bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Tests to Study Feasibility and Formability in Incremental Forming Process
Authors: Aldo Attanasio , Ceretti Elisabetta , Fiorentino Antonio , Mazzoni Luca , Giardini Claudio
Published: March 2009

This paper deals with Incremental Sheet Forming (ISF), a sheet metal forming process, that knew a wide development in the last years. It consists of a simple hemispherical tool that, moving along a defined path by means of either a CNC machine or a robot or a self designed device, locally deforms a metal sheet. A lot of experimental and simulative researches have been conducted in this field with different aims: to study the sheet formability and part feasibility as a function of the process parameters; to define models able to forecast the final sheet thickness as a function of the drawing angle and tool path strategy; to understand how the sheet deforms and how formability limits can be defined. Nowadays, a lot of these topics are still open. In this paper, the results obtained from an experimental campaign performed to study sheet formability and final part feasibility are reported. The ISF tests were conducted deforming FeP04 deep drawing steel sheet 0.8 mm thick and analyzing the influence of the tool path strategy and of the adopted ISF technique (Single Point Incremental Forming Vs. Two Points Incremental Forming). The part feasibility and formability were evaluated considering final sheet thickness, geometrical errors of the final part, maximum wall angle and depth at which the sheet breaks. Moreover, process forces measurements were carried out by means of a specific device developed by the Authors, allowing to obtain important information about the load acting on the deforming device and necessary for deforming sheet.
An Improved Two-Dimensional Constitutive Law for Shape Memory Alloys
Authors: Wang Wei , Yan Shi , Song Gang Bing , Jiao Li
Published: March 2009

An improved two-dimensional constitutive model for shape memory alloys (SMAs), which can describe both the shape memory effect (SME) and super elasticity effect (SE) of the SMAs, is developed in the paper based on the previous work of Boyd and Lagoudas, who used the thermodynamics theories of free energy and dissipation energy to derive the constitutive law of the SMAs. The improved model, which will combine the ideas of Brinsion’s one-dimensional constitutive law and the concepts of Boyd and Lagoudas’ two-dimensional one, has a simple but accurate expression. Two examples are used to numerically validate the efficiency of the improved model and the results of the simulations show that the developed constitutive model can qualitatively describe the thermo-mechanical behaviors of two-dimensional SMAs.
The Effects of Thickness on the Formability of 2000 and 7000 Series High Strength Aluminum Alloys
Authors: Zadpoor A.A. , Sinke J. , Benedictus R.
Published: March 2009

This paper studies the effects of sheet thickness on the forming limits of high strength aluminum alloys commonly used in the aircraft industry. The selected materials are 2024-T3 and 7075-T6 representing 2000 and 7000 series aluminum alloys. Two sets of experiments are carried out to identify the effects of sheet thickness on the forming behavior of the selected alloys. The first set of the experiments is tensile testing. The tensile properties of sheets with different thickness and different materials including the plasticity parameters are determined in the first set of experiments. The second set of the experiments is air bending. The minimum bending radius of the different series of materials is determined in the second set of experiments. The results of the tensile testing and air bending are studied both separately and in comparison with each other to identify the trends and to understand the mechanisms governing the observed trends. It is shown that the behavior of the studied alloys is to some extent different from the behavior of more ductile aluminum alloys and mild steels.
Material Behaviour Modelling for Finite Element Vehicle Crash Simulation
Authors: Rabbani Khawar , Daniels Mike , Walker Neil , Shirvani Bez
Published: March 2009

Vehicle safety has increasingly become an economical factor for vehicle manufacturers and this has become most apparent in car safety [1-4]. Manufacturers are now spending considerable resources on safety research. Government requirements on safety have compelled manufacturers to carry out considerable number of crash tests to validate the safety of their cars [6-7]. The data from these tests is important in the development of simulation models employing finite element (FE) software. Many companies predict crashworthiness using commercially available software such as PAMCARSH and LS-DYNA. These simulations are based on mathematical constitutive equations and hence any simulation created is only as representative as the constitutive equations used.
This project has studied the reliability of the material models used by LS-DYNA. Material models selected for analysis are used extensively by impact simulations software and were namely: Power Law Plasticity and Cowper/Symonds. Piecewise Linear Plasticity was also selected because it is based on a true stress/strain and is expected that the simulation would be representative. The models were developed using Belytschko-Lin-Tsay shell elements and were compared with experimental tests employing uni-axial tension strips carried out on three materials – aluminium, high strength steel and mild steel. The tests were carried out using a DARTEC tensile testing machine (up to strain rate of 2.0s-1) at UCE in Birmingham. Testing for the higher strain rates (aluminium up to 269.1s-1, mild steel up to 460s-1, and high strength steel up to 456.9s-1), were carried out at The Royal Military College, Shrivenham using a ROSAND tester.
Aluminium Alloy Self-Pierce Riveting for Joining of Aluminium Alloy Sheets
Authors: Abe Y. , Kato T. , Mori Kenichiro
Published: March 2009

To simplify the recycling of automobiles, aluminium alloy sheets were joined by means of a self-piercing rivet. Although steel rivets used in conventional self-pierce riveting are removed from the aluminium alloy sheets in recycling, the removal is not required for aluminium alloy rivets. The joined sheets with the rivets are directly melted due to the same material, aluminium. For the joining of aluminium alloy sheet by the aluminium rivets, the joinability was improved by the designed shape of the rivet and die. To pierce the upper sheet, the diameter and edge angle of the rivet are modified. The diameter of the depth and the cavity of the die were also designed from trial and error using finite element simulation. The effectiveness of the designed rivet and die were evaluated from an experiment on riveting. The aluminium alloy sheets were joined by the optimised aluminium alloy self-piercing rivet and their effectiveness measured.
The Microstructure of Mechanically Alloyed Nanocrystalline Aluminium-Magnesium
Authors: Gubicza Jenő , Kassem Magdy , Ungár Tamás
Published: March 2009

The effect of the nominal Mg content and the milling time on the microstructure of mechanically alloyed Al(Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. Magnesium gradually goes into solid solution during ball milling and after 3 h almost all of the Mg atoms are soluted into the Al matrix. With increasing milling time the Mg content in solid solution, the dislocation density as well as the hardness are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for a long milling period the dislocation density slightly decreases together with a slight reduction of the hardness.
Applicability of the Crystallite Group Method to Fibre Textured Specimens
Authors: Welzel U. , Mittemeijer Eric Jan
Published: March 2009

The so-called crystallite group (CGM) method, employed for diffraction stress analysis, involves that a possibly complex texture is approximated by a set of one or a few so-called ideal orientations. It has been shown that this approximation can lead to pronounced errors in the determined stress values. The range of applicability of the CGM has been investigated from a
theoretical point of view. Numerical simulations of diffraction strain measurements have been performed using orientation distribution functions representing textures of different strength and sharpness. Special emphasis has been put on the fibre-textured case.
Flattening Problem of Thermal Sprayed Particles
Authors: Fukumoto Masahiro , Tanaka Yasunori , Nishioka E.
Published: March 2009

Effect of both substrate temperature and ambient pressure on a flattening behavior of
thermal sprayed particles was systematically investigated. In the flattening of the sprayed particles
onto the flat substrate surface, critical conditions were recognized both in the substrate temperature
and the ambient pressure. That is, the flattening behavior changed transitionally on the critical
temperature and pressure range, respectively. A transition temperature, Tt, and a transition pressure,
Pt, for those critical conditions were defined and introduced, respectively. Equivalence in the
dependence both of transition temperature and transition pressure on the sprayed materials order
indicated that the wetting of the substrate by the molten particle is a common domination in the
flattening. Three dimensional transition map by combining both transition behavior in the flattening
was proposed as a controlling principle for the thermal spray process
Transformation Behavior of a Ti-Ni-Cu-Fe Alloy
Authors: Nam Tae Hyun , Kim Tae Yeon , Kim Ji Soon , Kang Seung Baik
Published: March 2009

Transformation behavior of a Ti-43.0Ni-5.0Cu-2.0Fe(at%) alloy has been investigated by means of electrical resistivity measurement, differential scanning calorimetry and X-ray diffraction. The alloy transformed in three-stage during each cooling and heating procedure. That is, the B2-R-B19-B19' on cooling and the B19'-B19-R-B2 on heating.
Self-Propagating High-Temperature Synthesis of Aluminum Nitride and its Characterization
Authors: Lee Jae Ryeong , Lee Ikkyu , Kim Dong Jin , Ahn Yang Kyu , Chung Hun Saeng
Published: March 2009

Aluminum nitride was synthesized by self-propagating high-temperature synthesis (SHS) with flaky aluminum powder in various conditions such as particle size, nitrogen pressure (PN 2), dilution factor f( Dil</sub), packing density, and bulk sample size. AlN content in the SHS product increases with an increase of fDil, and it eventually reaches about 95 % at fDil=0.6. Generally, reaction front velocity is significantly affected by PN2 and packing density, but not by fDil. The degree of AlN conversion reduces more or less with an increase of bulk sample size, but that could
be improved by using the SHS pre-prepared product as a diluent.
Role of Unstable Chemical Species (Non-Graphitic Carbon and Flowing NH3 Gas) on the Equilibrium Point of the Reaction Product (Carbide, Carbo-Nitride or Nitride)
Authors: Shohoji Nobumitsu
Published: March 2009

Elementary carbon in solid state might exist in variety of allotropic forms including graphite, diamond and amorphous carbon. Among them, graphite is in the stable form with chemical carbon activity a(C) = 1 whereas diamond is in meta-stable state and amorphous carbon is in un-stable state with a(C) higher than 1. Experimental evidences showed that carbide and carbo-nitride being in equilibrium with carbon possessing a(C) higher than 1 was with higher C content than the corresponding ones in equilibrium with graphite. In case of gaseous ammonia NH3, higher nitrogen activity a(N)and higher hydrogen activity a(H) than the ones corresponding to the equilibrium partial pressure levels, p(N2) and p(H2), might be gained by suppressing its dissociation to a level away from the equilibrium state for the given temperature T by flowing. Thus, under flowing NH3gas, nitride or carbo-nitride with N content higher than that in equilibrium with N2gas at p(N2) anticipated from the dissociation equilibrium at the given T might be obtained. Chronological development of this line of work started by Prof. Masahiro Katsura in early seventies at Osaka University is reviewed in this paper as I was one of collaborators involved in this very exciting research work from the early stage of its development.
Processing Technique for Wear Resistance Parts Using Ultra Fine Particles Reinforced Si3N4
Authors: Osumi Kazuo , Kita Hideki , Iizuka Tateoki , Hirai Takene
Published: March 2009

In this study, we developed silicon nitride with low friction, low wear and high strength for wear resistance parts. And this work is to study the basic synthetic process for ultra fine particles reinforced silicon nitride composites and the fabrication processes of wear resistance parts. The following results were obtained: 1) The basic synthetic and fabrication process for wear parts were
almost established, 2) In engine durability test, it has confirmed that the wear resistance could be improved by using developed silicon nitride.
Mechanical Alloying Effect of Hematite and Graphite
Authors: Lee Chung Hyo , Lee S.H. , Chun S.Y. , Lee Sang J. , Kim Joo Sun
Published: March 2009

The mechanochemical reaction of hematite with graphite by mechanical alloying
(MA) has been investigated at room temperature. The solid state reduction of hematite to Fe3O4 and FeO has been observed after 120 hours of MA by a planetary ball mill. Saturation magnetization is gradually increased with milling time up to 80 h, and then deceased after 120 h of MA, indicating the transformation of Fe3O4 into nonmagnetic FeO through further reduction. Neither the solid state reduction of Fe2O3 by graphite nor a sizable grain refinement is observed in the MA process using a horizontal ball mill.
Serration Phenomenon in High Purity Chromium
Authors: Harada Y. , Ohmori M. , Wang Lei
Published: March 2009

Serration phenomenon of sintered and cast chromium was investigated by means of
tension test at various strain rates. With increasing test temperature, tensile strength decreased gradually at first and showed a minimum at a certain temperature. Above this temperature, the strength continued to increase to a maximum value. Serrated flow appeared between the temperatures of the minimum and maximum tensile strengths. Tensile ductility minimum was also observed around the temperature of the maximum tensile strength. Relation between the strain rate and the temperature T of the maximum tensile strength could be well described by an Arrhenius equation. Activation energy of 101.3kJ/mol found in the present study is in good agreement with the activation energy for diffusion of nitrogen atom in chromium.
Synthesis of CuInSe2 and CuInGaSe2 Nanoparticles by Solvothermal Route
Authors: Kim Ki Hyun , Chun Young Gab , Park Byung Ok , Yoon Kyung Hoon
Published: March 2009

Chalcopyrite CuInSe 2 (CIS) and CuInGaSe 2</sub(CIGS) nanoparticles were directly synthesized by a solvothemal route in an autoclave with alkylamine as a solvent. The rod-like CIS nanoparticles with widths of 5-10 nm and lengths of 10-30 nm were obtained at 180°C for 36 hour whereas spherical nanoparticles with diameter in the range of 10-80 nm were observed at 200- 250 °C for 36 hour. A morphology change from spherical to rod-like CIS nanoparticles was observed at 190 °C as reaction time increased from 36 to 60 hour. The formation of the rod-like nanoparticles in diethylamine, without double N-chelation, was explained by the SLS (Solution- Liquid-Solid) mechanism. Spherical CIGS nanoparticles with diameter in the range of 30-80 nm were obtained in ethylenediamine at 280 °C for 14 hour. The products were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution scanning electron microscopy (HRSEM).
Preparation of W-C-B Composites by Reactive Resistance-Heated Hot Pressing
Authors: Sugiyama S. , Taimatsu H.
Published: March 2009

Dense WC-base W-C-B composites were prepared by the reaction sintering of B4C-WWC (mole ratio 1 : x : 80 or 130, x = 1-9) powder mixtures using resistance-heated hot pressing. Sintered bodies were composed of different products depending on x both in B4C-xW-80WC and - 130WC: WC + WB when x ≤ 3, WC + W2B + WB when x = 5, and WC + W2B + W2C when x ≥7. They had the highest Young's modulus values 706 and 705 GPa for -80WC and -130WC at x = 3, respectively. The hardness was increased with x, depending on a decrease in the grain size of WC. Its highest value was 24.5 GPa both for -80WC and -130WC at x = 9. For the fracture toughness, the highest value 6.1 MPa m1/2 was obtained for -130WC at x = 5.
Analysis of Waste Heat Recovery to Steel Scrap Preheating in an Enclosure Vessel
Authors: Wang T. , Kawakami Masahiro , Mori Kazuya , Shahidan S.H.
Published: March 2009

A method for preheating steel scraps using waste heat in a continuous casting process was proposed. Experiment and numerical analysis were carried out to examine the ability of scrap preheating and to determine the factors affecting the rise in scrap temperature. Coupled natural convection-radiation heat transfer was solved by three-dimensional FEM. The distance and the constant were found to influence the sample's temperature rise greatly. The overall Nusset number can be obtained as
Nu0=(-0.33α*D*0.8+7.08)Ra0.15t*-1- 32.4D*-0.99α*-1.98

*-1.98
Oxidation Behaviour of Nickel-Based Alloys Containing High Re Contents Comparable to the Third Generation Nickel-Based Superalloys
Authors: Murata Yoshinori , Morinaga Masahiko , Hashizume Ryokichi
Published: March 2009

In order to elucidate the Re effect on oxidation resistance, a high-temperature oxidation test was conducted with two groups of Ni-based superalloys. One group of alloys was characterized by 10mol%Al content (10-Al series). The other group of alloys was characterized by 15mol%Al content (15-Al series). The oxidation resistance decreased clearly with increasing Re content in the 10-Al series alloys, but did not in the 15-Al series alloys.
Plasma Characteristics of Supersonic Nitrogen/Hydrogen-Mixture and Ammonia Plasma Jets and Nitrided Material Properties
Authors: Tahara Hirokazu , Ando Yasutaka , Yoshikawa Takao
Published: March 2009

Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics under nitriding for a 10-kW-class direct-current arc plasma jet generator with a supersonic expansion nozzle in a low pressure environment. Heat fluxes into the plate from the plasma were also evaluated. Ammonia and mixtures of nitrogen and hydrogen were used as the working gas. The H-atom electronic excitation temperature and the N2molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. As approaching the titanium plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one. Both the electron number density near the plate and the heat flux increased with H2mole fraction for mixtures gases. In cases with mixtures of N2and H2, a radical of NH with a radially wide distribution is considered to contribute to the better nitriding as a chemically active and non heating process.
Reaction between Sn-In Solder and Under Bump Metallurgy
Authors: Choi J.H. , Jung B.Y. , Jun S.W. , Kim Y. , Oh Tae Sung
Published: March 2009

Reactions between 48Sn-52In solder and under bump metallurgies(UBM) such as 100nmTi/8µm Cu and 300nm Al/400nm Ni(V)/400nm Cu have been investigated, and the shear strength of 48Sn-52In solder bumps on each UBM has been evaluated. While intermetallic compounds with two different morphologies were continuously thickened on Ti/Cu with repeating the reflow process, the intermetallics on Al/Ni(V)/Cu spalled into the solder with increasing the number of reflow times.
The solder bumps on Ti/Cu exhibited higher shear strength than those on Al/Ni(V)/Cu.
Development of Ultra Fine Crystalline Diamond Film and Some Applications
Authors: Murakami Yoshihiko , Liu H. , Hanyu H.
Published: March 2009

We would like to report on the development of our new ultra fine crystalline CVD
diamond film and some applications. CVD Diamond films have good wear resistance, but the crystal size is too large. Therefore, in case of application of diamond films for cutting tools, we cannot get fine surface finish on work materials. Recently we succeed in production ultra fine crystalline CVD diamond film and various cutting tools as taps, drills and end mills. Aluminum alloys have lately been consumed more than ever in airplanes and automobiles for the purpose of decreasing the weight of structural materials.Copper alloys are used for the electrode of electric discharge machines (EDM) recently. EDM electrodes are required fine surface finish
because the surface quality of mold depends on accuracy of EDM electrodes. Soft materials such as aluminum and copper alloys have high viscosity and additionally activity. So during cutting aluminum and copper alloys we have sometimes adhesion between cutting tools and work pieces. Diamond film on tools is able to improve the reactivity to aluminum and copper alloys. But up to now the diamond film has a lot of course crystal and tend to supply rough surface finish on work pieces. We developed ultra fine crystalline diamond film on end mills by plasma chemical vapor deposition (CVD) method. Now our aircraft, automotive and molding customers can get smooth surface finish of work pieces.Keeping ISO14001, we recommend oil
free cutting with ultra fine crystalline diamond coated cutting tools. Here I introduce
background of the development and cutting examples with new fine diamond coated end mills.
Ferroelectric Characteristics of SrxBi2.4Ta2O9 Thin Films and Electrical Properties of the Pt/SrxBi2.4Ta2O9/TiO2/Si Structure
Authors: Choi J.H. , Oh Tae Sung
Published: March 2009

Ferroelectric characteristics of the 400 nm-thick SrxBi2.4Ta2O9(0.7≤x≤1.3) thin films processed by metalorganic decomposition were investigated, and electrical properties of the Pt/Sr0.85Bi2.4Ta2O9/TiO2/Si structure prepared using TiO2 buffer layer were characterized. The Sr-deficient SrxBi2.4Ta2O9 films exhibited well-developed ferroelectric hysteresis curves compared to those of the Sr-excess films. The Sr0.85Bi2.4Ta2O9 film exhibited optimum ferroelectric properties, such as high remanent polarization and low leakage current density, among SrxBi2.4Ta2O9 films. A
memory window of the Pt/SrxBi2.4Ta2O9/TiO2/Si structure was dependent upon the coercive field of the SrxBi2.4Ta2O9 film, and the Pt/SrxBi2.4Ta2O9/TiO2/Si exhibited a maximum memory window of 1.3 V at the sweeping voltage of ±5 V.
Epitaxial Growth of Mn-Doped ZnO Thin Films on Al2O3 (0001)
Authors: Vaithianathan Veeramuthu , Je Jung Ho , Lee Byung Teak , Kim Sang Sub
Published: March 2009

Growth behavior of Mn-doped ZnO thin films (Zn1-xMnxO) onAl2O3 (0001) substrates by pulsed laser deposition was investigated as a function of Mn content (0.00≤x≤0.35) mainly using synchrotron x-ray diffraction. We found that a small amount of Mn doping (x=0.05) significantly improves the crystalline quality, and also leads to a singly oriented film. The superior epitaxial growth of the film with an optimum Mn content seems to be associated with its microstructural evolution.
Characteristics of ZrO2/Al2O3 Bilayer Film for Gate Dielectric Applications Deposited by Atomic Layer Deposition Method
Authors: Kim Yang Do , Lee Jang Hee , Koo Jae Hyoung , Chang Ho Jung , Jeon Hyeong Tag
Published: March 2009

ZrO2/Al2O3 bilayer structure was investigated as one of potential replacements for SiO2 gate dielectric. Al2O3 and ZrO2 films were also examined and showed stoichiometric characteristics with negligible chlorine and carbon impurities. Al2O3 film exhibited an amorphous structure without interlayer formation while ZrO2 film showed a randomly
oriented polycrystalline structure with amorphous phase of interlayer. ZrO2/Al2O3bilayer film exhibited no interfacial layer between Si substrate and Al2O3 layers. The flat band voltage and hysteresis of ZrO2/Al2O3bilayer film were 0.8 V and 150 mV, respectively, with fully reversible hysteresis. The measured leakage current of ZrO2/Al2O3bilayer film was 1.2E-6 A/cm2 with EOT value of 1.4 nm. ZrO2/Al2O3 bilayer film showed significantly enhanced gate oxide properties compared to those of the individual Al2O3 and ZrO2 films.
Axial Pressing Method Using Pulse Magnetizing Field for the Preparation of Nd-Fe-B Sintered Magnets
Authors: Kim Dong Hwan , Kim Andrew S. , Kim Sang Myun , Jang Tae Suk
Published: March 2009

A new axial pressing method using pulse magnetizing field was studied to improve the remanence of Nd-Fe-B sintered magnets. In pulsed axial die pressing(PADP) process , tapping density of powders, method of pulse supply and strength of pulse field were optimized to increase magnetic alignment and remanence. As a results, we could find that an axial pressing under pulse magnetizing field was very effective to increase the degree of magnetic alignment of powder, yielding remanences even higher than those obtained by the transverse die pressing. The remanence of 14.1 kG was easily obtained by PADP process from 31R-68TM-1B (in wt.%) sintered magnet
Wear Behavior of Graphite-Dispersed Al-Sn-Si Alloys
Authors: Tagami M. , Sugafuji A. , Yabumoto Y. , Ohguchi Ken-Ichi , Muto A.
Published: March 2009

The stirring technique was used to produce Al-6mass%Sn-3mass%Si-1mass%Cu alloy with 5~8wt% graphite additions. The friction coefficient and wear loss of the graphite-dispersed Al-Sn-Si alloys were measured against commercial stainless steel (SUS304) in the boundary lubrication. Although the graphite particles added up to 8mass% do not improved the friction coefficient of as-cast alloys at the lower applied load, an applied load for the Al-Sn-Si alloy with 5~8wt% of graphite additions reaches 0.60MPa,whereas that for the non-added base alloy is only 0.45MPa.
Dislocation Plasticity and Complementary Deformation Mechanisms in Polycrystalline Mg Alloys
Authors: Koike Junichi
Published: March 2009

Deformation mechanisms of Mg-Al-Zn (AZ31) alloys were investigated by performing tensile test at room temperature. In fine grain Mg alloys deformed at room temperature, nonbasal slip systems were found to be active as well as basal slip systems because of grain-boundary compatibility effect. Slip-induced grain-boundary sliding occurred as a complementary deformation mechanism to give rise to c-axis component of strain. With increasing grain size, the activation of the nonbasal slip systems was limited near grain boundaries. Instead of grain-boundary sliding, twinning occurred as a complementary deformation mechanism in large grained samples. Orientation analysis of twins indicated that twinning is induced by stress concentration due to the pile up of basal dislocations. The grain-size dependence on deformation mechanism was found to affect yielding behavior both microscopically and macroscopically which can influence various mechanical properties such as fatigue and creep.
Microstructure and Mechanical Properties of DBC on Sputter Deposited Copper on Alumina Substrate
Authors: Lee Chung Hyo , Lee Young Sup , Cho Dong Choul , Lee Chang Hee
Published: March 2009

The process of Direct Bonding Copper (DBC) is performed by a spinel reaction between CuO and Al2O3. In order to develop DBC on alumina substrate with high bonding strength, alumina substrate was preformed as follows: Cu was sputter-deposited on alumina substrate. Sputter-Deposited Cu (SDC) on alumina substrate was oxidized at 673K for 30min in air atmosphere and then stabilized at 1273K for 30min in N2 gas atmosphere to improve bonding strtrength between preformed alumina substrate and SDC layer. Subsequently, the Cu-foil (300µm) was bonded on preformed-alumina substrate in N2 gas atmosphere at 1342~1345K. It was found that optimum condition of DBC on preformed-alumina substrate could be successfully obtained at 1345K for 30min. Consequently, bonding strength of DBC on alumina substrate was the high value of 80N/cm. Observation and analysis of microstructure for Cu sputtered DBC showed that reaction compounds such as CuAlO2 and CuAl2O4 approved to be formed in the vicinity of interface between Cu and alumina substrate.
Microstructures and Electrical Conductivity of Cu-Ca Alloys for High Efficiency Induction Motors
Authors: Sohn Keun Yong , Suh Dong Woo , Lee Sang Yong
Published: March 2009

The microstructures and electrical conductivity of newly developed Cu-Ca alloys for semi-solid forming have been investigated. High purity calcium was added to molten copper up to 1.4% by weight and mold-cast into a rod. Thermomechanical treatment (TMT) has been carried out to evaluate the variation in electrical conductivity and microstructures of Cu-Ca alloys. The electrical conductivity of copper was reduced linearly with the concentration of calcium by , where k is a constant having the values ranging from 16.7 to 20, depending on the processing condition. The introduction of prestrain significantly reduced the grain size during subsequent heating by recrystallization, influencing the electrical conductivity of Cu-Ca alloys.
Application of La2O3-B2O3-TiO2 Glass-Ceramic for Low Temperature Co-Fired Ceramic (LTCC) Materials
Authors: Jung Byung Hae , Hwang Seong Jin , Kim Hyung Sun
Published: March 2009

A low-temperature co-fired composition with sintering temperature of <900
°C was developed using rare earth derived borate glass (La2O3-B2O3-TiO2) and a conventional BNT (BaONd2O3-TiO2) ceramic. The sintering behavior, phase evaluation, sintered morphology, and microwave dielectric properties were investigated. It was found that increasing the sintering temperature from 750 to 850°C leads to increases in shrinkage, densities and microwave dielectric properties (≈ 20 for εr and >8000 for Q*f0). However, after 850 °C , the values of these properties decreased. It is suggested therefore that this new composite has good potential as a new candidate
for low temperature co-fired ceramic (LTCC) materials.
Evaluation of Solid Lubricant Coatings for Low Friction and Wear Resistance Using the Atmospheric Plasma Spray
Authors: Han Chang Min , Choi Han Shin , Lee Chang Hee , Kim Hyung Jun , Hwang S.Y.
Published: March 2009

A blended NiCr-Cr2O3-Ag-BaF2/CaF2 feedstock was sprayed using an atmospheric plasma spraying process. Due to the differences in physical and thermophysical properties of each constituent, coating microstructures and resulting coating properties were largely dependent on the interactions between each constituent phase and plasma jet in view of the physics of thermal spraying. Thus, hydrogen gas flow rate was changed to affect the plasma jet characteristics such as gas enthalpy and gas thermal conductivity in this study. According to it, evolutions of chemical composition and microstructures of the as-sprayed coatings were observed. As the hydrogen gas flow rate was increased, Cr2O3 weight fraction was increased with the decrease of Ag and porosity. Vickers microhardness and bond strength of the coatings showed consistent behaviors to the phase composition and microstructures. Friction coefficient and weight loss during a pin-on-disc dry sliding wear test were measured from room temperature to 500°C at the interval of 100°C. Finally, the effects of phase fraction and coating properties on the friction and wear were investigated.
Gas Analysis in Spark Plasma Sintering of Hydroxyapatite
Authors: Yamaguchi N. , Tanaka H. , Ohashi Osamu
Published: March 2009

In this paper, the effect of electric current on sintering of hydroxyapatite (HAp) in spark plasma sintering (SPS) process was investigated. The carbonate partially substituting hydroxyapatite was sintered up to 900 °C, and CO2 evolved from HAp powder were measured in situ by using mass spectroscopy apparatus in the same time. The same gas analysis was performed in thermal analysis as comparison. In the thermal analysis, CO2 gas was evolved at about 600 °C. On the other hand, in the SPS process, CO2 gas was detected at lower temperature than that of thermal analysis. This result indicates that the surface of hydroxyapatite particles would be heated up locally in SPS process due to electric current.
Synthesis of CNTs/Metal/Al2O3 Nanocomposite Powders by Chemical Vapor Deposition
Authors: Park C.D. , Jeon Hyung Jun , Wang H.J. , Choa Yong Ho , Oh Sung Tag , Kang Kae Myung , Kang Sung Goon
Published: March 2009

CNTs/metal/Al2O3 nanocomposite powders were fabricated by thermal chemical vapor deposition (CVD) of C2H2 gas over metal/Al2O3 nanocomposite catalysts prepared by the selective reduction of oxide/Al2O3 powders. The yield and diameter of CNTs significantly depended on the kind of metal catalyst and catalyst size. X-ray diffraction (XRD) was used for phase identification. The morphology of CNTs was determined using field emission scanning electron microscopy (FESEM). FT-Raman spectroscopy revealed that the CNTs have single- and multi-walled carbon nanotubes structure. The relationship between the CNT yield/diameter and the characteristics of the composite catalyst was systematically investigated.
Thermal Stability and Mechanical Properties of Nanocrystalline L12 Al3Hf and (Al+12.5 at.%Zn)3Hf Prepared by MA and SPS
Authors: Kang Chang Won , Jang Hee Sup , Kim Seon Jin
Published: March 2009

Thermal stability and mechanical properties of L12 Al3Hf and (Al+12.5 at.%Zn))3Hf
synthesized by mechanical alloying(MA) and spark plasma sintering(SPS) were investigated. Nanocrystalline L12 phase was produced after MA for 8 and 10 hrs in Al3Hf and (Al+12.5 at.%Zn))3Hf powders, respectively. The grain sizes were reduced to about 10 nm in both systems after MA for 20 hrs. After SPS, L12 phase was maintained only in Zn added system. In (Al+12.5 at.%Zn))3Hf, L12 to D023 phase transformation was started at about 850°C and finished at about 1150°C Microhardness was decreased with increasing the annealing temperature while fracture toughness was increased due to the grain growth. Fracture toughness of (Al+12.5 at.%Zn))3Hf was greater than that of Al3Hf in all annealing temperatures. Fracture toughness of (Al+12.5 at.%Zn))3Hf after annealing at 1200°C was about 5.38 MPam1/2.
Effect of β-Stabilizing Transition Elements on Elastic Modulus of Ti-M Systems
Authors: Jeong Hi Won , Kim Y.S. , Kim Seung Eon , Hyun Yong Taek , Lee Yont Tai , Park J.K.
Published: March 2009

New titanium alloys with a low elastic modulus have been developed for biomedical
applications to avoid the stress shielding effect of the artificial prosthesis. The newly developed alloys contained the transition elements like Nb, Ta, Zr which were non-cytotoxicity elements. These elements produced β, ω, and α'' phases with heat treatment conditions in titanium alloys and determined the elastic modulus of the alloys. However, the clear mechanism of the low elastic modulus alloys has not been known. In the present paper, the total energy and elastic modulus of β and α'' phases were calculated using a first principle calculation employing the generalized gradient approximation (GGA). The mechanism of the low elastic modulus was discussed with calculated values.
Formation of Shear Texture and Ultra-Fine Grains during Equal Angular Channel Rolling and Subsequent Annealing in AA 3003 Sheet
Authors: Huh Moo Young , Lee J.P. , Lee Jae Chun , Park Jong Woo , Chung Young Hoon
Published: March 2009

The evolution of texture and microstructure during the equal channel angular rolling
(ECAR) and subsequent annealing in aluminum alloy 3003 sheets was investigated. The tools of ECAR were designed to provide a constant shear deformation of the order of 0.5 per passage while preserving the original sheet shape. Samples of the aluminum alloy 3003 sheets were repeatedly deformed by ECAR up to twelve passages. Shear textures developed after the first passage of ECAR. However, the intensity of shear texture components decreased with increasing number of ECAR passages. After a large number of ECAR passages, a random texture developed at the expense of shear texture components. Observations by TEM and EBSD revealed that the degree of misorientations within the deformed grains increased with increasing number of ECAR passages. After recrystallization annealing, samples deformed by ECAR displayed pronounced {111}//ND fiber orientations. The annealed sheets comprising of ultra-fine grains were successfully produced in the samples deformed by a large number of ECAR passages.
Growth Kinetics of IMC Formed between Sn-3.5Ag-0.75Cu BGA Solder and Electroless Ni-P/Cu Substrate by Solid-State Isothermal Aging
Authors: Yoon Jeong Won , Lee Chang Bae , Jung Seung Boo
Published: March 2009

The growth kinetics of intermetallic compound (IMC) layers formed between Sn-3.5Ag-0.75Cu BGA (ball grid array) solder and electroless Ni-P/Cu substrate by solid state isothermal aging were examined at temperatures between 70 and 170°C for 0 to 100 days. In the solder joints between the solder ball and electroless Ni-P/Cu pads, the IMC layer was (Cu,Ni)6Sn5. Also, a P-rich Ni layer formed at the interface between (Cu,Ni)6Sn5 and original Ni-P deposit layer because of the phosphorous accumulation. These IMC layer thicknesses increased linearly with the square root of aging time and the growth was faster for higher aging temperatures. On the contrary, the shear strength decreased with the increasing temperature and time. The growth of IMC layer was mainly controlled by diffusion-controlled mechanism over the temperature range studied. The apparent activation energy calculated for the growth of the (Cu,Ni)6Sn5 IMC was 69.75 kJ/mol.
Thermoelectric Properties of Undoped CoSb3
Authors: Kim Il Ho , Choi G.S. , Han M.G. , Kim Ji Soon , Lee Jung Il , Ur Soon Chul , Hong Tae Whan , Lee Young Geun , Ryu Sung Lim
Published: March 2009

CoSb3 compounds were prepared by the arc melting and their thermoelectric properties were investigated at 300K-600K. Annealing effects were examined and they were correlated to phase transformation and homogenization. Undoped CoSb3 showed p-type conduction and intrinsic semiconducting behavior at all temperatures examined. Thermoelectric properties were changed with constituent phases because α-CoSb2, β-CoSb and Sb are metallic or semimetallic phases while δ-CoSb3 is semiconducting phase. Thermoelectric properties were remarkably improved by annealing in vacuum and they were closely related to phase transitions. Single phase δ-CoSb3 was successfully obtained by annealing at 400°C for 24hrs.
Optical and Microstructural Properties of TiO2, Al2O3 and SiO2 Single Layers Deposited by Plasma Assisted E-Beam Evaporation
Authors: Hong Sung Kil , Moon J.Y. , Kee W.K. , Chang Si Young
Published: March 2009

TiO2, Al2O3 and SiO2 single layer films were deposited in the oxygen gas atmosphere by plasma assisted e-beam evaporation(PAEBE) at various RF power and low temperature on p-type Si wafer(100) and glasses. The effects of plasma assistance on the optical and microstructual properties of three kinds of single layer films were investigated. In addition, those of the films were compared with the films deposited by conventional e-beam evaporation at high temperature(100~ 300 °C) condition. The n-values of TiO2 films gradually increased from 2.405 (λ =550nm) at 150W RF power to 2.54 at 200W. The XPS result indicated that TiO2 films deposited without plasma assistance have Ti2+, Ti3+ and Ti4+ charge states. Whereas the films prepared at 200W, 250W RF power have only Ti3+and Ti4+ charge states. Al2O3 layers had maximum reflective index (n=1.604 at λ =1200nm) at 200W RF power, but slightly decreased to 1.57 at 400W RF power. The measured transmittance spectra show that all the sample deposited by PAEBE are free from absorption and homogenous as well as the surface roughness, packing density and absorption of TiO2, Al2O3 films improved dramatically compared with films deposited conventional e-beam evaporation. However, The reflective index and surface morphologies of SiO2 films had no changed with increasing RF power.
Capillarity-Mediated Grain Growth in 3-D
Authors: Glicksman Martin E.
Published: March 2009

Space-filling in kinetically active 3-d network structures, such as polycrystalline solids at high temperatures, is treated using topological methods. The theory developed represents individual network elements—the polyhedral cells or grains—as a set of objects called average N-hedra, where N, the topological class, equals the number of contacting neighbors in the network. Average N-hedra satisfy network topological averages for the dihedral angles and quadrajunction vertex angles, and, most importantly, act as “proxies” for real irregular polyhedral grains with equivalent topology. The analysis provided in this paper describes the energetics and kinetics of grains represented as average N-hedra as a function of their topological class. The new approach provides a quantitative basis for constructing more accurate models of three-dimensional grain growth. As shown, the availability of rigorous mathematical relations for the curvatures, areas, volumes, free energies, and rates of volume change provides precise predictions to test simulations of the behavior 3-d networks, and to guide quantitative experiments on microstructure evolution in three-dimensional polycrystals.
Grain Growth Microstructures as Indicators of Sample Evolution
Authors: Jessell M.W.
Published: March 2009

Grain growth simulations using the microstructure simulation system Elle have been
performed in materials with a pre-existing grain shape preferred orientation. As might be expected, the microstructure is completely modified by the end of the experiment, and grain areas have increased by a factor of seven. The area of material swept by the migrating grain boundaries was monitored, and it was found that at every stage, virtually all of the grains which survived the grain growth process contain one and only one core of unswept material. Remarkably these remnant unswept cores preserve a useable record of the grain size and orientation of the original grains. This work suggests that it may be possible to see past a grain growth episode to estimate the original grain shape and grain size of the polycrystal, and perhaps even reconstruct the grain boundary kinematics. The identification of unswept cores also has the potential to help unravel the evolution of grain boundary chemistry during grain boundary migration.
Microstructure and Texture Evolution during Continuous Dynamic Recrystallization at Warm Deformation of Titanium
Authors: Mironov S.Yu. , Salishchev Gennady A. , Zherebtsov Sergey V.
Published: March 2009

The microstructure and texture evolutions in pure titanium during severe plastic deformation at T=400°C were investigated. Compressive deformation of prismatic samples was sequentially applied in three orthogonal directions up to 12 steps and a strain at each step of 40%. A radical microstructure refinement (from 20 to 0.2 µm) during strain has been found. The features of the deformation structure are a high level of internal stresses, high density of dislocations, a large number of deformation induced boundaries and the presence of twins. It is shown that during strain there is a significant change in disorientation angles and axes of individual high angle grain boundaries. At the same time the total set of high angle boundaries - Misorientation Distribution Function (MDF) and texture - does not change significantly with strain. The reasons for the change in disorientation angles and axes at new deformation-induced boundaries during plastic flow are discussed.
Study of Local Microstructure and Texture Heterogeneities in Hot Rolled CGO Fe-3%Si Sheets
Authors: Cruz-Gandarilla Francisco , Baudin Thierry , Penelle Richard , Mendoza León Hector
Published: March 2009

After secondary recrystallization, the Fe-3%Si alloys, grade Conventional Grain Oriented (C.G.O.), exhibit a Goss texture that is sought for minimizing watt losses in transformer cores. The mechanisms of Goss grain formation and their evolution during the processing route from hot rolling to decarburizing such as the early first steps of abnormal growth are not still well cleared up. This work deals with the influence of local microstructure and texture heterogeneities observed by X-ray diffraction (XRD) and Electron Back Scattered Diffraction (EBSD) at the hot rolling step. The present results complete those previously obtained by neutron diffraction [1]. Presence of Goss grain colonies at about the quarter of the hot rolled sheet is probably, as it has already been suggested, at the origin of the Goss grain presence at the primary recrystallized state.
A Recrystallisation Based Investigation for Efficiency of Processing Routes during Equal Channel Angular Extrusion
Authors: Suwas Satyam , Eberhardt André , Tóth László S. , Fundenberger Jean-Jacques , Grosdidier Thierry
Published: March 2009

The amount of stored energy of cold work for the processing routes A and Bc of Equal Channel Angular Extrusion (ECAE) process has been measured using differential scanning calorimetry. The study is preceded by the effect of amount of ECAE deformation on materials of different stacking fault energies, namely Cu and Ag. The results indicate that the different processing routes have significant effect on the stored energy, which is likely to affect the grain refinement process.
Recovery and Recrystallization Study after Low Deformation Amount by Cold Rolling in an IF-Ti Steel
Authors: Samet-Meziou Amel , Etter Anne Laure , Baudin Thierry , Penelle Richard
Published: March 2009

The first steps of recovery and recrystallization in an IF-Ti steel after 40% cold rolling have been studied using the Electron Back Scattered Diffraction (EBSD), Orientation Imaging Microscopy(™) (OIM) and the Transmission Electron Microscopy (TEM). As it is well known, for low deformation amounts by cold rolling, recrystallization texture exhibits the g fiber (ND // <111>) with a reinforcement of the {111}<110> orientation. In order to understand this {111}<110> development during recrystallization, characterization of the deformed state was performed. Different microstructures were distinguished: lamellar bands for the {111}<112> grains of the g fiber and coarse elongated cells for the {111}<110> orientation that belongs to the a and g fibers. Whatever the initial dislocation structure, the recovery step seems to be characterized by coalescence and growth of existing cells in the recovered matrix. Then nucleus growth seems to occur by sub-boundary migration. The first steps of recrystallization mainly take place by
continuous growth of subgrains including or not the bulging of grain boundaries.
Effect of Post Weld Heat Treatment on Microstructure and Mechanical Properties of Welded 2205 Duplex Stainless Steel
Authors: Badji R. , Belkessa B. , Maza H. , Bouabdallah M. , Bacroix Brigitte , Kahloun C.
Published: March 2009

Duplex stainless steels 2205 are widely used in constructional and petrochemical
applications because of their good mechanical and corrosion properties. The objective of this work was to study the influence of aging at high temperature on the austenite and d ferrite equilibrium. After welding by TIG process, duplex stainless steel was aged in the range of 800 – 1150 °C temperatures for 60 min. The microstructure was characterized by metallography and X-ray methods. The toughness of welded structure was also measured.