bluuebunny/crossref_metadata_2025 huggingface dataset:
Superficial Remelting of Cast Iron by Laser Radiation
Authors: Buza Gábor , Kálazi Zoltán , Kálmán Erika , Sólyom Jenő
Published: March 2009

A rarely applied technology of surface modifications is the remelting of surfaces by
a laser beam. This is so because in the case of laser remelting of surfaces, similarly to other processes used in production, such a competitive alternative surface modification technology is searched for in which the value in use of the component with new properties created by the new procedure is in proportion with the costs and time requirement needed for its production. According to such a point of view, a laser remelting of a surface is in general not worth applying this expensive technology, since the change, the improvement in the properties as a result of remelting is not sufficiently large. However, the laser remelting of cast iron surfaces represents a specific case, since the nature of the surface of this relatively cheap (as compared to cast steel) material of advantageous properties can be changed significantly by this technology. In addition, by the treatment with laser beam, an extraordinarily particular material structure unknown in mass production can be developed. This is why we turned our attention to the specificities and properties of this structure formed during laser beam treatment of cast iron surfaces.
A Comparative Examination of the Friction Coefficient of two Different Sliding Bearing
Authors: Svéda Mária , Roósz András , Buza Gábor , Kuzsella László
Published: March 2009

The aim of this research work is to investigate the sliding properties of the monotectic surface layers developed by a laser surface-treatment technology. The coatings-remelting technology has been chosen from the laser surface treatment methods. The surface of Al-Si alloy was coated with a lead layer by galvanizing, then the basic material and the surface layer were remelted together by using laser beam produced a monotectic Al- Pb surface layer. The structure of monotectic surface layer has been determined by means of a light microscope and scanning electron microscope. The sliding properties of the basic material (as cast, nearly eutectic Al-Si alloy), the Al-Si-Pb monotectic surface layer as well as the Al-Cu-Sn sliding bearing (Al-Cu matrix and Sn sliding layer) used in the gas industry have been investigated.
Dynamic Analysis of Silicone Elastomers
Authors: Huba Antal , Molnár László , Czmerk András , Fischl Tamás
Published: March 2009

The silicone elastomers offer in our days new perspective for the construction in the precision engineering and in the medicine because of their special mechanical, electrical, optical and chemical properties. Since the essential material parameters like storage modulus and loss modulus depend on temperature and frequency explicit it is important for simulations to know these characteristics. This report is about determining of relaxation behaviour of silicone rubbers and about finding the mathematical relation to describe time-temperature equivalence of silicone elastomers. As conclusion we can declare that the common used Williams–Landel-Ferry equation to describe temperature and time dependent behaviour of polymers is not applicable for silicone rubbers.
Studies on Tetrapod-Shaped ZnO Whisker Modified Polymer Composites
Authors: Zhou Zuo Wan , Hu Shuchun , Chu Long Sheng
Published: March 2009

Tetra-needle like ZnO whisker modified NR-SBR-BR and PPS composites were
prepared. The outcome of the investigation indicated that T-ZnO had an instinct effect on reinforcing polymer material isotropically. Further analysis showed that experiment results of T-ZnO/PPS composite gave much higher strength than that of the theoretical calculation from classical rule of mixing, and the explanations were put forward. The experimental tests on wear behavior of the composites of T-ZnO/NR-SBR-BR were carried out and got the conclusion that T-ZnO had a good effect of improving the wear resistance. The worn surfaces of the composites of
T-ZnO/NR-SBR-BR appeared an instinct character of fractal, and the values of both the fractal dimension and the abrasion loss decreased synchronously as the increasing of T-ZnO loading in the composites.
Synthesis of Titanium Dioxide Nanotubes by Ion Exchange Approach
Authors: Wang Ning , Lin Hong , Li Jian Bao , Yang Xiao Zhan , Chi Bo
Published: March 2009

Nanotube-shaped powders had been synthesized successfully from commercial anatasetype titanium dioxide powder by ion exchange approach. All nanotubes were open-ended with 3~5 nm in inner diameter, 8~12 nm in outside diameter and 200~400 nm in length. EDS result revealed that the nanotube was only composed of Ti and O. XPS analysis showed that two peaks located at 458.5 and 464.2 eV were assigned to Ti4+ in titanium dioxide. The formation mechanism of titanium dioxide nanotubes was also discussed in this paper.
Three-Dimensional Simulation of Sintering of Ceramics
Authors: Qin Xiangge , Sun Jianbo , Liu Guo Quan
Published: March 2009

In this paper, we have employed a kinetic Potts model to simulate sintering of ceramics in which grain growth and densification of microstructure are usually concerned about. Grain growth and pore evolution in three-dimension are simulated using the kinetic Potts model. Quantitative information about grain size distribution, density and surface area are also evaluated in evolution of the model. Morphologic changes and densification kinetics are used to verify the model.
Behavior of Oxygen in Fusion Candidate Vanadium Alloys during Oxidation and Annealing
Authors: Yao Zhenyu , Suzuki Akihiro , Nagasaka Takuya , Muroga Takeo
Published: March 2009

A V-4Cr-4Ti alloy and pure V were oxidized in flowing argon for 0.5-8h and
subsequently annealed in vacuum for 16h at 973K. The oxygen of 1000-9000ppm was introduced into the V-alloys with little nitrogen, where oxygen was concentrated in region near the surface. By the annealing, oxygen was homogeneously diffused into depth of 150µm. The diffusion depth of oxygen in V-4Cr-4Ti is much smaller than that of pure V, because of Ti-O precipitates formed as oxygen trap. The study indicated that it is feasible to control oxygen level and distribute in the surface region of the vanadium alloys.
The Damage Mechanisms under Different Fretting Modes of Bonded Molybdenum Disulfide Coating
Authors: Zhu Min Hao , Zhou Zhong Rong
Published: March 2009

Fretting wear tests of bonded MoS2 coating under radial and composite fretting mode have been carried out on a new fretting rig. The maximum applied load was respectively 200N, 400N and 800N with a constant loading speed of 12mm/min. Dynamic analyses in combination with microscopic examinations through SEM and XPS have been performed. Experimental results showed that such MoS2 coating exhibited an excellent radial fretting damage resistance, and its damage strongly depended upon the applied maximum loads and inclined angle under composite fretting condition. The fretting damage mechanism of MoS2 coating also discussed under different fretting modes. The XPS analysis revealed that the oxidation of MoS2 crystal was played an important role in damage. The fretting wear of MoS2 coating was mainly represented by the mechanism of delamination and oxidation wear under composite fretting conditions.
Development of Ti-30 mass% Ta Alloy for Biomedical Applications
Authors: Zhou Ying Long , Niinomi Mitsuo , Akahori Toshikazu , Fukui Hisao
Published: March 2009

In the present study, the effects of Ta content on the dynamic Young’s modulus and tensile properties of Ti−Ta alloys were investigated in order to find a Ti−Ta alloy that gives low modulus and high strength for biomedical applications. For this purpose, the ingots of Ti−Ta alloys with Ta contents from 10 to 50 mass % were melted, and then rolled into the plate of 3 mm thick. All the specimens were solution treated at 1223 K in the b field for 3.6 ks and then quenched in ice water. Subsequently, some of them were aged at 773 K for 259.2 ks followed by a rapid quenching in ice water. The corrosion capacity and biocompatibility of typical Ti−Ta alloy were also evaluated. The experimental results indicate that the Ti−30% Ta alloy has better mechanical biocompatibility, corrosion capacity and cyto-toxicity than Ti−6Al−4V alloy used as a standard biomaterial, and thus it will be of considerable development for biomedical applications.
Alloying Effects on Hydrogen Permeability of Niobium
Authors: Komiya Kenji , Shinzato Y. , Yukawa Hiroshi , Morinaga Masahiko , Yasuda Isamu
Published: March 2009

Niobium metal is one of the promising material for hydrogen purification because of its
high hydrogen permeability. In order to design and develop a new palladium-free hydrogen permeable membrane, it is important to understand the effects of alloying elements on the hydrogen permeability through metals. However, to the niobium metal, the alloying effects still remain unclear. In the present study, using a DC-polarization technique under the diffusion limiting condition, the hydrogen permeability of Nb-5mol%M alloys were investigated in high precision at 573K. Here, M’s were 4d transition metals, Zr, Mo, Ru and Pd. The permeability of niobium is found to be varied with the addition of a small amount of alloying element. For example, the hydrogen permeability of niobium increases by the addition of Zr but decreases by the addition of Ru.
Effect of Filler Wire Composition on the Nd:YAG Laser Weldability of 6061 Aluminum Alloy
Authors: Yoon Jong Won , Lee Young Sup , Lee Kyoung Don , Park Ki Young
Published: March 2009

2 mm thick 6061-T6 aluminum alloy sheets were I square butt welded using 3kW Nd:YAG laser. Filler wires of 1 mm diameter, 5183A(Al-4wt.%Mg), 4043A(Al-5wt.%Si) and 4047A (Al-12wt.%Si) were used. The welds made with 4047A wire showed the lowest solidification cracking among the welds investigated. Abundant amount of Al-12wt.%Si eutectic which was observed at the grain boundaries of the 4047A wire feed welds was closely related with the reduced
solidification cracking susceptibility. Yield and tensile strength, and formability of the welds made with 4047A wire were improved compared to the welds made with other filler wires, which is attributed to the reduced cracking susceptibility in the welds.
Slag Cleaning Processes: A Growing Concern
Authors: Acuna C.M. , Sherrington M.
Published: March 2009

In the last two decades copper metallurgy has faced tough challenges to comply with
environmental regulations and falling copper prices. Although in the last months copper price has increased, still the environmental issue and operation related costs remain and as long as foreseen they will continue to do so. To reduce emissions to the atmosphere and to shorten the converting cycle, most industrial
processes, as well as emerging ones, are aiming at production of high matte grade. However, the increase in oxygen potential required by these processes results in highly oxidised slags with significant copper contents, which require their treatment for copper recovery. Despite the fact that long established slag cleaning processes perform reasonaby well for slags in the range 1.5% - 2.5% in copper, i.e. coexisting matte in the order 60% in copper content, they must be reconsidered when
applying to slags equilibrating with high matte grades and/or white metal. The present study concentrates on the mechanism of copper losses into slags, its association to sulfur and oxygen, mainly, and methods for its recovery. Based on these considerations, high temperature liquid-liquid phase separation, i.e. Teniente type reactor, slag flotation and slag leaching methods technologies are discussed as specially applied in Chilean smelters. Also, a new approach based on material characteristics of both matte and slag, i.e. magnetic separation, is presented.
An Investigation of Cavity Growth Rate in Superplastic Al and Mg Alloys
Authors: Mabuchi Mamoru , Chino Yasumasa , Iwasaki Hajime
Published: March 2009

Fine-grained 5083 Al alloy and AZ91 Mg alloy showed superplastic behavior. The plasticitycontrolled growth rates of cavities during superplastic deformation for the Al alloy and Mg alloy were investigated. The cavity volume fraction for the Mg alloy was larger than that for the Al alloy. However, the cavity growth rate for the Mg alloy was lower than that for the Al alloy.
Evaluation of Wagner Interaction Parameter in Fe-Mn-Si-Nb-Ti-V-C System
Authors: Lee Sang Hwan , Lee Kyung Sub , Lee Kyung Jong
Published: March 2009

The dilute solution model is quite widely used because the chemical potential is more
easily defined than that in the sub-lattice model. In the present study, the thermodynamic model for the Fe-Mn-Si-Nb-Ti-V-C system was conducted by evaluating Wagner interaction parameters. The data used in this work was collected and modified by means of TCFE 2000-database in Thermo-Calc and up-to date references. The relationship of interaction parameters(L) in the sub-lattice model and Wagner interaction parameters in the dilute solution model was derived. The composition dependency of reference state and the higher order interaction parameters of the excess Gibbs energy were considered to evaluate Wagner interaction parameters. The equilibrium compositions of austenite and fractions of phases and the dissolution temperature of precipitates(NbC, VC, and TiC)
were evaluated by the dilute solution model and compared with the results by the sub-lattice model.
Development of Ni-Nb-Ta Metallic Glass Particle Reinforced Al Based Matrix Composites
Authors: Lee Myung Hyun , Kim J.H. , Park J.S. , Kim Won Tae , Kim Do Hyang
Published: March 2009

Metallic glass particle reinforced Al-6.5Si-0.25Mg (wt%) alloy matrix composites have been fabricated using infiltration casting process. The Al-Si-Mg alloy melt infiltrates into the porous Ni-Nb-Ta metallic glass pre-form by applying the pressure. The Ni60Nb20Ta20 metallic glass particles are homogeneously distributed in the matrix. The composite exhibits higher yield strength than the monolithic Al-6.5Si-0.25Mg (wt%) alloy.
Textures and Grain Growth in Nanocrystalline Fe-Ni Alloys
Authors: Seo J.H. , Kim Jong Kweon , Yim T.H. , Park Yong Bum
Published: March 2009

The texture evolution due to grain growth that takes place during annealing was
investigated in nanocrystalline Fe-Ni alloys fabricated by using a continuous electroforming method. In the current materials, grain growth occurred during annealing at much lower temperatures than in conventional coarse-grained counterparts. With regard to the macrotextures, the as-deposited textures
were of fibre-type characterized by strong <100>//ND and weak <111>//ND components, and the occurrence of grain growth resulted in the strong development of the <111>//ND fibre texture with the minor <100>//ND components. It was clarified using orientation imaging microscopy that
abnormal growth of the <111>//ND grains in the early stages of grain growth plays an important role
on the texture evolution. The origin of the abnormal grain growth has been discussed in terms of the
orientation dependence of energy density.
The Fabrication and Performance of CVD Diamond-Based X-Ray Detectors
Authors: Wang S.G. , Sellin P.J. , Zhang Q. , Lu Fan Xiu , Tang Wei Zhong , Lohstroh A.
Published: March 2009

In this study, X-ray detectors with coplanar metal-semiconductor-metal structure, were fabricated employing high quality chemical vapour deposited (CVD) diamond film grown by a direct current arc jet plasma system. In which the electrical contacts with dimension of 25 µm in width with a 25 µm inter-electrode spacing, were patterned on the growth side of the diamond film using lift-off technology. The performance of the fabricated detectors was evaluated by steady-state
X-ray illumination. The photoconductivity of the diamond detectors was found to linearly increase with increase in the X-ray photon flux. This demonstrates that high quality CVD diamond can be used for X-ray detectors.
TiC/a-C Nanocomposite Coatings for Low Friction and Wear Resistance
Authors: Pei Yu Tao , Galvan Damiano , de Hosson Jeff T.M.
Published: March 2009

TiC/a-C:H nanocomposite coatings have been deposited by magnetron sputtering and are composed of 2-5nm TiC nanocrystallites well separated by amorphous hydrocarbon (a-C:H) of about 2nm separation width. A transition from columnar to glassy microstructure has been observed with increasing substrate bias or carbon content. Micro-cracks induced by nanoindentation or wear
tests readily propagate through the column boundaries whereas the coatings without a columnar microstructure show supertough behavior. The nanocomposite coatings exhibit hardness of 5~20 GPa, superior wear resistance and strong self-lubrication effects with a friction coefficient of 0.05 in air and 0.01 in nitrogen under dry sliding against uncoated bearing steel balls. Especially, the transitions from low to ultralow friction or the reverse are repeatedly switchable if the atmosphere is
cycled between ambient air and nitrogen. The lowest wear rate is obtained at high humidity.
Influence of Service Temperature on Grain Growth and Thermal Diffusivity of Nanostructured Thermal Barrier Coating
Authors: Zhou Chungen , Wang Na , Gong Sheng Kai , Xu Hui Bin
Published: March 2009

The as-sprayed zirconia coating had an average grain size of 67 nm. Thermal treatment results showed that the grains of the nanostructured coating grew slightly below 900°C, whereas over 1000°C the gains grew rapidly. The thermal diffusivity of the coating increases with increasing heat-treatment temperatures.
Study of Donor Centres in n-InSb due to the Temperature Annealing
Authors: Sayad Y. , Nouiri A.
Published: March 2009

An increasing of donor centres has been detected in n-InSb when it was submitted to anneal/quench with various annealing temperature (450 °C - 850 °C) and various annealing time (5 - 100 hours). A theoretical study of the kinetics of the conduction conversion of n-InSb at temperature annealing above 250 °C has been made. The present analysis indicates that the donor concentration increases with increasing of annealing time. In order to study this variation and to give a model for donor centres generated, a proposed model based on the simple kinetic is used to fit the variation of donor concentration as a function of annealing time. However, from the best fit of experimental data using the proposed model, the activation energy is determined.
The Growth of Porous Layer on Resistive P-Type Silicon in HF/Ethylene Glycol under Illumination
Authors: Chiboub N. , Bellal F. , Gabouze N. , Sam S.
Published: March 2009

In the present work, a photoelectrochemical etching method had been performed on
resistive p-type Si (100) to eliminate the instability attributed to the high resistivity of substrate comparing to that of electrolyte. The anodization of p-type Si with resistivity ranging from 10 Ωcm to 30 kΩcm was done in HF/ethylene glycol. The resistivity of electrolyte was experimentally determinated by high frequency impedance measurements. As anodization proceeds structures of increasing characteristic size are formed then a steady state is reached, where macropore grow parallel. It shows that pore diameter increases with increasing HF concentration. Whereas, under laser He-Ne irradiation both of nanopores and macropores are observed during the anodization. The nanoporous layer showed to be varying with the light intensity and the anodization time.
The proprieties of the porous silicon were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX).
Preparation and Characterization of Thermoplastic Vulcanizates-Organoclay Nanocomposites
Authors: Herrero B. , Arroyo M. , López-Manchado Miguel A.
Published: March 2009

Thermoplastic vulcanizates nanocomposites based on polypropylene (PP) and ethylene–propylene-diene terpolymer rubber (EPDM) blends reinforced with organoclay modified montmorillonite have been prepared via melt intercalation. The silicate layers of the clay were intercalated and dispersed at a nanometer level in the matrix blends. The nanocomposites exhibit improved mechanical properties, this effect being more evident at high EPDM contents in the blend (above 80%). This behavior is attributed to the fact that the EPDM chains are more easily inserted into the galleries silicate, giving rise to a more intercalated structure as was observed by X-ray diffraction.
Correlationship between Microscopic Observations and Electrochemical Behaviour of Different Kind of Galvanized Steel
Authors: García-Jareño J.J. , Giménez-Romero D. , Vicente F.
Published: March 2009

Zinc anodic dissolution has been studied according to the steel galvanized method by means of the electrochemical impedance spectroscopy (EIS) and microscopic observations. Relevant information on the galvanized method is provided by the analysis of experimental data. The galvanized method has no influence on the kinetics parameters of the zinc anodic dissolution process. The galvanized method only changes the surface texture of the working electrode. Thus, the EIS fitting allows to calculate the fractal dimension of the surface of the working electrode.
Quenching of Luminescence Emission due to a Transient Bonding State of Donor-Acceptor Pairs at High Excitation Levels in GaAlAs Crystals Doped to Compensation
Authors: Zehe A. , Reynoso E. , Ramírez A.
Published: March 2009

A new kind of a bound state has been identified at strong external excitation levels in
semiconductors with high amphoteric doping, which is formed of a close donor-acceptor molecule and a neighboring second donor and/or acceptor. The recombination behavior of such a bound state is best described by AUGER-type transitions, reason for which this state is called an AUGER molecule. We have determined the existence region of such molecules in silicon-doped Ga1-xAlxAs
with respect to excess carrier density and temperature by means of electron-beam excited luminescence spectroscopy at low and medium temperatures. The donor-acceptor pair radiation intensity is affected in a characteristic manner by the existence of the AUGER molecule state at elevated excitation levels and not too low temperatures. A computerized model calculation of corresponding rate coefficients turns out to be in good agreement with experimental results.
Rheology and Heat Treatment of Zirconia Based Gels Synthesized from Sodium Glycozirconate Precursor
Authors: Ksapabutr Bussarin , Gulari Erdogan , Wongkasemjit Sujitra
Published: March 2009

Zirconia based gels were prepared by the sol-gel route using sodium tris(glycozirconate)complex as precursor synthesized directly from the reaction of inexpensive and readily available compounds via the one step method. Rheological technique was used to investigate the sol-gel transition of zirconium based materials at different water/alkoxide ratios and reaction temperatures. The gelation time was determined from the evolution of the storage and loss moduli versus time at
various frequencies using the Winter-Chambon criterion. The effect of an increase of the hydrolysis ratio and /or temperature was an enhancement of the kinetics of crosslink reactions, thus decreasing the gelation time. The variation of the gelation time versus temperature could be described by Arrhenius law. Furthermore, zirconia powders prepared from the thermal treatment at 500°C were analyzed by X-ray diffraction and the BET technique.
A Comparison of Quantum Correction Models for Nanoscale MOS Structures under Inversion Conditions
Authors: Li Yiming
Published: March 2009

Quantum correction model features the correction of the inversion layer charge on different classical transport models in semiconductor device simulation. This approach has successfully been of great interest in the recent years. Considering a metal-oxide-semiconductor (MOS) structure in this paper, the Hänsch, the modified local density approximation (MLDA), the density-gradient (DG), the effective potential (EP), and our models are investigated computationally and compared systematically with the result of the Schrödinger-Poisson (SP) model. In terms of the accuracy for (1) the position of the charge concentration peak, (2) the maximum of the charge concentration, (3)the total inversion charge sheet density, and (4) the average inversion charge depth, these well-established models are examined simultaneously. The DG model requires the solution of a boundary value problem, the EP model overestimates the position of the charge concentration peak and the maximum of the charge concentration, our explicit model demonstrates good accuracy among models.
Computer Calculations of the Thermally-Induced Magnetic and Electronic Properties of the Rare Earth Compounds RERu2Si2
Authors: Michalski Rafal , Radwanski Ryszard J.
Published: March 2009

The aim of this paper is to demonstrate the effectiveness of the calculation method, which takes into consideration the electrostatic ligands field as well as the the magnetic interactions. Our calculations method based on crystal field (CEF) together with the Zeeman effect in one Hamiltonian and allows calculating many of the temperature dependencies of the magnetic and electronic properties of the rare earth compounds. The result of the calculations shows the accuracy of the approach even for the intermetallic compounds. The obtained results for calculations of the compounds of the family in RERu2Si2 (RE – rare-earth element) are fully confirmed the experimental data such as: the easy magnetic direction of all the analyzed compounds, the thermal dependencies of magnetic properties; in particular the giant magnetocrystalline anisotropy of PrRu2S2 with the calculated anisotropy field BA>400T, in-plain anisotropy of ErRu2Si2, the cause of difficulty in magnetic ordering of compounds TmRu2Si2 and YbRu2Si2 as well as effects and dependencies not foreseen before. In this paper we have put together the elementary calculated magnetic properties for the chosen compounds of RERu2Si2 in the paramagnetic region. All Calculations are on the basis of the calculating computer package BIREC 1.51.
Design and Manufacturing Process of Skull Defect Prosthesis
Authors: Szakal Z. , Zsoldos Ibolya , Csernátony Z.
Published: March 2009

We want to help to the technical preparation of the implantation of individual prosthesis by using the newest means of computer aided manufacturing.
There are such cases when the factory-made implantations available are not suitable to replace the missing bone or joint. We have solved the replacement of an osteal skull defect with the Rapid Prototyping method in this paper. The advanced techniques has assured greater accuracy and simpler operative-technique in this case.
Synthesis of Crystalline Carbon Nitride by Microwave Plasma Chemical Vapor Deposition
Authors: Jiang Jin Chun , Cheng Wen Juan , Zhang Yang , Zhu He Sun , Shen De Zhong
Published: March 2009

Carbon nitride films were grown on Si substrates by a microwave plasma chemical vapor deposition method, using mixture of N2, CH4 and H2 as precursor. Scanning electron microscopy shows that the films consisted of a large number of hexagonal crystallites. The dimension of the largest crystallite is about 3 µm. The X-ray photoelectron spectroscopy suggests that nitrogen and carbon in the films are bonded through hybridized sp2 and sp3 configurations. The X-ray diffraction
pattern indicates that the major part of the films is composed of α-, β-, pseudocubic C3N4 and graphitic C3N4. The Raman peaks match well with the calculated Raman frequencies of α- and β-C3N4, revealing the formation of the α- and β-C3N4 phase.
Identification and Modelling of the Behaviour of a Duplex Stainless Steel by Methods of Scale Changing
Authors: Degallaix Suzanne , Jaupitre Florence , Kondo Djimedo , Quaegebeur Philippe , Forget Pierre
Published: March 2009

In order to model the mechanical behaviour of an austenitic-ferritic duplex stainless steel thanks to "composite" micromechanical non-linear models, its microstructure was analysed and the mechanical behaviour of each phase was characterised. The microstructural morphology of this steel was studied by selective dissolution of the austenitic phase. The microstructure consists of unconnected austenite islands dispersed in a ferritic matrix. Nano-indentation tests were carried out on each phase. These tests allowed to obtain the hardness and the Young modulus of each phase. A non-linear homogenization approach (secant and incremental formulations) was implemented and the results were compared to the monotonous macroscopic tensile tests carried out at constant strain rate. It allowed us to evaluate the relevance of the non-linear homogeneization models for the
description of the elasto-plastic behaviour of the studied duplex stainless steel.
Analysis of Fracture Morphology and Local Loading Modes in Torsional Fatigue
Authors: Slámečka Karel , Pokluda Jaroslav
Published: March 2009

The paper deals with a profile analysis of the fracture surface generated by pure cyclic torsion. Roughness and fractal characteristics studied in two mutually perpendicular directions were found to be sensitive to the crack front position. The investigation of surface topography revealed the presence of the opening Mode I in all investigated crack front locations.
Elastic Properties of Structural Phases in Shape Memory Alloys Investigated by Resonant Ultrasound Spectroscopy
Authors: Landa Michal , Novák Václav , Sedlák Petr , Mañosa Lluís , Sittner Petr
Published: March 2009

Elastic constants of solids were, until recently, evaluated predominantly by pulse-echo ultrasonic methods which are based on measuring the speed of ultrasonic waves propagation in solids. Resonant ultrasound spectroscopy (RUS) is a relatively novel method in which all components of elastic tensor are determined from measured resonance frequencies of a freely vibrating specimen. The RUS technique has been employed in this work to investigate temperature dependence of the elastic properties of the parent austenite phase in CuAlNi shape memory alloy single crystals. This phase exhibits very high elastic anisotropy (anisotropy factor A 12) and softening the shear coefficient C0 upon cooling when approaching the Ms transformation temperature. The complications (need for large number of resonant frequencies) emerging when one tries to determine all elastic constants of highly elastically anisotropic materials by the RUS technique are discussed. It is concluded that the shear coefficients C0 and C44, which are the most important
for shape memory alloys, are, nevertheless, determined reliably.
Influence of Temperature on Fracture Mechanisms of Magnesium Composites
Authors: Gärtnerová Viera , Chalupová M. , Jäger Aleš , Trojanová Zuzanka
Published: March 2009

Magnesium alloy AZ91 (9 % Al, 1 % Zn, 0.2 % Mn in wt.%) with different
reinforcements has been used to study fracture mechanisms and crack development. SiC particles and /or Saffil fibres were used as the reinforcement. Fracture surfaces of specimens prepared by impact tests in the temperature range from room temperature to 300 °C were investigated by scanning electron microscope (SEM). Possible mechanisms of fracture are discussed in the relation
to the test temperature.
Atomic Force Microscopy Study of the Early Fatigue Damage
Authors: Polák Jaroslav , Man Jiří , Obrtlík Karel
Published: March 2009

The possibilities of atomic force microscopy in studying surface features and early
fatigue damage in materials are reviewed. Examples of a true relief arising on the surface of cyclically strained materials as recorded by atomic force microscopy are given. Characteristic features of the surface relief are well-defined persistent slip markings consisting of extrusions and intrusions. The shape of extrusions and intrusions can be obtained by observation of metal surface and replicas and in combination with high resolution scanning electron microscopy. The growth of
extrusions during fatigue life is reported for austenitic and ferritic stainless steels. The experimental data are compared with models of the localized cyclic plastic straining and predictions of the fatigue crack nucleation models.
Electrical and Thermal Properties of Carbon-Coated Porous Ceramic Fiber Composites
Authors: Yu Jun Suh , Park Sung , Lee Jae Chun , Hahn In Sup , Woo Sang Kuk
Published: March 2009

Porous ceramic fiber composites were coated with pyrolytic carbon by the decomposition of propane in a nitrogen atmosphere at 900°C. The amount of carbon coating was varied through adjusting deposition time to tailor the electrical conductivity of the carbon-coated composites. The electrical and thermal conductivity of the composites were measured at room temperature using a
two-point method and a hot-wire method, respectively. Up to 7 wt% pyrolytic carbon, the electrical conductivity σ is linearly increased to 0.02 S/cm and well fitted by the effective conductivity according to the parallel rule of a mixture σ eff = Σ Χ i ·σ i with a conductivity of pyrolytic carbon σ c= 20 S/cm .The thermal conductivity of the uncoated and coated composites is in the range 0.065-0.075 W/mK and little affected by carbon coating presumably owing to the small amount of coated carbon in this work.
Sound Absorbing Properties of Foamed Glasses
Authors: Cho Hae Yong , Choi Chang Ha , Kim Jin Young , Choi Dae Ho , Lee Soo Wohn
Published: March 2009

“Glass wool” and “rock wool” had been used as sound absorbing materials over several decades because they have excellent sound absorbing properties as well as being very productive and economical. Unfortunately, they were found to be toxic because of flying glass whiskers. To replace glass wool and rock wool as the sound absorbing panels, the recycled glass powders with zeolite and Na2SiO were foamed, adding foaming agents such as NaOH and CaCO3 at different foaming temperatures and time in an electrical furnace. Recycled glass powders from crushed passenger car window were heated up to 720°C in an electrical furnace for an optimal foaming condition. The compressive strength of the foamed glasses was measured using a dynamic materials tester. On the basis of microstructure observation of the foamed glasses, the excellent sound absorbing materials was tried to be fabricated by measuring the sound absorbing coefficient of the foamed glass materials by adding various amounts of NaOH and water.
Particle-Stimulated Nucleation of Dynamic Recrystallization in AZ31 Alloy at Elevated Temperatures
Authors: Jiang Lan , Huang Guang Jie , Godet Stéphane , Jonas John J. , Luo Alan A.
Published: March 2009

Particle-stimulated nucleation (PSN) was investigated in magnesium alloy AZ31 to study the effect of the evolution of second-phases during extrusion and other metal forming processes. Compression tests were carried out on samples taken from coarse-grained as-cast magnesium alloy billets containing a lamellar Mg17All2 eutectic phase and (Al, Mn) particles. These revealed that particle-stimulated DRX nucleation (PSN) was taking place during hot deformation and that this is facilitated by the fragmentation of the Mg17All2. When Mg17All2 dissolves into the matrix at about 350°C, the (Al, Mn) particles remain effective in producing PSN at temperatures up to at least 400°C. This suggests that alloy design leading to a suitable distribution of second-phase particles can improve the properties and formability of wrought magnesium alloys.
Newly Developed Heat Resistant Magnesium Alloy by Thixomolding®
Authors: Tsukeda Tadayoshi , Saito Ken , Suzuki Mayumi , Koike Junichi , Maruyama Kouichi
Published: March 2009

We compared the newly developed heat resistant magnesium alloy with conventional ones by Thixomolding® and aluminum alloy by die casting. Tensile properties at elevated temperatures of AXEJ6310 were equal to those of ADC12. In particular, elongation tendency of AXEJ6310 at higher temperature was better than those of the other alloys. Creep resistance of AXEJ6310 was larger than that of AE42 by almost 3 orders and smaller than that of ADC12 by almost 2 orders of magnitude. Fatigue limits at room temperature and 423K of AXEJ6310 was superior among conventional
magnesium alloys.
Variations of Solute Concentration in the Crucible during Hot Chamber Die-Casting Process
Authors: Kang Min Cheol , Ye Dea Hee , Kim Kyung Hyun , Sohn Keun Yong
Published: March 2009

Compositional variations of magnesium alloys AZ91D and AM60B in a crucible during
hot-chamber die casting process have been investigated. The sampling of molten metal for chemical composition analysis was carried out at three positions (A: bottom, B and C: 100 and 300 mm upside from the bottom, respectively) within a crucible of 600 mm in depth. The picked molten metal was poured into a steel mold to cast into a rod 40mm diameter and 120mm length. Results show that heavier elements such as Al, Zn, Mn, Fe, etc. were concentrated at the bottom of crucible,
which is resulted from long-time, repeated casting operations without bailing out. The macro segregation of alloying elements and impurities are partly caused by the reaction between the alloying elements. Short-periods of holding time up to 250 minutes, however, did not significantly change the concentration of Al and Zn at the entrance of gooseneck.
Grain Refinement in Magnesium Alloy AZ31 during Multidirectional Forging under Decreasing Temperature Conditions
Authors: Xing Jie , Yang Xu Yue , Miura Hiromi , Sakai Taku
Published: March 2009

Grain refinement in a magnesium alloy AZ31 was studied in multi-directional forging
(MDF) at a strain rate of 3×10-3s-1 with decreasing temperature from 623K to 423K. The MDF was carried out up to large cumulative strains with changing the loading direction during decreasing temperature from pass to pass. The structural changes were characterized by generation of many mutually crossing kink bands at low strains, followed by development of very fine grains at large strains. The results showed that MDF with decreasing temperature can accelerate uniform generation
of much finer grains, resulting in the minimal grain size of 0.36µm in a cumulative strain of 4.8 at 423K. The mechanism of grain refinement was discussed.
A Study on the Pretreatment of Direct Electroless Nickel Plating on Magnesium Alloys AZ91D
Authors: Song Yong Wei , Shan Da Yong , Han En-Hou
Published: March 2009

Magnesium alloys are considered as “difficult to plate” metal. The pretreatment
processes play a key role for plating. The pretreatments of alkaline cleaning, chromic acid etching and hydrofluoric acid activating were carried out and the microstructures investigated by SEM and EDAX in detail. The hydrofluoric acid activating time of 8 minutes was determined by Potential-Time curve. The experimental results showed that the alkaline cleaning moved the grease and oils off the substrate surface, but there was no apparent surface morphology change. The
chromic acid etching was a very critical step, and the optimum etching time of 1 minute was chosen; the eutectic α was severely etched, and the chromic compounds were mainly formed on the surface. During the hydrofluoric acid activating, the white activating product of magnesium fluoride was preferentially generated on the β–phase, and obvious morphology change has been observed on the alloy substrate surface.
Properties of Cu-W Functionally Graded Materials Produced by Segregation and Infiltration
Authors: Janković Ilić D. , Fiscina J. , González-Oliver C.J.R. , Mücklich F.
Published: March 2009

The Cu/W functionally graded material (FGM) was produced by vibration of W
agglomerates in order to obtain the W skeleton with a gradient in porosity, which after pressureless sintering was infiltrated with molten Cu. Certain sintering mechanisms are suggested for these complex W structures. The segregation of two different sizes of W agglomerates was controlled by vibration time. Different vibration duration resulted in different types of microstructure: skeleton type microstructure after shorter vibration time and graded type microstructure after extended vibration times. The final Cu-infiltrated FGMs were characterized microstructurally and their
electrical resistivity (r) was measured using the 4-probe technique. The values of r were in between those for pure W and Cu, depending strongly on the vibration times of the initial W agglomerates, and exhibiting particular r vs. T (K) behavior.
Densification of Step-Graded Al2O3-Al2O3/ZrO2 Composites
Authors: Novak Saša , Beranič Klopčič Sabina
Published: March 2009

The preparation of functionally graded materials requires specially adapted shaping techniques and special attention need to be paid to changes in the amount of shrinkage through the cross-section of the graded material during sintering, to avoid high residual stresses leading to crack formation. In this work we report on the results of investigations of FGMs of Al2O3, ZrO2 and ZTA and their densification as a function of the starting suspensions’ properties (alumina/zirconia ratio, solids content and dispersion state), with the aim of compensating for the different amount of sintering shrinkage of the outer and inner materials in step-graded Al2O3-ZTA composites. The sintering studies revealed that the green density and hence the densification of the slip-cast ceramic parts are almost independent on the solids content, while significant effect was observed for dispersion state of the suspensions. Hence, different amounts of total sintering shrinkage in stepgraded Al2O3-ZTA may be achieved by modification of the zeta-potential by adjusting the pH of well-dispersed suspensions.
Micro-Arc Nitriding of Titanium Surface
Authors: Matsuura Kiyotaka , Arita Hiroshi , Ohmi Tatsuya , Kudoh Masayuki , Miyamoto Yoshinari
Published: March 2009

When a surface of a titanium disk was melted in an atmosphere of pure nitrogen using a 3D Micro Welder which was designed by the present authors, the surface was nitrided to a depth of 90 to 260μm depending on the arc current of 6 to 24 A. The concentration of nitrogen in the nitrided layer was approximately 50 mol% at the surface, and the concentration decreased as the distance from the surface increased. A TiN layer was formed at the surface, and beneath the TiN layer, a dual phase layer of TiN and α-Ti was formed. Vickers hardness was approximately 1800 in the TiN layer and it varied from 900 to 200 in the dual phase layer as the distance from the surface increased.
Optimization of Material Composition of FGM Coating under Steady Heat Flux Loading by Micro-Genetic Algorithms
Authors: Wang Jian Ping , Chen Gang , Zhai Peng Cheng
Published: March 2009

This paper studies the optimization problem of composition distribution of functionally
graded material (FGM) coating subjected to steady heat flux loading. The investigation object of the paper is an infinite plate substrate with FGM coating in the surface. The materials are heated at the ceramic surface (upside) with a steady high-intensity heat flux input, and cooled at the metal surface (underside) with flowing liquid nitrogen. The thermal stress distribution and the temperature distribution are obtained by formulation. For optimization, the design variables are the thickness of each interlayer and the volume fraction distribution of the coating. The objective function is the danger coefficient and the restricted condition is the total thickness of FGM plate and heat insulation coefficient. In the paper, three different optimization schemes are considered and compared. The µGA and related parameters are discussed in detail. Optimizing the thermal stress distribution and
minimizing the danger coefficient are carried out by µGA. The optimization results of composition distribution are gained, and the results show the optimum composition distribution can distinctly reduce the danger coefficient.
Polyimide Surface Modification by Low Energy Ion Beam Irradiation
Authors: Lee Won Jun , Lee Youn Seoung , Rha Sa Kyun , Lim Kwang Yong , Lee Hee Soo , Whang Chung Nam
Published: March 2009

The surface modification of polyimide (PI) by the irradiation of 3 keV He+, Ne+ and Ar+ ions was studied using XPS and AFM at various ion dose ranging from 1􀂯1014 to 1􀂯1017 ions/cm2. The change of surface roughness of PI by 3 keV inert ions was closely connected to the change of surface composition. At low doses below 5􀂯1015 ions/cm2, the surface of polyimide was carbonized by ion irradiations, showing rough surfaces. At higher ion doses, the surface composition was saturated due to the accumulation of damages, and the surface morphology became smoother as compared with the low dose case.
Layered Boron Carbide-Aluminum Composites with Large Changes in Microstructure
Authors: Kim Hyun Jun , Trumble Kevin P. , Bowman Keith J.
Published: March 2009

Melt infiltration of preforms prepared by sequential centrifugal casting and by tape
casting and lamination has been accomplished using a short-time infiltration process that significantly suppresses reaction product formation. For layered materials produced via infiltration of laminated ceramic tapes, of particular interest is the effect that a large change in microstructure has on infiltration, phase formation and mechanical properties.
Technology of Low Cost Production of FGMs
Authors: Kisara Katsuto , Niino Masayuki , Noguchi Hironori
Published: March 2009

In this paper, we introduced research and development of technology of low cost
production of FGMs. This research is designated for development of mass production technology for production of ceramic wares with induction heating (IH) function. Slurry lamination method has advantage in forming graded layers due to its simplicity and easiness. However, this method has a disadvantage to generate cracks during drying process. Therefore, freeze-dry in vacuum was introduced in drying process of slurry lamination. By doing so, mass production could be achieved.
In this trial production, we adopted SPS sintering method to production technique. In the future, we will further develop other applications of FGMs into industrial products.
Lattice Parameters of Gd-Doped Ceria Electrolytes
Authors: Matović B. , Bošković Snezana , Živković Ljiljana , Vlajić M.D. , Krstić Vladimir D.
Published: March 2009

This paper deals with Gd-doped ceria solid solutions: Ce1−XGdXO2−d with "x" ranging from 0 to 0.2. Four different powders were synthesized by modified glycine nitrate procedure with very precise stoichiometry according to tailored composition. The method was modified by decreasing glycine/nitrate ratio to 0.5. All obtained solid solutions exhibit a fluorite-type crystal structure with composition dependent lattice parameters. The variation of the lattice parameter was studied and correlated with the equation describing the ion-packing model. It has been found that the change of lattice parameter versus Gd concentration obeys Vegard's rule very well. Results also show that all powders are nanometric in size. The average size of Ce1−XGdXO2−d particles is about 20 nm.
Thermogravimetric Analysis of Superabsorbing Polyacrylic Hydrogel
Authors: Janković B. , Adnadjević B. , Jovanović J. , Minić D. , Kolar-Anić Lj.
Published: March 2009

The thermogravimetric analysis of superabsorbing polyacrylic hydrogel dehydration,
performed under non-isothermal conditions at different heating rates was discussed. Particularly, the influence of the heating rate on the obtained results is given in detail. For this purpose the Weibull distribution function was applied. The thermogravimetric curve when the heating rate tends to zero was evaluated. The activation energy E = 63 kJ/mol, pre-exponential factor A = 2.97 × 108 min−1, and rate constant k = 2.76 × 10−3 min−1 were determined on the basis of this curve.