bluuebunny/crossref_metadata_2025 huggingface dataset:
XPS Analysis and Atomic Force Microscopy Observation of Micro-Liquids Adsorbed on Pure Iron and Copper Surfaces
Authors: Wang Rong Gang , Kido Mitsuo , Suzumura Fumihiro
Published: March 2009

The adsorptive on pure iron and copper surfaces was investigated with angle resolved
X-ray photoelectron spectroscopy (ARXPS) and atomic force microscope (AFM). Organic species
and a little amount of water (micro-droplets surrounded with nanometer-scale film-like-domains)
were detected on the oxidized and/or hydrated metallic surfaces for both specimens and their minute
structures were discussed.
A Study on the Process Design of Cold-Forged Automobile Parts
Authors: Choi Hyoung Jin , Hwang Beong Bok , Ko B.D. , Jang D.H. , Lim Joong Yeon
Published: March 2009

The cold forging processes of automobile parts such as piston-pin, valve-spring retainer(VSR) and power-assisted steering part (PAS) are analyzed by the rigid-plastic finite element method. The results of the simulation on the piston-pin are summarized in terms of the strain distribution and load-stroke relationship. Based on the analysis on the current processes of VSR and PAS, the new novel processes for improving the conventional process sequences are designed. As a design criterion, the improved processes satisfy the new condition such as an initial billet size, the production time and the limit value of forming load and pressure etc. The present simulation results and the newly developed process gave rise to an improvement in manufacturing processes for cold-forged automobile parts. Furthermore, the numerical analysis for the processes in this study provides a new
design concept for forming processes and a basis for the selection of forging equipments.
Properties of Nd-Fe-B Magnetic Powder Prepared by Reduction-Diffusion Process Using a Spray-Dried Precursor
Authors: Jang Tae Suk , Lee Dae Hoon , Choi Chul Jin , Kim Byoung Kee
Published: March 2009

Effect of washing step in R-D process on the structure and magnetic properties of Nd-Fe-B
powder fabricated by the process using a spray-dried precursor was investigated. Although the
powder washed in water contained much more residual CaO than that washed in dilute acetic acid,
magnetic properties of the former were much better than those of the latter due to less removal of
Nd-rich phase. In the powder washed in water Nd2Fe14B particles were enclosed with thin layer of
Nd-rich phase, and each particle consisted of one or more subgrains of the size 50 ~ 100 nm or more.
Milling the powder before water washing was effective to remove more CaO, thereby increased the
remanence of the powder.
Mechanical Properties of Binary Ti-Ta Alloys for Biomedical Applications
Authors: Zhou Ying Long , Niinomi Mitsuo , Akahori Toshikazu
Published: March 2009

The effect of Ta content on the mechanical properties of the quenched binary TiTa alloys with different mass percentage of Ta from 10 to 80% was investigated in order to find a Ta content that gives a good balance of low modulus and high strength for biomedical applications. The mechanical properties of binary TiTa alloys depend strongly on the microstructures caused by Ta content. Among all the studied TiTa alloys, Ti30 mass % Ta alloy with martensite  and Ti70 mass % Ta alloy with metastable phase have the potential to be the new candidates for biomedical applications
Porous TiNi Biomaterial Produced by Self-Propagating High-Temperature Synthesis: Pore Structure, Mechanical Property and Application
Authors: Kim Ji Soon , Yang S.G. , Kang J.H. , Kang Suk Bong , Yoon Kang Sup , Kwon Young Soon
Published: March 2009

Porous TiNi shape-memory alloy (TiNi SMA) bodies were produced from the (Ti+Ni)
powder mixture by self-propagating high-temperature synthesis (SHS) method. Various processing
variables such as ignition temperature and heating schedule were used to control the pore structure.
Relationship between pore structure and mechanical property was also investigated. An in vivo test
was performed to evaluate bone tissue response and biocompatibility of porous TiNi SMA. It
showed no apparent adverse reactions such as inflammation and foreign body reaction. Bone
ingrowth was found in the pore space of all implanted blocks.
Introduction
Titanium-nickel intermetallic compound is well known as one
Modification of the Recrystallization Texture by Means of Cross Rolling in Ferritic Stainless Steel Sheets
Authors: Lee Jong Heun , Park Soo Ho , Huh Moo Young
Published: March 2009

In order to optimize the recrystallization texture of ferritic stainless steel sheets, the
crystallographic texture was modified by means of cross rolling. The as-received hot band displayed pronounced through-thickness texture gradients with a strong rotated cube orientation in the sheet center layer. After the conventional normal rolling, the strong initial texture was retained. Pronounced{001}<110> in the rolling textures led to the formation of {334}<483> in the final recrystallization texture. Cross rolling in the present work was performed by a 45° rotation of RD around ND.
Cross-rolling led to a weakening of {001}<110> orienations. After recrystallization annealing the cross-rolled samples displayed stronger {111}//ND orientations. The orientation stability during the rolling deformation was tackled by means of Taylor deformation model.
Synthesis of Nano Metal Powder by Electrochemical Reduction of Metal Oxides
Authors: Lee Kyung Jong , Lee Jai Sung
Published: March 2009

This work has attempted to find a new low temperature reduction process for fabrication of
Cu nanopowder from fine CuO powder. For this purpose, we used electrochemical reduction method
which is conducted in an electrolyte of NaCl aqueous solution at room temperature. It was found that
ball-milled CuO powder (particle size ~100 nm and grain size ~40 nm) was completely reduced
under the conditions of 20 V power, 0.5 mol NaCl solution and 2 h reaction time, producing Cu
nanopowder (particle size ~80 nm and crystallite size ~25 nm). Simultaneously, we observed that
sintering of nanopowders occurred during the reduction process, leading to agglomeration of
nanopowder. Based upon the experimental results, the correlation between electrochemical reduction
process and its related powder characteristics was discussed in terms of material transport.
Formation of Nanocrystalline Structure in Steels by Air Blast Shot Peening and Particle Impact Processing
Authors: Todaka Yoshikazu , Umemoto Minoru , Watanabe Yu , Tsuchiya Koichi
Published: March 2009

Surface nanocrystallization in various steels by shot peening (both air blast and
ultrasonic) and particle impact processing was investigated. Nanocrystalline layers with several µm
thick were successfully fabricated by these methods. In all the case, the nanocrystalline layers have
extremely high hardness and separated from adjacent deformed structure regions with sharp
boundaries. By annealing, the nanocrystalline layers showed substantially slow grain growth
without recrystallization. Those characteristics are similar to those observed in the samples
experienced ball milling and ball drop deformation.
Comparison of III- Nitride Nanotubes: Atomistic Simulations
Authors: Kang Jeong Won , Hwang Ho Jung
Published: March 2009

We have investigated the single-wall boron-, aluminum- and gallium-nitride nanotubes
using atomistic simulations based on the Tersoff potential. The Tersoff potential for III-nitride
effectively describes the properties of III-nitride nanotubes. Structures, energetic and
nanomechanics of III-nitride nanotubes were investigated and compared with each other. Youngs
moduli of III-N nanotubes were lower than that of CNT. Though the graphite-like sheet formation
of AlN was very difficult, since the elastic energy per atom to curve the sheet into cylinder for AlN
was very low, if graphite-like sheets of AlN were formed, the extra cost to produce the tubes would
be very low
Magnetorheological Characterization of Polymer-Iron Composite Suspensions
Authors: Cho Min Seong , Choi Hyoung Jin
Published: March 2009

Composite particles (CIPMMA) of carbonyl iron (CI) and poly (methyl methacrylate)
(PMMA) were prepared by a suspension polymerization method using CI dispersions in MMA
monomer, and these were adopted as dispersed phase of magnetorheological (MR) fluids. The
CIPMMA can resolve several problems of MR fluids having CI alone such as severe sedimentation
and poor dispersion stability. Flow and viscelastic properties of the MR fluids were analyzed via a
rotational rheometer equipped with a magnetic field supplier using measuring system of a parallel
plate. The MR characteristics like yield stress were affected by the CI contents in the composite
particles.
Ultrasonic Characterization of Degradation of Aging Epoxy Coating
Authors: Kim Noh Yu , Nah Hwan Seon
Published: March 2009

Acoustic impedance of aging epoxy coating in nuclear plant is measured for evaluation of
the degradation of the epoxy coating using a new ultrasonic measurement technique that uses a
specially designed conical acoustic lens to determine the reflection coefficient (reflectance) of the
epoxy coating. Reflection waves measured at two different vertical positions slightly apart from each
other are subtracted and used to calculate the acoustic impedance of the epoxy coating. Epoxy coated
concrete specimens are fabricated and degraded artificially under accelerated aging conditions to
determine the acoustic impedance of the films. Experimental results show that the acoustic
impedance is very sensitive to the degradation of coating and can be applied to evaluate the quality of
the epoxy coating quantitatively.
Fabrication of Al2O3/5 vol% Cu Nanocomposites Using Various Powder Mixtures and Its Properties
Authors: Oh Sung Tag , Choa Yong Ho , Kim Young Do
Published: March 2009

An optimum route to fabricate the Al2O3/Cu nanocomposites with sound microstructure
and improved mechanical properties was investigated. Three powder mixtures of Al2O3 and Cu,
CuO or Cu-nitrate were used to obtain Al2O3/5 vol% Cu composites. Microstructural investigations
for the composite from Al2O3/Cu-nitrate showed that fine Cu particles, about 150 nm in diameter,
were homogeneously distributed within the Al2O3 matrix grains and at the grain boundaries.
Fracture toughness of 4.8 MPam and strength of 953 MPa were measured for the Al2O3/5 vol% Cu
nanocomposites prepared from Al2O3/Cu-nitrate mixture. The toughening and strengthening of the
composites are explained by the crack bridging/deflection and the refinement of the microstructure,
respectively.
Hydrophilicity and Bactericidal Effects of TiO2 Thin Films Prepared by RF Sputtering
Authors: Song Yo Seung , Kim Seon Hwa , Kim Bae Yeon , Lee Deuk Yong
Published: March 2009

TiO2 thin films were prepared by RF sputtering on Si wafer to investigate hydrophilicity
and bactericidal effects by using AFM, XRD, standard plate count method and wetting angle
measurement. Experimentally, the survival rate of E. coli was above 74% and the wetting angle of
water for the 30 min UV illuminated films was 4.2o. It was found that the bactericidal efficiency was
closely related to the large specific surface area caused by the roughness, however, hydrophilicity was
governed by the surface defective sites rather than the roughness.
Nanostructured WC-Co Coatings from Different Feedstock Powders
Authors: Baik Kyeong Ho , Jang Jun Ho , Hwang S.Y.
Published: March 2009

Nanostructured WC-Co coatings have been manufactured by high velocity oxyfuel
(HVOF) spraying using commercially available nanocomposite powders. The effect of feedstock
powder characteristics on coating microstructure has been investigated. A significant loss of carbon
occurred during HVOF spraying, which was much greater for a porous, irregular powder than for a
dense, spherical powder. The decarburization promoted the formation of several additional phases in
the coating, including W2C, W and CoxWxC. The microstructural differences in each coating arose
from the different extent of feedstock powder melting because of initial powder morphology.
Surface Modification and Characterization of Perovskite-Type Mixed Ionic-Electronic Conductors
Authors: Lee Shi Woo , Shin Tae Ho , Lee Kee Sung , Han In Sub , Seo Doo Won , Hong Kee Seog , Woo Sang Kuk
Published: March 2009

Surface modification effects have been investigated for perovskite-type mixed
ionic-electronic conductors. As the mixed conducting oxides show both ionic and electronic
conductivity, these can be applied as oxygen permeable membranes. We have coated surfaces of the
perovskite-type mixed conductors, LaSrCoFeO3 and LaSrGaFeO3, with LaSrCoO3 and investigated
the effects on oxygen permeability. Enhanced oxygen permeability was achieved when the
LaSrGaFeO3 membrane was surface-modified with LaSrCoO3. However, there was no effect on
oxygen permeability of LaSrCoFeO3 even when the surface of which was modified. The
morphological factors related with electrochemical reactions have also been discussed
Cold Spray Process ~ Overview and Application Trends ~
Authors: Sakaki Kazuhiko
Published: March 2009

In Cold Spray method, a coating is formed by exposing a substrate to high velocity
solid-phase particles, which have been accelerated by supersonic gas flow at a temperature much
lower than the melting or softening temperature of the feedstock. Therefore, the nozzle geometry is
important with regard to the cold spray method. This Cold Spray process is an exciting new spray
technology that has the potential to overcome limitations of more traditional thermal spray processes
for some important commercial applications. With this emerging technology, it is possible for the first
time to rapidly deposit thin or very thick layers (mm to cm+) of a wide range of metals, and even some
composite materials, without melting or vaporization, at or near room temperature, in an ambient air
environment.
Some potential areas of interest include:  corrosion protection,  wear reduction, highly conductive
coatings (electrical or thermal), metal/glass or metal/ceramic joints (with less residual stress),
ceramic/metal or graded metal/metal composites,  thick deposits (mm to several cm range),
reclamation of worn or mis-machined parts, metallization of glass or ceramics.
The applications of Cold Spray can be examined in the field of an automobile and a rocket engine.
Clinical Application of TiNi Shape Memory Alloy Bone Fastener
Authors: Kang Seung Baik , Yoon Kang Sup , Nam Tae Hyun , Kim Ji Soon
Published: March 2009

Titanium-Nickel shape memory alloy (TiNi SMA) has great potential as a biomaterial in
orthopaedic applications due to its unique thermal shape memory effects, superelasticity and high
damping properties. We designed and manufactured bone fasteners using newly developed TiNi
SMA wire (Af, 35 2.C). Several types of bone fastener designs were prepared for the application of
orthopedic treatment of bone fracture. We applied this fastener to 82 fracture patients. Fracture
types according to the anatomic location included distal fibular (21), femur shaft (periprosthetic
fracture, 17), distal tibia (15), distal femur (10), metacarpal bone (9), and subtrochanter of femur (5),
distal clavicle (5). Serial radiographs, complete blood count (CBC) and urine analysis were
performed postoperatively. Radiological union was achieved without complications at due time
after operation. There were no abnormal findings on follow-up CBC or urine analysis. On a
subjective level, use and application of the TiNi SMA fastener was not as demanding as
conventional fixation methods, such as circumferential wiring (cerclage) or the Dall-Miles
technique. The efficacy of SMA bone fastener in this study is very excellent as demonstrated in this
clinical study. It gives the new armament to orthopedic surgeon.
Notch Effects on Impact Tensile Properties in A6061-T6 Aluminum Alloy
Authors: Masuda Tomokazu , Toda Hiroyuki , Kobayashi Toshiro
Published: March 2009

The strain rate sensitivity of a A6061-T6 aluminum is examined as a function of triaxial stress. The triaxial stress state is changed by changing the notch acuity of notched specimens. Under the high strain rate conditions, increasing triaxiality increases flow stress. Plastic constraint factor decreases in notched specimens under high strain rate conditions. Reduction-of-area in notched
specimen increases with increasing strain rate. The relaxation of plastic constraint takes place under high strain rate in the notched specimens. The effects of triaxial stress and strain rate on the fracture surfaces are discussed.
Effect of Electromagnetic Force on the Silicon Size in Hypoeutectic Al-Si Alloy
Authors: Choi Jung Pyung , Kim Ki Bae , Yoon Eui Pak
Published: March 2009

In general, the element (Sr, Na, Sb, etc.) is used as a modifier of eutectic Si phase in the hypoeutectic Al-Si system. When these elements are added into the hypoeutectic Al-Si melt, the flake shaped Si phase transforms to fibrous shape and the size of Si phase is also decreased. In this study, the electromagnetic vibration is adopted for modifying eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration(EMV), the finer the size of eutectic Si phase. The tensile strength and elongation of EMVed alloy were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000Hz was approximately six times as high as that of the normal alloy and a half of that of Sr modified alloy. The mechanism for the increase in twin density due to EMV during solidification could be supposed from the fact that the preferential growth along <112> in silicon was suppressed by preventing Si atom from attaching to the growing interface of Si phase and by changing the solid/liquid interfacial energy of silicon.
Modeling Precipitate Microstructure Evolution in Alloys with First-Principles Energetic Information
Authors: Vaithianathan Veeramuthu , Wolverton C. , Chen Long Qing
Published: March 2009

This short article reports our recent effort to integrate the mesoscale phase-field
method with first-principles total energy calculations, linear response theory, as well as mixedspace cluster expansion. A particular example of applying such a multiscale approach to the case of precipitation of semicoherent θ' particles in an Al-matrix is presented.
Surface Amorphization in Intermetallic Compounds by Shot Peening
Authors: Nakayama Hiroyuki , Tsuchiya Koichi , Todaka Yoshikazu , Umemoto Minoru , Morii K. , Shimizu Takamitsu
Published: March 2009

Surface amorphization by shot peening in intermetallic compounds was examined. The formation of amorphous layer has been verified in Ti-Ni and Zr-Co-Ni alloys. In Ti-Ni alloy, an amorphous phase and nanocrystalline grains were detected by TEM for 120 s peening duration. However, recrystallization and grain growth occurred, when peening duration was up to 400 s. In Zr-Co-Ni alloy, an amorphous phase coexisting with nanocrystalline grains was observed in Zr-37Co-13Ni alloy. For other alloy compositions (Zr-50Co and Zr-50Ni), an amorphous phase was not observed, and nanocrystalline grains were observed. All the observed nanocrystalline grains may be recrystallized from amorphous phase, because their shape was spherical.
Morphology of Carbon Micro-Coils
Authors: Fujii M. , Motojima S.
Published: March 2009

The double helical carbon micro-coils were obtained by chemical vapor deposition.
As-grown carbon micro-coils with amorphous structure were heat-treated at various
temperatures up to 3000°C . By heat treatment, the shape of the coils was not changed. The morphology of these coils was observed in detail using electron microscope. The lattice structure was analyzed by X-ray diffraction method. Heat treatment temperature dependence of the magnetoresistance and the measurement of Raman spectra suggest that the coils heattreated at higher temperature are more highly graphitized.
Abnormal Crystal Growth in the Sintered (Bi0.2Sb0.8)2Te3 Alloys Induced by Silver Addition
Authors: Yoo Hyun Jae , Park Yong Ho , Park Ik Min
Published: March 2009

The bulk (Bi0.2iSb0.8)2Te3
thermoelectric alloys added with Ag up to 2.0 mass% were prepared by mechanical alloying and pulse discharge sintering (MA-PDS). Microstructures of the sintered samples were investigated. In the two samples with 1.0 and 2.0 mass% Ag, an abnormal growth of the (Bi,Sb)2Te3
phase, manifested by the formation of coarse crystals that are visible with eye, has been revealed during the PDS process of the alloyed powders. The local temperature rise in
the compact induced by the compositional fluctuation as a result of Ag addition was suggested to be responsible for the observed abnormal growth. In addition, the electrical transport properties, i.e., electrical resistivity and Seebeck coefficient, of the sintered samples were studied.
Production Mechanism of Superfine Powders by Jet Mill
Authors: Yang Yun Chuan , Liu Chang Jiang , Li Guo Kang
Published: March 2009

With the help of the scanning electron microscope, the superfine powders produced from 8 kinds of materials by Jet Mill were experimentally investigated and were qualitatively analyzed based on the stress wave theory and the crystallography theory. It was found that the crystal structure had a decisive influence on the shape of particles, and the shape of non-crystal particles occurred at random. The particle materials produced from intensive impulsive loading maintained their original roperties. The unbalanced crack extension, which caused by the defects of materials or other factors, was the main factor of material destruction.
Processing and Alloy Development to Optimise the Properties and Cost-Effectiveness of Components Manufactured from TiAl-Based Alloys
Authors: Wu Xin Hua , Hu D. , Loretto M.H.
Published: March 2009

The IRC has carried out a major research programme over the last ten or so years aimed at developing the processing and optimisation of TiAl-based alloys. This work has covered melting, the production of shaped castings, powder processing and a range of thermomechanical processing routes in parallel with alloy development. In this paper the work aimed at understanding the factors that influence the properties of thermo-mechanically processed and cast samples of TiAl-based alloys will be reviewed. It is shown that the use of boron to control the grain size of castings leads to limited ductility in the stronger and more highly alloyed TiAl alloys because ribbon-like borides up to 200µm in length can be formed. It is also shown that although a fully lamellar microstructure offers a good balance of properties their plastic anisotropy leads to pre-yield fracture and to reduced fatigue life. It is clear that grain size control is essential if an acceptable balance of properties is to be obtained
but that if casting is to be used grain refinement via boron addition is not totally satisfactory. A simple heat treatment can be used to refine the microstructure of cast boron-free alloys, which leads to ductility comparable with that in wrought samples and the associated convoluted microstructure should also eliminate pre-yield cracking.
Electrochemical Kinetics Study of Electroless Copper Plating for Electronics Application
Authors: Kim Dae Geun , Bae Jin Soo , Lee Jae Ho , Kim Yang Do , Ahn Yoo Min
Published: March 2009

Electroless copper plating was investigated for the electronics applications, such as a metallization for ULSI and MEMS etc. The role of electrolyte composition on the kinetics and mechanism of the electroless copper deposition process was described. Electrochemical techniques were employed for the investigations. The mixed potential and current were determined and then those were compared with experimental deposition rate. The kinetics is strongly influenced by the pretreatment and additive concentrations.
A Study on Interfacial Reaction between Electroless Plated Ni-P/Au UBM and Sn-Bi Eutectic Solder Using AEM
Authors: Choi J.K. , Kang H.B. , Lee J.W. , Jung Seung Boo , Yang Cheol Woong
Published: March 2009

Interfacial reaction between electroless plated Ni-P/Au UBM(Under Bump Metallization and eutectic Sn-58mass%Bi solder was studied by using AEM(Analytical Electron Microscopy). UBM is prepared by the electroless plating of Au (0.15μm ) / Ni-15at%P (7 μm ) on bare Cu substrate, and then it is reacted with Sn-58Bi solder at 220°C for 1 min. The chemical analysis using AEM
provided us very consequential information about microstructure of the interface and phases formed. CBED(Convergent Beam Electron Diffraction) technique is used for phase identification of intermetallic compounds. In this study, the AEM results indicate that Ni3Sn is formed at the P-rich Ni layer/Ni3Sn4 interface by crystallographic analysis. The measured primitive cell volume(104.10 Å3)of this phase is close to the Ni3Sn(103.19 Å3) rather than Ni2SnP(235.24 Å3).
Characteristics of CO2 Laser Welded 800MPa Grade TRIP Steel
Authors: Han Tae Kyo , Kim Ki Heok , Kim Byoung Ik , Kang Chung Yun , Woo In Su , Lee Jong Bong
Published: March 2009

The effect of welding conditions on defects, microstructure, mechanical properties and formability of CO2welded 800MPa grade TRIP steel was investigated. Bead-on-plate welding was carried out under the various welding speed in 6kW with a shield gas of Helium. Extensive porosity was observed in the joints produced at a 4m/min of welding speed but was not observed in the joints when a welding speed greater than 6m/min was used. The maximum hardness was obtained at the weld metal and the HAZ near the weld metal and was the same regardless of the welding speed. The HAZ hardness near the base metal was reduced due to retained ferrite but was higher than that of the base metal. In a parallel tensile test to weld axis, the strength of the joints was higher than that of the base metal. Elongation was found to be lower than that of the raw material because a crack was initiated in the bead at the strength levels corresponding to the tensile strength of the base metal and was propagated perpendicular to tensile direction. The formability of joints was found to be 63% that of the raw material.
Observation of Crystallization Behavior in ITO Thin Films Prepared by RF-Magnetron Sputtering with and without External Heating
Authors: Park Ju O. , Lee Joon Hyung , Kim Jeong Joo , Cho Sang-Hee
Published: March 2009

ITO films were deposited on the Corning 1737 glass by the RF-magnetron sputtering method with and without external heating as a function of deposition time. The as-grown ITO film, deposited on room temperature substrate without external heating for 10 min, was amorphous in nature. Continuous deposition over 20 min resulted in the development of crystallization of the films. The crystallization by prolonged deposition was initiated from the top surface of the film where energetic ions bombard. When the films were deposited with external heating, the crystallization was initiated from the beginning of the deposition at the surface of the substrate.
Effects of Pre-Strain and Aging Treatment on the Mechanical Properties of 1.0wt.%Cu Containing Hot Rolled Steel Sheet
Authors: Kim In Gon , Kim Yang Do , Kim In Bae
Published: March 2009

The effects of pre-strain and aging treatment on the mechanical properties of hot rolled steel sheet containing 1.0wt.%Cu were investigated. As the amount of pre-strain increased, the maximum hardness increased and the time to reach its peak hardness decreased. Tensile strength of 10% pre-strained steel was 600MPa. This value was about 150MPa higher than that of hot rolled steel. In case of 30% pre-strained steel, the strength was further increased to 657MPa. Such a strength increase was due to the strain hardening and enhanced precipitation reaction of Cu-clusters. TEM study revealed that fine Cu-clusters were uniformly dispersed throughout the grain. This means that the precipitation of Cu-clusters was mainly controlled by the vacancies introduced during the pre-straining process. The size of Cu-clusters was about 10~20nm at peak aged condition and they had spherical shape.
Mechanical Behavior of As-Cast and High Temperature Exposed Ni-Base Superalloy B1900
Authors: Kim I.S. , Choi Baig Gyu , Seo Seong Moon , Jo Chang Yong
Published: March 2009

Microstructural evolution during high temperature exposure and its effects on tensile and stress rupture properties of the Ni-base superalloy B1900 have been studied. Tensile deformation of the as-cast specimen was concentrated in the localized slip bands in general. Stacking faults and deformation twins were observed in the as-cast tensile specimen tested at 871°C where the alloy exhibited the lowest ductility. Dense dislocation network formed at γ/γ´ interface during thermal exposure caused homogenous deformation in the thermally exposed tensile specimen. Thermal exposure did not have significant effect on the stress rupture lives of the alloy at 760°C and at and above 871°C but it reduced stress rupture life of the alloy at 816°C γ´ coarsening and coherency loss at the γ/γ´ interface during thermal exposure were primarily responsible for the deterioration of mechanical properties and characteristic deformation behavior of the alloy.
Effect of Melt Treatment on the Microstructure and Creep-Rupture Behavior of M963 Cast Nickel-Base Superalloy
Authors: Guan Heng Rong , Yin Feng Shi , Sun Xiao Feng , Hu Zhuang Qi
Published: March 2009

The effect of melt treatment on the microstructure and creep-rupture behavior of
M963 superalloy at 1248K under 225MPa has been investigated. The microstructure of the as-cast superalloy without melt treatment consists of γ solid solution matrix, γ´precipitate, coarse blocky MC carbide and (γ+γ´)eutectic. The striking difference in microstructure is that the melt treatment changes the MC carbide from the coarse blocky morphology into the fine script-like morphology. After heat-treated at 1483K for 4h followed by air-cooling, both the creep life and rupture elongation of the melt-treated alloy are all doubled those of the alloy without melt treatment. The mechanism of the melt treatment on the creep-rupture behavior of the M963 superalloy is discussed.
Effect of PWHT on Behaviors of Precipitates and Hardness Distribution of 6061 Al Alloy Joints by Friction Stir Welding Method
Authors: Lee Won Bae , Jang Hyung Sun , Yeon Yun Mo , Jung Seung Boo
Published: March 2009

The hardness distribution related to the precipitates behaviors as friction stir welded and PWHT (post weld heat treated) 6061 Al alloy have been investigated. Frictional heat and plastic flow during friction stir welding created a fine, eqiuaxed and elongated microstructure near the weld zone due to dynamic recovery and recrystallization. A softened region which had been formed near the weld zone couldn't be avoidable due to the dissolution and coarsening of the strengthening precipitates. PWHT (SHT+ Aging) homogeneously recovered the hardness distribution over that of the base metal without softening region, resulted from non-homogeneously distributed hardness only aging treated. 36ks aging followed by SHT gave a higher hardness overall weld than that of the base metal due to a higher density of the spherical shaped precipitate.;
Measurement and Analysis of Sound Absorption of Porous Magnesium
Authors: Xie Zhen Kai , Ikeda Teruyuki , Okuda Yosiyuki , Nakajima Hideo
Published: March 2009

Lotus-type porous magnesium whose long cylindrical pores were aligned in one direction was fabricated by unidirectional solidification of the melt dissolving hydrogen in a pressurized hydrogen atmosphere. The sound absorption coefficient of porous magnesium whose specimen face has many open pores was measured by standing-wave method in the range up to the frequency of sound of 4 kHz. The relationship between absorption coefficient and pore structure of porous magnesium was studied. The absorption coefficient increases with decrease of the pore size, while it increases with increase of the porosity. Moreover, the peak value with high absorption coefficient is shifted toward higher frequency of sound when the thickness of the porous magnesium specimen decreases.
Energetics of Native Defects in Al2O3 and SiO2
Authors: Yoshino M. , Shinzato Y. , Morinaga Masahiko
Published: March 2009

Formation energies of various defects in Al2O3 and SiO2 are calculated by using the plane-wave pseudopotential method. Also, the formation energies of Schottky defects and Frenkel defects are evaluated on the basis of these calculations. It is shown that formation energies of these defects are higher in SiO2 than in Al2O3. In other words, less defects are formed in SiO2 than in Al2O3. It is also found that the principal defect is the cation Frenkel defect in Al2O3 but the anion Frenkel defect in SiO2. These results agree with the experimental results that Al ions diffuse preferably in Al2O3 but oxygen ions diffuse in SiO2 at high temperatures.
Dynamic Damage Behavior during Cooling Process of Ceramic Coatings
Authors: Nishinoiri Satoshi , Nozawa Kei , Enoki Manabu
Published: March 2009

Ceramic functional coating is frequently applied to the structure material of turbine blades, and it is very important to investigate its properties during thermal shock, thermal cycle and thermo-mechanical fatigue. In this study, we measured acoustic emission (AE) caused by microfracture of the coatings to investigate the fracture mechanism during thermo-mechanical test of coatings. We have developed the method to detect AE signal using laser interferometer, and it was demonstrated that it was very powerful tool for non-contact measurement of AE. This technique was applied to the thermal cycle test of coatings, and microfracture mode was analyzed by simulation of wave propagation using finite element method (FEM). The change in energy release rate of interfacial cracks in the specimen due to heating and cooling was also calculated by FEM and correlation between propagation of interfacial crack and AE behavior was evaluated.
Effect of Mo Addition on Microstructure and Properties of Nb/Nb5Si3 In-Situ Composite
Authors: Li Wei , Yang Hai Bo , Shan Ai Dang , Wu Jian Sheng
Published: March 2009

Nb/Nb5Si3 in-situ composites are very attractive structural materials for these materials perform a good balance in mechanical properties, including a high strength at high temperature (>1373K) and reasonably high fracture toughness at room temperature. Metastable phase Nb3Si plays an important role in the properties of Nb/Nb5Si3 composites by affecting microstructure and volume fracture of ductile phase. In this paper, Nb-10Si-xMo and Nb-18Si-xMo (x=0,5,15) are prepared by arc melting and annealed at 1473K for 100h. Single edge-notched bending (SENB) test was used to study the fracture toughness of Nb-Si-Mo alloys. The stability of metastable phase is analyzed by XRD. The room temperature fracture toughness of Nb-10Si is 10.47MPa(m)1/2 and higher than that of binary Nb-18Si alloys at near-eutectic compositions. The addition of Mo improves the fracture toughness of as cast Nb-Si alloys from 4.1 MPa(m)1/2 to 9.9MPa(m)1/2 at near-eutectic compositions and decreases it from 10.47 MPa(m)1/2 to 8.8MPa(m)1/2 at hypoeutectic compositions.
Rapid Tooling for Injection Moulding Process
Authors: Lours Philippe , Bui H.V. , Nafi Abdelhak , Mercier Omer , Bernhart Gérard
Published: March 2009

CROMeP (Research Centre on Tools, Materials and Processes) experience in rapid tooling development is related. Focus is placed on two processes, namely the Direct Metal Laser Sintering/DMLSⓇ and STRATOCONCEPTⓇ currently under consideration for the manufacturing of thermoplastic injection moulds. The principle of the two processing routes as well as the benefits attainable by using those processes will be briefly reviewed. Recent results on the microstructure and the mechanical performances of sample tools built up using both processes are presented.
Breakage Mechanism of Al2O3 Layer on Nano Al Powder by Magnetic Pulsed Dynamic Compaction
Authors: Lee Geun Hee , Rhee Chang Kyu , Kim Wheung Whoe , Ivanov Victor
Published: March 2009

Magnetic Pulse Compaction (MPC), as a dynamic compaction, can be possible to reach higher relative density of nano metallic compacts owing to sufficiently high pressure and adiabatic heating in very short duration of an order of µsec. The present work is concerned with the magnetic pulsed compaction of the nano-sized aluminum powders, which particle size was a range of 50 ~ 100 nm passivated in air. The compaction pressure was 1.5 GPa for 300 µsec in the temperature range from 20°C to 500°C. The grain size of compacts was maintained less than 50 nm, which was analyzed by X-ray diffraction (XRD) using Scherrer method. From the calculation of adiabatic heat and of pressure induced by thermal expansion, and the observation by transmission electron microscopy (TEM), it was found that Al2O3 could be broken and dispersed with a few nano-meter sizes in the Al matrix and that the ultra fine and uniform bulk structure was maintained up to 400°C of compaction temperature.e
Phase Relation and Room Temperature Mechanical Property of Cr2Zr Based Laves Phase
Authors: Kim Won Yong , Yeo In Dong , Kim Mok Soon , Takasugi Takayuki
Published: March 2009

Phase relation and mechanical property of Cr2Zr Laves phase alloy systems were investigated in terms of ternary alloying based on geometric concept of atomic sizes of constituent alloying elements. Ternary phase diagrams at 1573 K of Cr-Zr-Nb and Cr-Zr-Hf alloy systems were examined using SEM-EPMA analysis in order to understand the site occupation behavior of ternary elements and the phase stability of Laves phase. In the Cr-Zr-Nb alloy system, Laves phase had a broad off-stoichiometry range in the middle of Cr2Zr-ZrNb2 pseudo-binary line, while a limited and uniform range of Laves phase field was found in the Cr-Zr-Hf alloy system. For both Laves phase alloys, 0.2% offset yield strength decreased with increasing content of allying element, on the other hand compressive ductility increased with increasing content of alloying elements. Details will be discussed in conjunction with microstructure, phase stability and atomic size considerations.
High Temperature Wear Properties of Multiphase Composite: The Role of Transfer Film
Authors: Kim Seong Jin , Park Sang Jin , Basch Rena H. , Fash James W. , Jang Ho
Published: March 2009

The role of transfer film on high temperature wear properties of a multiphase composite for a brake friction material was investigated using a pad-on-disk type tribometer. A novolac resin-bonded composite based on a simple formulation with 6 ingredients (aramid pulp, cashew dust, Cu fiber, graphite, potassium titanate, and zirconium silicate) was used in this study. Results showed that the wear properties of the composite were significantly affected by the temperature at the frictioninterface when the transfer film was present on the counter face during sliding. In particular, the transfer film on the disk surface was well developed at approximately 200°C, resulting in theimproved wear resistance. It suggested that the transfer film on the disk surface effectively prevented direct contacts of the composite onto the counterface. On the other hand, no apparent relationship between transfer film thickness and friction coefficient was found in this experiment.
High Temperature Background Characterization of Internal Friction for Fine-Grained Nickel/Zirconia Composite
Authors: Kang Chang Seog , Hong Sung Kil
Published: March 2009

A mechanical spectroscopy study has been made on fine-grained Ni-10vol%TZP(ZrO2-3mol.%Y2O3) composite in an attempt to assess the following micromechanical prediction. A dual-phase material with fine-grained constituents deforming by Coble-type boundary-diffusion creep exhibits viscoelastic behavior. Dynamic Young's modulus and internal friction are measured over a temperature range of 25 to 800oC at frequencies of 0.01, 0.05 and 0.1Hz using a specially designed tension-compression apparatus. Two relaxation peaks are observed in the composite. An exponential involved in the peak and background components are determined and, by making a further analysis based on the micromechanical formulation and also taking the well-known relaxation due to viscous grain-boundary sliding into account, the implications of these quantities are discussed in terms of constituent material parameters(boundary diffusivity, grain size, etc.).
White Light Emitting Diodes of GaN-Based Sr2SiO4:Eu and the Luminescent Properties
Authors: Park J.K. , Kim Chang Hoi , Choi Kyung Joo , Park H.D. , Choi Se Young
Published: March 2009

We have synthesized a Eu2+-activated Sr2SiO4yellow phosphor and
investigated an attempt to develop white LEDs by combining it with a GaN blue LED
chip. Two distinct emission bands from the GaN-based LED and the Sr2SiO4:Eu phosphor are clearly observed at 400 nm and at around 550 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (400 nm chip)-based Sr2SiO4:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.
Annealing Temperature Effect of PbZr0.4Ti0.6O3 Film on La1/2Sr1/2CoO3 Bottom Electrode
Authors: Kim Jai Hyun , Koh Kyung Shin , Choo Woong Kil
Published: March 2009

We have investigated the ferroelectric and electrical properties of PZT 40/60 films on the bottom La1/2Sr1/2CoO3(LSCO) electrode. The LSCO bottom electrode was sputtered on the SiO2/Si(100). As the annealing temperature of PZT capacitors on the LSCO is increased, the ferroelectric properties gradually increase with the annealing temperature up to 650°C. However, for the PZT capacitors annealed above 650°C, electrical measurement cannot be performed.
Temporal Evolution of Grain Size Distributions in Two-Dimensional Pinned Cells
Authors: Wörner C.H. , Olguín A.
Published: March 2009

The distribution of sizes for grain growth in presence of pinning centers (Zener pinned growth) is communicated at different times. The experimental approach uses the well-known similitude between growth in polycrystalline aggregates and cellular soap froths. Two-dimensional results are communicated with grain growth limited by a set of randomly distributed rounded pins.
Dynamic Recrystallization and Grain Growth in a ZK60 Magnesium Alloy Sheet Produced by Isothermal Rolling
Authors: Galiyev Arthur , Kaibyshev Rustam
Published: March 2009

A ZK60 magnesium alloy was subjected to isothermal rolling (IR) at 275 and 300°C. This processing resulted in grain refinement through dynamic recrystallization (DRX) at both temperatures. The recrystallized volume fractions of 82 and 95% and average sizes of fine grains of 2.5 and 3.7 µm were achieved after IR at 275 and 300°C, respectively. It was shown that the ultrafine-grained structure produced by DRX at 300°C exhibited higher stability under following static and dynamic annealing than that produced at 275°C. This fact was attributed with the formation of a less constrained DRX structure at higher temperature of IR. As a result, the sheet
produced from the ZK60 alloy at 300°C showed superior superplastic properties. Conversely, it was not feasible to enhance the superplastic properties in the ultrafine-grained alloy produced at 275°C because significant grain growth occurred during further processing of the as-rolled alloy.
Mechanisms of Grain Refinement in Aluminum Alloys during Severe Plastic Deformation
Authors: Kaibyshev Rustam , Mazurina I.
Published: March 2009

The mechanisms of grain refinement during severe plastic deformation have been studied, by comparing the microstructure evolution in an AA2219 aluminium alloy, containing Al3Zr nanoscale particles, with that in a dilute Al-3%Cu alloy deformed identically by equalchannel angular extrusion (ECAE) at 250oC to a maximum strain of ~12. Transmission electron microscopy (TEM) was used on the AA2219 alloy to reveal the misorientations of deformationinduced boundaries. Microstructural evolution in the Al-3%Cu alloy was studied by electron-back scattering diffraction (EBSD) orientation mapping. It was shown that the mechanism of grain refinement in the AA2219 alloy is continuous dynamic recrystallization (CDRX) consisting of two main elementary processes. In the initial stages of plastic deformation, the formation of threedimensional arrays of low-angle boundaries (LABs) takes place. Further strain results in increasing misorientation of these boundaries providing their gradual transformation into high-angle boundaries (HABs). A fully recrystallized structure with an average grain size of ~0.9 µm is evolved after a total strain of ~12. In the dilute Al-Cu alloy the evolution of ultrafine grains with an average size of ~6 µm is attributed to the formation of deformation bands outlined by HABs and extended medium to high-angle boundaries at moderate strains. The subdivision of these deformation bands into fine grains rarely occurs through the mechanism of geometric recrystallization (GRX). In this alloy the main contribution in the grain refinement gives CDRX occurring within fibrous structural features. At e~12, a partially recrystallized structure is formed in the Al-3%Cu alloy.
Investigation of the Primary Recrystallisation Microstructure of Cold Rolled and Annealed Fe 3% Si Single Crystals with Goss Orientation
Authors: Dorner Dorothée , Lahn Ludger , Zaefferer Stefan
Published: March 2009

A silicon steel single crystal with {110}<001> Goss orientation was cold rolled up to 89 % thickness reduction and subsequently annealed. The evolution of the macroscopic cold rolling texture was investigated by x-ray diffraction. Local orientation relationships and the microstructure around and within Goss grains of deformed and annealed samples were analysed using the electron backscatter diffraction (EBSD) technique. During cold rolling a texture consisting of two strong
{111}<112> components and a minor {110}<001> Goss component develops. After primary recrystallisation the texture is characterized by a strong Goss component. Goss-oriented grains that remain after high deformation are considered to be the origin for the primary recrystallisation texture.
Recrystallization Kinetics in the Bulk and at the Surface
Authors: Juul Jensen Dorte , Lund M.D. , Larsen A.W. , Bowen Jacob R.
Published: March 2009

Possible variations in recrystallization kinetics from the sample surface to the center have been investigated in 90% homogeneously cold rolled aluminium (AA1050). It was found that whereas the average growth rates are quite similar, the nucleation characteristics are different at the surface and in the bulk.
Recovery and Recrystallization in Cold Worked Fe – O Steels
Authors: Belyakov Andrey , Sakai Yuushi , Hara Toru , Kimura Yuuji , Tsuzaki Kaneaki
Published: March 2009

Several Fe – O samples containing different fractions of dispersed oxides were processed by mechanical milling followed by consolidating rolling. The samples were annealed at 1000oC and then compressed to strains of 0.35, 1.2, and 1.9 at an ambient temperature. Dispersed oxides with size of about 20 nm were homogeneously distributed throughout the ferrite matrix and their volume fractions varied from about 0.3% to 2.0%. To study the annealing softening mechanisms, the coldworked specimens were annealed for an hour at 700oC and 800oC. The fine dispersion of oxide particles was very effective to suppress any softening processes. Primary recrystallization fully developed in the samples with volume fraction of dispersed oxides of about 0.3%. Increase in the fraction of dispersed oxides resulted in decrease of the fraction recrystallized. In the samples containing 2.0 vol.% of dispersed oxides, only recovery was the annealing softening process irrespective of the preceding cold strain. The critical volume fraction of dispersed particles for development of the primary recrystallization is considered to range from 0.5 to 2.0%.