Metals

2338 KiB

Open AccessArticle

Experimental Study of the Mg-Ni-Y System at 673 K Using Diffusion Couples and Key Alloys

by Mohammad Mezbahul-Islam, Dmytro Kevorkov and Mamoun Medraj

Metals 2015, 5(3), 1746-1769; https://doi.org/10.3390/met5031746 - 22 Sep 2015

Cited by 18 | Viewed by 5639

Three solid-solid and two solid-liquid diffusion couples together with 32 key samples were used to construct the isothermal section of the Mg-Ni-Y system at 673 K. The present investigation revealed 12 ternary intermetallic compounds. Crystal structures of two ternary compounds τ₁ (Gd [...] Read more.

Three solid-solid and two solid-liquid diffusion couples together with 32 key samples were used to construct the isothermal section of the Mg-Ni-Y system at 673 K. The present investigation revealed 12 ternary intermetallic compounds. Crystal structures of two ternary compounds τ₁ (Gd₄RhIn prototype with lattice parameter of a = 1.3666 nm) and τ₂ (Mo₂FeB₂ prototype with lattice parameters of a = 0.7395 nm and c = 0.3736 nm) were determined. The phase relations and ternary solubility of the binary and ternary compounds at 673 K were determined using scanning electron microscopy (SEM), wave dispersive X-ray spectrometer (WDS) and X-ray diffraction (XRD) analysis. Full article

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1350 KiB

Open AccessArticle

Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation

by Seul-Kee Kim, Ki-Yeob Kang, Myung-Soo Kim and Jae-Myung Lee

Metals 2015, 5(3), 1732-1745; https://doi.org/10.3390/met5031732 - 18 Sep 2015

Cited by 21 | Viewed by 7284

Abstract

Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS) because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of [...] Read more.

Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS) because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior. Full article

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1179 KiB

Open AccessArticle

Constitutive Relationship Modeling and Characterization of Flow Behavior under Hot Working for Fe–Cr–Ni–W–Cu–Co Super-Austenitic Stainless Steel

by Li-Chih Yang, Yeong-Tsuen Pan, In-Gann Chen and Dong-Yih Lin

Metals 2015, 5(3), 1717-1731; https://doi.org/10.3390/met5031717 - 18 Sep 2015

Cited by 23 | Viewed by 6509

Abstract

The hot deformation behavior of a Fe–22Cr–25Ni–3.5W–3Cu–1.5Co super-austenitic stainless steel was investigated using isothermal compression tests with a wide range of temperatures (1173–1373 K) and strain rates (0.1–10 s−1). The results showed that all the flow curves gradually turned to balanced stress state [...] Read more.

The hot deformation behavior of a Fe–22Cr–25Ni–3.5W–3Cu–1.5Co super-austenitic stainless steel was investigated using isothermal compression tests with a wide range of temperatures (1173–1373 K) and strain rates (0.1–10 s−1). The results showed that all the flow curves gradually turned to balanced stress state without notable peak stress characteristics during the entire deformation, which indicated that the dynamic recovery behavior played a main restoration mechanism in the steel. Modeling constitutive equations relating to the temperature, strain rate and flow stress were proposed to determine the materials constants and activation energy necessary for deformation. In order to give the precise predicted values of the flow behavior, the influence of strain was identified using polynomial functions. The relationship of flow stress, temperature and strain rate was represented by the Zener-Hollomon parameter including the Arrhenius term. The predicted results validated that the developed constitutive equations can describe high temperature flow behavior well. Furthermore, a modified Zener-Hollomon parameter map of the studied steel was developed to clarify the restoration mechanism based on the constitutive modeling data and microstructural observation. Full article

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1712 KiB

Open AccessArticle

Characterization of Microstructure and Mechanical Properties of Resistance Spot Welded DP600 Steel

by Ali Ramazani, Krishnendu Mukherjee, Aydemir Abdurakhmanov, Mahmoud Abbasi and Ulrich Prahl

Metals 2015, 5(3), 1704-1716; https://doi.org/10.3390/met5031704 - 17 Sep 2015

Cited by 42 | Viewed by 11235

Abstract

Resistance spot welding (RSW) as a predominant welding technique used for joining steels in automotive applications needs to be studied carefully in order to improve the mechanical properties of the spot welds. The objectives of the present work are to characterize the resistance [...] Read more.

Resistance spot welding (RSW) as a predominant welding technique used for joining steels in automotive applications needs to be studied carefully in order to improve the mechanical properties of the spot welds. The objectives of the present work are to characterize the resistance spot weldment of DP600 sheet steels. The mechanical properties of the welded joints were evaluated using tensile-shear and cross-tensile tests. The time-temperature evolution during the welding cycle was measured. The microstructures observed in different sites of the welds were correlated to thermal history recorded by thermocouples in the corresponding areas. It was found that cracks initiated in the periphery region of weld nuggets with a martensitic microstructure and a pull-out failure mode was observed. It was also concluded that tempering during RSW was the main reason for hardness decrease in HAZ. Full article

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1707 KiB

Open AccessArticle

Effect of Post Heat Treatment on the Microstructure and Microhardness of Friction Stir Processed NiAl Bronze (NAB) Alloy

by Yuting Lv, Liqiang Wang, Xiaoyan Xu and Weijie Lu

Metals 2015, 5(3), 1695-1703; https://doi.org/10.3390/met5031695 - 16 Sep 2015

Cited by 33 | Viewed by 6717

Abstract

NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of [...] Read more.

NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of heat treatment on the microstructure and microhardness is studied. The results show that the microstructure of the FSP NAB alloy consists of high density dislocations, retained β phase (β′ phase) and recrystallized grains. When annealed at 675 °C, discontinuous static recrystallization (DSRX) takes place. The content of β′ phase gradually decreases and fine κ phase is precipitated. After annealing for 2 h, both the microhardness of the FSP sample in the stir zone (SZ) and the difference in hardness between the SZ and base metal decrease due to the reduction of the dislocation density and β′ phase, accompanying recrystallized grain coarsening. With further increasing of the annealing time to 4 h, the aforementioned difference in hardness nearly disappears. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1754 KiB

Open AccessArticle

Mechanical Properties of Nanoporous Au: From Empirical Evidence to Phenomenological Modeling

by Giorgio Pia and Francesco Delogu

Metals 2015, 5(3), 1665-1694; https://doi.org/10.3390/met5031665 - 16 Sep 2015

Cited by 13 | Viewed by 6220

Abstract

The present work focuses on the development of a theoretical model aimed at relating the mechanical properties of nanoporous metals to the bending response of thick ligaments. The model describes the structure of nanoporous metal foams in terms of an idealized regular lattice [...] Read more.

The present work focuses on the development of a theoretical model aimed at relating the mechanical properties of nanoporous metals to the bending response of thick ligaments. The model describes the structure of nanoporous metal foams in terms of an idealized regular lattice of massive cubic nodes and thick ligaments with square cross-sections. Following a general introduction to the subject, model predictions are compared with Young’s modulus and the yield strength of nanoporous Au foams determined experimentally and available in literature. It is shown that the model provides a quantitative description of the elastic and plastic deformation behavior of nanoporous metals, reproducing to a satisfactory extent the experimental Young’s modulus and yield strength values of nanoporous Au. Full article

(This article belongs to the Special Issue Nanoporous Metallic Alloys)

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1749 KiB

Open AccessArticle

Beeswax-Colophony Blend: A Novel Green Organic Coating for Protection of Steel Drinking Water Storage Tanks

by Sara Abdikheibari, Reza Parvizi, Mohammad Hadi Moayed, Seyed Mojtaba Zebarjad and Seyed Abdolkarim Sajjadi

Metals 2015, 5(3), 1645-1664; https://doi.org/10.3390/met5031645 - 15 Sep 2015

Cited by 12 | Viewed by 8513

Abstract

Beeswax-colophony blend is mainly used as a sealant mixture for preservation applications. The beeswax itself, however, has had a long way in history taking part in conservation processes including mummification. In this research, this blend was used as a protective coating for drinking [...] Read more.

Beeswax-colophony blend is mainly used as a sealant mixture for preservation applications. The beeswax itself, however, has had a long way in history taking part in conservation processes including mummification. In this research, this blend was used as a protective coating for drinking water distribution tanks. Initially, a layer with 400 μm thickness was applied on a sand blasted mild steel plate. The long-term electrochemical behavior of the coating was investigated by open circuit potential (OCP) and electrochemical microbiological characteristics of the coating, microbial and chemical examinations were performed on drinking water samples that had been in contact with the coating. Furthermore, its behavior in an up-flow anaerobic sludge blanket reactor (UASBR) in a wastewater treatment plant was investigated using the scanning electron microscopy (SEM) technique. Regarding the consistency of experimental results, it was concluded that this proposed recyclable blend could be considered as a novel green organic coating and also a good corrosion barrier even in aggressive environments. Full article

(This article belongs to the Special Issue Oxidation of Metals)

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1483 KiB

Open AccessArticle

Nickel Extraction from Olivine: Effect of Carbonation Pre-Treatment

by Rafael M. Santos, Aldo Van Audenaerde, Yi Wai Chiang, Remus I. Iacobescu, Pol Knops and Tom Van Gerven

Metals 2015, 5(3), 1620-1644; https://doi.org/10.3390/met5031620 - 11 Sep 2015

Cited by 46 | Viewed by 12910

Abstract

In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)₂SiO₄). The precept is that by altering the morphology and the mineralogy of [...] Read more.

In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)₂SiO₄). The precept is that by altering the morphology and the mineralogy of the ore via mineral carbonation, the comminution requirements and the acid consumption during hydrometallurgical processing can be reduced. Furthermore, carbonation pre-treatment can lead to mineral liberation and concentration of metals in physically separable phases. In a first processing step, olivine is fully carbonated at high CO₂ partial pressures (35 bar) and optimal temperature (200 °C) with the addition of pH buffering agents. This leads to a powdery product containing high carbonate content. The main products of the carbonation reaction include quasi-amorphous colloidal silica, chromium-rich metallic particles, and ferro-magnesite ((Mg_1−x,Fe_x)CO₃). Carbonated olivine was subsequently leached using an array of inorganic and organic acids to test their leaching efficiency. Compared to leaching from untreated olivine, the percentage of nickel extracted from carbonated olivine by acid leaching was significantly increased. It is anticipated that the mineral carbonation pre-treatment approach may also be applicable to other ultrabasic and lateritic ores. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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908 KiB

Open AccessArticle

Exploring the Possibilities of Biological Fabrication of Gold Nanostructures Using Orange Peel Extract

by Laura Castro, María Luisa Blázquez, Felisa González, Jesús Ángel Muñoz and Antonio Ballester

Metals 2015, 5(3), 1609-1619; https://doi.org/10.3390/met5031609 - 11 Sep 2015

Cited by 9 | Viewed by 5118

Abstract

Development of nanotechnology requires a constant innovation and improvement in many materials. The exploration of natural resources is a promising eco-friendly alternative for physical and chemical methods. In the present work, colloidal gold nanostructures were prepared using orange peel extract as a stabilizing [...] Read more.

Development of nanotechnology requires a constant innovation and improvement in many materials. The exploration of natural resources is a promising eco-friendly alternative for physical and chemical methods. In the present work, colloidal gold nanostructures were prepared using orange peel extract as a stabilizing and reducing agent. The initial pH value of the solution and the concentration of the gold precursor had an effect on the formation and morphology of nanoparticles. The method developed is environmentally friendly and allows control of nanoparticles. By controlling the pH and, especially, the gold concentration, we are able to synthesize crystalline gold nanowires using orange peel extract in the absence of a surfactant or polymer to direct nanoparticle growth, and without external seeding. UV-VIS spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the nanoparticles obtained by biosynthesis. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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1324 KiB

Open AccessArticle

Heavy Metal Behavior in Lichen-Mine Waste Interactions at an Abandoned Mine Site in Southwest Japan

by Yuri Sueoka, Masayuki Sakakibara and Koichiro Sera

Metals 2015, 5(3), 1591-1608; https://doi.org/10.3390/met5031591 - 2 Sep 2015

Cited by 10 | Viewed by 8112

Abstract

The lichen, Stereocaulon exutum Nylander, occurring in a contaminated abandoned mine site was investigated to clarify (1) the behavior of heavy metals and As during the slag weathering processes mediated by the lichen; and (2) the distribution of these elements in the lichen [...] Read more.

The lichen, Stereocaulon exutum Nylander, occurring in a contaminated abandoned mine site was investigated to clarify (1) the behavior of heavy metals and As during the slag weathering processes mediated by the lichen; and (2) the distribution of these elements in the lichen thallus on slag. The heavy metals and As in the slag are dissolved from their original phases during the weathering process by lichen substances (organic acids) and hypha penetration, in addition to non-biological weathering. The dissolved elements are absorbed into the lichen thallus. Some of these dissolved elements are distributed in the cells of the hyphae. The others are distributed on the surface of the hyphae as formless particles and show lateral distribution inside the cortex of the thallus. The Cu and Zn concentrations in the thalli are positively correlated with the concentrations in the corresponding substrata and a positive intercept in the regression curve obtained using a linear function. These chemical characteristics make this lichen a good biomarker for Cu and Zn contamination of the substrata of the lichen. Therefore, the present study supposes that Stereocaulon exutum has a possible practical application in biomonitoring or risk assessment of heavy metal pollution at abandoned mine sites. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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1008 KiB

Open AccessArticle

Experimental and Numerical Studies on Self-Propagating High-Temperature Synthesis of Ta₅Si₃ Intermetallics

by Chun-Liang Yeh, Chi-Chian Chou and Po-Wen Hwang

Metals 2015, 5(3), 1580-1590; https://doi.org/10.3390/met5031580 - 1 Sep 2015

Cited by 11 | Viewed by 5850

Abstract

Formation of Ta₅Si₃ by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion [...] Read more.

Formation of Ta₅Si₃ by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion wave velocity and reaction temperature. The apparent activation energy, E_a ≈ 108 kJ/mol, was determined for the synthesis reaction. Based upon numerical simulation, the Arrhenius factor of the rate function, K₀ = 2.5 × 10⁷ s⁻¹, was obtained for the 5Ta + 3Si combustion system. In addition, the influence of sample density on combustion wave kinetics was correlated with the effective thermal conductivity (k_eff) of the powder compact. By adopting 0.005 ≤ k_eff/k_bulk ≤ 0.016 in the computation model, the calculated combustion velocity and temperature were in good agreement with experimental data of the samples with compaction densities between 35% and 45% theoretical maximum density (TMD). Full article

(This article belongs to the Special Issue Intermetallics 2016)

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721 KiB

Open AccessArticle

Chalcopyrite Dissolution at 650 mV and 750 mV in the Presence of Pyrite

by Yubiao Li, Gujie Qian, Jun Li and Andrea R. Gerson

Metals 2015, 5(3), 1566-1579; https://doi.org/10.3390/met5031566 - 28 Aug 2015

Cited by 9 | Viewed by 6091

Abstract

The dissolution of chalcopyrite in association with pyrite in mine waste results in the severe environmental issue of acid and metalliferous drainage (AMD). To better understand chalcopyrite dissolution, and the impact of chalcopyrite’s galvanic interaction with pyrite, chalcopyrite dissolution has been examined at [...] Read more.

The dissolution of chalcopyrite in association with pyrite in mine waste results in the severe environmental issue of acid and metalliferous drainage (AMD). To better understand chalcopyrite dissolution, and the impact of chalcopyrite’s galvanic interaction with pyrite, chalcopyrite dissolution has been examined at 75 °C, pH 1.0, in the presence of quartz (as an inert mineral) and pyrite. The presence of pyrite increased the chalcopyrite dissolution rate by more than five times at E_h of 650 mV (SHE) (Cu recovery 2.5 cf. 12% over 132 days) due to galvanic interaction between chalcopyrite and pyrite. Dissolution of Cu and Fe was stoichiometric and no pyrite dissolved. Although the chalcopyrite dissolution rate at 750 mV (SHE) was approximately four-fold greater (Cu recovery of 45% within 132 days) as compared to at 650 mV in the presence of pyrite, the galvanic interaction between chalcopyrite and pyrite was negligible. Approximately all of the sulfur from the leached chalcopyrite was converted to S⁰ at 750 mV, regardless of the presence of pyrite. At this E_h approximately 60% of the sulfur associated with pyrite dissolution was oxidised to S⁰ and the remaining 40% was released in soluble forms, e.g., SO₄²⁻. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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947 KiB

Open AccessReview

New Approaches to Aluminum Integral Foam Production with Casting Methods

by Ahmet Güner, Mustafa Merih Arıkan and Mehmet Nebioglu

Metals 2015, 5(3), 1553-1565; https://doi.org/10.3390/met5031553 - 28 Aug 2015

Cited by 24 | Viewed by 9246

Abstract

Integral foam has been used in the production of polymer materials for a long time. Metal integral foam casting systems are obtained by transferring and adapting polymer injection technology. Metal integral foam produced by casting has a solid skin at the surface and [...] Read more.

Integral foam has been used in the production of polymer materials for a long time. Metal integral foam casting systems are obtained by transferring and adapting polymer injection technology. Metal integral foam produced by casting has a solid skin at the surface and a foam core. Producing near-net shape reduces production expenses. Insurance companies nowadays want the automotive industry to use metallic foam parts because of their higher impact energy absorption properties. In this paper, manufacturing processes of aluminum integral foam with casting methods will be discussed. Full article

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422 KiB

Open AccessArticle

Separation and Recycling for Rare Earth Elements by Homogeneous Liquid-Liquid Extraction (HoLLE) Using a pH-Responsive Fluorine-Based Surfactant

by Shotaro Saito, Osamu Ohno, Shukuro Igarashi, Takeshi Kato and Hitoshi Yamaguchi

Metals 2015, 5(3), 1543-1552; https://doi.org/10.3390/met5031543 - 27 Aug 2015

Cited by 11 | Viewed by 8341

Abstract

A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE) using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, [...] Read more.

A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE) using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, In, Ir, La, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Re, Rh, Ru, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Te, Ti, Tl, Tm, V, W, Y, Yb, Zn, and Zr) were examined. By changing pH from a neutral or alkaline solution (pH ≥ 6.5) to that of an acidic solution (pH < 4.0), gallium, zirconium, palladium, silver, platinum, and rare earth elements were extracted at >90% efficiency into a sedimented Zonyl FSA^® (CF₃(CF₂)_n(CH₂)₂S(CH₂)₂COOH, n = 6–8) liquid phase. Moreover, all rare earth elements were obtained with superior extraction and stripping percentages. In the recycling of rare earth elements, the sedimented phase was maintained using a filter along with a mixed solution of THF and 1 M sodium hydroxide aqueous solution. The Zonyl FSA^® was filtrated and the rare earth elements were recovered on the filter as a hydroxide. Furthermore, the filtrated Zonyl FSA was reusable by conditioning the subject pH. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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811 KiB

Open AccessReview

Tannins in Mineral Processing and Extractive Metallurgy

by Jordan Rutledge and Corby G. Anderson

Metals 2015, 5(3), 1520-1542; https://doi.org/10.3390/met5031520 - 27 Aug 2015

Cited by 42 | Viewed by 11265

Abstract

This study provides an up to date review of tannins, specifically quebracho, in mineral processing and metallurgical processes. Quebracho is a highly useful reagent in many flotation applications, acting as both a depressant and a dispersant. Three different types of quebracho are mentioned [...] Read more.

This study provides an up to date review of tannins, specifically quebracho, in mineral processing and metallurgical processes. Quebracho is a highly useful reagent in many flotation applications, acting as both a depressant and a dispersant. Three different types of quebracho are mentioned in this study; quebracho “S” or Tupasol ATO, quebracho “O” or Tupafin ATO, and quebracho “A” or Silvafloc. It should be noted that literature often refers simply to “quebracho” without distinguishing a specific type. Quebracho is most commonly used in industry as a method to separate fluorite from calcite, which is traditionally quite challenging as both minerals share a common ion—calcium. Other applications for quebracho in flotation with calcite minerals as the main gangue source include barite and scheelite. In sulfide systems, quebracho is a key reagent in differential flotation of copper, lead, zinc circuits. The use of quebracho in the precipitation of germanium from zinc ores and for the recovery of ultrafine gold is also detailed in this work. This analysis explores the wide range of uses and methodology of quebracho in the extractive metallurgy field and expands on previous research by Iskra and Kitchener at Imperial College entitled, “Quebracho in Mineral Processing”. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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658 KiB

Open AccessArticle

Use of Nanoscale Zero-Valent Iron (NZVI) Particles for Chemical Denitrification under Different Operating Conditions

by Alessio Siciliano

Metals 2015, 5(3), 1507-1519; https://doi.org/10.3390/met5031507 - 21 Aug 2015

Cited by 37 | Viewed by 5496

Abstract

The nitrate pollution of waters and groundwaters is an important environmental and health concern. An interesting method to remove the oxidized forms of nitrogen from waters and wastewaters is chemical denitrification by means of metallic iron (Fe⁰). Particularly advantageous is the [...] Read more.

The nitrate pollution of waters and groundwaters is an important environmental and health concern. An interesting method to remove the oxidized forms of nitrogen from waters and wastewaters is chemical denitrification by means of metallic iron (Fe⁰). Particularly advantageous is the use of nanoscopic zero-valent iron particles due to the elevated surface area, which allows reaching extremely high reaction rates. In the present paper, the efficiency of nitrate reduction by means of nanoscopic Fe⁰ has been investigated under several operating conditions. The iron nanoparticles were synthesized by the chemical reduction of ferric ions with sodium borohydride. The effects of Fe⁰ dosage, initial N–NO₃⁻ concentration and pH on chemical denitrification were identified. In particular, the results of the tests carried out showed that it is possible to reach an almost complete nitrate reduction in treating solutions with a nitrate nitrogen concentration higher than 50 mg/L. Moreover, the process performance was satisfactory also under uncontrolled pH. By means of the trends detected during the experiments, the kinetic-type reaction was identified. Furthermore, a relation between the kinetic constant and the process parameters was defined. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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1747 KiB

Open AccessArticle

A Creep Damage Model for High-Temperature Deformation and Failure of 9Cr-1Mo Steel Weldments

by Mehdi Basirat, Triratna Shrestha, Lyudmyla L. Barannyk, Gabriel P. Potirniche and Indrajit Charit

Metals 2015, 5(3), 1487-1506; https://doi.org/10.3390/met5031487 - 21 Aug 2015

Cited by 13 | Viewed by 7593

Abstract

A dislocation-based creep model combined with a continuum damage formulation was developed and implemented in the finite element method to simulate high temperature deformation behavior in modified 9Cr-1Mo steel welds. The evolution of dislocation structures was considered as the main driving mechanism for [...] Read more.

A dislocation-based creep model combined with a continuum damage formulation was developed and implemented in the finite element method to simulate high temperature deformation behavior in modified 9Cr-1Mo steel welds. The evolution of dislocation structures was considered as the main driving mechanism for creep. The effect of void growth, precipitate coarsening, and solid solution depletion were considered to be the operating damage processes. A semi-implicit numerical integration scheme was developed and implemented in the commercial finite element code ABAQUS-Standard as a user material subroutine. Furthermore, several creep tests of modified 9Cr-1Mo steel welded specimens were conducted at temperatures between 550–700 °C and stresses between 80–200 MPa. The accuracy of the model was verified by comparing the finite element results with experiments. The comparison between the experimental and computational results showed excellent agreement. The model can be used to simulate and predict the creep-damage behavior of Cr-Mo steel components used as structural applications in power plants. Full article

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3836 KiB

Open AccessArticle

Water Impingement Erosion of Deep-Rolled Ti64

by Dina Ma, Ahmad Mostafa, Dmytro Kevorkov, Pawel Jedrzejowski, Martin Pugh and Mamoun Medraj

Metals 2015, 5(3), 1462-1486; https://doi.org/10.3390/met5031462 - 18 Aug 2015

Cited by 23 | Viewed by 10680

Abstract

In this work, the Liquid Impingement Erosion (LIE) performances of deep-rolling (DR) treated and non-treated Ti64 were investigated. Various erosion stages, from the incubation to the terminal erosion stages, could be observed. A full factorial design of experiments was used to study the [...] Read more.

In this work, the Liquid Impingement Erosion (LIE) performances of deep-rolling (DR) treated and non-treated Ti64 were investigated. Various erosion stages, from the incubation to the terminal erosion stages, could be observed. A full factorial design of experiments was used to study the effect of DR process parameters (Feed Rate, Spindle Velocity, Number of Passes, Pressure) on the residual stress distribution, microhardness and surface roughness of the treated Ti64 specimens. The DR-treated Ti64 specimens exhibited improved surface microhardness, surface roughness, and large magnitude of compressive residual stresses, which were attributed to the amount of cold work induced by the DR process. Although DR improved the mechanical properties of the Ti64, the results showed that the treatment has little or no effect on the LIE performance of Ti64 but different damage modes were observed in these two cases. Evolution of the erosion stages was described based on water-hammer pressure, stress waves, radial wall jetting, and hydraulic penetration modes. The initial erosion stages were mainly influenced by water-hammer pressure and stress waves, whereas the intermediate erosion stages were influenced by the combination of the four modes together. The final erosion stages contain the four modes, however the erosion was greatly driven by the radial jetting and hydraulic penetration modes, where more material was removed. The failure mechanism of the final stages of the LIE test of both DR-treated and non-treated Ti64 was characterized as fatigue fracture. However, a brittle fracture behavior was observed in the initial and intermediate erosion stages of the DR-treated Ti64, whereas a ductile fracture behavior was observed in the non-treated Ti64. This was concluded from the micrographs of the LIE damage through different erosion stages. Full article

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539 KiB

Open AccessArticle

A Straightforward Route to Tetrachloroauric Acid from Gold Metal and Molecular Chlorine for Nanoparticle Synthesis

by Shirin R. King, Juliette Massicot and Andrew M. McDonagh

Metals 2015, 5(3), 1454-1461; https://doi.org/10.3390/met5031454 - 18 Aug 2015

Cited by 41 | Viewed by 16363

Abstract

Aqueous solutions of tetrachloroauric acid of high purity and stability were synthesised using the known reaction of gold metal with chlorine gas. The straightforward procedure developed here allows the resulting solution to be used directly for gold nanoparticle synthesis. The procedure involves bubbling [...] Read more.

Aqueous solutions of tetrachloroauric acid of high purity and stability were synthesised using the known reaction of gold metal with chlorine gas. The straightforward procedure developed here allows the resulting solution to be used directly for gold nanoparticle synthesis. The procedure involves bubbling chlorine gas through pure water containing a pellet of gold. The reaction is quantitative and progressed at a satisfactory rate at 50 °C. The gold(III) chloride solutions produced by this method show no evidence of returning to metallic gold over at least twelve months. This procedure also provides a straightforward method to determine the concentration of the resulting solution using the initial mass of gold and volume of water. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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1076 KiB

Open AccessArticle

Material Properties of Various Cast Aluminum Alloys Made Using a Heated Mold Continuous Casting Technique with and without Ultrasonic Vibration

by Mitsuhiro Okayasu, Yuta Miyamoto and Kazuma Morinaka

Metals 2015, 5(3), 1440-1453; https://doi.org/10.3390/met5031440 - 14 Aug 2015

Cited by 13 | Viewed by 9179

Abstract

This work was carried out to develop high-quality cast aluminum alloys using a new casting technology. For this purpose, commercial Al alloys were created by heated mold continuous casting (HMC) with ultrasonic vibration (UV). With the HMC process, the grain size and the [...] Read more.

This work was carried out to develop high-quality cast aluminum alloys using a new casting technology. For this purpose, commercial Al alloys were created by heated mold continuous casting (HMC) with ultrasonic vibration (UV). With the HMC process, the grain size and the crystal orientation of the Al alloys were controlled, i.e., fine grains with a uniformly organized lattice formation. In addition, an attempt was made to modify the microstructural formation by cavitation. These microstructural characteristics made excellent mechanical properties. Using UV in the continuous casting process, more fine and spherical grains were slightly disordered, which was detected using electron backscattered diffraction. The mechanical properties of the UV HMC Al alloys were slightly higher than those for the related cast Al alloys without UV. Moreover, the severe vibration caused higher mechanical properties. The lattice and dislocation characteristics of the cast samples made with and without UV processes were analyzed systematically using electron backscattered diffraction. Full article

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352 KiB

Open AccessEditorial

Titanium Alloys

by Mark T. Whittaker

Metals 2015, 5(3), 1437-1439; https://doi.org/10.3390/met5031437 - 14 Aug 2015

Cited by 9 | Viewed by 5242

Abstract

Although originally discovered in the 18th century [1], the titanium industry did not experience any significant advancement until the middle of the 20th century through the development of the gas turbine engine [2]. Since then, the aerospace sector has dominated worldwide titanium use [...] Read more.

Although originally discovered in the 18th century [1], the titanium industry did not experience any significant advancement until the middle of the 20th century through the development of the gas turbine engine [2]. Since then, the aerospace sector has dominated worldwide titanium use with applications in both engines and airframe structures [3]. The highly desirable combination of properties, which include excellent corrosion resistance, favourable strength to weight ratios, and an impressive resistance to fatigue, has led to an extensive range of applications [4], with only high extraction and processing costs still restricting further implementation. [...] Full article

(This article belongs to the Special Issue Titanium Alloys)

279 KiB

Open AccessEditorial

Manganese-based Permanent Magnets

by Ian Baker

Metals 2015, 5(3), 1435-1436; https://doi.org/10.3390/met5031435 - 11 Aug 2015

Cited by 2 | Viewed by 4101

Abstract

There is a significant gap between the energy product, BH, where B is the magnetic flux density and H is the magnetic field strength, of both the traditional ferrite and AlNiCo permanent magnets of less than 10 MGOe and that of the rare [...] Read more.

There is a significant gap between the energy product, BH, where B is the magnetic flux density and H is the magnetic field strength, of both the traditional ferrite and AlNiCo permanent magnets of less than 10 MGOe and that of the rare earth magnets of greater than 30 MGOe. This is a gap that Mn-based magnets could potentially, inexpensively, fill. This Special Issue presents work on the development of both types of manganese permanent magnets. Some of the challenges involved in the development of these magnets include improving the compounds’ energy product, increasing the thermal stability of these metastable compounds, and producing them in quantity as a bulk material.[...] Full article

(This article belongs to the Special Issue Manganese-based Permanent Magnets)

318 KiB

Open AccessEditorial

Advances in Solidification Processing

by Hugo F. Lopez

Metals 2015, 5(3), 1432-1434; https://doi.org/10.3390/met5031432 - 11 Aug 2015

Viewed by 4035

Abstract

Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern [...] Read more.

Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern technological societies. As a result, there have been innumerable efforts and full conferences dedicated to this important subject [1–6]. In addition, there are various scientific journals fully devoted to investigating the various aspects which give rise to various solidification microstructures [7–9]. [...] Full article

(This article belongs to the Special Issue Advances in Solidification Processing)

1860 KiB

Open AccessArticle

A Computationally-Efficient Numerical Model to Characterize the Noise Behavior of Metal-Framed Walls

by Arun Arjunan, Chang Wang, Martin English, Mark Stanford and Paul Lister

Metals 2015, 5(3), 1414-1431; https://doi.org/10.3390/met5031414 - 7 Aug 2015

Cited by 28 | Viewed by 5637

Abstract

Architects, designers, and engineers are making great efforts to design acoustically-efficient metal-framed walls, minimizing acoustic bridging. Therefore, efficient simulation models to predict the acoustic insulation complying with ISO 10140 are needed at a design stage. In order to achieve this, a numerical model [...] Read more.

Architects, designers, and engineers are making great efforts to design acoustically-efficient metal-framed walls, minimizing acoustic bridging. Therefore, efficient simulation models to predict the acoustic insulation complying with ISO 10140 are needed at a design stage. In order to achieve this, a numerical model consisting of two fluid-filled reverberation chambers, partitioned using a metal-framed wall, is to be simulated at one-third-octaves. This produces a large simulation model consisting of several millions of nodes and elements. Therefore, efficient meshing procedures are necessary to obtain better solution times and to effectively utilise computational resources. Such models should also demonstrate effective Fluid-Structure Interaction (FSI) along with acoustic-fluid coupling to simulate a realistic scenario. In this contribution, the development of a finite element frequency-dependent mesh model that can characterize the sound insulation of metal-framed walls is presented. Preliminary results on the application of the proposed model to study the geometric contribution of stud frames on the overall acoustic performance of metal-framed walls are also presented. It is considered that the presented numerical model can be used to effectively visualize the noise behaviour of advanced materials and multi-material structures. Full article

(This article belongs to the Special Issue Serration and Noise Behavior in Advanced Materials)

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3033 KiB

Open AccessArticle

Mechanical Properties Analysis of an Al-Mg Alloy Connecting Rod with Submicrometric Structure

by Javier León, Daniel Salcedo, Óscar Murillo, Carmelo J. Luis, Juan P. Fuertes, Ignacio Puertas and Rodrigo Luri

Metals 2015, 5(3), 1397-1413; https://doi.org/10.3390/met5031397 - 31 Jul 2015

Cited by 7 | Viewed by 6270

Abstract

Over these last few years, there has been a growing interest in developing mechanical components from submicrometric materials due to the significant improvement that these materials present compared to their original state. This present research work deals with the study of the mechanical [...] Read more.

Over these last few years, there has been a growing interest in developing mechanical components from submicrometric materials due to the significant improvement that these materials present compared to their original state. This present research work deals with the study of the mechanical properties of a connecting rod isothermally forged from different starting materials. These materials are as follows: annealed aluminum alloy (AA) 5754, the same alloy previously deformed through equal channel angular pressing (ECAP) and a third case where the previously ECAP-processed material is subjected to a recovery heat treatment. A comparison is made between finite volume (FV) simulations and experimental tests with respect to hardness, plastic strain and forging force. Furthermore, the improvement in the mechanical properties of the connecting rod forged from predeformed material is evaluated in comparison to the connecting rod forged with annealed material. The microstructure of both cases is also compared at the end of the manufacturing process. Full article

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1140 KiB

Open AccessArticle

Effect of Material and Process Atmosphere in the Preparation of Al-Ti-B Grain Refiner by SHS

by Iban Vicario, Angeline Poulon-Quintin, Miguel Angel Lagos and Jean-François Silvain

Metals 2015, 5(3), 1387-1396; https://doi.org/10.3390/met5031387 - 30 Jul 2015

Cited by 13 | Viewed by 6086

Abstract

Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in [...] Read more.

Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in a combustion wave. The advantages of SHS are the low energy requirement, simplicity and product purity. However, the raw material used has to be very pure, with a very small size leading to the necessity of a reactor with a protective gas to produce the reaction. The purpose of this investigation is to fabricate SHS master alloys with commercial standard raw materials, with lower purity and higher grain size without a reactor or protective gas in order to (1) decrease the price and (2) improve the productivity of master alloy manufacturing. The possibility of using cheap borated salts instead of expensive pure boron has been studied. Different compositions of aluminum master alloy have been developed. Bigger TiB₂ grain size has been obtained when using bigger commercial raw materials. Larger titanium powder can produce an aluminum master alloy with a maximum of 30% of aluminum without reactor. In comparison, SHS reaction is much more difficult when using finer titanium powder. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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322 KiB

Open AccessReview

Gas Sensors Based on Electrodeposited Polymers

by Boris Lakard, Stéphanie Carquigny, Olivier Segut, Tilia Patois and Sophie Lakard

Metals 2015, 5(3), 1371-1386; https://doi.org/10.3390/met5031371 - 29 Jul 2015

Cited by 64 | Viewed by 7889

Abstract

Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene) and their derivatives can be used as [...] Read more.

Electrochemically deposited polymers, also called “synthetic metals”, have emerged as potential candidates for chemical sensing due to their interesting and tunable chemical, electrical, and structural properties. In particular, most of these polymers (including polypyrrole, polyaniline, polythiophene) and their derivatives can be used as the sensitive layer of conductimetric gas sensors because of their conducting properties. An important advantage of polymer-based gas sensors is their efficiency at room temperature. This characteristic is interesting since most of the commercially-available sensors, usually based on metal oxides, work at high temperatures (300–400 °C). Consequently, polymer-based gas sensors are playing a growing role in the improvement of public health and environment control because they can lead to gas sensors operating with rapid detection, high sensitivity, small size, and specificity in atmospheric conditions. In this review, the recent advances in electrodeposited polymer-based gas sensors are summarized and discussed. It is shown that the sensing characteristics of electrodeposited polymers can be improved by chemical functionalization, nanostructuration, or mixing with other functional materials to form composites or hybrid materials. Full article

(This article belongs to the Special Issue Synthetic Metals)

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409 KiB

Open AccessReview

Pyrrolyl Squaraines–Fifty Golden Years

by Daniel E. Lynch

Metals 2015, 5(3), 1349-1370; https://doi.org/10.3390/met5031349 - 27 Jul 2015

Cited by 29 | Viewed by 7184

Abstract

Pyrrolyl squaraines, both dyes and polymers, were first reported in 1965 and since then a fascinating body of work has been produced investigating the chemistry of these interesting molecules. A major aspect of these molecules that makes them so appealing to those researchers [...] Read more.

Pyrrolyl squaraines, both dyes and polymers, were first reported in 1965 and since then a fascinating body of work has been produced investigating the chemistry of these interesting molecules. A major aspect of these molecules that makes them so appealing to those researchers who have contributed to this field over the last 50 years is their chemical versatility. In this review, subjects, such as the synthetic history, an understanding of the molecular structure, an overview of the optical properties, a discussion of both the electrical conduction properties, and magnetic properties, plus use of the particles of pyrrolyl squaraines, are presented. Furthermore, previously published results are not just presented; they are in certain cases collated and used to both highlight and explain important aspects of pyrrolyl squaraine chemistry. Full article

(This article belongs to the Special Issue Synthetic Metals)

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666 KiB

Open AccessArticle

Copper Recovery from Polluted Soils Using Acidic Washing and Bioelectrochemical Systems

by Karin Karlfeldt Fedje, Oskar Modin and Ann-Margret Strömvall

Metals 2015, 5(3), 1328-1348; https://doi.org/10.3390/met5031328 - 23 Jul 2015

Cited by 30 | Viewed by 6196

Abstract

Excavation followed by landfilling is the most common method for treating soils contaminated by metals. However, as this solution is not sustainable, alternative techniques are required. Chemical soil washing is one such alternative. The aim of this experimental lab-scale study is to develop [...] Read more.

Excavation followed by landfilling is the most common method for treating soils contaminated by metals. However, as this solution is not sustainable, alternative techniques are required. Chemical soil washing is one such alternative. The aim of this experimental lab-scale study is to develop a remediation and metal recovery method for Cu contaminated sites. The method is based on the washing of soil or ash (combusted soil/bark) with acidic waste liquids followed by electrolytic Cu recovery by means of bioelectrochemical systems (BES). The results demonstrate that a one- or two-step acidic leaching process followed by water washing removes >80 wt. % of the Cu. Copper with 99.7–99.9 wt. % purity was recovered from the acidic leachates using BES. In all experiments, electrical power was generated during the reduction of Cu. This clearly indicates that Cu can also be recovered from dilute solutions. Additionally, the method has the potential to wash co-pollutants such as polycyclic aromatic hydrocarbons (PAHs) and oxy-PAHs. Full article

(This article belongs to the Special Issue Hydrometallurgy)

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1674 KiB

Open AccessArticle

High Temperature Flow Response Modeling of Ultra-Fine Grained Titanium

by Seyed Vahid Sajadifar and Guney Guven Yapici

Metals 2015, 5(3), 1315-1327; https://doi.org/10.3390/met5031315 - 22 Jul 2015

Cited by 17 | Viewed by 5254

Abstract

This work presents the mechanical behavior modeling of commercial purity titanium subjected to severe plastic deformation (SPD) during post-SPD compression, at temperatures of 600-900 °C and at strain rates of 0.001-0.1 s−1. The flow response of the ultra-fine grained microstructure is modeled using [...] Read more.

This work presents the mechanical behavior modeling of commercial purity titanium subjected to severe plastic deformation (SPD) during post-SPD compression, at temperatures of 600-900 °C and at strain rates of 0.001-0.1 s−1. The flow response of the ultra-fine grained microstructure is modeled using the modified Johnson-Cook model as a predictive tool, aiding high temperature forming applications. It was seen that the model was satisfactory at all deformation conditions except for the deformation temperature of 600 °C. In order to improve the predictive capability, the model was extended with a corrective term for predictions at temperatures below 700 °C. The accuracy of the model was displayed with reasonable agreement, resulting in error levels of less than 5% at all deformation temperatures. Full article

(This article belongs to the Special Issue Ultrafine-grained Metals)

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Metals, Volume 5, Issue 3 (September 2015) – 41 articles , Pages 1127-1769

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