bluuebunny/crossref_metadata_2025 huggingface dataset:
Recycling of Silicon Carbide and Corn Starch as Binder Originating from Commercial Starch Consolidation
Authors: Marins E.M. , Lucena E.F. , Santos F.P. , de Campos Élson , Zacharias M. , Rodrigues J.A.J.
Published: March 2009

The main goal of this work is to demonstrate that the use of recycled material originated from SiC ceramics is viable. These ceramics were produced by commercial starch consolidation process. Before calcination stage, surplus of these materials always appears. This surplus is rich in SiC and starch. Samples were made by material previously milled in automatic mortar and sieved (100 Tyler). Later, 10% of distilled water was added to the material and the mixture was pressed at 40 MPa. In order to characterize the ceramic, three point flexural test were made, according to the ASTM C1161/94 norm. The results were analyzed by Weibull statistical method. Apparent density and porosity measures also were made, according to ASTM C20/87 norm. A verification of the surface was made in the fracture area by the depth from focus method and SEM image analysis. The results showed that the recycling process is fully viable, being a good economic option and reduce possible pollutant effect to the environment.
A Method to Optimize Ceramic Masses for Coatings through Delineation of Experiments
Authors: Silveira Jair , Pontes Luiz Renato de A.P. , Leite Josinaldo P. , Echude-Silva Jorge H.
Published: March 2009

This article presents a method to optimize the formulation of ceramic masses for coatings using the statistical design of experiments. The project of simplex mixtures in pseudocomponents considered six control factors (wt. %): talc, quartz, limestone, phyllite, dolomite and clay and three response variables: linear retraction, bending resistance and water absorption. The proposed method was implemented in the stages: (1) identification of the problem, (2) planning and execution of the experiments and (3) optimization and discussion of the results. The optimization method is defined through the simulation, imposing the restrictions that each response demands.
Electron Beam-Physical Vapour Deposition of Zirconia Co-Doped with Yttria and Niobia
Authors: Almeida D.S. , Silva Cosme Roberto Moreira , Nono Maria do Carmo de Andrade , Cairo Carlos Alberto Alves
Published: March 2009

Turbine blades of airplanes and thermoelectric plants work in adverse conditions, with corrosive environment and high temperature and pressure. One way to improve the life or the working temperature of the blades is by the use of special coatings over metallic material applied by Electron Beam – Physical Vapour Deposition (EB-PVD). The most usual material for this application is zirconia doped with yttria. Addition of niobia, as a co-dopant in the Y2O3-ZrO2 system, can reduce the thermal conductivity and improve mechanical properties of the coating. The purpose of this work is to show the influence of the addition of niobia on microstructure of ceramic coating taking in to consideration X-ray diffraction and scanning electron microscopy observations. First result shows a columnar structure with only tetragonal phase in the ceramic coating in the chemical composition range studied.
Tetragonal-to-Monoclinic Transformation Influence on the Mechanical Properties of CeO2- ZrO2 Ceramics
Authors: Nono Maria do Carmo de Andrade
Published: March 2009

CeO2- ZrO2 ceramics are considered a candidate material for applications as structural high performance ceramics. In this work are presented and discussed the tetragonal-to-monoclinic stress-induced transformation influence on the mechanical properties in these ceramics. Sintered ceramics were fabricated from powders mixtures containing ZrO2 and 8 to 14 CeO2 % mol. SEM observations were used to study de ceramic microstructures and X-rays diffraction to identification and determination of tetragonal and monoclinic phases. It was adopted the 4-point bending tests, Vickers surface hardness and fracture toughness technique to the determination of the mechanical parameters. The results showed that the mechanical properties were strongly dependent of the CeO2 content, the microstructure and the fraction of tetragonal-to-monoclinic stress-induced transformation.
Thermal Characterization of Sintered Clay-Petroleum Waste Mix by the Photoacoustic Technique
Authors: Rodrigues M.F. , Sthel M.S. , Vargas H. , Holanda J.N.F.
Published: March 2009

In Campos oil Basin (Brazil), which is responsible for more than 80 % of the national petroleum production, it is generated a great amount of wastes from deep crude oil extraction related activities. Particularly, the oil sludge waste has been intensely studied in order to search alternatives for the reuse of the waste in treated form in the ceramic industry. the present work focuses on the photoacoustic thermal characterization of sintered ceramic bodies containing up to 5 wt.% added waste. Specimens were uniaxially pressed at 25 MPa, and sintered between 850 °C and 1000 °C. The results of thermal diffusivity indicate that the use of petroleum waste in structural ceramic up to 5 wt.% does not cause significant changes in the structure or composition of the clay/waste system, resulting in great advantages in waste minimization.
Sintering, Microstructure and Mechanical Properties of Ba2HoWO5.5 Ceramics
Authors: Lapa Camila M. , Ferreira Ricardo Arthur Sanguinetti , Aguiar J. Albino , Silva Charles L. da , Souza Dulcina P.F. , Yadava Yogendra Prasad
Published: March 2009

In high technology industries ceramics have several uses, especially at high temperature, e.g. inert crucibles, electrodes and catalysts. We are working on production and development of new oxide ceramics, based on complex cubic perovskite structure, for fabrication of crucibles for metallurgical applications. In the present work, we have produced and studied sintering behavior of a new ordered complex cubic perovskite oxide ceramic Ba2HoWO5.5. Microstructural characteristics of the Ba2HoWO5.5, sintered between 1200 to 1400°C for 48h, were studied by scanning electron microscopy. The mechanical behavior was studied by Vickers microhardness tests. Our studies show a gradual improvement in microstructural characteristics of sintered Ba2HoWO5.5, both on polished and fractured surface. This homogeneity of grain sizes and particle size distribution increases with the increasing of the sintering temperature, which results in higher sintered density and increased mechanical hardness.
Biofunctionalization of Glass Powder by Cold-Plasma Technique
Authors: Assis Odilio B.G. , Paterno Leonardo G.
Published: March 2009

The present work deals with cold plasma organosilicon treatment of glass powder surfaces. The treated material underwent subsequent chemical derivations by storing samples inside an evacuated chamber, allowing chemical penetration at controlled pressures. The radicals’ inductions were characterized by XPS within each stage of modification. The enzyme peroxidase was immobilized using functionalized materials to check the resultant biocompatibility. A sequence of surface tailoring is proposed suggesting the anchoring of enzyme via C = O groups implanted on the glass surface. The experimental results demonstrate that the proposed process is suitable for the functionalization of materials with irregular shapes.
Evaluation of Procera/Porcelain Interface in Metal-Free Prosthesis
Authors: Yasuda S.H. , Guastaldi Antonio C. , Vedovato E.
Published: March 2009

Prosthetic substructures for dental application are veneered by porcelain comprising a structure with different elastic modulus and thermal expansion coefficients layers. This structure may present residual stresses in different layers leading to crack propagation and delamination. Although veneering porcelain remains basically on same strength than standard feldspathic porcelains, new ceramic cores have been developed with higher mechanical properties overcoming metal substructures, improving esthetics and biocompatibility. The interface between the Procera dense sintered alumina core and the manufacturer recommended veneering porcelain (AllCeram-Degussa) were evaluated using SEM in coping shaped specimen simulating the standard dental preparation. There were neither crack presences at the interface nor porcelain delamination.
Ce0.8Gd0.2O1.9 Powders Synthesized by Co-Precipitation and Amorphous Citrate Processes
Authors: Brant Márcia Caldeira , Possa Felipe da Silva , Lameiras Fernando Soares
Published: March 2009

Powders of Ce0.8Gd0.2O1.9 were synthesized by co-precipitation and amorphous citrate routes and their compositions and structures were compared. Co-precipitation process was carried out at room temperature, while amorphous citrate synthesis was performed at 60-70 °C. The powders obtained were calcined at 700 °C for 1 h. X-ray diffraction analyses showed that a single fluorite structure was formed by both synthesis techniques. Pellets from these powders were prepared by compaction at 30 kN/cm2 and sintered at 1593 °C in air. WDS analysis confirmed the homogeneity of the pellets. The sintered pellets obtained by amorphous citrate and by coprecipitation routes showed relative densities over 97 % of the theoretical density. These results indicated that the citrate amorphous route is an interesting and simple technique to prepare gadolinium-doped ceria powders with high sinterability.
Combustion Synthesis of Cu1-xNixCr2O4 Spinel for Catalytic Applications
Authors: Pimentel P.M. , Ginani M.F. , Martinelli Antonio Eduardo , Melo D.M.A. , Pedrosa A.M. Garrido , Melo M.A.F.
Published: March 2009

Transition-metal spinels are efficient catalysts in a number of heterogeneous processes, such as CO oxidation, catalytic combustion of hydrocarbons and oxychlorination of methane. The properties of catalytic materials are highly dependent on the synthesis route. Spinels are often produced at high temperatures by the calcination of precursors such as powder mixtures, slurries or resins. Combustion synthesis is a cost-efficient method used to produce homogeneous and fine particles with high reproducibility. Cu0.8Ni0.2Cr2O4 spinel was obtained by the combustion of metallic nitrates using urea as fuel. The resulting powders were calcinated at different temperatures and characterized by thermogravimetric and particle size analyses, X ray diffraction, and scanning electron microscopy. The effect of urea on the control of the process and particle morphology was investigated. The results revealed the formation of porous powders with increasing crystallinity as the calcination temperature increased. Crystallization of spinel started at 700 oC.
Complex Carbon-Mineral Sorbents from Common Clay
Authors: Cosin Shirley , Pinto Carolina A. , Souza Santos P. , Valenzuela-Díaz Francisco Rolando
Published: March 2009

Carbon/mineral complexes are materials with surfaces covered partially or totally by carbon materials contains. They have high industrial potential uses as material adsorbents and ceramic filters. The objective of this work is to evaluate the corrosion strength in acid and alkaline solutions, and the adsorption capacity of methylene blue of some materials prepared in the LMPSol. The compositions were prepared with an industrial common clay named “taguá” and organic and inorganic additives from industrial residues up to 50%. The corrosion test was performed in water at 60°C and in aqueous solutions of HCl and NaOH at room temperature, with mass losses measured after 15 days. The samples were pressed manually and heated at different temperatures: 110°C, 350°C and 500°C. The performed tests were transverse flexural strength, porosity and water absorption.
Corrosion Protection of AISI 304 Stainless Steel Filters by a Surface Treatment
Authors: De Micheli L. , Costa Isolda
Published: March 2009

In this study a corrosion protection method was used with AISI 304 SS filters and its effect on their corrosion resistance was evaluated in a sodium chloride solution (0.5 mol/L). The corrosion resistance of the surface treated filters was investigated at increasing temperatures, from 22 oC to 100 oC. It was found that the treatment improved the corrosion resistance of the filters at all temperatures tested. The film formed was maintained on the filters surface during the whole period of test (3 weeks). Surface analysis of untreated and treated filters, after corrosion tests, supported the indication of the beneficial effect of the corrosion protection treatment evaluated in this study.
Analysis of Mn Effect on Recrystallization Kinetics in High Nb Steels
Authors: Zurob Hatem S. , Zhu G. , Subramanian S.V. , Purdy Gary R. , Hutchinson Christopher R. , Bréchet Yves
Published: March 2009

A physically based model is used to analyze quantitatively, the relative contributions of solute Nb and strain-induced NbC precipitation to the retardation of static recrystallization during the interpass time. The model explicitly takes into account the time evolution of strain-induced precipitation and its interaction with recovery and recrystallization. It is thus possible to quantitatively model the recrystallization kinetics taking into account: i) the effect of solute drag on the boundary mobility, ii) the effect of particle pinning (Zener drag) on the driving force for boundary motion, and iii) the effect of dislocation pinning by strain-induced precipitates, on the recovery kinetics and the nucleation of recrystallization. The analysis shows that there is an optimum partitioning of Nb between matrix solute and strain induced precipitates. This optimum partitioning maximizes particle pinning while ensuring an adequate solute drag effect to prevent the boundary from breaking away from solute atmosphere. The optimum partitioning of Nb between the matrix and the precipitates is shown to depend upon the temperature window of rolling, pass reduction and interpass time. The effect of delaying the kinetics of strain-induced precipitation of NbC through large Mn addition is shown to be an advantage for ensuring adequate solute drag in the low temperature, large pass deformation schedule used in near-net shape processing of thin slab or thick strip castings.
Microstructural Evolution of Two Medium Carbon Microalloyed Steels during Hot Forging Process
Authors: Al Omar A. , Chenaoui A. , Dkiouak Rachid , Cabrera Jose María , Prado Jose Manuel
Published: March 2009

The main aim of the present investigation was to study the flow behaviour of two medium carbon microalloyed steels under hot forming conditions, and to analyse its microstructural evolution. The dependence of recrystallized grain size (Drec) on the Zener-Hollomon parameter Z shows a bimodal behaviour with transition from single to cyclic dynamic recrystallization. Also we observed that the variation of Drec normalized by Burgers vector (b) with sss normalized by shear modulus ( µ) shows the same bimodal behaviour cited above. The Derby’s universal equation cited in literature for recrystallized grain sizes was not followed; it seems that the presence of fine precipitated particles has a clear effect on this disagreement.
Effect of Nb and V in the Development of Texture and Plastic Strain Ratio in Low Carbon Microalloyed Steels Produced by A.S.T. Technology
Authors: Mapelli Carlo , Venturini Roberto , Guindani Antonio
Published: March 2009

The effects of Nb and V on the anisotropy and textures featuring the hot rolled low carbon microalloyed steels produced by A.S.T. (Arvedi Steel Technology) have been studied as a function of the final coiling temperatute Tcoiling. Mechanical properties and r-values for twelve steels have been determined through tensile tests performed on three main different directions: 0°, 45°, 90° to the rolling one. The samples have been analysed by EBSD (Electron Back Scattering Diffraction) to identify the textures developed during the process. The relations among the chemical composition of the steels (i.e. C, N, Nb, V contents), the mechanical properties, the temperature during the coiling operations, the textures and the formability properties have been pointed out.
Study on Ferrite Intragranular Nucleation in a V-Microalloyed Steel
Authors: Medina S.F. , Gómez Manuel , Chaves J.I. , Gómez P.P. , Adeva P.
Published: March 2009

The intragranular nucleation of ferrite has been studied in a V-microalloyed steel
(C=0.102; Mn=1.479; V=0.140; N=0.016, %wt). By means of hot torsion tests, recrystallizationprecipitation-time-temperature (RPTT) diagrams have been drawn which show the precipitation kinetics and the recrystallization-precipitation interaction at any temperature. RPTT diagrams were determined at two strains, 0.20 and 0.35 respectively. Deformation tests were carried out at 890°C and different holding times, corresponding to moments before the start of precipitation, during
precipitation and after precipitation had ended, respectively. In order to relate the precipitation state with the intragranular nucleation, the strengthening of austenite was measured taking into account the non-recrystallized austenite fraction prior to the phase transformation. In this way, the possibility of V-nitrides acting as nucleation sites was evaluated by comparison of ferrite grain size versus holding time. Thus it was found that the precipitate size and precipitated volume are influencing the intragranular nucleation, although this is not a strong influence.
Modeling Ferrite Grain Size Distributions during the Transformation of Hot Worked Austenite
Authors: Zubialde R. , López Beatriz , Rodriguez-Ibabe J.M.
Published: March 2009

A model has been developed to predict the ferrite grain size distribution resulting after the austenite to ferrite transformation in slowly cooled low carbon steels. The model uses the austenite grain size distribution present before transformation as input and provides the size distribution of ferrite grains at any instant in the transformation range, whether the microstructure is partially either completely transformed. The model is based on empirical equations relating the mean austenite and ferrite grain sizes and log-normal shape grain size distributions. A validation of
the model was carried out in the laboratory by torsion tests for Nb and Nb-V microalloyed steels.
Development of High Performance Nb-Added Hot Rolled Bainitic Steels Presenting a TRIP Effect
Authors: Georges C. , Godet Stéphane , Jacques Pascal J.
Published: March 2009

The present work describes the correlation between the microstructure and the mechanical properties of multiphase steels processed through a Continuous Annealing Process Line (CAPL). The mechanical and microstructural properties of one of the former experimental steel compositions was also processed via Batch Annealing (BA) and the results have been included for comparison reasons.
Advanced Metallic Structural Materials and a New Role for Microalloyed Steels
Authors: Korchynsky Michael
Published: March 2009

The recent worldwide surge of steel consumption, mainly of low-strength carbon grades, has created raw-materials shortages and price increases. These supply-demand strains could be relaxed by satisfying engineering needs with less steel. However, materials used for such a substitution must combine high weight reducing potential with low cost. Microalloyed (MA) steels are cost- effective substitutes, since their high strength is the result of grain refinement and precipitation hardening. The optimum alloy design of MA steels combines superior properties with lowest processing cost. The growing use of EAF and thin slab casting technology improve the economics of MA steels, especially when alloyed with vanadium. The monetary value of weight reduction is sufficient to increase the profitability of steel makers
and to lower the material cost to steel users. This “win-win” situation is financed by the elimination of efforts spent in producing inefficient steel, yielding an increase in wealth formation. To gain acceptance of substitution by the consumer, a long-term strategic plan is needed to be implemented by the beneficiaries – steel producers and steel users. The successful substitution is of importance to the national economy, resources and energy conservation, and the environment. Since microalloyed steels, used as a replacement for carbon steels, offer low-cost weight savings, they deserve to be classified as advanced structural materials.
The Unique Features of Reinforcing Steel Microalloyed with Nitrogen and Vanadium
Authors: Panfilova Lyudmila M. , Smirnov Leonid A. , Mitchell Peter S.
Published: March 2009

The chemical composition of a new vanadium-nitrogen containing steel grade
(17Mn2NV) and process technology for production of At500S-class reinforcing bar, have been designed. The steel alloyed with vanadium and nitrogen possesses a uniquely high level of strength, fatigue, high ductility and notch toughness. At the same time it possesses good high temperature properties, resistance to stress-corrosion and mechanical ageing and its lower carbon level should ensure good weldability. Production and application of this reinforcing steel will enable considerable improvement in the quality, reliability and longevity of reinforced concrete structures, used in extreme Arctic and seismic regions and will ensure considerable lowering of cost.
Influence of Severe Accumulative Rolling in a Low Carbon Microalloyed Steel
Authors: Sim Ho Sup , Lee Kon Bae , Yang Hyung Ryul , Kwon Hoon
Published: March 2009

Effect of the severe deformation by multi-pass rolling on microstructure and tensile properties was analyzed in terms of rolling temperature, plate thickness, and cooling rate for a modified API X65 steel containing B. The plates, 80 and 50 mm thickness, were rolled six times by 20%/pass (total 75%) to 20 and 12 mm, at 1023 K of unrecrystallized γ region or 973 K of intercritical (α+γ) region, and then quenched in water or oil. All specimens except one oil-quenched condition showed relatively high UTS 700-830 MPa and the continuous yielding(YR～0.6), typical mode of the (ferrite + martensite (bainite)) dual phase microstructure. In contrast, one oil-quenched specimen with the 973 K-20 mm condition, exhibited the discontinuous yielding (YR～0.8), indicating that the microstructure basically consists of ferrite plus pearlite, as well as a relatively low UTS 660 MPa. The degree of deformation really occurring within materials, i.e., strain hardening seems to be enhanced with a decrease in deformation temperature. As the degree of deformation increases, the remaining austenite, not dynamically transformed to fine ferrite, becomes increasingly unstable. A lower hardenability of this remaining austenite thus would lead to a higher possibility to transform into the (ferrite + pearlite) structure of lower strength rather than the (ferrite + martensite (bainite)) of higher strength.
Precipitation of Microalloy Carbo-Nitrides Prior, during and after γ/α Transformation
Authors: Zajac Stanislaw
Published: March 2009

A brief summary is given of the desired effects of precipitation of microalloy nitrides and carbides in austenite and ferrite prior, during and after g−a transformation. Precipitation of microalloy compounds of Nb(C,N), TiC and V(C,N) is discussed in relation to several grain refinement and precipitation strengthening mechanisms. An improved understanding of the thermodynamics and kinetics of precipitation and phase transformations is presented using the approach based on the chemical driving force. Nucleation of intragranular polygonal ferrite on VN particles that grow in austenite and the formation of acicular ferrite inside the austenitic grains in Vsteels is described. The role of carbon in increasing the driving force for nucleation is elucidated and the benefits of using microalloy carbo-nitrides for precipitation strengthening of bainitic steels are reviewed. An expanded view on the role of microalloy carbo-nitrides in grain refinement and precipitation strengthening is presented.
Influence of Vanadium Microaddition on the Microstructure and Mechanical Properties of High Strength Large Diameter Wire-Rods
Authors: Mendizabal L. , Iza-Mendia Amaia , López Beatriz , Rodriguez-Ibabe J.M.
Published: March 2009

This paper analyses the application of vanadium microaddition for the production of high strength 16mm diameter wire-rods. Laboratory trials, simulating industrial cooling conditions after hot rolling, were made in a range between 3 and 8°C/s. The results show that introducing vanadium means that it is possible to optimise chemical composition by reducing elements susceptible to segregation. Besides, high strength values are maintained by means of precipitation hardening. The influence of vanadium microalloying on the crystallographic ferrite unit size was also evaluated.
Effect of Hot Band Grain Size on the Anisotropy of Warm Rolled Low Carbon Steels
Authors: Sánchez-Araiza M. , Godet Stéphane , Jacques Pascal J. , Jonas John J.
Published: March 2009

In warm rolled steels, the intensity of the <111>//ND annealing texture, which favours
formability, has been related to the formation of shear bands during rolling. Coarse hot band grain sizes (HBGS’s) facilitate flow localization, the mechanism associated with the formation of shear bands.In this work, the effect of grain size after hot rolling was studied in a low carbon steel containing small additions of Cr and Mn. The formation of shear bands and their subsequent influence on the normal anisotropy rm and planar anisotropy Dr in the annealed steels were of particular interest. Two HBGS’s (18 and 30mm) were employed and the specimens were warm rolled to reductions of 65 and 80% at various temperatures between 640 and 700°C. The results show that the frequency of shear banding is slightly lower for the smaller grain size. The normal anisotropy was not affected by the HBGS; by contrast, much lower Dr values were associated with the finer grained steel.
Mechanical Properties of Low Young's Modulus Amorphous Carbon Reinforced Aluminum Composites
Authors: Imai Tsunemichi , Dong Shang Li , Shigematsu Ichinori , Saito Naobumi , Suzuki Kazutaka , Osamura Kozo
Published: March 2009

The XN-05C/2017, XN-05C/MESO-10 and BGC152/MESO-10 aluminum composites reinforced by low young’s modulus amorphous carbon fiber and particle, respectively, were fabricated by a PM route followed by hot extrusion and rolling in this study. The mechanical properties of the prepared composites were investigated subsequently. The XN-05C/2017 and XN-05C/MESO-10 were found to exhibit low elastic modulus of 50~60GPa within the fiber volume fraction of 0.10~0.15, while the BGC152/MESO-10 shows a data of 50GPa with a particle volume fraction of 0.10. The tensile strength of XN-05C/MESO-10 was evaluated to be 400~600MPa in the case of Vf=0.10~0.15, and become to decease with increasing fiber volume fraction. Damping application would be a potential consideration for the amorphous carbon fiber reinforced aluminum composites.
Laser-Assisted CMP for Copper Wafer
Authors: Ha Taeho , Kimura Keiichi , Miyoshi Takashi , Takaya Yasuhiro
Published: March 2009

This paper presents a laser-assisted Cu-CMP (Chemical Mechanical Polishing) method for obtaining higher planarized surface by forming laser aggregation particles on recessed areas of uneven copper surface before polishing. At first, the laser trapping of fine particles in slurry and the formation of aggregated marks on the copper wafer surface were investigated by fundamental experiments based on optical radiation pressure. Next, proposed planarization method for uneven surface of copper wafer was attempted. As the polishing processed, the height of aggregated marks was reduced. Then, it was confirmed that the aggregated marks played a role of masks, and no material removal at the bottom surface of recessed areas took place during polishing. This process made it possible to realize high planarity on copper wafer surface.
EB Induced Stress Relaxation of Tight Network Structure in Silica and Soda Glasses
Authors: Nishi Yoshitake , Yamaguchi Naoki , Takahashi Kousuke , Oguri Kazuya , Tonegawa Akira
Published: March 2009

This paper mainly describes that nano-scale surface structure change in dangling bond density related to free volume caused the reinforcement of inorganic glass irradiated by electron beam. Based on the results of electron spin resonance experiments, EB irradiation enhanced the density of dangling bonds at the glass surface. To confirm the strengthening principle, we have employed EB irradiation of inorganic glass. The EB reinforcement was explained as caused by stress relaxation induced by dangling bonds formation in the tight network structure of silica and soda glasses.
Interface Behavior in Liquid Phase Impact Diffusion Welding of Aluminum Matrix Composite
Authors: Niu Ji Tai , Guo Wei , Zhai Jin Fan , Yu Jie , Zhang Bao You
Published: March 2009

In this paper, the interface behavior in Liquid Phase Impact Diffusion Welding (LPIDW) of Aluminum Matrix Composite has been studied. Results show that by LPI diffusion welding, the interface state between reinforcement (SiC particle) and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint. Moreover, dislocation density in both matrix and interface are higher than that of parent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.
Performance of Thick TiN Composite Coating as High Heat Resistant TBC
Authors: Kobayashi Akira
Published: March 2009

Titanium nitride (TiN) coating has excellent properties and has been already used in the various field of industry. But TiN film has problems in the formation process: i.e., low deposition rate and poor thickness of the film. TiN thick coatings can be formed by means of the gas tunnel type plasma reactive spraying in a short time operation. In this study, the fundamental characteristics of this method were investigated by measuring the properties of the titanium nitride (TiN) coatings formed on the traversed stainless steel substrate. Consequently, TiN coatings of 200µm thickness were obtained at P=27kW, within t=5s, and some coating characteristics which depend on the spraying distance, the environmental gas, traverse number etc. were clarified. And the performance of TiN thick composite coating was discussed as a heat resistant TBC.
Formation of Grain Structures of Thermal Sprayed Nickel Coatings and the Coating Properties
Authors: Murakami Kenji
Published: March 2009

Pure nickel powder was low pressure plasma sprayed onto a steel substrate held at different temperatures during spraying. The as-sprayed coatings consist of columnar grains whose axes are nearly perpendicular to the lamellae composing the coatings. As the coating temperature becomes higher, the length of the columnar grains increases and is longer than the thickness of the lamellae, indicating the growth of the grains across the lamellar interfaces during spraying. On the other hand, the coatings that were heat treated after spraying consist of coarse equiaxed grains. The coatings that experienced high temperatures during spraying or the heat treated coatings have large porosity and contain large globular pores. The hardness, apparent density and the tensile strength of the coating itself were the highest for the coating prepared at a low temperature and became low on heat treatment. The thermal conductivity in the direction perpendicular to the coating was the largest for the coating that consisted of long columnar grains.
The Liquidus Surface of the Ternary System Cu-In-Ti
Authors: Berbecaru Adina , Schuster Julius C.
Published: March 2009

The phases occurring upon lead free soldering of copper substrates using indium, which contains for improved wetting additions of Ti, belong to the ternary system Cu-In-Ti. Thus, the liquidus surface of the ternary system Cu-In-Ti is determined using DTA data. Alloys were prepared from high purity metals by arc melting under pure argon. Before measuring the heating curves, all alloys were equilibrated at appropriate temperatures and XRD phase analysis were performed. A reaction scheme linking the phase equilibria found in the annealed alloys to the liquid phase is obtained. A projection of the resulting liquidus surface, which is dominated by the primary crystallisation field of the congruently melting Heusler phase t1-Cu2TiAl, is presented. In the In-rich composition corner the liquid phase solidifies in a ternary eutectic (In) + Ti2In5 + Cu11In9 at 155°C.
Crystal Growth of CdTe by Gradient Freeze in Universal Multizone Crystallizator (UMC)
Authors: Su Ching Hua , Lehoczky Sandor L. , Li Chao , Raghothamachar Balaji , Dudley Michael , Szőke János , Bárczy Pál
Published: March 2009

In this study, crystals of CdTe were grown from melts, which have undergone different thermal history, by the unseeded gradient freeze method using the Universal Multizone Crystallizator (UMC). The effects of melt conditions on the quality of grown crystal were studied by various characterization techniques, including Synchrotron White Beam X-ray Topography (SWBXT), atomic force microscopy (AFM), electrical conductivity and Hall measurements.
Macrosegregation Caused by Deformation of the Mushy Zone
Authors: Nicolli Lilia C. , Martin Christophe L. , Mo Asbjørn , Ludwig Olivier
Published: March 2009

An experimental set-up for investigating macrosegregation formation due to deformation of an isotropic metallic mushy zone is presented. In the experiment, a semisolid Al-5.9wt%Cu sample is isothermally and non-uniformly compressed. Concentration and eutectic fraction are measured along selected lines, after quenching the sample. Results show that interdendritic liquid is pressed out of the central part of the sample to its outer part, increasing the concentration in this region. The experimental test is then addressed by a two-phase continuum model recently presented elsewhere. The modelling results show the same tendencies observed experimentally, although local variations in composition are not well correlated. Suggestions for future work are made.
Solidification of AlSi Alloys in the ARTEMIS and ARTEX Facilities Including Rotating Magnetic Fields – A Combined Experimental and Numerical Analysis
Authors: Hainke Marc , Steinbach Sonja , Dagner Johannes , Ratke Lorenz , Müller Georg
Published: March 2009

The solidification microstructure is the consequence of a wide range of process
parameters, like the growth velocity, the temperature gradient and the composition. Although the influence of these parameters is nowadays considerably well understood, an overall theory of the influence of convection on microstructural features is still lacking. The application of time dependent magnetic fields during directional solidification offers the possibility to create defined
solidification and flow conditions. In this work, we report about solidification experiments in the ARTEMIS and ARTEX facilities including rotating magnetic fields (RMF). The effect of the forced melt flow on microstructural parameters like the primary and secondary dendrite arm spacing is analyzed for a wide range of magnetic field parameters. The experimental analysis is supported by a
rigorous application of numerical modeling. An important issue is hereby the prediction of the resulting macrosegregation, i.e., differences in the composition on the scale of the sample (macroscale) due to the RMF. For the considered configuration and parameters an axial enrichment of Si is found beyond a certain magnetic field strength. The results are compared to available
theories and their applicability is discussed.
Ceramic Particle Dispersion Analysis in LASER Surface Alloying
Authors: Bitay Enikő
Published: March 2009

The present work aims to analyze the dispersion process (path) of the solid particles by moving a spherical particle from the feeding-nozzle outlet till the penetration of the melted surface (by the laser beam) and then its path in the metal bath. In laser surface treatment technologies with injection of hard particles in the melting bath it is necessary for the particles to work against the surface stress to penetrate through the surface of the bath into the melt. The theory shown was used in precalculations for the experiments carried out dispersing carbide particles (WC, TaC, NbC). Powder of particles of all three types were dispersed by means of the Ar carrying gas into an C15 steel melt by CO2laser. Evaluating the results of this process taking into consideration different specific technological parameters (speed of the beam, powder feeding speed) one can conclude that all three carbide types can penetrate into the melt.
Formation of the Microstructure in a Rapid Directionally Solidified Immiscible Alloy
Authors: Zhao Jiu Zhou , Ratke Lorenz
Published: March 2009

A model has been developed by taking into account the common action of the nucleation, the diffusional growth, the collisions and coagulations of the minority phase droplets and the spatial phase segregation to describe the microstructure evolution in an immiscible alloy solidified rapidly under the vertical directional solidification conditions. The model is satisfactorily verified by comparison with an analytically solvable case first, and then applied to predict the microstructure
evolution in a directionally solidified Al-Pb alloy. The numerical results show that at a high solidification velocity a constitutional supercooling region appears in front of the solid/liquid interface and the liquid-liquid decomposition takes place there. A higher solidification velocity leads to a higher nucleation rate for a given temperature gradient and, therefore, a higher number density of the minority phase droplets. As a result, the average radius of droplets in the melt at the solid/liquid interface decreases with the solidification velocity.
Nonequilibrium Kinetics of Phase Boundary Movement in Cellular Automaton Modelling
Authors: Burbelko Andriy A. , Fraś Edward , Kapturkiewicz Wojciech , Olejnik Ewa
Published: March 2009

A mathematical crystallization model in the meso scale (the intermediate dimension scale between interatomic distance in solids and grain size in metals and alloys) is presented with the use of a kinetic-diffusion cellular automaton model. The model considers the non-equilibrium character of real processes of phase transformations, where the kinetic undercooling of the solid-liquid interface is a measure of this non-equilibrium level. Anisotropy of the interface mobility is assumed. The modelling results are compared to the experimental data.
Global Modeling of Directional Solidification of Aluminum Alloys Using the Software Package CrysVUn
Authors: Dagner Johannes , Weiß A. , Hainke Marc , Zimmermann Gerhard , Müller Georg
Published: March 2009

A global numerical model of a Bridgman furnace is developed and validated. The
model includes heat transfer due to radiation and conduction in a stationary setup. The rotating magnetic field (RMF) device mounted on the facility is implemented into the model also. A numerical study on the flow field caused by the axial non-uniform RMF and natural convection is performed, helping to get a better understanding of the convective conditions during the directional solidification experiments.
Approximate Analytical Models for Microsegregation Considering the Effect of Dendrite Arm Coarsening
Authors: Turkeli Altan
Published: March 2009

In this study, simple analytical microsegregation models for constant cooling and parabolic growth are proposed considering dendrite arm coarsening effect with and without back diffusion. These simple models are compared with the Mortensen exact model and Voller’s models. It is shown that these analytical models can be used to predict approximately microsegregation in a binary alloy.
Single Crystal Growth – New Techniques on Old Base
Authors: Bárczy Pál , Szőke János , Su Ching Hua , Lehoczky Sandor L. , Schweizer M. , Volz Martin P. , Szofran F.R.
Published: March 2009

The progress in advanced single crystal growth demands versatile, advanced equipment. Multizone furnaces are able to fulfill unusual technological requirements providing versatile and reliable all-in-one tools for laboratories on the ground or in space. The concept of the Universal Multizone Crystallizator (UMC), its hardware and software components along with several application examples are demonstrated.
Experimental Performance within the SCA Prototype Test 1 Using ESA`s Solidification and Quench Furnace (MSL-SQF) on Ground
Authors: Rex S. , Hecht U. , Drevermann A.
Published: March 2009

The preparation of the solidification experiments planned onboard the ISS within the
SETA research program was supported by a first full test run within the SQF- Solidification and Quench Furnace of the Materials Science Lab (MSL) using an eutectic alloy of the Al-Cu-Ag system as test sample. This first SCA prototype test in the SQF comprises a directional melting, solidification and subsequent quenching of the sample. The test evaluation presented in this paper is limited mainly to the evaluation of the recorded sample temperatures and focuses on the experimental performance in the view of a scientific user of the SQF. The thermal gradient achieved in the sample reaches about 10.6 K/mm and showed a good stability over the pulling length. The position of the solidification interface relative to the middle of the adiabatic zone, however, is shifted considerably towards the cooling zone. The quenching performance reached a starting value of 27 K/s.
Mesh-Free Simulation of Transport Phenomena in Continuous Castings of Aluminium Alloys
Authors: Šarler Božidar , Vertnik Robert
Published: March 2009

This paper introduces a general numerical scheme for solving convective-diffusive problems that appear in the solution of microscopic and macroscopic transport phenomena in continuous castings and the heat treatment of aluminium alloys. The numerical scheme is based on spatial discretisation that involves pointisation only. The solution is based on diffuse collocation with multi-quadric radial basis functions. The application of the method is demonstrated in a simplified model of a billet DC casting and verified by a comparison with the classical finite volume method.
The Effect of Fluid Flow on Heat Transfer and Shell Growth in Continuous Casting of Copper
Authors: Vapalahti Sami , Louhenkilpi Seppo , Räisänen Tuomo
Published: March 2009

Molten metal is cooled in a continuous casting mould forming initially a thin shell that
grows thicker. The main phenomena in the mould are: fluid flow, heat transfer and solidification. A lot of mathematical models have been developed to simulate these phenomenons in continuous casting machines but most of the models developed are not calculating the fluid flow at all. In these models, it is assumed that the strand (solid and liquid) is withdrawn through the machine with a constant velocity field (= casting speed) and the convective heat transfer generated by the fluid flow is taken into account by using an effective thermal conductivity method. Also at the Helsinki University of Technology, these kinds of heat transfer models have been developed (TEMPSIMU for steels and CTEMP3D for coppers). The flow in the mould is three-dimensional and turbulent. Coupled models calculate the fluid flow, heat transfer and solidification simultaneously. The fluid flow is affected by many things: inlet flow rate, design of the inlet nozzle (SEN), immersion depth of the SEN, movement of the solid shell, natural convection, solidification shrinkage, etc. and the fully coupled, turbulent fluid flow and heat transfer models are generally subjected to convergence difficulties and they need a lot of computing time. Due to these reasons, these kinds of models are not so much used in industry so far. In the present study, a commercial FLOW-3D package is used to make coupled simulations of heat transfer, turbulent fluid flow and solidification in a copper continuous casting machine. The effect of thermophysical material data are also studied and presented. The material data are calculated by a model developed at the Helsinki University of Technology, called CASBOA.
Surface Tension Measurements of Industrial Alloys
Authors: Schmidt-Hohagen Frank , Egry Ivan
Published: March 2009

Industrial alloys are generally multi-component systems with volatile and highly reactive components. Consequently, their processing in the liquid state requires special precautions. Therefore, an existing electromagnetic-levitation device with a high-vacuum chamber, designed for surface tension measurements, was modified and improved. For the measurements of the surface tensions with the help of the oscillating drop technique the temperatures and the video sequences of the levitated, molten alloy were recorded without contact by pyrometer and by high-speed camera, respectively. This method yields the frequencies of the surface oscillations of the sample around the equilibrium shape and - using the modified Rayleigh law - eventually the values of the surface tension. With the
help of this method two commercial industrial steels were processed in the new EML-apparatus for ESA`s Thermolab project [1]. The results of these measurements are presented and discussed
Thermodynamic Properties of CMSX-4 Superalloy: Results from the ThermoLab Project
Authors: Palumbo Mauro , Baldissin Daniele , Battezzati Livio , Tassa O. , Wunderlich Rainer , Fecht Hans Jorg , Brooks R. , Mills K.
Published: March 2009

This contribution reports the results of calorimetric measurements of the enthalpy of
fusion and liquid specific heat carried out in different laboratories as part of the ground campaign of the Thermolab project. Different equipments and calibration methods have been used and critically evaluated. Thermodynamic calculations using the Thermocalc software have been performed and a comparison has been carried out with the experimental results.
Phase Equilibria and Solidification of Mg-Rich Al-Mg-Si Alloys
Authors: Valdes R. , Freulon A. , Deschamps J.-B. , Qian Ma , Lacaze Jacques
Published: March 2009

The solidification and solid-state phase equilibria of four Al-Mg-Si alloys containing 30- 70%Mg and 0.5-3.5%Si, selected on the basis of an isothermal section of the Al-Mg-Si system calculated at 300 °C, have been investigated. Solidification paths of Mg-rich Al-Mg-Si alloys finish on ternary eutectics and the temperatures of two of these eutectic reactions, i.e. L↔(Al)+β+ Mg2Si and L↔(Mg)+γ+ Mg2Si, have been determined to be at ~ 448 °C and ~ 436 °C respectively by DTA. The characteristic temperatures recorded on the DTA curves are analysed and a linear relationship is found between the peak temperature and the square root of the scanning rate.
In Situ Deformation at 850°C of Standard and Rafted Microstructures of Nickel Base Superalloys
Authors: Clément Nicole , Benyoucef Mustafa , Legros M. , Caron Pierre , Coujou Armand
Published: March 2009

An in situ study of the plastic deformation of <001> single crystals of an industrial superalloy has been performed at 850 °C in a TEM to observe directly the micromechanisms which control the deformation under the actual temperature and stress conditions experienced by this material in aeroengines. A comparison between the creation and propagation modes of moving dislocations in the standard microstructure after annealing and the rafted microstructure after 20 h of creep at 1050°C evidence the important role of the width of the γ channels as well as the strength of the γ/γ’ interface in controlling the shearing events of γ’ channels.
Compressive Deformation Behaviour of a Closed-Cell Aluminum
Authors: Yamada Yasuo , Banno Takumi , Xie Zhen Kai , Wen Cui E
Published: March 2009

The mechanical properties of a closed-cell aluminium foam were investigated by
compressive tests, and the deformation behaviours of the aluminium foams were studied using Xray microtomography. The results indicate that the deformation of the aluminium foams under compressive loading was localized in narrow continuous deformation bands having widths of order of a cell diameter. The cells in the deformation bands collapsed by a mixed deformation mechanism,
which includes mainly bending and minor buckling and yielding. Different fractions of the three deformation modes led to variations in the peak stress and energy absorption for different foam samples with the same density. It was also found that the cell morphology affects the deformation mechanism significantly, whilst the cell size shows little influence.