Stir Lap Welded 7B04 Aluminum Alloy
Metals 2016, 6(4), 87; doi:10.3390/met6040087
Received: 9 March 2016 / Revised: 6 April 2016 / Accepted: 11 April 2016 / Published: 15 April 2016
Cited by 3 | PDF Full-text (9746 KB) | HTML Full-text | XML Full-text
Abstract
Friction stir lap welding of 7B04 aluminum alloy was conducted in the present paper, and the effect of welding speed on the defect features and mechanical performance of lap joints was investigated. The results indicate that the hook defect at the advancing side
[...] Read more.
Friction stir lap welding of 7B04 aluminum alloy was conducted in the present paper, and the effect of welding speed on the defect features and mechanical performance of lap joints was investigated. The results indicate that the hook defect at the advancing side (AS) can reduce the effective thickness of the top sheet, and the sheet thinning level is gradually lowered by increasing the welding speed. The cold lap defect at the retreating side (RS) can result in effective thickness reduction in both top and bottom sheets, and the total height of the cold lap defect varies slightly with the welding speed. The tensile properties of the lap joints are largely related to the sheet thinning levels caused by the defects. The fracture strength of AS-loaded lap joints is progressively increased with increasing welding speed, while that of RS-loaded lap joints evolves slightly with welding speed. It is found that the affecting characteristic of loading configuration on the joint performance is also dependent on the welding speed. At lower welding speeds, the AS-loaded lap joints show lower fracture strength than the RS-loaded lap joints. When the welding speed is high, the AS-loaded lap joints present superior tensile properties to RS-loaded lap joints. Full article
(This article belongs to the Special Issue Aluminum Alloys)
Figures

Open AccessArticle Preparation of Metallic Iron Powder from Pyrite Cinder by Carbothermic Reduction and Magnetic Separation
Metals 2016, 6(4), 88; doi:10.3390/met6040088
Received: 16 February 2016 / Revised: 31 March 2016 / Accepted: 11 April 2016 / Published: 16 April 2016
Cited by 2 | PDF Full-text (4971 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The reduction and magnetic separation procedure of pyrite cinder in the presence of a borax additive was performed for the preparation of reduced powder. The effects of borax dosage, reduction temperature, reduction time and grinding fineness were investigated. The results show that when
[...] Read more.
The reduction and magnetic separation procedure of pyrite cinder in the presence of a borax additive was performed for the preparation of reduced powder. The effects of borax dosage, reduction temperature, reduction time and grinding fineness were investigated. The results show that when pyrite cinder briquettes with 5% borax were pre-oxidized at 1050 °C for 10 min, and reduced at 1050 °C for 80 min, with the grinding fineness (<0.44 mm) passing 81%, the iron recovery was 91.71% and the iron grade of the magnetic concentrate was 92.98%. In addition, the microstructures of the products were analyzed by optical microscope, scanning electron microscope (SEM), and mineralography, and the products were also studied by the X-ray powder diffraction technique (XRD) to investigate the mechanism; the results show that the borax additive was approved as a good additive to improve the separation of iron and gangue. Full article
(This article belongs to the Special Issue Recycling of Metals)
Open AccessArticle Development and Characterization of a Metal Injection Molding Bio Sourced Inconel 718 Feedstock Based on Polyhydroxyalkanoates
Metals 2016, 6(4), 89; doi:10.3390/met6040089
Received: 31 March 2016 / Revised: 11 April 2016 / Accepted: 14 April 2016 / Published: 18 April 2016
Cited by 1 | PDF Full-text (2955 KB) | HTML Full-text | XML Full-text
Abstract
The binder plays the most important role in the metal injection molding (MIM) process. It provides fluidity of the feedstock mixture and adhesion of the powder to keep the molded shape during injection molding. The binder must provide strength and cohesion for the
[...] Read more.
The binder plays the most important role in the metal injection molding (MIM) process. It provides fluidity of the feedstock mixture and adhesion of the powder to keep the molded shape during injection molding. The binder must provide strength and cohesion for the molded part and must be easy to remove from the molded part. Moreover, it must be recyclable, environmentally friendly and economical. Also, the miscibility between polymers affects the homogeneity of the injected parts. The goal of this study is to develop a feedstock of superalloy Inconel 718 that is environmentally friendly. For these different binders, formulations based on polyethylene glycol (PEG), because of his water solubility property, and bio sourced polymers were studied. Polyhydroxyalkanoates (PHA) were investigated as a bio sourced polymer due to its miscibility with the PEG. The result is compared to a standard formulation using polypropylene (PP). The chemical and rheological behavior of the binder formulation during mixing, injection and debinding process were investigated. The feedstock was characterized in the same way as the binders and the interactions between the powder and the binders were also studied. The results show the well adapted formulation of polymer binder to produce a superalloy Inconel 718 feedstock. Full article
(This article belongs to the Special Issue Metal Injection Moulding)
Figures

Open AccessArticle Characterization of Precipitates in a Microalloyed Steel Using Quantitative X-ray Diffraction
Metals 2016, 6(4), 90; doi:10.3390/met6040090
Received: 29 February 2016 / Revised: 29 March 2016 / Accepted: 8 April 2016 / Published: 19 April 2016
Cited by 1 | PDF Full-text (2564 KB) | HTML Full-text | XML Full-text
Abstract
Quantitative X-ray diffraction (QXRD) (also known as the Rietveld method) was used to analyze the precipitates present in Grade 100 microalloyed steel. The precipitates were extracted from the steel using electrolytic dissolution and the residue from the dissolution was analyzed using XRD. The
[...] Read more.
Quantitative X-ray diffraction (QXRD) (also known as the Rietveld method) was used to analyze the precipitates present in Grade 100 microalloyed steel. The precipitates were extracted from the steel using electrolytic dissolution and the residue from the dissolution was analyzed using XRD. The XRD pattern exhibited three (3) distinct diffraction peaks, and significant broadening of a fourth peak corresponding to the <10 nm size precipitates. QXRD analysis was applied to the XRD pattern to obtain precipitate size, composition, and weight fraction data for each of the four diffraction peaks observed. The predicted mean precipitate diameter and average atomic composition of the nano-size (<10 nm) precipitates was 4.7 nm and (Nb0.50Ti0.32Mo0.18)(C0.59N0.41), respectively. The predicted precipitate size correlates well with the average size of precipitates measured in previous work by the authors using both transmission electron microscopy (TEM) and small angle neutron scattering (SANS). The average atomic composition correlates well with the composition measured in this work using energy dispersive X-ray (EDX) analysis of individual nano-sized precipitates. The calculated weight fraction of the nano-size precipitates in the extracted residue was 42.2 wt. %. The calculated atomic compositions of the other three diffraction peaks were TiN, (Ti0.87Nb0.13)N, and (Nb0.82Ti0.18)(C0.87N0.13) with weight fraction values of 12.9 wt. %, 31.7 wt. %, and 13.1 wt. %, respectively. The sizes of both the (Ti0.87Nb0.13)N and the (Nb0.82Ti0.18)(C0.87N0.13) groups of precipitates were directly measured and were observed to range from 150 nm to 570 nm and from 90 nm to 475 nm, respectively. QXRD was unable to determine a reasonable mean precipitate size for either of these two groups of precipitates. The wide compositional range (i.e., varying levels of Nb and Ti) of these precipitates (as measured by EDX) resulted in XRD peak broadening that was erroneously interpreted as a size broadening effect. Full article
(This article belongs to the Special Issue Microalloyed Steel)
Open AccessArticle Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM
Metals 2016, 6(4), 91; doi:10.3390/met6040091
Received: 3 February 2016 / Revised: 21 March 2016 / Accepted: 6 April 2016 / Published: 19 April 2016
Cited by 1 | PDF Full-text (11081 KB) | HTML Full-text | XML Full-text
Abstract
The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy
[...] Read more.
The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy (SKPFM) was used to map the Volta potential differences. Co-localization of SKPFM with Energy Dispersive Spectroscopy (EDS) measurements enabled spatially resolved correlation of potential differences with composition and subsequent galvanic corrosion behavior. Following exposure to the aggressive solution, corrosion damage morphology was characterized to determine the mode of attack and likely initiation areas. When exposed to 0.6 M NaCl, corrosion occurred at the braze-316L interface preceded by preferential dissolution of the Cu-rich phase within the braze alloy. Braze corrosion was driven by galvanic couples between the braze alloys and stainless steel as well as between different phases within the braze microstructure. Microgalvanic corrosion between phases of the braze alloys was investigated via SKPFM to determine how corrosion of the brazed joints developed. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Figures

Open AccessArticle Intermetallic Reactions during the Solid-Liquid Interdiffusion Bonding of Bi2Te2.55Se0.45 Thermoelectric Material with Cu Electrodes Using a Sn Interlayer
Metals 2016, 6(4), 92; doi:10.3390/met6040092
Received: 26 February 2016 / Revised: 13 April 2016 / Accepted: 19 April 2016 / Published: 22 April 2016
Cited by 1 | PDF Full-text (4463 KB) | HTML Full-text | XML Full-text
Abstract
The intermetallic compounds formed during the diffusion soldering of a Bi2Te2.55Se0.45 thermoelectric material with a Cu electrode are investigated. For this bonding process, Bi2Te2.55Se0.45 was pre-coated with a 1 μm Sn thin film
[...] Read more.
The intermetallic compounds formed during the diffusion soldering of a Bi2Te2.55Se0.45 thermoelectric material with a Cu electrode are investigated. For this bonding process, Bi2Te2.55Se0.45 was pre-coated with a 1 μm Sn thin film on the thermoelectric element and pre-heated at 250 °C for 3 min before being electroplated with a Ni barrier layer and a Ag reaction layer. The pre-treated thermoelectric element was bonded with a Ag-coated Cu electrode using a 4 μm Sn interlayer at temperatures between 250 and 325 °C. The results indicated that a multi-layer of Bi–Te–Se/Sn–Te–Se–Bi/Ni3Sn4 phases formed at the Bi2Te2.55Se0.45/Ni interface, ensuring sound cohesion between the Bi2Te2.55Se0.45 thermoelectric material and Ni barrier. The molten Sn interlayer reacted rapidly with both Ag reaction layers to form an Ag3Sn intermetallic layer until it was completely exhausted and the Ag/Sn/Ag sandwich transformed into a Ag/Ag3Sn/Ag joint. Satisfactory shear strengths ranging from 19.3 and 21.8 MPa were achieved in Bi2Te2.55Se0.45/Cu joints bonded at 250 to 300 °C for 5 to 30 min, dropping to values of about 11 MPa for 60 min, bonding at 275 and 300 °C. In addition, poor strengths of about 7 MPa resulted from bonding at a higher temperature of 325 °C for 5 to 60 min. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessArticle Processing Mineralogy Study on Lead and Zinc Oxide Ore in Sichuan
Metals 2016, 6(4), 93; doi:10.3390/met6040093
Received: 16 February 2016 / Revised: 8 April 2016 / Accepted: 9 April 2016 / Published: 22 April 2016
Cited by 1 | PDF Full-text (1615 KB) | HTML Full-text | XML Full-text
Abstract
The processing mineralogy characteristics of an oxidized lead-zinc ore from Sichuan were studied systematically using numerous modern instruments. Results showed that lead and zinc oxide content in the ore exceeded the minimum industrial grade, and also included a relatively high concentration of silver
[...] Read more.
The processing mineralogy characteristics of an oxidized lead-zinc ore from Sichuan were studied systematically using numerous modern instruments. Results showed that lead and zinc oxide content in the ore exceeded the minimum industrial grade, and also included a relatively high concentration of silver and iron. This ore is composed of many different minerals. Major zinc-containing minerals include sphalerite, hemimorphite, smithsonite, hydrozincite, zinc-containing baileychlore, and zinc-containing dolomite and calcite. Lead-containing minerals are primarily galena and cerussite with small amounts of dechenite, cesaronite, anglesite, limonite and coronadite. Gangue minerals include dolomite and calcite. Dissemination size for the main minerals ranges from medium (0.04 mm) to fine (0.02 mm). All the valuable minerals are well liberated, including galena, sphalerite, cerussite, calamine, and smithsonite. However, the dissemination relationships are complex. Lead is concentrated mainly in galena and cerussite, while zinc occurs primarily in sphalerite, calamine, and smithsonite. The theoretical recovery for lead and zinc were estimated at 72% and 67%, respectively. Full article
(This article belongs to the Special Issue Recycling of Metals)
Open AccessArticle The Effect of the Si Content on the Morphology and Amount of Fe2SiO4 in Low Carbon Steels
Metals 2016, 6(4), 94; doi:10.3390/met6040094
Received: 3 March 2016 / Revised: 8 April 2016 / Accepted: 12 April 2016 / Published: 22 April 2016
Cited by 5 | PDF Full-text (3513 KB) | HTML Full-text | XML Full-text
Abstract
In order to study the effect of the Si content on the morphology, amount, and distribution of fayalite (Fe2SiO4), three low-carbon steels with different Si contents were selected, and reheating tests were conducted in an industrial furnace in a
[...] Read more.
In order to study the effect of the Si content on the morphology, amount, and distribution of fayalite (Fe2SiO4), three low-carbon steels with different Si contents were selected, and reheating tests were conducted in an industrial furnace in a hot strip plant. The results show that Si distributes in two forms—first, Fe2SiO4, in the innermost layer of the oxide scale, and, second, granular SiO2, dispersively distributed in the matrix near the scale. In addition, Fe2SiO4 appears in a net-like form in the innermost layer of the oxide scale close to the iron matrix when the Si content is 1.21 wt. %. However, no obvious net-like Fe2SiO4 is observed when the Si content is less than 0.25 wt. %. Moreover, the inhibition effect of the solid Fe2SiO4 on the oxidation reaction plays a more important role than the promotion effect of the liquid Fe2SiO4 during the entire oxidation reaction. Therefore, the total thickness of the scale decreases with the increase in Si content. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Figures

Journal Contact

MDPI AG
Metals Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
E-Mail: 
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Metals Edit a special issue Review for Metals
logo
loading...
Back to Top