Next Issue
Previous Issue

Table of Contents

Metals, Volume 7, Issue 5 (May 2017)

  • 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.
Cover Story The pine-like dendrites produced by a galvanostatic electrodeposition at a current density of 13.05 [...] Read more.
View options order results:
result details:
Displaying articles 1-32
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Aluminium Wires Have the Free Air Balls (FABs): Electronic Flame-Off, Fracture Strength, Electrical Properties, and Bonding Characteristics of Nano Zn Film Al–Si Bonding Wires
Metals 2017, 7(5), 152; doi:10.3390/met7050152
Received: 18 November 2016 / Revised: 21 March 2017 / Accepted: 20 April 2017 / Published: 25 April 2017
PDF Full-text (9493 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum wire is a common material for wire bonding due to its resistance to oxidation and low price. It does not melt when becoming a free air ball (FAB) during the electronic flame-off (EFO) process with wettability and is applied by wedge bonding.
[...] Read more.
Aluminum wire is a common material for wire bonding due to its resistance to oxidation and low price. It does not melt when becoming a free air ball (FAB) during the electronic flame-off (EFO) process with wettability and is applied by wedge bonding. This study used 20 μm Zn-coated Al–0.5 wt % Si (ZAS) wires to improve the FAB shape after the EFO process, while maintaining the stability of the mechanical properties, including the interface bonding strength and hardness. In order to test circuit stability after ball bonding, the current-tensile test was performed. During the experiment, it was found that 80 nm ZAS with wire bonding had lower resistance and its fusing current was higher. For the bias tensile test, the thicker Zn film diffused into the Al–Si matrix easily, after which the strength was reduced. The ball-bond interfaces had no change in their condition before and after the bias. Accordingly, the ZAS wire could be a promising candidate for ball bonding in the future. Full article
Figures

Figure 1

Open AccessArticle Non-Isothermal Gas-Based Direct Reduction Behavior of High Chromium Vanadium-Titanium Magnetite Pellets and the Melting Separation of Metallized Pellets
Metals 2017, 7(5), 153; doi:10.3390/met7050153
Received: 14 March 2017 / Revised: 11 April 2017 / Accepted: 20 April 2017 / Published: 26 April 2017
PDF Full-text (6945 KB) | HTML Full-text | XML Full-text
Abstract
The non-isothermal reduction behavior of high chromium vanadium-titanium magnetite (HCVTM) pellets by gas mixtures was investigated using different heating rates (4, 8, and 12 K/min) and varied gas compositions (H2/CO = 2/5, H2/CO = 1/1, and H2/CO
[...] Read more.
The non-isothermal reduction behavior of high chromium vanadium-titanium magnetite (HCVTM) pellets by gas mixtures was investigated using different heating rates (4, 8, and 12 K/min) and varied gas compositions (H2/CO = 2/5, H2/CO = 1/1, and H2/CO = 5/2 volume ratios); the pellets were then used for melting separation. It was observed that the temperature corresponding to the maximum reduction ratio increased with the increasing heating rate. The HCVTM pellets reached the same final reduction ratio under a given reducing gas composition, although the heating rates were different. Under the same heating rate, the gas mixture with more H2 was conducive for obtaining a higher reduction ratio. The phase transformations during the non-isothermal reduction were ordered as follows: Fe2O3 → Fe3O4 → FeO → Fe; Fe9TiO15 + Fe2Ti3O9 → Fe2.75Ti0.25O4 → FeTiO3 → TiO2; V1.7Cr0.3O3 → V2O3 → Fe2VO4; Fe1.2Cr0.8O3 → Cr2O3 → FeCr2O4. The non-isothermal reduction kinetic model was established based on the unreacted core model with multiple reaction interfaces. The correlation coefficients were greater than 0.99, revealing that this kinetic model could properly describe the non-isothermal reduction of the HCVTM pellets by gas mixtures. Iron containing V and Cr along with the Ti-rich slag was obtained through the melting separation of the metallized HCVTM pellets. The mass fractions and recovery rates of Fe, V, and Cr in the iron were 93.87% and 99.45%, 0.91% and 98.83%, and 0.72% and 95.02%, respectively. The mass fraction and recovery rate of TiO2 in the slag were 38.12% and 95.08%, respectively. Full article
Figures

Figure 1

Open AccessFeature PaperArticle Discrete Element Method Investigation of Bulk Density and Electrical Resistivity of Calcined Coke Mixes
Metals 2017, 7(5), 154; doi:10.3390/met7050154
Received: 17 January 2017 / Revised: 21 April 2017 / Accepted: 24 April 2017 / Published: 26 April 2017
PDF Full-text (3040 KB) | HTML Full-text | XML Full-text
Abstract
Packing density and electrical resistivity of particles assemblies are important factors for a variety of applications of granular materials. In the present work, a three-dimensional imaging technique is coupled with the discrete element method (DEM) to model anode grade calcined coke particles. Three-dimensional
[...] Read more.
Packing density and electrical resistivity of particles assemblies are important factors for a variety of applications of granular materials. In the present work, a three-dimensional imaging technique is coupled with the discrete element method (DEM) to model anode grade calcined coke particles. Three-dimensional DEM models of samples with different size distribution of particles were studied to obtain the inter-particle contact information. As the content of fine particles increased, a higher inter-particle contact density and smaller average contact radius was observed in the samples. Confronting the DEM data and experimental measurements of electrical resistivity showed the simultaneous effects of packing density and contact density. Samples with higher contact density and smaller contact radius in general held high electrical resistivities. However, if increasing the contact density does not modify contacts between large particles, this will have a positive effect on packing density, so a lower electrical resistivity was obtained. Full article
Figures

Figure 1

Open AccessArticle Surface Modelling of Nanostructured Copper Subjected to Erosion-Corrosion
Metals 2017, 7(5), 155; doi:10.3390/met7050155
Received: 4 March 2017 / Revised: 17 April 2017 / Accepted: 20 April 2017 / Published: 27 April 2017
Cited by 1 | PDF Full-text (9870 KB) | HTML Full-text | XML Full-text
Abstract
The last decade has witnessed considerable advancements in nanostructured material synthesis and property characterization. However, there still exists some deficiency in the mechanical and surface property characterization of these materials. In this paper, the erosion corrosion (E-C) behavior of nanostructured copper was studied.
[...] Read more.
The last decade has witnessed considerable advancements in nanostructured material synthesis and property characterization. However, there still exists some deficiency in the mechanical and surface property characterization of these materials. In this paper, the erosion corrosion (E-C) behavior of nanostructured copper was studied. The nanostructured copper was produced through severe plastic deformation (SPD) by applying four passes of equal channel angular pressing (ECAP). The combined effects of the testing time, impact velocity, and concentration of erosive solid particles (i.e., sand concentration) on the E-C behavior of nanostructured copper were then examined. Based on a defined domain for the testing time, impact velocity, and sand concentration, E-C tests were performed for numerous combinations of test points via the slurry pot method. The test points were selected using the face-centered center composite design of experiments to enable visualization of the test results through surface plots. The extent of E-C on the test specimens was determined by measuring the mass loss. Polynomial regression and Kriging were used to fit surfaces to the experimental data, which were subsequently used to generate surface plots. The results showed that the E-C of nanostructured copper is best described by a quadratic function of testing time, velocity, and erosive solid particle concentration. The results also revealed that E-C increases with an increasing testing time, impact velocity, and erosive solid particle concentration. In addition, it was observed that the effect of the erosive solid particles on E-C is further intensified by an increased impact velocity. Full article
Figures

Figure 1

Open AccessFeature PaperArticle Lattice Softening in Fe3Pt Exhibiting Three Types of Martensitic Transformations
Metals 2017, 7(5), 156; doi:10.3390/met7050156
Received: 24 March 2017 / Revised: 25 April 2017 / Accepted: 26 April 2017 / Published: 27 April 2017
Cited by 2 | PDF Full-text (679 KB) | HTML Full-text | XML Full-text
Abstract
We have investigated the relation between the softening of elastic constants and martensitic transformation in Fe3Pt, which exhibits various kinds of martensitic transformation depending on its long-range order parameter S. The martensite phases of the examined alloys are BCT (
[...] Read more.
We have investigated the relation between the softening of elastic constants and martensitic transformation in Fe3Pt, which exhibits various kinds of martensitic transformation depending on its long-range order parameter S. The martensite phases of the examined alloys are BCT (S = 0.57), FCT1 (S = 0.75, c/a < 1) and FCT2 (S = 0.88, c/a > 1). The elastic constants C′ and C44 of these alloys decrease almost linearly with decreasing temperature. Although the temperature coefficient of C′ decreases as S increases, C′ at the transformation temperature is the smallest in the alloy with S = 0.75, which transforms to FCT1. This result implies that softening is most strongly related to the formation of the FCT1 martensite with tetragonality c/a < 1 among the three martensites. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2017)
Figures

Open AccessFeature PaperArticle Characterization of the Effect of Melt Treatments on Melt Quality in Al-7wt %Si-Mg Alloys
Metals 2017, 7(5), 157; doi:10.3390/met7050157
Received: 22 February 2017 / Revised: 12 April 2017 / Accepted: 27 April 2017 / Published: 29 April 2017
PDF Full-text (14771 KB) | HTML Full-text | XML Full-text
Abstract
The effects of degassing, holding time and melt additions (Sr, Sr + Ti, Ti, B and B + Sr) on the quality of A356 melts were examined. A total of 120 reduced pressure test samples were collected. Pores in these samples were analyzed
[...] Read more.
The effects of degassing, holding time and melt additions (Sr, Sr + Ti, Ti, B and B + Sr) on the quality of A356 melts were examined. A total of 120 reduced pressure test samples were collected. Pores in these samples were analyzed via digital image processing to determine the number density of pores as well as the statistical distribution of their sizes. Results showed that in all cases, degassing with argon reduced the number of defects regardless of the additions made to the melts. Moreover, all additions were found to degrade melt quality. The lowest number density of pores in all melts was achieved in melts with no additions that were degassed. In both degassed and non-degassed melts, Sr additions degraded the melt quality significantly. The mechanisms of melt quality improvement or degradation with different melt treatments are discussed in the paper. Full article
Figures

Figure 1

Open AccessArticle Experimental Investigation on the Fatigue Life of Ti-6Al-4V Treated by Vibratory Stress Relief
Metals 2017, 7(5), 158; doi:10.3390/met7050158
Received: 1 April 2017 / Revised: 28 April 2017 / Accepted: 28 April 2017 / Published: 3 May 2017
Cited by 1 | PDF Full-text (6532 KB) | HTML Full-text | XML Full-text
Abstract
Vibratory stress relief (VSR) is a highly efficient and low-energy consumption method to relieve and homogenize residual stresses in materials. Thus, the effect of VSR on the fatigue life should be determined. Standard fatigue specimens are fabricated to investigate the fatigue life of
[...] Read more.
Vibratory stress relief (VSR) is a highly efficient and low-energy consumption method to relieve and homogenize residual stresses in materials. Thus, the effect of VSR on the fatigue life should be determined. Standard fatigue specimens are fabricated to investigate the fatigue life of Ti-6Al-4V titanium alloy treated by VSR. The dynamic stresses generated under different VSR amplitudes are measured, and then the relationship between the dynamic stress and vibration amplitude is obtained. Different specimen groups are subjected to VSRs with different amplitudes and annealing treatment with typical process parameters. Residual stresses are measured to evaluate the stress relieving effects. Finally, the fatigue behavior under different states is determined by uniaxial tension–compression fatigue experiments. Results show that VSR and annealing treatment have negative effects on the fatigue life of Ti-6Al-4V. The fatigue life is decreased with the increase in VSR amplitude. When the VSR amplitude is less than 0.1 mm, the decrease in fatigue limit is less than 2%. Compared with specimens without VSR or annealing treatment, the fatigue limit of the specimens treated by VSR with 0.2 mm amplitude and annealing treatment decreases by 10.60% and 8.52%, respectively. Although the stress relieving effect is better, high amplitude VSR will lead to the decrease of Ti-6Al-4V fatigue life due to the defects generated during vibration. Low amplitude VSR can effectively relieve the stress with little decrease in fatigue life. Full article
(This article belongs to the Special Issue Fatigue Damage) Printed Edition available
Figures

Figure 1

Open AccessArticle Comparative Morphological and Crystallographic Analysis of Electrochemically- and Chemically-Produced Silver Powder Particles
Metals 2017, 7(5), 160; doi:10.3390/met7050160
Received: 27 March 2017 / Revised: 25 April 2017 / Accepted: 28 April 2017 / Published: 5 May 2017
Cited by 2 | PDF Full-text (4330 KB) | HTML Full-text | XML Full-text
Abstract
Silver powders chemically synthesized by reduction with hydrazine and those produced by electrolysis from the basic (nitrate) and complex (ammonium) electrolytes were examined by X-ray diffraction (XRD) and scanning electron microscopic (SEM) analysis of the produced particles. Morphologies of the obtained particles were
[...] Read more.
Silver powders chemically synthesized by reduction with hydrazine and those produced by electrolysis from the basic (nitrate) and complex (ammonium) electrolytes were examined by X-ray diffraction (XRD) and scanning electron microscopic (SEM) analysis of the produced particles. Morphologies of the obtained particles were very different at the macro level. The needle-like dendrites, as well as the mixture of irregular and regular crystals, were formed from the nitrate electrolyte, while the highly-branched pine-like dendrites with clearly noticeable spherical grains were formed from the ammonium electrolyte. The agglomerates of spherical grains were formed by reduction with hydrazine. In the particles obtained from the nitrate electrolyte, Ag crystallites were strongly oriented in the (111) plane. Although morphologies of Ag particles were very different at the macro level, the similarity at the micro level was observed between chemically-synthesized particles and those obtained by electrolysis from the ammonium electrolyte. Both types of particles were constructed from the spherical grains. This similarity at the micro level was accompanied by the similar XRD patterns, which were very close to the Ag standard with a random orientation of Ag crystallites. For the first time, morphologies of powder particles were correlated with their crystal structure. Full article
Figures

Figure 1

Open AccessArticle Critical Condition of Dynamic Recrystallization in 35CrMo Steel
Metals 2017, 7(5), 161; doi:10.3390/met7050161
Received: 15 April 2017 / Revised: 1 May 2017 / Accepted: 4 May 2017 / Published: 9 May 2017
Cited by 1 | PDF Full-text (7429 KB) | HTML Full-text | XML Full-text
Abstract
The compression deformation behaviors of 35CrMo steel at different conditions was studied by using Gleeble-3810 thermo-simulation machine under large strain. The results indicate that the flow stress curves of 35CrMo steel is affected by strain rate and deformation temperature, showing the characteristics of
[...] Read more.
The compression deformation behaviors of 35CrMo steel at different conditions was studied by using Gleeble-3810 thermo-simulation machine under large strain. The results indicate that the flow stress curves of 35CrMo steel is affected by strain rate and deformation temperature, showing the characteristics of dynamic recovery (DRV) and dynamic recrystallization (DRX), which is the main softening mechanism of 35CrMo steel. The activation energy (Q) and Zener–Hollomon parameter (Z parameter) expression for thermal deformation of this steel was calculated by linear regression. The inflection point on the curve of strain hardening rate and flow stress (θ-σ curve) corresponds to the beginning of DRX, and the critical strain of DRX increases with the decrease of deformation temperature and the increase of strain rate. Based on the inflection point criterion, the constitutive equation of the critical strain of DRX of 35CrMo steel was established: εc = 0.000232Z0.1673, which reflects the variation of the critical strain of DRX with the Z parameter. In addition, through metallographic observation, the rationality of the inflection point criterion in determining the critical strain of DRX of 35CrMo steel was verified, and the DRX state diagram was established. Full article
(This article belongs to the Special Issue Alloy Steels)
Figures

Figure 1

Open AccessArticle The Phase Composition and Microstructure of AlxCoCrFeNiTi Alloys for the Development of High-Entropy Alloy Systems
Metals 2017, 7(5), 162; doi:10.3390/met7050162
Received: 3 April 2017 / Revised: 3 May 2017 / Accepted: 4 May 2017 / Published: 9 May 2017
Cited by 2 | PDF Full-text (3765 KB) | HTML Full-text | XML Full-text
Abstract
Alloying aluminum offers the possibility of creating low-density high-entropy alloys (HEAs). Several studies that focus on the system AlCoCrFeNiTi differ in their phase determination. The effect of aluminum on the phase composition and microstructure of the compositionally complex alloy (CCA) system Alx
[...] Read more.
Alloying aluminum offers the possibility of creating low-density high-entropy alloys (HEAs). Several studies that focus on the system AlCoCrFeNiTi differ in their phase determination. The effect of aluminum on the phase composition and microstructure of the compositionally complex alloy (CCA) system AlxCoCrFeNiTi was studied with variation in aluminum content (molar ratios x = 0.2, 0.8, and 1.5). The chemical composition and elemental segregation was measured for the different domains in the microstructure. The crystal structure was determined using X-ray diffraction (XRD) analysis. To identify the spatial distribution of the phases found with XRD, phase mapping with associated orientation distribution was performed using electron backscatter diffraction. This made it possible to correlate the chemical and structural conditions of the phases. The phase formation strongly depends on the aluminum content. Two different body-centered cubic (bcc) phases were found. Texture analysis proved the presence of a face-centered cubic (fcc) phase for all aluminum amounts. The hard η-(Ni, Co)3Ti phase in the x = 0.2 alloy was detected via metallographic investigation and confirmed via electron backscatter diffraction. Additionally, a centered cluster (cc) with the A12 structure type was detected in the x = 0.2 and 0.8 alloys. The correlation of structural and chemical properties as well as microstructure formation contribute to a better understanding of the alloying effects concerning the aluminum content in CCAs. Especially in the context of current developments in lightweight high-entropy alloys (HEAs), the presented results provide an approach to the development of new alloy systems. Full article
(This article belongs to the Special Issue High-Entropy Alloys (HEAs))
Figures

Figure 1

Open AccessArticle Economic and Qualitative Determinants of the World Steel Production
Metals 2017, 7(5), 163; doi:10.3390/met7050163
Received: 20 March 2017 / Revised: 20 April 2017 / Accepted: 3 May 2017 / Published: 9 May 2017
PDF Full-text (572 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this paper is to highlight the influence of economic and qualitative factors on steel production globally, as well in the EU, US, and China, using a dataset corresponding to the period 2000–2015. The research methods used are the study of
[...] Read more.
The aim of this paper is to highlight the influence of economic and qualitative factors on steel production globally, as well in the EU, US, and China, using a dataset corresponding to the period 2000–2015. The research methods used are the study of specialist literature, problematisation, modelling, and simulation using Statistical Package for the Social Sciences (SPSS) software. The main conclusion of this paper is that, on long term, the steel production is largely influenced by the rate of real economic growth and by car production, even if in the short term the correlation is not obvious. Likewise, qualitative factors affect the steel industry in the context of current regulations on reducing carbon emissions and ensuring sustainable development. An additional aim of the present study is to define entropy in the sustainable development of steel production, as well as illustrate some of its properties and the quality management modelling of the research process in steel production. Full article
Figures

Figure 1

Open AccessArticle The Microstructure and Mechanical Properties of Die-Cast Mg-6Al-2Sm-xCu Alloys
Metals 2017, 7(5), 164; doi:10.3390/met7050164
Received: 8 March 2017 / Revised: 4 May 2017 / Accepted: 5 May 2017 / Published: 10 May 2017
PDF Full-text (32490 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, the effect of Cu content on the microstructure and mechanical properties of die-cast Mg-6Al-2Sm-xCu (x = 1, 3, 5) alloys has been investigated. The microstructure and components of the alloys were observed and identified by optical
[...] Read more.
In the present study, the effect of Cu content on the microstructure and mechanical properties of die-cast Mg-6Al-2Sm-xCu (x = 1, 3, 5) alloys has been investigated. The microstructure and components of the alloys were observed and identified by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS), respectively. The phases of the alloys were analyzed via X-ray diffractometer (XRD). The mechanical properties at different temperatures were studied by tensile tests. The experimental results show that all die-cast Mg-6Al-2Sm-xCu alloys consist of α-Mg, β-Mg17Al12, Al4Cu9, Al3Sm, and Mg2Cu6Al5 phases. These components, i.e., Al3Sm and Al4Cu9 phases, have high thermal stability and can prohibit dislocation movement and grain boundary sliding. TEM analysis shows that the Al3Sm phase possesses a tetragonal structure. With the increase in Cu content, the microstructure is refined firstly and then becomes coarsened. Moreover, the tensile strength increases firstly and then decreases as Cu content increases at room temperature and an elevated temperature. All fractures of the alloys at room temperature show a complex mode of brittle and ductile fracture. However, at an elevated testing temperature, the fractures of the alloys exhibit more ductile fractures. Full article
Figures

Figure 1

Open AccessArticle Analytical Modelling of Energy Density and Optimization of the EDM Machining Parameters of Inconel 600
Metals 2017, 7(5), 166; doi:10.3390/met7050166
Received: 5 April 2017 / Revised: 28 April 2017 / Accepted: 3 May 2017 / Published: 11 May 2017
Cited by 1 | PDF Full-text (5460 KB) | HTML Full-text | XML Full-text
Abstract
In this present research work, a new modelling of energy density in EDM (Electrical Discharge Machining) is proposed. Energy density can be defined as the amount of energy needed to get a unit volume of material removed, and for its modelling, the whole
[...] Read more.
In this present research work, a new modelling of energy density in EDM (Electrical Discharge Machining) is proposed. Energy density can be defined as the amount of energy needed to get a unit volume of material removed, and for its modelling, the whole EDM process has been taken into account. This new definition lets us quantify the energy density that is being absorbed by the workpiece and the electrode. Results are compared to those obtained by die sinking EDM in an Inconel ®600 alloy using Cu-C electrodes. Currently, this material is of great interest for industrial applications in the nuclear, aeronautical and chemical sectors, due to their combinations of good mechanical properties, corrosion resistance and extreme hardness at very high temperatures. The experimental results confirm that the use of negative polarity leads to a higher material removal rate, higher electrode wear and higher surface roughness. Moreover, the optimal condition to obtain a maximum MRR (Material Removal Rate) of 30.49 mm3/min was: 8 A, 100 µs and 0.6, respectively, for the current intensity, pulse time and duty cycle. Full article
Figures

Figure 1

Open AccessArticle TiO2 Nanotubes on Ti Dental Implant. Part 1: Formation and Aging in Hank’s Solution
Metals 2017, 7(5), 167; doi:10.3390/met7050167
Received: 11 April 2017 / Revised: 4 May 2017 / Accepted: 8 May 2017 / Published: 11 May 2017
Cited by 2 | PDF Full-text (2235 KB) | HTML Full-text | XML Full-text
Abstract
Self-organized TiO2 nanotube layer has been formed on titanium screws with complex geometry, which are used as dental implants. TiO2 nanotubes film was grown by potentiostatic anodizing in H3PO4 and HF aqueous solution. During anodizing, the titanium screws
[...] Read more.
Self-organized TiO2 nanotube layer has been formed on titanium screws with complex geometry, which are used as dental implants. TiO2 nanotubes film was grown by potentiostatic anodizing in H3PO4 and HF aqueous solution. During anodizing, the titanium screws were mounted on a rotating apparatus to produce a uniform structure both on the peaks and on the valleys of the threads. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) and electrochemical characterization were used to evaluate the layer, chemical composition and electrochemical properties of the samples. Aging in Hank’s solution of both untreated and nanotubes covered screw, showed that: (i) samples are covered by an amorphous oxide layer, (ii) the nanotubes increases the corrosion resistance of the implant, and (iii) the presence of the nanotubes catalyses the formation of chemical compounds containing Ca and P. Full article
Figures

Figure 1

Open AccessArticle Effects of Micro-Sized Ferrite and Austenite Grains on the Pitting Corrosion Behavior of Lean Duplex Stainless Steel 2101
Metals 2017, 7(5), 168; doi:10.3390/met7050168
Received: 1 March 2017 / Revised: 9 May 2017 / Accepted: 9 May 2017 / Published: 12 May 2017
PDF Full-text (20596 KB) | HTML Full-text | XML Full-text
Abstract
The connection between the austenite transformation and pitting corrosion of lean duplex stainless steel LDX 2101 was investigated at different annealing temperatures in the range 950–1200 °C. Optical microscopy, scanning electron microscopy, and electrochemical techniques were employed in the present work. Results indicated
[...] Read more.
The connection between the austenite transformation and pitting corrosion of lean duplex stainless steel LDX 2101 was investigated at different annealing temperatures in the range 950–1200 °C. Optical microscopy, scanning electron microscopy, and electrochemical techniques were employed in the present work. Results indicated that micro-sized ferrite and austenite grains, formed with the increase of annealing temperature, influenced the pitting corrosion resistance of the studied stainless steel. As the austenite phase transformed into ferrite, the micro-sized ferrite grains were produced in austenite domains with temperature increase from 1000 °C to 1100 °C, especially at 1050 °C. In these conditions, the corrosion resistance of LDX 2101 was reduced by the micro-sized ferrite grains. A further increase of annealing temperature to 1150 °C produced the presence of micro-sized austenite grains in the ferritic phase, due to an incomplete transformation of austenite to ferrite. They represent new sites for severe pitting attacks and therefore the corrosion resistance of LDX 2101 was the weakest. The sample annealed at 1200 °C, with few micro-sized austenite grains in the ferritic matrix, exhibited excellent corrosion resistance. Moreover, a schematic was used to illustrate the pitting corrosion of the samples annealed at different temperatures. Full article
Figures

Figure 1

Open AccessArticle Diatoms and Their Capability for Heavy Metal Removal by Cationic Exchange
Metals 2017, 7(5), 169; doi:10.3390/met7050169
Received: 23 February 2017 / Revised: 4 May 2017 / Accepted: 8 May 2017 / Published: 12 May 2017
PDF Full-text (3064 KB) | HTML Full-text | XML Full-text
Abstract
This work shows the physicochemical behavior of two different diatoms from the country of Mexico (State of Jalisco and Hidalgo) with similar compositions. These were used to eliminate toxic cations from a synthetic solution containing 5.270 mg As3+/L; 4.280 mg Ag
[...] Read more.
This work shows the physicochemical behavior of two different diatoms from the country of Mexico (State of Jalisco and Hidalgo) with similar compositions. These were used to eliminate toxic cations from a synthetic solution containing 5.270 mg As3+/L; 4.280 mg Ag+/L; 3.950 mgNi2+/L; 4.090 mg Cr6+/L; and 4.081 mg Pb2+/L. These diatoms were used as filters, and the quantity of cations remaining in the solution after filtering was measured. According to the most important results found, for the recovery of metals, both minerals achieved arsenic, silver, lead, and nickel recoveries up to 95%, and lower than 10% for chromium. This could be due to the absence of an environment to reduce Cr6+ to Cr3+. On the other hand, it was observed that there was no selectivity during the recovery of the other cations present in the solution. According to efficiency of interchange, the mineral from Hidalgo is slightly better than the mineral from Jalisco for the removal of arsenic, lead, and silver. For nickel, and particularly Cr6+, the efficiency is higher for the sample from Jalisco. Full article
(This article belongs to the Special Issue Heavy Metal Determination and Removal)
Figures

Figure 1

Open AccessArticle Characteristics of Cold and Hot Pressed Iron Aluminum Powder Metallurgical Alloys
Metals 2017, 7(5), 170; doi:10.3390/met7050170
Received: 4 March 2017 / Revised: 29 April 2017 / Accepted: 3 May 2017 / Published: 12 May 2017
PDF Full-text (5100 KB) | HTML Full-text | XML Full-text
Abstract
Iron powders having average particle sizes of ~40 µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt. %, with an average particle size of ~10 µm. Two different powder metallurgy (PM) techniques, cold and hot pressing, are
[...] Read more.
Iron powders having average particle sizes of ~40 µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt. %, with an average particle size of ~10 µm. Two different powder metallurgy (PM) techniques, cold and hot pressing, are used to study the effect of the additive element powder on the mechanical properties, wear properties, and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature reaching up to 500 °C at 445.6 MPa. The cold pressing technique was performed at 909 MPa at room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the Brinell hardness number was decreased from 780 to 690 and the radial strength from 380 to 228 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to five times was achieved, compared to the alloy without Al addition for different wear parameters: wear time and sliding speed. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
Figures

Open AccessArticle Mechanical and Corrosion Behavior of Al-Zn-Cr Family Alloys
Metals 2017, 7(5), 171; doi:10.3390/met7050171
Received: 9 February 2017 / Revised: 29 April 2017 / Accepted: 3 May 2017 / Published: 12 May 2017
Cited by 2 | PDF Full-text (4200 KB) | HTML Full-text | XML Full-text
Abstract
Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and powder metallurgy techniques. Cr additions ranged between 5 to 10 wt. %, while Zn was added in an amount between 0 and 20 wt. %. Heat treatment processes were
[...] Read more.
Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and powder metallurgy techniques. Cr additions ranged between 5 to 10 wt. %, while Zn was added in an amount between 0 and 20 wt. %. Heat treatment processes were performed during powder metallurgy process, at different temperatures, followed by water quenching. Similar alloys were extruded with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the alloys investigated. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys, containing 10 wt. % Cr and heat treated at 500 °C for one hour followed by water quenching, exhibited the highest wear resistance and better mechanical properties. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
Figures

Open AccessArticle Grain Refinement Mechanism of the As-Cast and As-Extruded Mg–14Li Alloys with Al or Sn Addition
Metals 2017, 7(5), 172; doi:10.3390/met7050172
Received: 13 April 2017 / Revised: 8 May 2017 / Accepted: 9 May 2017 / Published: 13 May 2017
Cited by 1 | PDF Full-text (7146 KB) | HTML Full-text | XML Full-text
Abstract
The microstructures of the as-cast and as-extruded Mg–14 wt. % Li–1 wt. % Al (LA141) and Mg–14 wt. % Li–2 wt. % Sn (LT142) were observed by optical and scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The effects
[...] Read more.
The microstructures of the as-cast and as-extruded Mg–14 wt. % Li–1 wt. % Al (LA141) and Mg–14 wt. % Li–2 wt. % Sn (LT142) were observed by optical and scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The effects of Al and Sn on the grain refinement on the Mg–14Li alloy were investigated. In addition, the mechanism of grain refinement on the as-cast and as-extruded alloys was discussed from the view of the solute effect and heterogeneous nucleation effect via edge-to-edge matching model. The results showed that the average grain sizes of the as-cast LA141 and LT142 alloys were similar due to the close solute effect of 1.1 wt. % Al and 1.8 wt. % Sn, while, in the as-extruded alloys, the average grain size of LT142 was over two times finer than that of LA141. This was attributed to the reason that Li2MgSn particles can serve as heterogeneous nucleation sites for the β-Li matrix during the process of dynamic recrystallization (DRX), but LiMgAl2 cannot serve the same way. Therefore, Sn can act as a more effective grain refiner for the Mg–14Li alloy compared to Al. Full article
(This article belongs to the Special Issue Microstructure based Modeling of Metallic Materials)
Figures

Open AccessArticle Variable-Frequency Ultrasonic Treatment on Microstructure and Mechanical Properties of ZK60 Alloy during Large Diameter Semi-Continuous Casting
Metals 2017, 7(5), 173; doi:10.3390/met7050173
Received: 7 April 2017 / Revised: 4 May 2017 / Accepted: 4 May 2017 / Published: 16 May 2017
Cited by 1 | PDF Full-text (5043 KB) | HTML Full-text | XML Full-text
Abstract
Traditional fixed-frequency ultrasonic technology and a variable-frequency ultrasonic technology were applied to refine the as-cast microstructure and improve the mechanical properties of a ZK60 (Mg–Zn–Zr) alloy during large diameter semi-continuous casting. The acoustic field propagation was obtained by numerical simulation. The microstructure of
[...] Read more.
Traditional fixed-frequency ultrasonic technology and a variable-frequency ultrasonic technology were applied to refine the as-cast microstructure and improve the mechanical properties of a ZK60 (Mg–Zn–Zr) alloy during large diameter semi-continuous casting. The acoustic field propagation was obtained by numerical simulation. The microstructure of the as-cast samples was characterized by optical and scanning electron microscopy. The variable-frequency ultrasonic technology shows its outstanding ability in grain refinement compared with traditional fixed-ultrasonic technology. The variable-frequency acoustic field promoted the formation of small α-Mg globular grains and changed the distribution and morphology of β-phases throughout the castings. Ultimate tensile strength and elongation are increased to 280 MPa and 8.9%, respectively, which are 19.1% and 45.9% higher than the values obtained from billets without ultrasonic treatment and are 11.6% and 18.7% higher than fixed-frequency ultrasound treated billets. Different refinement efficiencies appear in different districts of billets attributed to the sound attenuation in melt. The variable-frequency acoustic field improves the refinement effect by enhancing cavitation-enhanced heterogeneous nucleation and dendrite fragmentation effects. Full article
Figures

Figure 1

Open AccessArticle Leaching Process of Rare Earth Elements, Gallium and Niobium in a Coal-Bearing Strata-Hosted Rare Metal Deposit—A Case Study from the Late Permian Tuff in the Zhongliangshan Mine, Chongqing
Metals 2017, 7(5), 174; doi:10.3390/met7050174
Received: 15 February 2017 / Revised: 7 May 2017 / Accepted: 11 May 2017 / Published: 15 May 2017
Cited by 2 | PDF Full-text (887 KB) | HTML Full-text | XML Full-text
Abstract
The tuff, a part of coal-bearing strata, in the Zhongliangshan coal mine, Chongqing, southwestern China, hosts a rare metal deposit enriched in rare earth elements (REE), Ga and Nb. However, the extraction techniques directly related to the recovery of rare metals in coal-bearing
[...] Read more.
The tuff, a part of coal-bearing strata, in the Zhongliangshan coal mine, Chongqing, southwestern China, hosts a rare metal deposit enriched in rare earth elements (REE), Ga and Nb. However, the extraction techniques directly related to the recovery of rare metals in coal-bearing strata have been little-studied in the literature. The purpose of this paper is to investigate the extractability of REE, Ga and Nb in the tuff in the Zhongliangshan mine using the alkaline sintering-water immersion-acid leaching (ASWIAL) method. The results show that ASWIAL can separate and extract REE, Ga and Nb effectively under the optimized conditions of calcining at 860 °C for 0.5 h with a sample to sintering agent ratio of 1:1.5, immersing at 90 °C for 2 h with 150 mL hot water dosage, and leaching using 4 mol/L HCl at 40 °C for 2 h with a liquid-solid ratio of 20:1 (mL:g). The final leaching efficiencies of REE and Ga are up to 85.81% and 93.37%, respectively, whereas the leaching efficiency of Nb is less than 1%, suggesting the high concentration of Nb in the leaching residue, which needs further extraction. Full article
Figures

Figure 1

Open AccessArticle Microstructure and Properties of the Interface Area in the Laser Cladded Ni Based Coatings on the 1Cr10Mo1NiWVNbN Steel
Metals 2017, 7(5), 175; doi:10.3390/met7050175
Received: 21 January 2017 / Revised: 14 April 2017 / Accepted: 10 May 2017 / Published: 15 May 2017
Cited by 1 | PDF Full-text (3640 KB) | HTML Full-text | XML Full-text
Abstract
The Ni-based coatings were deposited on the 1Cr10Mo1NiWVNbN steel by using laser cladding process. The microstructure and properties of the coatings interface area were investigated by OM (Optical Microscopy), SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction) microhardness test and EDS (Energy Spectrum Analysis)
[...] Read more.
The Ni-based coatings were deposited on the 1Cr10Mo1NiWVNbN steel by using laser cladding process. The microstructure and properties of the coatings interface area were investigated by OM (Optical Microscopy), SEM (Scanning Electron Microscope), XRD (X-Ray Diffraction) microhardness test and EDS (Energy Spectrum Analysis) analysis. The results show that the bonding condition of the coatings interface is different in the monolayer and the trilayer. The monolayer coatings have a small dilution area. The dilution rate in a coating layer increases by layers. The scale of ferrite (α) phase increases with the layer increases. The surface cladding quality of a monolayer is better than that of the trilayer coatings. The width of the interface increases with the increase of the layer. The width of the interface region in the trilayer coatings increases significantly. The microhardness of the interface zone is much higher than that in the coatings zone and the substrate zone. The microhardness of trilayer coatings is higher than that of the monolayer. Full article
Figures

Figure 1

Open AccessArticle Transparent Conducting Film Fabricated by Metal Mesh Method with Ag and Cu@Ag Mixture Nanoparticle Pastes
Metals 2017, 7(5), 176; doi:10.3390/met7050176
Received: 7 March 2017 / Revised: 18 April 2017 / Accepted: 11 May 2017 / Published: 16 May 2017
Cited by 1 | PDF Full-text (2858 KB) | HTML Full-text | XML Full-text
Abstract
Transparent conducting electrode film is highly desirable for application in touch screen panels (TSPs), flexible and wearable displays, sensors, and actuators. A sputtered film of indium tin oxide (ITO) shows high transmittance (90%) at low sheet resistance (50 Ω/cm2). However, ITO
[...] Read more.
Transparent conducting electrode film is highly desirable for application in touch screen panels (TSPs), flexible and wearable displays, sensors, and actuators. A sputtered film of indium tin oxide (ITO) shows high transmittance (90%) at low sheet resistance (50 Ω/cm2). However, ITO films lack mechanical flexibility, especially under bending stress, and have limitation in application to large-area TSPs (over 15 inches) due to the trade-off in high transmittance and low sheet resistance properties. One promising solution is to use metal mesh-type transparent conducting film, especially for touch panel application. In this work, we investigated such inter-related issues as UV imprinting process to make a trench layer pattern, the synthesis of core-shell-type Ag and Cu@Ag composite nanoparticles and their paste formulation, the filling of Ag and Cu@Ag mixture nanoparticle paste to the trench layer, and touch panel fabrication processes. Full article
(This article belongs to the Special Issue Metal Matrix Composites)
Figures

Open AccessArticle Mechanical Behavior and Sliding Wear Studies on Iron Aluminide Coatings Reinforced with Titanium Carbide
Metals 2017, 7(5), 177; doi:10.3390/met7050177
Received: 11 April 2017 / Revised: 5 May 2017 / Accepted: 8 May 2017 / Published: 16 May 2017
PDF Full-text (10181 KB) | HTML Full-text | XML Full-text
Abstract
Wear-resistant iron aluminide-based composites were coated on steel substrates with the High-Velocity Oxy-Fuel (HVOF) technique using ball milled Fe3Al and TiC powders as feedstock. The phase composition, microstructure, microhardness, elastic modulus and dry sliding wear performance of unreinforced Fe3Al
[...] Read more.
Wear-resistant iron aluminide-based composites were coated on steel substrates with the High-Velocity Oxy-Fuel (HVOF) technique using ball milled Fe3Al and TiC powders as feedstock. The phase composition, microstructure, microhardness, elastic modulus and dry sliding wear performance of unreinforced Fe3Al and Fe3Al–TiC composite coatings (reinforced with 30 and 50 vol. % TiC particles) were evaluated in order to reveal the relationship between the mechanical and tribological behaviors. Compared to the unreinforced coatings, the composite coating with 30 vol. % TiC particles exhibited much greater hardness and higher elastic modulus. The increase of the elastic modulus of the composite coatings did not result in deterioration of sliding wear behavior. The addition of 50 vol. % TiC resulted in a further increase in hardness, however, both composite coatings showed the same elastic modulus. The fractured cross sectional surface of the unreinforced coating showed a weakly bonded microstructure promoting delamination in wear tests, whereas the composite fractured surface showed strong mechanical bonding between the matrix and carbide particles, leading to better cohesion. The Fe3Al–TiC coatings showed almost three orders of magnitude higher wear resistance under the dry sliding wear test compared to the unreinforced coatings. Full article
Figures

Figure 1

Open AccessArticle Flat-Top Cylinder Indenter Examination of Duplex Stainless Steel 2205 after Different Heat Treatments
Metals 2017, 7(5), 178; doi:10.3390/met7050178
Received: 5 April 2017 / Revised: 10 May 2017 / Accepted: 12 May 2017 / Published: 17 May 2017
PDF Full-text (7529 KB) | HTML Full-text | XML Full-text
Abstract
The duplex stainless steel 2205 was heat treated at 750 °C, 850 °C, and 900 °C for increasing durations of up to 10 h. The samples were investigated through light microscopy (LM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to characterize the
[...] Read more.
The duplex stainless steel 2205 was heat treated at 750 °C, 850 °C, and 900 °C for increasing durations of up to 10 h. The samples were investigated through light microscopy (LM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to characterize the volume fraction and morphology of the precipitated secondary phases. The samples were then tested via flat-top cylinder indenter for mechanical characterization (FIMEC) testing to determine the yield stresses that were found to be significantly affected by the different heat treatments. The yield stress evolution with heat treatments resulted in being correlated to both the relative volumes of the secondary phases and the morphology of the σ phase. The FIMEC test proved to be capable of detecting the effects of small amounts of secondary phases on yield stress in DSS 2205 and seems to be a promising technique for industrial applications. Full article
Figures

Figure 1

Open AccessArticle Effect of Deep Cryogenic Treatment on the Microstructure and the Corrosion Resistance of AZ61 Magnesium Alloy Welded Joint
Metals 2017, 7(5), 179; doi:10.3390/met7050179
Received: 28 March 2017 / Revised: 30 April 2017 / Accepted: 12 May 2017 / Published: 17 May 2017
PDF Full-text (12340 KB) | HTML Full-text | XML Full-text
Abstract
The effect of deep cryogenic treatment on the microstructure and corrosion resistance of an AZ61 magnesium alloy metal inert-gas (MIG) welded joint was investigated. The welded joints were deep-cryogenically treated using different parameters, and were analyzed by metallographic observations, X-ray diffraction, microhardness, and
[...] Read more.
The effect of deep cryogenic treatment on the microstructure and corrosion resistance of an AZ61 magnesium alloy metal inert-gas (MIG) welded joint was investigated. The welded joints were deep-cryogenically treated using different parameters, and were analyzed by metallographic observations, X-ray diffraction, microhardness, and NaCl immersion test. The results show that the treatment changes the microstructure of the entire joint by causing grain refinement and increase in the β-phase. The crystal structure, chemical composition, and electrode potentials are different for the α and the β-phases. Therefore, any change in content, status, and distribution of the β phase has important implications on the corrosion resistance of the samples. With an increase in the holding time, the microhardness value of the whole joint increases, and the difference between the three regions of the joint decreases. The results of the NaCl immersion test show that there is an improvement in the corrosion resistance of the treated joints. Compared with the untreated samples, the corrosion potential of the samples treated by deep cryogenic treatment for 4 h at −180 °C is about 0.017 V higher, and the corrosion current density decreased by one order of magnitude (from about 2.769 × 10−5 A·cm−2 to 1.578 × l0−6 A·cm−2). Full article
Figures

Figure 1

Open AccessArticle A Phase Field Model for Rate-Dependent Ductile Fracture
Metals 2017, 7(5), 180; doi:10.3390/met7050180
Received: 17 April 2017 / Revised: 29 April 2017 / Accepted: 5 May 2017 / Published: 17 May 2017
Cited by 1 | PDF Full-text (4600 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a phase field viscoplastic model is proposed to model the influence of the loading rate on the ductile fracture, as one of the main causes of metallic alloys’ failure. To this aim, the effects of the phase field are incorporated
[...] Read more.
In this study, a phase field viscoplastic model is proposed to model the influence of the loading rate on the ductile fracture, as one of the main causes of metallic alloys’ failure. To this aim, the effects of the phase field are incorporated in the Peric’s viscoplastic model; the model can efficiently be converted to a standard rate-independent model. The novel aspects of this work include: Describing a coupling between rate-dependent plasticity and phase field formulation by defining an energy function that contains the energy dissipation caused by plastic deformation as well as the fracture process and elastic energy. In addition, the equations required to develop the numerical solution are presented. The governing equations are determined by a minimization principle that results in balance laws for the coupled displacement-phase field problem. Furthermore, an implicit integration algorithm for a viscoplasticity model coupled with a phase field is presented for a three-dimensional stress state. The proposed algorithm can be utilized for different constitutive models of rate-dependent and rate-independent plasticity models coupled with fracture by changing the definition of the plastic multiplier. In addition, to control the influence of the plastic deformation and its work on the crack propagation, a threshold variable is defined in the model. Finally, using the proposed model, the influence of the loading rate on the responses of the different specimens in one-dimensional and multi-dimensional cases is investigated and the accuracy of the results was verified by comparing them with existing experimental and numerical results. The obtained result proves that the model can simulate the impact of the loading rate on the material response, and the gradual change of the fracture phase from ductile to brittle, caused by increasing the loading rate. Full article
(This article belongs to the Special Issue Microstructure based Modeling of Metallic Materials)
Figures

Figure 1

Open AccessArticle Effect of Calcium Oxide on the Crushing Strength, Reduction, and Smelting Performance of High-Chromium Vanadium–Titanium Magnetite Pellets
Metals 2017, 7(5), 181; doi:10.3390/met7050181
Received: 18 March 2017 / Revised: 16 May 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
PDF Full-text (5886 KB) | HTML Full-text | XML Full-text
Abstract
The effect of calcium oxide on the crushing strength, reduction, and smelting performance of high-chromium vanadium–titanium magnetite pellets (HCVTMP) was studied in this work. The main characterization methods of an electronic universal testing machine (EUTM), X-ray fluorescent (XRF), inductively-coupled plasma-atomic emission spectroscopy (ICP-AES),
[...] Read more.
The effect of calcium oxide on the crushing strength, reduction, and smelting performance of high-chromium vanadium–titanium magnetite pellets (HCVTMP) was studied in this work. The main characterization methods of an electronic universal testing machine (EUTM), X-ray fluorescent (XRF), inductively-coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), and scanning electron microscope-energy disperse spectroscopy (SEM-EDS) were employed. The crushing strength was affected by the mineral phases generated during oxidative baking and the subsequently-formed pellet microstructures owing to CaO addition. The reduction and smelting properties of HCVTMP with different CaO additives were measured and characterized with different softening-melting-dripping indices. Although HCVTMP showed the highest crushing strength with CaO addition of ca. 2 wt %, more CaO addition may be needed to achieve high permeability of the furnace burdens and a good separation condition of the slag and melted iron. In the formation process of the slag and melted iron, it can be determined that CaO could have a relationship with the transformation behavior of Cr, V, and Ti to some extent, with respect to the predominant chemical composition analysis of ICP-AES and XRF. With the microscopic examination, the restraining formation of Ti(C,N) and the promoting formation of CaTiO3 are in accordance with the improved melting-dripping indices, including the decrease of the maximum external static load and gas permeability, and the increase of the melting-dripping zone and dripping difficulty. Full article
Figures

Figure 1

Open AccessArticle Corrosion Behavior of Pipeline Carbon Steel under Different Iron Oxide Deposits in the District Heating System
Metals 2017, 7(5), 182; doi:10.3390/met7050182
Received: 21 April 2017 / Revised: 11 May 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
PDF Full-text (4229 KB) | HTML Full-text | XML Full-text
Abstract
The corrosion behavior of pipeline steel covered by iron oxides (α-FeOOH; Fe3O4 and Fe2O3) was investigated in simulated district heating water. In potentiodynamic polarization tests; the corrosion rate of pipeline steel is increased under the iron
[...] Read more.
The corrosion behavior of pipeline steel covered by iron oxides (α-FeOOH; Fe3O4 and Fe2O3) was investigated in simulated district heating water. In potentiodynamic polarization tests; the corrosion rate of pipeline steel is increased under the iron oxide but the increaseing rate is different due to the differnet chemical reactions of the covered iron oxides. Pitting corrosion was only observed on the α-FeOOH-covered specimen; which is caused by the crevice corrosion under the α-FeOOH. From Mott-Schottky and X-ray diffraction results; the surface reaction and oxide layer were dependent on the kind of iron oxides. The iron oxides deposit increases the failure risk of the pipeline and localized corrosion can be occurred under the α-FeOOH-covered region of the pipeline. Thus, prevention methods for the iron oxide deposit in the district pipeline system such as filtering or periodic chemical cleaning are needed. Full article
Figures

Open AccessArticle Laser Beam Welding of a Ti–6Al–4V Support Flange for Buy-to-Fly Reduction
Metals 2017, 7(5), 183; doi:10.3390/met7050183
Received: 12 April 2017 / Revised: 5 May 2017 / Accepted: 16 May 2017 / Published: 20 May 2017
Cited by 2 | PDF Full-text (7366 KB) | HTML Full-text | XML Full-text
Abstract
Titanium and its alloys are increasingly being used in aerospace, although a number of issues must be addressed. Namely, in the framework of welding to produce complex parts, the same mechanical strength and a reduced buy-to-fly ratio are desired in comparison with the
[...] Read more.
Titanium and its alloys are increasingly being used in aerospace, although a number of issues must be addressed. Namely, in the framework of welding to produce complex parts, the same mechanical strength and a reduced buy-to-fly ratio are desired in comparison with the same components resulting from machining. To give grounds to actual application of autogenous laser beam welding, Ti–6Al–4V L- and T-joints have been investigated in this paper, as they are a common occurrence in general complex components. Discussions in terms of possible imperfections, microstructure, and microhardness have been conducted. Then, a real part consisting of a support flange for aerospace application has been chosen as a valuable test-article to be compared with its machined counterpart both in terms of strength and buy-to-fly. The feasibility and the effectiveness of the process are shown. Full article
(This article belongs to the Special Issue Laser Welding)
Figures

Review

Jump to: Research

Open AccessReview Transferring Nanoscale Bainite Concept to Lower C Contents: A Perspective
Metals 2017, 7(5), 159; doi:10.3390/met7050159
Received: 27 March 2017 / Revised: 16 April 2017 / Accepted: 28 April 2017 / Published: 4 May 2017
PDF Full-text (3453 KB) | HTML Full-text | XML Full-text
Abstract
The major strengthening mechanisms in bainitic steels arise from the bainitic ferrite plate thickness rather than the length, which primarily determines the mean free slip distance. Both the strength of the austenite from where the bainite grows and the driving force of the
[...] Read more.
The major strengthening mechanisms in bainitic steels arise from the bainitic ferrite plate thickness rather than the length, which primarily determines the mean free slip distance. Both the strength of the austenite from where the bainite grows and the driving force of the transformation, are the two factors controlling the final scale of the bainitic microstructure. Usually, those two parameters can be tailored by means of selection of chemical composition and transformation temperature. However, there is also the possibility of introducing plastic deformation on austenite and prior to the bainitic transformation as a way to enhance both the austenite strength and the driving force for the transformation; the latter by introducing a mechanical component to the free energy change. This process, known as ausforming, has awoken a great deal of interest and it is the object of ongoing research with two clear aims. First, an acceleration of the sluggish bainitic transformation observed typically in high C steels (0.7–1 wt. %) transformed at relatively low temperatures. Second, to extend the concept of nanostructured bainite from those of high C steels to much lower C contents, 0.4–0.5 wt. %, keeping a wider range of applications in view. Full article
(This article belongs to the Special Issue Bainite and Martensite: Developments and Challenges)
Figures

Figure 1

Open AccessReview A Broad Literature Review of Density Measurements of Liquid Cast Iron
Metals 2017, 7(5), 165; doi:10.3390/met7050165
Received: 13 April 2017 / Revised: 13 April 2017 / Accepted: 27 April 2017 / Published: 10 May 2017
PDF Full-text (1374 KB) | HTML Full-text | XML Full-text
Abstract
The literature on density measurements, with a particular interest in methods suitable for liquid cast iron, is reviewed. Different measurement methods based on a number of physical properties are highlighted and compared. Methods for the calculation of density are also reviewed, and the
[...] Read more.
The literature on density measurements, with a particular interest in methods suitable for liquid cast iron, is reviewed. Different measurement methods based on a number of physical properties are highlighted and compared. Methods for the calculation of density are also reviewed, and the influence of alloying elements on density is, to some extent, discussed. The topic is of essence for the understanding of the material behaviour at solidification, which is pivotal in software applications for casting simulation. Since a deeper understanding of the relationship between the density of liquid cast iron and volume expansion is necessary, the conclusion that further research within the field is needed lies close at hand. Full article
Figures

Figure 1

Back to Top