bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Carbon Cryogel Synthesized by Sol-Gel Polycondensation and Freeze-Drying
Authors: Babić B. , Kaludjerović B. , Djokić D. , Krstajić N.
Published: March 2009

Resorcinol-formaldehyde (RF) cryogels were synthesized by sol-gel polycondensation of resorcinol with formaldehyde and freeze-drying carried out with t-butanol. Carbon cryogels were obtained by pyrolyzing RF cryogels in an inert atmosphere. Characterization by nitrogen adsorption showed that carbon cryogels were micro- and mesoporous materials with high surface areas (500 m2/g< SBET <700 m2/g). Cyclic voltammetry experiments at various scan rates (2 to 200 mV s-1) were carried out to study the electrical double-layer charging of carbon cryogel electrodes in 0.5 mol dm-3 HClO4 solution. It has been demonstrated that the total specific capacitance can further be divided into mesoporous and microporous specific capacitance by analyzing the linear dependence of the specific capacitance (C) on the reciprocal of the square root of the potential scan rate ( ν -1/2), as well as linear dependence of the reciprocal specific charge (1/C) on the square root of the potential scan rate ( ν 1/2).
2-D Computer Simulation of Rapid Solidification
Authors: Nikolić Z.S. , Yoshimura M. , Araki S.
Published: March 2009

Two-dimensional numerical model is adopted to analyze the heat transfer process during solidification of the sample melted in an Arc-image furnace. Numerical solution of this complex problem enabled us to calculate the temperature distribution in both sample and substrate, including the phase change phenomena. Also, the effects of process parameters on the solidification of the sample melted on substrate that is cooled by water can be investigated numerically. The parameters include sample size, contact area size between the sample and the substrate, and degree of undercooling associated with rapid phase change and moving interface. The results obtained reveal that these parameters have strong effect on temperature distribution during solidification.
Mechanically Activated Synthesis of CaTiO3 from Mixture of CaO and TiO2
Authors: Vukotić V.M. , Radojević N. , Živković Ljiljana , Vuković Z. , Stojanović B.D.
Published: March 2009

Crystalline calcium titanate was synthesized by mechanical activation of a mixture of
CaO, obtained by thermal treatment of CaCO3, and TiO2 in anatase or rutile form, in a planetary ball mill for 30, 60, 120 and 240 min.. The effect of milling on the solid-state reaction was followed by X-ray diffraction. Changes in powder size and morphology due to milling were determinate by SEM, while BET analysis was made to determine the specific surface area of powders. It was pointed out that the formation of calcium titanate was more easily achieved by mechanical activation synthesis of the mixture of calcium oxide and anatase modification of titanium oxide
compared to the rutile form.
Comparison of Hydroxyapatite Sorption Properties towards Cadmium, Lead, Zinc and Strontium Ions
Authors: Smičiklas I. , Onjia A. , Marković J. , Raičević S.
Published: March 2009

Apatites are well known matrix for heavy metal immobilization and remediation of ground water and contaminated soils. In this work, capacities of different synthetic hydroxyapatite (HAP) samples for Pb, Cd, Sr and Zn sorption were analyzed, from single metal solutions and their equimolar mixture. Initial concentration of each metal in single metal solutions and total metal concentration in the mixture was 10-2 mol/dm3. Initial pH was adjusted to 5.0 ± 0.1. After 24 h equilibration of HAP samples with heavy metal solutions (solid/liquid ratio 1:200), the concentration of metals and of Ca2+ released from crystal lattice, as well as the final pH values were measured. The selectivity of all samples, regardless of the differences in their compositions, crystallinities, specific surface areas, points of zero charge and sorption capacities, was as follows: Pb > Cd > Zn > Sr. The same order was obtained for both single metal solutions and their mixture. In all cases, the sorption was followed by a decrease in final pH values, which are lower than the pHPZC values obtained by equilibration of HAP samples with an inert electrolyte (KNO3). A linear relationship between the amount of metals sorbed and Ca2+ released from HAP was observed. Also, a correlation between sorption capacities and physicochemical properties of HAP samples was found.
Kinetics of Interaction between Fullerol C60(OH)24 and Polyacrylic Hydrogels
Authors: Matija L. , Jovanović J. , Adnadjević B. , Koruga Dj.
Published: March 2009

In this paper kinetics of binding of fullerol to polyacrylic hydrogel at different temperatures, 298, 308 and 318 K, has been investigated. Time dependences of specific capacity of fullerol binding to hydrogel at defined temperatures are determined. Kinetic curves of specific binding capacity of fullerol for hydrogel are described by equations: t x k t x k x max 1 2 max 1 1+ = and x=k2tn. Rate constants k1 and k2 of the specific fullerol binding capacity at various temperatures are determined. Based on changes in constants k1 and k2 with temperature, kinetic parameters of the investigated process are calculated. Also, due to a great difference in values of kinetic parameters k1 and k2 obtained by varying the temperature, kinetic parameters are determined by using Friedman’s isoconversion method. The values of kinetic parameters based on temperature changes in k2 correspond to the values of kinetic parameters for 9 . 0 » a , while the values of kinetic parameters calculated according to the temperature change in k1, correspond to the Ea values. According to the obtained results it is concluded that the investigated process is controlled by diffusion.
Texture Prediction of an AA3004 Aluminum Alloy with the Occurrence of Strain Localization during Simple Shear Using a Multi-Scale Modeling Procedure
Authors: Hu Xiaohua , Gaspérini Monique , van Houtte Paul
Published: March 2009

Although the Taylor-type models gives reasonable texture prediction of the monotonic cold deformation of annealed aluminum alloys both qualitatively and quantitatively, results are less satisfactory for the simple shear test when the alloy is heavily pre-deformed by cold rolling. The reason for this less good prediction originates from strain localization. A virtual stress-strain curve is proposed in which the texture aspects are dealt with by the FC Taylor simulation and the microstructure aspects by a model for the development of intragrain dislocations structure. This virtual yield law is used in a finite element simulation. A strain localization behavior is observed during the finite element simulation similar to that observed during experimental simple shear test. The strain profile of a specific global strain is discretized into a series of strain and the volume fractions of the regions deformed to these strain levels, using the statistical method of histogram. A secondary FC-Taylor simulation is performed, in order to generate the deformation textures, corresponding to this series of deformation strains. The global texture is generated by merging these textures with consideration of these volume fractions. Using this procedure of multi-level modeling, quite satisfactory texture prediction is observed, compared with the measured texture at this strain.
A Study of the γ-to-α Transformation Using EBSD Techniques
Authors: He You Liang , Godet Stéphane , Jacques Pascal J. , Jonas John J.
Published: March 2009

The crystallographic relationship between the g and a phases in samples of the Gibeon meteorite and a TRIP steel was investigated by means of EBSD techniques. The orientations of the two phases were measured and are represented in pole figures. The results are compared to predictions made on the basis of the Bain, Kurdjumov-Sachs (K-S), Nishiyama-Wassermann (NW), Greninger-Troiano (G-T) and Pitsch orientation relationships. The local misorientation between individual fcc and bcc crystals along their common interface was measured to demonstrate the way in which the exact orientation relationship varies along the boundary. The local orientations within lamellae and laths of kamacite and bainite are compared to that in recrystallised ferrite polygons. The occurrence of variant selection during the transformation of deformed austenite is analyzed using a recent dislocation-based model.
The Effects of a High Magnetic Field on Microstructure, Grain Boundary Structures and Texture in a Medium Carbon Steel under Different Cooling Rates
Authors: Zhang Yu Dong , Vincent G. , He Chang Shu , Zhao X. , Zuo Liang , Esling Claude
Published: March 2009

A 12-Tesla magnetic field was applied during the transformation from austenite to ferrite and then pearlite in a medium plain carbon steel at two different cooling rates. Results show that when cooling is slow, the magnetic field shows an effect of promoting proeutectoid ferrite grains to grow along the field direction that results in an elongated grain microstructure. However, when cooling is fast, the magnetic field mainly shows an effect of reducing the amount of low angle misorientations and increasing the amount of CSL boundaries. In addition, the magnetic field exhibits a slight enhancement of the <001> texture component in the direction that is perpendicular to the field direction (TFD).
Texture Studies on Borocarbide Thin Films
Authors: Subba Rao K. , Tamm R. , Wimbush S.C. , Cao G.H. , Oertel C.G. , Skrotzki Werner , Holzapfel B.
Published: March 2009

Epitaxial thin films of the superconducting borocarbide compound YNi2B2C were grown on single crystal MgO (100) substrates without and with Y2O3 buffer layer using pulsed laser deposition (PLD). In both cases YNi2B2C grows with [001] normal to the substrate. However, the in-plane texture depends on the starting condition. For samples without buffer layer, oxygen from the substrate diffuses into the film and forms an Y2O3 reaction layer at the interface. As a consequence, a deficiency of Y is generated giving rise to the formation of secondary phases. On the other hand, using an artificial Y2O3 buffer layer secondary phases are suppressed. The texture of the Y2O3 layers determines the texture of the YNi2B2C film. The superconducting properties of the borocarbide films are discussed with respect to texture and phase purity.
X-Ray Study of Microstresses in Lamellar Pearlite
Authors: Zolotorevsky Nikolay Y. , Vasiliev D.M. , Titovets Yuri
Published: March 2009

The material studied was commercial pearlitic steel deformed by cold drawing. Internal stresses appearing due to the plastic interaction of cementite and ferrite phases of the lamellar pearlite (interphase stresses) were examined in order to clarify the mechanisms controlling plastic behavior of the lamellar pearlite. It was shown that, while the interphase stress level is high at relatively small drawing strain, it is significantly reduced with true strain increasing up to e = 2. The high level of the interphase stress is restored after annealing of the heavily drawn wire and its repeated straining. This result is considered to support a suggestion that the reduction of interphase stress under severe cold drawing is caused by a transformation of the cementite lamellae substructure.
Effect of Plastic Anisotropy on Forming Limit Prediction
Authors: He S. , Van Bael Albert , van Houtte Paul
Published: March 2009

A model based on Marciniak-Kuczynski (M-K) theory [1] for the prediction of forming limit diagrams (FLDs) for anisotropic sheet metals is presented. The plastic anisotropy is taken into account by the shape of the yield locus generated on the basis of measured crystallographic texture. As a result, not only the material behavior during the monotonic loading can be well described and predicted, but also the complex strain-path changes during the forming process can be taken into account. Examples of predicted FLDs for two aluminum alloys are given. Comparisons with experimental results are presented.
Thermal Stress and Texture Development in a Cu/Nb Composite between 4K and 1273 K
Authors: Ye Wen-Hai , Priesmeyer Hans Georg , Brokmeier Heinz Günter
Published: March 2009

Cu-Nb composites are characterized by some special properties, which were discussed since a long time by many different authors [1, 2, 3, and 4]. For manufacturing linear accelerator units it is a great advantage that Cu-Nb don’t form intermetallic compounds. One of the basic questions during application is the influence of the thermal expansion of copper and niobium. Thermal expansion of Cu-Nb was widely discussed by Nadeau and Ferrari [5]. Our research program consists of investigations on Cu50%-Nb50% composites and on Cu-Nb tubes, which on one hand have different textures and on the other hand the grain boundaries are much different in the composite with a curling microstructure and in co-extruded tubes. The present paper will concentrate on thermal stresses and the texture behavior in the temperature range 4K -1273K.
An EBSD Analysis of the Origins of Ridging in AISI 430 Steel Sheets
Authors: Costa Viana Carlos Sergio da , Candido F.S. , Pinto Andre Luiz
Published: March 2009

In the present work the characterisation of both the microstructure and the microtexture of two ferritic stainless steel sheets - AISI 430 (Fe17% Cr) and AISI 434 (17% Cr, 1% Mo) - known to display different ridging behaviours, was carried out by optical metallography, EBSD and OIM techniques. It was concluded that severe ridging is a consequence of: (a) presence of {111} and {001} colonies of grains alternating throughout the sheet plane; (b) through thickness texture inhomogeneity with layers of {001}<110> oriented large grains of low Rvalues sandwiched between layers of higher R-value textured material.
Automated Twin Identification Technique for Use with Electron Backscatter Diffraction
Authors: Henrie B.L. , Mason Thomas A. , Bingert J.F.
Published: March 2009

Historically, twinning classification has been obtained by optical microscopy, bulk x-ray and neutron diffraction, and transmission electron microscopy (TEM). Recent research has shown that automated electron backscatter diffraction (EBSD) can be used to quantify twin content and thereby greatly improve the reliability of twinning statistics. An automated twin identification technique for use with EBSD has facilitated a greater understanding of deformation twinning in materials. The key features of this automated framework are the use of the crystallographic definition of twin relationships, and the correct identification of the parent orientation in a parent/twin pair. The complex nature of the parent/twin interactions required the use of a voting scheme to correctly identify parent orientations. In those few cases where the voting scheme was unable to determine parent orientation (< 2%) the algorithm allows for manual selection. Twin area fractions are categorized by operative twin systems along with secondary and tertiary twinning. These statistics
are reported for deformation and annealing twin populations in deformed a-zirconium and asannealed 316L stainless steel, respectively. These improved twin statistics can help provide insight into the effect of deformation processes on microstructural evolution, as well as provide validation of plasticity models for materials that exhibit deformation twinning.
Effect of Orientation Noise on the Determination of Percolation Thresholds from Electron Back-Scatter Pattern Data
Authors: Chen H.S. , Godfrey Andrew , Liu Qing
Published: March 2009

The effect of orientation noise in EBSP data on measurement of percolation threshold
values has been investigated by use of computer simulated microstructures. A 2-D Monte Carlo Potts model run on a square lattice of size 200 x 200 was used to generate a microstructure containing approximately 150 grains. Orientations were then assigned to each of these grains to generate single texture component microstructures of differing texture tightness (“model” data). In order to simulate
the effect of orientation noise on the experimental data, the orientation at each point in the 200 x 200 grid was adjusted in a manner consistent with experimental observations of the effect of orientation noise. The model data represent therefore an underlying real grain structure, and the noise-adjusted data represent the orientation map that would be measured using EBSP analysis at a given orientation
noise level. The misorientation angle q70% at which 70% of the grains were percolatively connected was then determined for both the ideal data and for the orientation noise adjusted data. A comparison of the two allows calibration of the extent to which percolation data may be incorrectly estimated by EBSP measurements.
Combined Synchrotron and Neutron Strcutural Refinement of R-Phase in Ti50.75.Ni47.75.Fe1.50 Shape Memory Alloy
Authors: Sitepu H. , Wright J.P. , Hansen T. , Chateigner Daniel , Brokmeier Heinz Günter , Ritter Clemens , Ohba Takaomi
Published: March 2009

The crystal structure of R-phase in Ti50.75.Ni47.75.Fe1.50 shape memory alloy (SMA) has been studied at a temperature of (290 ± 7) K on cooling by combined synchrotron and neutron powder diffraction using Rietveld refinement with generalized spherical harmonic (GSH) description for preferred orientation (PO). The results showed that (i) no significant improvement in the crystallographic RWP-factor was found when the inversion center was removed from the 3 P model, suggesting that the space group was indeed 3 P and not lower symmetry 3 P neither m P31 and (ii) the refined atomic parameters were converging only when the 3 P space group was used in the refinement.
Rolling and Recrystallization Textures in Asymmetrically Rolled Silicon Steel Thin Strip
Authors: Sha Y.H. , Zhou S.C. , Zou Z.K. , Zhang F. , Zuo Liang
Published: March 2009

Fe-3.10%Si thin strips were prepared from commercial grain oriented silicon steel sheet by cold rolling with different speed ratios and annealed at 1123K in vacuum, the cold rolling and recrystallization textures were analyzed. Cold rolling texture consists mainly of {111}<112>, {554}<225> and {332}<113> components, while their orientation densities vary with speed ratio and layer through strip thickness. Recrystallization texture development depends on speed ratio obviously, and the peak orientation density deviates from {110}<001> towards {210}<001> with the increase in speed ratio.
Texture Formation during High Temperature Deformation of Al-3mass%Mg Solid Solution
Authors: Okayasu Kazuto , Fukutomi Hiroshi
Published: March 2009

Uniaxial compression tests were conducted on Al-3mass%Mg alloy under various temperatures and strain rates. High temperature yielding was observed at the temperatures higher than 623K. Texture examination elucidated that fiber textures are constructed in all the deformation conditions examined in this study. It was found that the kinds and intensities of texture components varied depending on deformation temperature, strain rate and the amount of strain.
Texture Evaluation of Titanium Aerospace Alloy Ti 834 Using Hot Axisymmetric Compression Tests
Authors: Thomas M.J. , Wynne Bradley P. , Rainforth Mark W.
Published: March 2009

The effect of hot working strain on texture evolution in the near-α titanium alloy Ti 834 has been investigated using hot axisymmetric compression testing and EBSD. Testing was undertaken sub β transus with 22% α, which upon cooling produced a bimodal microstructure of primary α in a matrix of transformed β. Two distinct deformation induced texture components were identified: i) transverse [(0001)||compression direction] and ii) off-basal [(0001) »^ compression direction]. Orientation image mapping was then used to identify the microstructure associated with each texture component. The transverse texture is associated with the transformed β and the offbasal component is the deformation texture of the primary α.
Effect of Thermomechanical Parameters on Texture of 90-10 Brass Sheets
Authors: Salari M. , Akbarzadeh A. , Saffari M.M.
Published: March 2009

Optimized conditions of hot and cold rolling followed by annealing can result in a balance between recrystallization and rolling textures in order to reduce the planar anisotropy of brass sheets. In this work, the effect of finish rolling temperature, cold reduction and annealing temperature on texture development has been investigated. It is shown that uniform deformation at higher finishing temperature is responsible of formation of a severe Cube and G texture components. In contrast, mechanical twinnings are widely formed at low finishing temperatures. There is also a direct relation between the intensity of Cube component and the amount of cold reduction.
High Tensile Strength of Drawn Gold
Authors: Kang Suk Hoon , Jung Hee Suk , Bang Woong Ho , Cho Jae Hyung , Oh Kyu Hwan , Kim Dong Sup , Cho Jong Soo , Park Yong Jin , Park Sang Hoon
Published: March 2009

This paper studies the microstructure of drawn gold wires to equivalent strain of 10 and to equivalent strain of 8.5 then heat-treated. The texture of gold wire drawn to strain of 10 is mainly composed of <100> and <111> fibers. Tensile strength of the gold wire increases with <111> fiber fraction, while the grain size does not appear to affect the tensile property. With an exception at heat treatment at 600oC, the texture of gold wire drawn the strain of 8.5 is replaced with <100> fiber component by heat treatment process at 400~700oC. Heat treatment at 600oC produces <110> fiber or <112> fiber, depending upon annealing time.
Neutron Diffraction Measurements of Deformation and Recrystallization Textures in Cold Wire-Drawn Copper
Authors: Gerber Ph. , Jakani S. , Mathon Marie Helene , Baudin Thierry
Published: March 2009

The crystallographic texture of electrolytic tough pitch copper has been investigated by neutron diffraction after deformation by cold wire-drawing (reduction of area between 51 and 94 %) and after static recrystallization. The deformation texture characterized by a strong <111> fiber is reinforced with increasing strain, while the volume fraction of <100> fiber is reduced. In turn, we show that the <100> fiber is strongly reinforced after recrystallization when intensity of the <100> maxima increases with the level of deformation. Since the <111> fiber disappears first during annealing, the static recrystallization has been followed “in situ” by measurements of the diffracted intensity evolution in the center of the {111} pole figure. From these experimental data and taking into account the Arrhenius equation, the activation energy of the recrystallization process has been determined for each deformation rate.
Quantitative X-Ray Analysis of Deformation Microtexture within Individual Grains
Authors: Ermakova N.Yu. , Zolotorevsky Nikolay Y. , Titovets Yuri
Published: March 2009

The method is described which enables to determine the microtexture that is the orientation distribution within individual grains of a polycrystal. The microtexture is evaluated on the base of X-ray pole distributions measured for separate reflections, referred to as microscopic pole figures (MPF). The procedure for treatment of experimental MPF and the following computation of orientation distribution function is described in detail. Precision of the microtexture evaluation and possible ways of its improvement are discussed. As an example of the method application, orientation distribution within a single grain of aluminum polycrystal deformed by uniaxial compression up to 50% has been examined.
Determination of the Constants of Magnetocrystalline Anisotropy in Sintered Magnets with Uniaxial Texture
Authors: de Campos Marcos Flavio
Published: March 2009

The usual process for producing the high energy magnets based on rare-earth-transition metals as for example NdFeB, SmCo5 or Sm(CoFeCuZr)z involves powder metallurgy. In many cases, it is necessary the determination of anisotropy constants (K1 – first order and K2 second order) from polycrystalline samples. This is not the ideal situation because for more accurate determinations a single crystal is necessary. Nevertheless, in many cases it is very difficult, or not possible, obtaining a single crystal. Then, for these situations, the anisotropy constants can be evaluated from polycrystalline samples with uniaxial texture. In this study, the methodology for making such determination is described. It includes the measurement of Schulz Pole figure by X-Ray diffraction in a surface perpendicular to the c-axis, the axis of easy magnetization. The measured Pole figure can be adjusted with a Gaussian distribution f(q)=exp(-q2/2s2) or with a distribution of type f(q) = cosn q. A model to evaluate the remanence from quantitative metallography is also described. From these distributions, and using the microstructural model, it is possible to estimate the initial magnetization curves for polycrystalline samples, including the effect of the 2nd order anisotropy constant (K2) which produces a curvature in initial magnetization curve. With all these data it is finally possible to estimate the initial magnetization curves for single crystal samples (theoretical), and the anisotropy constants K1 and K2. The inadequacy of Sucksmith-Thompson plots for determination of anisotropy constants from polycrystalline samples is also commented. The described method can be used either for rare-earth transition magnets or for Barium or Strontium ferrites.
Preparation of Nb-40Ti Powders by High-Energy Milling
Authors: Giffoni Y.A. , Ramos Erika Coaglia Trindade , Ramos Ana Sofia , Sandim Hugo Ricardo Zschommler , Pacheco M.T.T.
Published: March 2009

Porous Ti-Nb alloys are promising candidates for biomedical applications. In the present study, alloy powders containing 60 wt-% Nb were prepared by high-energy milling of Nb, Ti, and/or TiH2 powders. The high-energy milling process was carried out in a planetary ball mill. The starting and as-milled materials were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM). Elemental (Nb, and Ti) and TiH2 powder mixtures with composition Nb-40wt%Ti were mechanically alloyed for 2 to 30 h. The formation of a BCC Nb(Ti) solid solution by high-energy milling using elemental Ti powder to produce Nb-40Ti was observed after milling for 30 h. A HCP-Ti solid solution was formed after milling for 30 h due to the partial decomposition of titanium hydride powder mixture during high-energy milling.
Combustion Synthesis of Mechanically-Activated Nb-Al Mixtures
Authors: Buracovas Fabiana , Gonçalves Valéria S. , da Rocha Cláudio José , Neto Ricardo Mendes Leal
Published: March 2009

In this work shake milling were used to mechanically activate Nb – Al powder mixtures at different relative proportions (Nb80Al, Nb65Al, Nb54Al e Nb42Al). All milling process parameters were unchanged, e.g., powders mass, ball/powder mass ratio, balls diameter, quantity and kind of process control agent. Uniaxially compacted cylindrical pellets of milled powders were vacuum reacted. After a two-step degassing treatment (290°C for 0.5 h and 400°C for 4 h), samples were heated at 30°C/min. Ignition and combustion temperatures were measured by a thermocouple inserted in a hole drilled into the pellets. The microstructure of milled powders and reacted pellets were characterized by X-ray diffraction and SEM analysis. Bulk density of the pellets was measured by water immersion (Archimedes). The results showed a decrease of both ignition and combustion temperature with mechanical activation as seen by comparison with reacted pellets of the same composition not mechanically activated (simple mixtures). By increasing the heating hate the completeness of the reactions were improved. The lower the aluminum contents the lower the ignition and combustion temperatures and also the densification. The decrease on ignition temperature was caused by a more effective dispersion (and so more activation) attained by samples with lower aluminum content.
Production and Characterization of Aluminium NbAl3 Composite by Mechanical Alloying and In Situ - A Process Comparison
Authors: Urtiga Filho Severino L. , Earthman James C. , Nieves I. , Robert Maria Helena , Waked T.P.
Published: March 2009

This work analyses the production of Al based composites with particulate reinforcement, via mechanical alloying. Composites were produced by mixing Al and NbAl3 powders by high energy mechanical alloying, under liquid nitrogen atmosphere, followed by cold pressing and hot sintering; and by controlling NbAl3 phase precipitation in liquid Al (in situ formation of the reinforcement). Results on composite produced from powders showed better distribution and incorporation, besides finer dispersion of particles in the matrix when mechanical alloying is employed. In this case, high dispersion on particulate phase was found despite predominance of small particles; there are no evidence of interface formation. When composites are produced by in situ formation of NbAl3 intermetallics, results showed that the formation of the reinforcement directly from the liquid matrix and the peritectic reaction between NbAl3 and liquid Al, provide a perfect reinforcement/matrix interface. Products showed good mechanical properties, good wear behavior and reduced thermal expansion.
Safe Use of Natural Gas in Ceramic Furnace Burners
Authors: Metropolo P.L. , Brown A.E.P.
Published: March 2009

Heat radiation source in ceramic furnaces can be either electric or with combustible, such as LPG or natural gas (NLG). Recently, due to electric shortage and costs, natural gas turned up to be a better alternative to provide heat source to furnaces. Paper presents a study on risk analysis of the use of natural gas in burners of ceramic furnaces. Safety concern to identify hazard causes and consequences was performed, people vulnerability was also studied. Prevention and protection analysis was elaborated by PHA (Preliminary Hazard Assessment) technique. After hazard identification, explosion shock wave consequences as well as people and or material vulnerabilities were performed with the TNO method. Natural gas leakage followed by fire jet and CVE – confined vapour cloud explosion calculations and its effects to the people and facility materials were also provided. Finally, safety measures to prevent and or protect equipment and furnace operators were proposed.
Synthesis of La0.8 Sr0.2 MnO3±δ Powders by Amorphous Citrate and Pechini Techniques
Authors: Brant Márcia Caldeira , Zani Jarlys Arthuri , Lameiras Fernando Soares
Published: March 2009

La0.8Sr0.2MnO3±d (LSM) powders were prepared by a Pechini-type polymerizable complex process and by amorphous citrate technique. Both processes involve the complexation of the LSM cations from their nitrates or carbonates. The aim of this work is to determinate the differences between the powers obtained by these techniques. The powders synthesized by the Pechini-type process were calcined between 500 °C and 1100 °C. The powders prepared by amorphous citrate technique were calcined at 900 °C. No contamination of either of the powders was observed by X ray fluorescence analysis. X ray diffraction results showed that a perovskitetype structure phase was obtained. BET results showed that the specific surface areas of the powders prepared by the polymerizable complex process and the amorphous citrate route were 6.6 m2g-1 and 5.7 m2g-1, respectively.
Physical Characterization of K-Doped 0.9PMN-0.1PT Synthesized by an Association of the Columbite Route and the Polymeric Precursor Method
Authors: Cavalheiro A.A. , Bruno Juliana C. , Zaghete M.A. , Varela José Arana
Published: March 2009

The solid solution 0.9PbMg1/3Nb2/3O3-0.1PbTiO3 is one of the most widely investigated relaxor ceramic, because of its high dielectric constant and low sintering temperatures. PMN-PT powders containing single perovskite phase were prepared by using a Ti-modified columbite precursor obtained by the polymeric precursor method. Such precursor reacts directly with stoichiometric amount of PbO to obtain pyrochlore-free PMNPT powders. The structural effects of K additive included in the columbite precursor and 0.9PMN-0.1PT powders were also studied. The phase formation at each processing step was verified by XRD analysis, being these results used for the structural refinement by the Rietveld method. It was verified the addition of K in the columbite precursor promotes a slight increasing in the powder crystallinity. There was not a decrease in the amount of perovskite phase PMN-PT for 1mol% of K, and the particle and grain size were reduced, making this additive a powerful tool for grain size control.
Hazardous Wastes Disposal: Stabilization/Solidification of Tannery Residue in the Presence of Chromium
Authors: Pinto Carolina A. , Sansalone John J. , Dweck Jo , Cartledge Frank K. , Valenzuela-Díaz Francisco Rolando , Büchler Pedro M.
Published: March 2009

Disposal or reuse of hazardous waste is a major consideration in chemical manufacturing and processing. Waste residuals from the tannery industry can contain high levels of chromium. Considered as a hazardous waste by the Brazilian environmental laws, the chromium-containing waste requires treatment before final disposal. This paper proposes a solution for the disposal of tannery wastes, which are rich in chromium by solidification in a Portland cement matrix using combinations of sodium bentonite and organoclay admixtures. This research is part of a series of experimental studies where Brazilian sodium bentonite, and organoclay materials are used to adsorb both inorganic and organic chromium. The solidified matrix is formed by Type II Portland cement, in which the hydration process stabilizes the tannery waste. Wyoming sodium bentonite and a commercial organoclay are analyzed and compared with the Brazilian clays. X-ray Diffraction is used to characterize the samples and leaching tests are performed to analyze the chromium concentration in the extract solution. In terms of leachate tests, the stabilization by solidification with cement is a process that can be used in the treatment of tannery waste.
Factors Limiting the Achievable Ferrite Grain Refinement in Hot Worked Microalloyed Steels
Authors: Novillo E. , Cotrina E. , Iza-Mendia Amaia , López Beatriz , Gutiérrez Isabel
Published: March 2009

Nb is added to C-Mn steels in order to use the solute drag and/or strain induced precipitation as a useful tool to condition the austenite in the hot rolling mill and produce during the subsequent cooling a refined ferrite grain size. The highest degree of refinement is obtained in conventional rolling mills by accumulating the deformation in austenite during the last passes, followed by early cooling in the run out table to produce a high density of nucleated ferrite grains. However, the maximum refinement is to a certain extent attenuated due to the ferrite grain coarsening taking place during the transformation. The present work analyses the different aspects limiting the final achievable ferrite grain refinement.
TRIP-Assisted Multiphase Steels with Niobium Additions. Microstructures and Properties
Authors: Andrade-Carozzo V. , Jacques Pascal J.
Published: March 2009

It seems completely clear that the combination within the same microstructure of various steel phases (ferrite, bainite, martensite) and the existence of the TRIP effect (i.e. a mechanically induced martensitic transformation) improves in a large way the properties of strength and ductility of low-alloy steels. TRIP-aided multiphase steels have been studied for several years and arouse a growing industrial interest. This project deals with the influence of a large Nb addition on the microstructure and mechanical properties of TRIP-assisted multiphase steels. It is shown that Nb influences in a large way the different phase transformations as well as the recrystallisation of the ferrite matrix occurring during the heat-treatment of cold-rolled TRIP-aided steels. As a consequence, the mechanical properties also depend on the parameters of the thermomechanical process and on the content and stability of the retained austenite.
Effect of Heat Treatment and Microalloying on Toughness of Cast Low Carbon Steel
Authors: Jandová Dagmar , Kasl Josef
Published: March 2009

The possibility of mechanical properties improvement in cast low carbon manganese
steels for thin-walled castings via appropriate microalloying and heat treatment was studied. The steels (0.15 C and 1.2 Mn) microalloyed by vanadium, titanium and niobium were undergone the solution heat treatment. Mechanical testing and detailed microstructural analyses were performed using light, transmission and scanning electron microscopy. Precipitation processes in individual steels were discussed and the steel with the most promising composition was selected for following experiments.
Development of NbTiB Microalloyed HSLA Steels for High-Strength Heavy Plate
Authors: Meuser H. , Grimpe F. , Meimeth S. , Heckmann C.J. , Träger C.
Published: March 2009

This paper deals with the development of low carbon NbTiB micro-alloyed high strength low alloy steel for heavy plates with high wall thickness. In the production of heavy plate it is remarkably difficult to achieve a combination of high strength and good low-temperature toughness. Bainitic microstructures have shown the capability to attain such requirements. To achieve a bainitic microstructure even for heavy wall products the formation of bainite can be promoted and supported by the use of small amounts of boron as a micro-alloying element. This industrial research project is based on the addition of small amounts of boron to promote the desired bainitic structure. Mill rolling trials were carried out to determine the optimum process parameters. The results of experimental mill rolling trials on 35 mm plates will be presented in this paper.
Development of Process Technology for Vanadium Containing, High-Strength, Low-Carbon, Heavy Plate and Its Trial Manufacture
Authors: Belenky Boris Z. , Smirnov Leonid A. , Srogovich Iosif M. , Mitchell Peter S.
Published: March 2009

The effects of adding vanadium (up to 0.1%) and niobium (0.02%) to a steel containing 0.07%C – 1.5%Mn – 0.29%Si – 0.035%Al – 0.01%N have been studied in the laboratory. It was determined that a steel containing 0.05%V had a yield stress, after accelerated cooling, greater than 480 MPa and toughness, as measured by U-notch and Vee-notch impact specimens, improving as the finish rolling temperature was lowered from 950oC to 750oC. Consequently, a semi-industrial trial, involving the manufacture of a steel containing 0.07%V, rolled to 22 mm and 32 mm thick, narrow plates, was carried out. This demonstrated that after finish rolling at 750oC, followed by air cooling, the steel had a yield strength in excess of 470 MPa accompanied by excellent toughness. The work demonstrates the potential for achievement of high levels of strength and toughness in heavy plate steels, micro-alloyed with vanadium.
Influence of Deformation and Coiling Temperature on Mechanical Properties of a High Strength Pipeline Steel
Authors: Elwazri A.M. , Bai D.Q. , Siciliano Fulvio , Yue Steve
Published: March 2009

One of the components required to successfully produce high strength pipeline steel is to optimize precipitation strengthening. Some high strength pipeline grades rely on increased levels of Nb; in these grades, it is important to ensure that all the Nb is effectively employed. It is generally accepted that choice of coiling temperature is critical in maximizing the Nb precipitation in ferrite. Additional control of this precipitation may be attained by deformation at these coiling temperatures, an approach termed ‘cool deformation’. In this work, steel specimens were heated to
temperature of 1200°C and held at temperature for 20 minutes to ensure significant dissolution of Nb precipitates. Some specimens were aged at 400°C for times ranging from 10 minutes to 10 hours followed by air-cooling. Others were subjected to deformation at 400°C (‘cool deformation’) prior to aging. It was found that the cool deformation improves the mechanical properties by microstructure; both yield and tensile strengths are significantly higher than that of the aged only specimens. By using low voltage imaging on a field emission gun scanning electron microscopy (FE-SEM), precipitates were observed and identified. The effects of the thermal and cool deformation schedules on the precipitate characteristics are described in this paper.
Characterization of the Interaction of the Interstitial Atoms with the Substitutional Atoms and with the Dislocations in Extra-Mild Steels through Coupled Use of Thermoelectric Power and Internal Friction Measurements
Authors: Massardier-Jourdan Véronique , Le Patézour E. , Thiery F. , Lavaire N. , Merlin Jacques
Published: March 2009

In Fe-C-Mn steels, the carbon atoms in solution can be either completely free in the iron matrix or in interaction with manganese atoms. In this context, a methodology based on the combined use of thermoelectric power and internal friction measurements was developed in order to evaluate quantitatively these two populations of carbon atoms. This methodology was used to determine the binding energy of the C-Mn dipoles and to follow the precipitation kinetics of the two populations of carbon atoms and/or their segregation kinetics to the dislocations during an isothermal treatment. Lastly, the influence of each population of carbon atoms on the strain aging of extra-mild steels was discussed.
Dual-Phase Steels Characterization Using Magnetic Barkhausen Noise Measurements
Authors: Hug-Amalric Aurélie , Kleber Xavier , Merlin Jacques , Petitgand Hélène
Published: March 2009

Magnetic Barkhausen noise measurements have been carried out to characterize ferritemartensite duplex microstructures and industrial Dual-Phase steels. We have first studied ferritemartensite duplex steels, for which the volume fraction and the carbon content of martensite were higher than for industrial Dual-Phase steels. We found linear evolutions between ferrite peak parameters and its proportion. We applied these results to industrial Dual-Phase steels and show that Barkhausen noise measurement can be successfully used for Dual-Phase steels characterization, and in particular for assessment of ferrite proportion.
Discussion on the Rate Controlling Process of Coarsening of Niobium Carbonitrides in a Niobium Microalloyed Steel
Authors: San Martín David , Caballero Francisca García , Capdevila Carlos , García de Andrés Carlos
Published: March 2009

Austenite grain growth in microalloyed steels is governed by the coarsening of fine precipitates present at grain boundaries below the grain coarsening temperature. Zener model is widely used in metals to describe the pinning effect of second phase particles precipitated in the matrix. In this work it has been discussed whether grain boundary or volume diffusion is the rate controlling process for the coarsening of the niobium carbonitrides. Calculations on austenite grain growth kinetics, obtained coupling Zener theory and both rate controlling processes of precipitate coarsening, have been compared against experimental austenite grain size results under nonisothermal heating conditions. In this sense, it has been concluded that the coarsening of niobium carbonitrides is mainly controlled by volume diffusion of Nb in austenite.
Computer Simulation of C-N-V Precipitates Evolution Based on Local Concentration Fluctuations
Authors: Aldazabal J. , García-Mateo Carlos
Published: March 2009

From a “macroscopic” point of view, steel composition is assumed to vary smoothly along its microstructure. A closer look reveals that, on the atomic level the material composition does not change so smoothly. Single atoms jump randomly along the crystal lattice due to their thermal energy. These random jumps create sporadic zones of the crystal with higher concentration of certain species, and they are responsible for many phenomena, such as precipitation, Ostwald ripening, some phase transformations… This paper proposes a model to simulate the evolution of
C-N-V precipitates in microalloyed steels heat treated in the range of warm temperatures (800-900 °C); when the matrix is austenite (fcc), thus taking into account for the local composition fluctuations. The model works by dividing the space into very small cells, containing a single atomic cell each. If during the random movement of atoms a cell that touches a precipitate reaches some critical composition, it is very easy to stick it to the precipitate by changing its “phase”. But it is also possible that some atoms escape from the precipitate by jumping to the austenitic matrix. Both processes happening simultaneously, and which one is leading depends on the atoms energy, i.e. system temperature.
Cleavage Initiation in Ti-V-N and V-N Microalloyed Forging Steels
Authors: Balart M.J. , Davis Claire L. , Strangwood Martin , Knott J.F.
Published: March 2009

The effects of matrix microstructure and features of non-metallic inclusion (morphology, type, volume fraction and size) on cleavage initiation in medium-carbon Ti-V-N and V-N microalloyed resulphurized forging steels have been determined by examining fracture surfaces produced in room temperature Charpy impact tests. The steels were generally Al-deoxidised but one V-N steel was Si-deoxidised. It has been found that, in the Ti-treated steel, having a ferrite-pearlite microstructure, brittle fracture initiation occurred at cracked coarse (Ti,V)(C,N) single phase or [(Ti,V)(C,N)/Al2O3/MnS] multi-phase inclusions. In the Ti-free steels, cleavage initiation was dependent on matrix microstructure and non-metallic inclusions. In the low strength Ti-free steels, with a ferrite-pearlite microstructure, the absence of a continuous grain boundary ferrite layer led to initiation from interfacing pearlite colonies. For the bainitic microstructure, cleavage initiated close to the notch, but the microstructural feature responsible could not be identified. For the ferritepearlite microstructure in the Si-deoxidised V-N steel, cleavage initiated at cracked Mn-Al-(Ca) silicate inclusions. The higher matrix strength and more continuous nature of grain boundary allotriomorphic ferrite in the V-N steel deoxidised with Al was associated with cleavage initiation from V-rich (V,Ti)(C,N)-containing inclusions. These were generally of smaller size than those in the Ti-treated steels.
In Situ TiB Reinforced Titanium Metal Matrix Composites Prepared by Spark Plasma Sintering
Authors: Zhou Yu , Feng Hai Bo , Jia De Chang
Published: March 2009

In situ synthesized TiB reinforced titanium matrix composites of Ti-B and Ti-TiB2 systems have been prepared by spark plasma sintering at 800-1200 °C under 20 MPa for 5 min. The effects of sintering temperature and reinforcement volume fraction on flexural strength, Young’s modulus and fracture toughness of the composites were investigated. The in situ synthesized TiB reinforcements are randomly and uniformly distributed in titanium matrix. The TiB whiskers are aligned along [010] direction, and the crystallographic planes of the TiB needles are always of the type (100), (101) and (10 1) . The parallel TiB were observed in β-Ti grains in both of the investigated composites. The in situ TiB needle is likely to grow along [010] direction which is parallel to [111] direction of cubic lattice of β-Ti phase.