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 Subjects -> MATHEMATICS (Total: 1040 journals)     - APPLIED MATHEMATICS (83 journals)    - GEOMETRY AND TOPOLOGY (23 journals)    - MATHEMATICS (770 journals)    - MATHEMATICS (GENERAL) (43 journals)    - NUMERICAL ANALYSIS (23 journals)    - PROBABILITIES AND MATH STATISTICS (98 journals) MATHEMATICS (770 journals)            First | 1 2 3 4
 Showing 401 - 538 of 538 Journals sorted alphabetically Journal of Humanistic Mathematics       (Followers: 1) Journal of Hyperbolic Differential Equations Journal of Indian Council of Philosophical Research Journal of Industrial Mathematics       (Followers: 2) Journal of Inequalities and Applications Journal of Infrared, Millimeter and Terahertz Waves       (Followers: 2) Journal of Integrable Systems       (Followers: 1) Journal of K-Theory Journal of Knot Theory and Its Ramifications       (Followers: 1) Journal of Kufa for Mathematics and Computer       (Followers: 1) Journal of Liquid Chromatography & Related Technologies       (Followers: 7) Journal of Logical and Algebraic Methods in Programming Journal of Manufacturing Systems       (Followers: 4) Journal of Mathematical Analysis and Applications       (Followers: 4) Journal of mathematical and computational science       (Followers: 7) Journal of Mathematical and Fundamental Sciences Journal of Mathematical Behavior       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108) Order ORiON P-Adic Numbers, Ultrametric Analysis, and Applications PAMM : Proceedings in Applied Mathematics and Mechanics       (Followers: 1) Parallel Processing Letters       (Followers: 3) Peking Mathematical Journal Periodica Mathematica Hungarica       (Followers: 1) Perspectivas da Educação Matemática Petroleum Science       (Followers: 1) Philosophia Mathematica       (Followers: 1) Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences       (Followers: 6) PNA. 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Similar Journals
 Metals and Materials InternationalJournal Prestige (SJR): 0.724 Citation Impact (citeScore): 2Number of Followers: 0      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1598-9623 - ISSN (Online) 2005-4149 Published by Springer-Verlag  [2574 journals]
• Effects of Ni and Cr on Cryogenic Impact Toughness of Bainite/Martensite
Multiphase Steels
• Abstract: In the present research, the effects of Nickel (Ni) and Chromium (Cr) on cryogenic impact toughness (CIT) of low-carbon bainite/martensite multiphase steels [processed by two different cooling processes: isothermal transformation process (ITP) and continuous cooling process (CCP)] were investigated. It was found that due to the formation of carbides during isothermal treatment, the addition of Ni and Cr yielded no significant improvements in CIT. However, during CCP treatment, the addition of Ni manifested a considerable enhancement in CIT, whereas the addition of both Ni and Cr caused a decrease in CIT. Further, after ITP treatment, the microstructure of all steels consisted of bainite and martenite, while Ni + Cr steel contained the largest amount of bainite. The microstructures of the CCP-treated steels mainly also consisted of bainite and martensite, but no retained austenite and carbides were observed, thus resulting in a superior CIT.
PubDate: 2019-03-22

• A Kinetics of Hydrogen Reduction of Nickel Oxide at Moderate Temperature
• Abstract: Nano-metallic nickel powders are highly-valued materials applied in energy, electronic devices and aerospace, which is known to be produced by the gaseous phase reduction method of NiCl2. In the case of a gaseous reduction method, size control is difficult due to the agglomeration of nickel powders. Therefore, a method of producing highly-valued nickel nano-powders from Ni(OH)2 has been proposed. Considering the reduction behavior of bulk nickel oxide has been reported to follow the topo-chemical model. However, reduction behavior of nano-particle is expected to be unknown state. It is necessary to clarify the mechanism of nickel oxide nano-particle reduction. Therefore, in this study, the temperature dependence and particle size dependence on the reduction behavior of from micro scale to nano scale particle was confirmed through TGA experiment. Also, the reduction mechanism of nickel oxide powder was also investigated based on kinetic considerations using the grain topo-chemical model. It was confirmed that the reduction reaction of nickel oxide powder undergoes through the 2nd Avrami model and reduction rate can be expressed by function of temperature and particle size of the powder. Due to the part of the diffusion, the particle size of the powder also affects the rate constant of the reduction reaction. $${\text{g}}_{{({\text{x}})}} = {\text{k}} \cdot {\text{f}}({\text{d}}) \cdot {\text{t}}$$
PubDate: 2019-03-19

• Correction to: Study on Aging Effect of Adhesion Strength Between
Polyimide Film and Copper Layer
• Abstract: Unfortunately, the acknowledgements were missing in the original version of this article. The information is given below:
PubDate: 2019-03-14

• Investigation of Weld Corrosion Effects on the Stress Behavior of a Welded
Joint Pipe Using Numerical Simulations
• Abstract: In this paper, the influence of weld corrosion on the mechanical behavior of a welded joint pipeline was investigated using corrosion and mechanical simulations simultaneously. In the corrosion simulation, the modeling results (i.e., the corrosion potential and current density) revealed that the welded joint is preferentially corroded and the corrosion rate is higher in the outside environment due to the severe corrosion factors. The increase in corrosion degradation according to the operation time increases the stress concentration on the welded joint, indicating that the failure risk of the welded joint is increased with increasing corrosion degradation. These results can be used to evaluate the lifetime of welded joints exposed to corrosion and suggest guidelines for the maintenance of structures.
PubDate: 2019-03-13

• Role of Austenitization Temperature on Structure Homogeneity and
Transformation Kinetics in Austempered Ductile Iron
• Abstract: This paper considers the important factors of the production of high-strength ADI (Austempered Ductile Iron); namely, the austenitization stage during heat treatment. The two series of ADI with different initial microstructures were taken into consideration in this work. Experiments were carried out for castings with a 25-mm-walled thickness. Variable techniques (OM, SEM, dilatometry, DSC, Variable Magnetic Field, hardness, and impact strength measurements) were used for investigations of the influence of austenitization time on austempering transformation kinetics and structure in austempered ductile iron. The outcome of this work indicates that the austenitizing temperature has a very significant impact on structure homogeneity and the resultant mechanical properties. It has been shown that the homogeneity of the metallic matrix of the ADI microstructure strongly depends on the austenitizing temperature and the initial microstructure of the spheroidal cast irons (mainly through the number of graphite nodules). In addition, this work shows the role of the austenitization temperature on the formation of Mg–Cu precipitations in ADI.
PubDate: 2019-03-08

• Morphology of Iron and Agglomeration Behaviour During Reduction of Iron
Oxide Fines
• Abstract: The morphology of iron and agglomeration behaviour in the reduction progress of iron oxide fines were investigated in terms of isothermal reduction at 800 °C in an atmosphere of CO and H2. Agglomeration index was employed to evaluate the agglomeration behaviour during reduction. Sticking and agglomeration occurred regardless of the iron oxides and reducing atmosphere. Reduction by CO showed a higher tendency for sticking due to the formation of iron whiskers. The addition of CaO and MgO to Fe2O3 in sintering process could improve the reduction, and also decrease the sticking by forming calcio/magnesio-wustite on the surface. Iron whiskers were still formed with the addition of CaO and MgO, and the shape of whiskers were different from that of pure Fe2O3. Uniform coating layer on the surface of particles might be one of the important factors affecting the decrease in sticking between particles.
PubDate: 2019-03-06

• Correction to: Effects of V or Cu Addition on High-Temperature Tensile
Properties of High-Ni-Containing Austenitic Cast Steels Used for
High-Performance Turbo-Charger Housings
• Abstract: The original version of this article unfortunately contained a mistake. The acknowledgements section was incomplete. The correct information is given.
PubDate: 2019-03-01

• Effect of TiAl 3 Coating Thickness and Morphology, Formed Using the
Immersion of Titanium Sheets in Molten Aluminum, on Titanium Oxidation
Behavior
• Abstract: In this research, TiAl3 layers with different thicknesses were deposited on a titanium sheet by immersion of titanium in molten aluminum for different times. The oxidation behavior of the coated titanium at 850 °C was investigated and the comparison of the results was made with the oxidation behavior of the uncoated titanium sheet. The results showed that the produced TiAl3 layer could protect the titanium substrate against the oxidation if it contains an appropriate quality and morphology, otherwise not only it cannot withstand the oxidation, but also it accelerates the oxidation process of the titanium substrate. The protection mechanisms of the layers were probed into, performing the XRD analysis. It was found that the TiAl3 layer morphology affects oxidation mechanism and oxidation products.
PubDate: 2019-03-01

• High-Speed Synthesis of Rice-Ear-Shaped Cu Dendritic Particles at Room
Temperature via Galvanic Displacement Using Zn Particles
• Abstract: Rice-ear-shaped Cu dendritic particles were fabricated via fast galvanic displacement reactions for 3–5 min under ambient conditions by adding Zn particles into an aqueous electrolyte without chloride ions. The obtained Cu dendritic particles have a small average size (4.44 μm) and short, multiple branches that seemed to be aggregates of nanoparticles formed on stem-like backbones, and their surface area is large. The prepared Cu dendrites could be protected against oxidation during drying via post-treatment with chelating or complexing agents. While the dendrite stem is found to be a Cu polycrystal grown only on the (111) plane, the branches consist of three planes of Cu, viz., (111), (200), and (220), indicating that they were formed by random attachment of nanoparticles and aggregates. A possible low-temperature and high-speed synthesis mechanism is proposed based on the results of time-dependent SEM investigations as well as the crystal structure of the dendrites. This novel technique to synthesize modified dendrites is extremely simple and suitable for mass production.
PubDate: 2019-03-01

• Effects of Addition of Si and Sb on the Microstructure and Thermoelectric
Properties of GeTe
• Abstract: The effects of the addition of Si and Sb on the microstructure and thermoelectric properties of GeTe were investigated in this study. Pure GeTe showed a typical herringbone structure that consisted of regularly aligned domains with alternating bright and dark contrast areas. When Sb atoms were added to the GeTe, a clean herringbone structure was not formed. Instead, many sharp lines that are likely narrow domains were observed, and their formation can be ascribed to the cubic stabilizing nature of Sb in GeTe. The co-addition of Si and Sb to GeTe resulted in a breakdown of the herringbone structure and formation of SiGe and Si precipitates. Even though Si and Ge can form a complete solid solution, the solubility of Si in GeTe remained low. The addition of Sb to GeTe significantly reduced the electrical conductivity due to the aliovalent donor nature of Sb. Its thermal conductivity was also very low due to the mass fluctuation in the solid solution and narrow domain structure. Therefore, the best figure-of-merit (ZT) of 0.67 at 570 K was obtained. However, Ge1−x−ySbxSiyTe compounds with both Si and Sb addition showed a relatively low ZT value.
PubDate: 2019-03-01

• Corrosion and Wear Characteristics of Electroless Ni–P, Ni–P–W and
Composite Ni–P–W/Al 2 O 3 Coatings on AZ91 Sheet
• Abstract: Electroless Ni–P–W was coated on AZ91 sheets with various W contents and both the corrosion and wear resistance characteristics of these coatings were observed. The increase in W content resulted in a decrease in P content and an increase in the crystallinity of the electroless coatings. The corrosion resistance of the electroless coatings increased upon increase in W content of the electroless coatings up to approximately 5%. Above this content, however, the corrosion resistance tended to decrease due to the disturbed grain structure of the electroless coating. But both the surface hardness and wear resistance increased concurrently due to the positive contribution of W solid solution hardening. The applied heat treatment resulted in a decrease in the corrosion resistance due to the disappearance of the amorphous structure and increase in both the surface hardness and wear resistance due to the precipitation hardening. Al2O3 dispersion was better with the nonionic surfactant, as compared to the anionic and cationic surfactants. Composite coating reduced the corrosion resistance and increased the wear resistance of the electroless Ni–P–W coatings. The applied heat treatment was observed to have positive contribution to Ni–P–W coatings in getting the optimum corrosion and wear resistance combination.
PubDate: 2019-03-01

• Prediction of Grain Structure of Thin Bronze Slab Produced by Horizontal
Continuous Casting
• Abstract: The grain structure of a thin bronze slab produced by horizontal continuous casting was investigated using heat-transfer calculation and cellular automaton (CA). The composition of the bronze was Cu–22wt%Sn, which has been widely used in Korean history. The solid form of Cu–22wt%Sn was assumed as a single phase for simplicity. To simulate the macrostructure of the alloy, the heat transfer in the horizontal continuous casting was calculated as a steady-state one-dimensional lumped system. The CA was used for simulating the grain structure. Since the temperature profile was in the steady state, the cell information was shifted along the casting direction at a rate of one cell per time step during the simulation. The grains were nucleated at the slab surface and grown as columnar grains. The effects of the process parameters, such as initial melt temperature and casting speed, on the grain structure of the slab were investigated. It was found that the casting speed is a critical factor determining the angle between the columnar grains and the casting direction.
PubDate: 2019-03-01

• Porous Titanium Scaffolds with Aligned Lamellar Pore Channels by
Directional Freeze-Casting from Aqueous TiH 2 Slurries
• Abstract: Porous titanium scaffolds with aligned lamellar pore channels and smooth inner walls were fabricated by directional freeze casting using aqueous TiH2 slurries. The formation of dendrites was inhibited by increasing the TiH2 content in slurry. The pore structures and compression strengths of porous titanium scaffolds that were made with different solid contents were characterized. The formation mechanism of aligned lamellar pore channels and the reason for the improvement of compression strength were analyzed. With increasing TiH2 content in slurry, the open porosity reduced from 38.57 to 29.03% while lamellar spacing decreased. Young’s modulus was decreased with the increasing open porosity. Directional lamellar pore channels were obtained by controlling the TiH2 content in slurry, which can reduce the number of branches and prevent stress concentrations during compression. Also, the porous titanium scaffolds prepared by this process had a good biocompatibility with osteoblasts.
PubDate: 2019-03-01

• Wear Resistant Duplex Stainless Steels Produced by Spray Forming
• Abstract: In this work, boron-modified duplex stainless steels were prepared by spray forming using design guidelines provided by thermodynamic calculations. Firstly, an investigation of stable phases and phase formation sequence in duplex steels containing high levels of boron was conducted. The calculation indicated that there was an eutectic point at around 1 wt% boron with different primary phase formations upon equilibrium solidification. For hypoeutectic compositions, the primary phase was δ-Ferrite, whereas for hypereutectic a metallic boride (M2B) should form. Additionally, eutectic reactions for both compositions should lead to the formation of borides M2B and M3B2. Secondly, spray forming experiments were conducted based on the thermodynamic calculations. Sample preparation was carried out using a conventional superduplex steel (2507) as starting material. Two different compositions were selected: one hypoeutectic (0.8 wt% B) and one hypereutectic (2.5 wt% B). The microstructural investigation revealed the formation of different types of borides embedded in an austenitic-ferritic matrix. Finally, the wear resistance was evaluated with the dry sand/rubber wheel test and a significant improvement was observed for boron-containing steels in comparison with the same steel without boron. This improvement was attributed to the presence of fine and well-distributed boride particles that protected the austenitic-ferritic matrix from material removal.
PubDate: 2019-03-01

• Subgrain Effect on Grain Scale Plasticity of NiTi Shape Memory Alloy Under
Canning Compression: A Crystal Plasticity Finite Element Analysis
• Abstract: The subgrain effect of NiTi shape memory alloy during canning compression at 400 °C is investigated through electron back-scattered diffraction (EBSD) experiment, transmission electron microscope (TEM) experiment and crystal plasticity finite element (CPFE) simulation in explicit consideration of subgrain within each grain. Experimental investigations based on TEM and EBSD measurements confirm that the formation of subgrain actually results from the dislocation motion during canning compression. Numerical simulations based on the constructed polycrystalline models with various subgrains are used to investigate the subgrain effect during canning compression from a different point of view. In terms of texture evolution, subgrain effect does not change the tendency of texture evolution, but it contributes to the dispersed distribution with respect to the deformed grain/subgrain orientations. As for accumulative shear strain, subgrain effect contributes to sustaining larger plastic strain inside each grain, and it also results in the strain concentration near grain boundaries. With respect to von Mises stress, the subgrain effect facilitates the ease of stress concentration near grain boundaries and it contributes to possessing a homogeneous stress distribution within the inner part of each grain.
PubDate: 2019-03-01

• Microstructure and Mechanical Features of Electron Beam Welded Dissimilar
Titanium Alloys: Ti–10V–2Fe–3Al and Ti–6Al–4V
• Abstract: We studied the relationship between phase transformation and mechanical property of electron beam welded dissimilar titanium (Ti) alloy between Ti–10V–2Fe–3Al (Ti1023) and Ti–6Al–4V (Ti64). A new chemical composition in the fusion zone generated a moderately high beta (β) phase stability which made the precipitation of acicular alpha double-prime martensite, resulting in enhanced hardness. Fracture took place during tensile test in the heat affected zone (HAZ) of Ti1023 because secondary alpha (αs) phase transformed into β during welding, resulting in a loss of strength during welding. Post weld heat treatment (PWHT) successfully regained αs and improved the mechanical properties in Ti1023 HAZ, resulting in preventing failure at Ti1023 HAZ but occurring at Ti64 base during tensile test. A development of tri-modal structure, consisting of a globular and lamellar structure of primary alpha and fine αs precipitation, in both Ti64 base and Ti64 HAZ occurred after PWHT. The tensile property was improved after PWHT showing tensile strength with 1065 MPa and 9% elongation.
PubDate: 2019-03-01

• Phase Stability Diagrams of Ti–M–O–C (M = Zr, Hf, Nb, and Ta)
Systems at 1800 K
• Abstract: Phase stability diagrams of Ti–M–O–C (M = Zr, Hf, Nb, and Ta) systems at 1800 K were constructed as a function of the carbon activity, oxygen partial pressure, and solution formation characteristics, in order to determine the optimum conditions for the formation of (Ti0.75M0.25)C via carbothermal reduction of oxide mixtures. The tendency to form (Ti0.75M0.25)C was predicted on the basis of the standard Gibbs free energies of formation $$(\Delta {\text{G}}_{f}^{^\circ } )$$ of (Ti0.75M0.25)C solid-solution carbides, calculated by first-principles simulations. It was concluded that at 1800 K, the (Ti0.75Nb0.25)C and (Ti0.75Ta0.25)C phases are more stable than the TiC–NbC and TiC–TaC mixtures, whereas the (Ti0.75Zr0.25)C and (Ti0.75Hf0.25)C phases are less stable than the corresponding TiC–ZrC and TiC–HfC mixtures. The phase stability diagrams of the Ti–M–O–C systems were then drawn using the calculated $$\Delta {\text{G}}_{f}^{^\circ }$$ values and used to predict the tendencies to form solid-solution phases. The validity of the theoretical predictions was then verified using experimental results.
PubDate: 2019-03-01

• Microstructural Degradation and Creep Fracture Behavior of Conventionally
and Thermomechanically Treated 9% Chromium Heat Resistant Steel
• Abstract: The microstructural degradation and the creep fracture behavior of conventionally and thermomechanically treated Grade 91 steel were investigated after performing small punch creep tests. A remarkable reduction in creep ductility was observed for the samples thermomechanically treated in comparison to those conventionally treated under the tested conditions of load (200 N) and temperature (700 °C). A change in the fracture mechanism from a ductile transgranular fracture to a brittle intergranular fracture was observed when changing from the conventionally treated to the thermomechanically treated processing condition, leading to this drop in creep ductility. The change in the fracture mechanism was associated to the localized concentration of creep deformation, close to coarse M23C6 carbides, at the vicinity of prior austenite grain boundaries (PAGB) in the thermomechanically treated samples. The preferential recovery experienced at the vicinity of PAGB produced the loss of the lath structure and the coarsening of the M23C6 precipitates. The electron microscopy images provided suggest that the creep cavities nucleate in these weak recovered areas, associated to the presence of coarse M23C6. After the coalescence of the cavities the propagation of the cracks was facilitated by the large prior austenite grain size produced during the austenitization which favors the propagation of the cracks along grain boundaries triggering the intergranular brittle fracture. This fracture mechanism limits the potential use of the proposed thermomechanical processing routes.
PubDate: 2019-03-01

• Increase in the Dehydrogenation Rate of Mg–CMC (Carboxymethylcellulose,
Sodium Salt) by Adding Ni via Hydride-Forming Milling
• Abstract: In our previous work, samples with a composition of 95 wt% Mg + 5 wt% CMC (Carboxymethylcellulose, Sodium Salt, [C6H7O2(OH)x(C2H2O3Na)y]n) (named Mg–5 wt% CMC) were prepared through hydride-forming milling. Mg–5 wt% CMC had a very high hydrogenation rate but a low dehydrogenation rate. Addition of Ni to Mg is known to increase the hydrogenation and dehydrogenation rates of Mg. We chose Ni as an additive to increase the dehydrogenation rate of Mg–5 wt% CMC. In this work, samples with a composition of 90 wt% Mg + 5 wt% CMC + 5 w% Ni (Mg–5 wt% CMC–5 wt% Ni) were made through hydride-forming milling, and the hydrogenation and dehydrogenation properties of the prepared samples were investigated. The activation of Mg–5 wt% CMC–5 wt% Ni was completed at the 3rd hydrogenation–dehydrogenation cycle (N = 3). Mg–5 wt% CMC–5 wt% Ni had an effective hydrogen-storage capacity of 5.83 wt% at 593 K in 12 bar hydrogen at N = 3. Mg–5 wt% CMC–5 wt% Ni released hydrogen of 2.73 wt% for 10 min and 4.61 wt% for 60 min at 593 K in 1.0 bar hydrogen at N = 3. Mg–5 wt% CMC–5 wt% Ni dehydrogenated at N = 4 contained Mg and small amounts of MgO, β-MgH2, Mg2Ni, and Ni. Hydride-forming milling of Mg with CMC and Ni and Mg2Ni formed during hydrogenation–dehydrogenation cycling are believed to have increased the dehydrogenation rate of Mg–5 wt% CMC. As far as we know, this study is the first in which a polymer CMC and Ni were added to Mg by hydride-forming milling to improve the hydrogenation and dehydrogenation properties of Mg.
PubDate: 2019-03-01

• Microstructures and Mechanical Properties of Multiphase-Reinforced In Situ
Aluminum Matrix Composites
• Abstract: We investigated the microstructures and mechanical properties of multiphase-reinforced in situ aluminum matrix composites (AMCs) prepared with various combinations and contents of Li, Mg, Si, Cu, Zn, Sn, and Ni. The area fractions of the secondary phases in the as-cast AMCs ranged from 26% to 58%, and the types of secondary phases depended on the alloy chemical compositions. The type and amount of secondary phases were more important than matrix strengthening in determining the alloy mechanical properties. Composite hardness and compressive stress increased while fracture strain decreased with increasing total area fraction of the secondary phases up to 40%. The formation of coarse primary and soft/heavy Sn-containing phases significantly deteriorated the alloy mechanical properties. Annealing also influenced the mechanical properties of the AMCs by changing the microstructures of the secondary phases and Al matrices.
PubDate: 2019-03-01

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