bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear Analysis during Friction Stir Processing of A359+20%SiC MMC
Authors: Contorno D. , Faga M.G. , Fratini Livan , Settineri Luca , Gautier di Confiengo G.
Published: March 2009

Metal Matrix Composites (MMC) are very interesting materials for applications in the automotive and aerospace fields, since they combine the lightness of Aluminium with the strength of the ceramic reinforcement.
These materials are very difficult to join and conventional welding techniques are not applicable, whereas solid-state welding techniques, like Friction Stir Welding (FSW), could be a solution. However very hard tool materials will need to be chosen in order to overcome the problem of heavy abrasive tool wear.
In this work the wear behaviour of coated and uncoated steel tools has been investigated in the Friction Stir Processing of extruded bars in A359 + 20%SiC. AISI 1040 steel was used as the tool material in the hardened uncoated and annealed and coated versions. In the latter case the steel was coated with multilayer PVD AlSiCrN or AlSiTiN.
Coatings were fully characterised, in terms of thickness, hardness, adhesion and tribological behaviour. Further, tool wear analysis has been carried out using optical and electronic microscopy, with EDS analysis. The results gave some interesting information on the choice of tool in the FSW of MMC materials.
Feasibility Evaluation of Sheet Metal Hydroformed Components through Shape Factors Application
Authors: Del Prete Antonio , Primo Teresa , Papadia Gabriele , Manisi Barbara
Published: March 2009

Sheet hydroforming has gained increasing interest in the automotive and aerospace industries because of its many advantages such as higher forming potentiality, good quality of the formed parts which may have complex geometry. The main advantage is that the uniform pressure can be transferred to any part of the formed blank at the same time [1].
In this paper, a “shape factors” set has been defined with the proper goal to understand if it can be used to help engineers to define “process rules” for the studied non conventional technology [2]. A specific prediction model, obtained thanks to a numerical factorial fractional plane, has been used in order to preview the process responses vs each defined shape factor. These shape factors have been used to track the process performances through their variation thanks to the usage of the numerical simulation that has been validated with an appropriate experimental campaign executed thanks to the usage of a specific equipment properly designed.
Manufacturing of Innovative Car Seat Components by Forming of Advanced High Strength Steels – Fundamental Research and Application
Authors: Merklein Marion , Kaupper Markus
Published: March 2009

Nowadays advanced high strength steel sheets and related forming technologies play an important role in lightweight construction in the transportation sector. Since especially car seat components are subject to very strict safety demands, the application of these modern steel grades, which provide enhanced strength levels, seems to be a promising strategy to meet the challenge of reducing the sheet metal thickness while maintaining the crash energy absorption capacity. Concerning the high required level of part complexity and accuracy both the reduced formability and the increased springback tendency of advanced high strength steels are challenges for forming technologies compared to conventional steel grades. Against this background the forming potentials of advanced high strength steels are investigated and are made accessible for an application in structural car seat components. The analysis is to be done both experimentally and numerically, focusing on the finite element method (FEM) regarding a reliable process design.
Modelling the Effect of Pre-Strain and Inter-Stage Annealing on the Stretch Forming of a 2024 Aluminium Alloy
Authors: McMurray Robert J. , O’Donnell M. , Leacock Alan G. , Brown Desmond
Published: March 2009

The severe double curvatures often encountered in aerospace fuselage and nacelle skins often necessitate multistage stretch forming operations. Each stage adds value to the component and rejection, particularly at later stages, must be avoided. Therefore process optimisation using accurate modelling tools to predict the strain levels is essential. This paper presents a novel method for modelling the aforementioned stages of the process using a tailored material model based on strain history and heat treatment. The modelling process is implemented within the PAMSTAMP Finite Element code, by modifying the material properties in the input file using an Excel based algorithm. The proposed method is validated using profiled stretch formed specimens, thereby imposing a variable strain gradient in a single specimen without having to resort to the complexity of double curvature. The model results are shown to represent the observed behaviour well.
A Contribution to the Optimisation of a Simple Shear Test
Authors: Merklein Marion , Biasutti M.
Published: March 2009

The finite element method is a widely used tool in sheet metal forming. The quality of the results of such an analysis depends largely on the applied constitutive model and its material parameters, which have to be determined experimentally. These data are relevant on the choice of the yield criterion among the wide range of options available in the commercial applications implementing the finite element method. Since the accuracy of material parameters estimation is therefore crucial, investigations were performed with an Al-Mg sheet alloy and a mild steel sheet to optimize a Miyauchi-based simple shear test. This method is one of the basic ways to investigate the plastic properties of a sheet metal up to large strains, which is very important for numerical analysis of sheet metal forming processes. Aim of the test is to determine the shear stress-strain correlation. In order to enhance the quality of the experimental results the detection of the deformation’s field, trough an optical measurement system, and the methodology for its evaluation are focus of the present study.
Flexible Draw Bending of Profiles
Authors: Rosenberger Jürgen , Behrens Bernd-Arno , Hübner Sven , Süße Dietmar , Ulbricht Volker
Published: March 2009

The technology of draw bending represents an alternative to produce flexible load-adapted sheet metal profiles. In addition to the adaptability of profile configuration low machine costs and an uncomplicated system control make this a very flexible production method. Hence it is particularly suitable for the production of profiles in small batch series or the fabrication of prototypes.
Prevention of Partial Draw-In During High Speed Deep Drawing
Authors: Wielage Hanna , Vollertsen Frank
Published: March 2009

Due to an ongoing trend of function compaction miniaturization gets more and more important in industrial production. Through the growing miniaturization new difficulties have overcome like scaling effects. However, on the other hand scaling towards smaller parts enables the application of new technologies which do not work in macro engineering. One such method is high speed deep drawing which is based on TEA-CO2-laser induced shock waves. This process utilizes an initiated plasma shock wave on the target surface, which leads to forming of the sheet. Several pulses can be applied at one point and therefore a high forming degree can be reached without increasing the energy density. In this article this non-mechanical forming process is applied and a concept for the prevention of partial draw-in is discussed. Therefore potentially influencing factors are investigated.
Process Parameter Effects on the LDR in Warm Deep Drawing of Magnesium Alloys
Authors: Ambrogio Giuseppina , Filice Luigino , Forcellese Archimede , Manco G. Leonardo , Simoncini M.
Published: March 2009

The present work is focused on the investigation of the role of temperature and punch speed in warm deep drawing of AZ31 magnesium alloy. To this purpose, an experimental campaign, defined using a proper DOE approach, has been performed. The experimental results, in terms of the Limiting Drawing Ratio, have shown that drawability is strongly affected by the process parameters. In particular, Limiting Drawing Ratio exhibits the peak value at 250°C. As far as the effect of punch speed is concerned, it depends on temperature: at 200°C drawability increases with decreasing punch speed whilst a reverse behaviour is observed at 250 and 300°C. The experimental results have been analysed by ANOVA in order to evaluate the effect of the single independent factors and their interactions on the dependent one.
Enhancing Deep Drawing Processes by Using a Thermomechanical Tool Design
Authors: Voges-Schwieger Kathrin , Hübner Sven , Behrens Bernd-Arno
Published: March 2009

The nature of phase transformation in metastable austenitic steels due to strain- induced ’-martensite formation is used as new contribution to lightweight construction in crash safety applications. A thermomechanical tool design was developed to enhance the ’-martensite evolution in local areas. Draw and stop beads allow a concerted stretch-out of material by increasing true strain . The local warming of defined regions avoids the phase transformation to retain the original austenitic lattice while a regional cooling enforce this nature by realizing a constant true strain .
Effect of Coiling Temperature on the Formation and Pickling Behaviour of Tertiary Scale on Hot-Rolled Carbon Steel Strip
Authors: Chandra-Ambhorn Somrerk , Ieamsupapong Supati , Thanateponake V. , Suksamai Walairat
Published: March 2009

Steel strips covered by a tertiary thermal oxide scale from a hot rolling process were studied in this research work. In case that the clean strip is required, i.e. for the cold rolling process, this tertiary scale formed on the steel surface is typically removed by a pickling process. In this work, a finishing temperature – the temperature at the exit of strip from a finishing mill – was kept constant at 830 °C. A coiling temperature – the temperature that the strip was coiled at a down coiler – was varied in a real hot rolling line to obtain different types of tertiary scales formed on low carbon steel strips. Physico-chemical characteristics and pickling behaviour of the scales were further investigated. It was found from a scanning electron microscope (SEM) that the thickness of scale at the centre of strip was in the range of 3-5 m and reduced with the decrease in coiling temperature. A laser Raman spectroscopy was also applied to make a depth profile of scale. Additionally, with the results observed from SEM and X-ray diffraction (XRD), it is concluded that the tertiary scale is a non-homogeneous single layer of a eutectoid structure consisting of magnetite and iron. Moreover, the samples were further immersed in a 10%v/v HCl pickling solution at 80 °C. It was found that the time needed to remove the tertiary scale was reduced with the decreased scale thickness, which was obtained by lowering the coiling temperature. Kinetics of scale removal during pickling is discussed in the paper.
Neutron Diffraction Study on Intermetallic Er5Mg24 and Tm5Mg24
Authors: Schäfer Wolfgang , Buschow K.H.J.
Published: March 2009

Neutron powder diffraction on the binary intermetallics Er5Mg24 and Tm5Mg24 confirms their isostructural and pure crystallization in the Ti5Re24-type structure (space group I 4 3m, Z = 2)with rare earths located in 2a(0,0,0) and 8c(x,x,x) and Mg in two different 24g(x,y,x) sites. Room temperature lattice constants are 11.263(2) Å and 11.215(1) Å for the Er and Tm compound, respectively. Atomic positions have been refined. Both compounds order ferromagnetically below Curie temperatures of 17.5(5) K and 7.5(5) K for Er5Mg24 and Tm5Mg24, respectively. The magnitudes of the Er moments at 4.2 K are 7.5(2) µB and 4.4(2)µB on the 2a and the 8c sites, respectively. The Tm moments which have been refined from 2 K measurements amount to 3.0(3)µB and 2.8(2) µB, respectively. The temperature dependencies of the magnetic Bragg intensities reveal distinct deviations from Brillouin curves for J = 15/2 (Er) and J = 6 (Tm) systems and indicate a complex magnetic exchange.
Antireflection Layer Coatings on the Si Solar Cell Using SiO2 and Si3N4
Authors: Chang Gee Keun
Published: March 2009

With new models of AM1 solar spectra and Si refractive indices in the wavelength range
of 0.4

0.97

, effective absorption powers of Si solar cells coated with the single and
double AR layers were theoretically calculated for the first time. The SiO2, Si3N4 and
SiO2/Si3N4 easily obtainable in the standard Si process were used as the AR layers of Si solar
cell. Optimum thicknesses showing the maximum absorption power for AR layers of SiO2,
Si3N4 and SiO2/Si3N4 were as follows: d(SiO2)=10001, d(Si3N4)=7001 and d(SiO2/Si3N4) =500
1 /3001 . Effective absorption powers in the solar cells of SiO2-Si, Si3N4-Si and SiO2/Si3N4-Si were
520W/m2, 565W/m2 and 607W/m2 at AM1 in the optimum conditions of AR coating, respectively
Microstructures and Magnetic Property of Bulk and Thin Film Co2MnGe Heusler Compound
Authors: Tsuchiya Koichi , Washio Takehiro , Hashimoto Tatsuya , Miyanaka Kohji , Umemoto Minoru
Published: March 2009

Half metallic ferromagnets are candidate materials for novel electronic devices, which can
control the spin character of the conducting electrons. Electronic band calculation predicted that
Co2MnGe Heusler compounds may has the half metallic band structure. In the present study,
structure and magnetic properties have been investigated of the Co2MnGe for bulk and thin films. In
the bulk sample, plate defects have been found.
Magnetotransport Properties in Semimetallic Bismuth Thin Films
Authors: Lee K.I. , Jeun M.H. , Lee J.M. , Chang J.Y. , Han S.H. , Ha J.G. , Lee W.Y.
Published: March 2009

The magnetotransport properties of the electroplated and sputtered Bi thin films have been
investigated in the range 4  300 K. A marked increase from 5,200 % to 80,000 % in the ordinary
magnetoresistance (MR) for the electroplated Bi thin film was observed after thermal anneal at 4 K.
The MR ratios for the as-grown and the annealed Bi thin films were found to exhibit 560 % and 590
%, respectively, at 300 K. On the other hand, the MR for the sputtered Bi film grown by sputtering
was hardly observed at 4 and 300 K, whereas the MR ratios after anneal were found to reach 30,000 %
at 4 K and 600 % at 300 K. We find that the room temperature MR in the sputtered films depends on
the trigonal-axis oriented microstructures and grain size, in contrast to the electroplated films. Our
results demonstrate the very large room temperature MR in the electroplated and sputtered Bi thin
films, which can be used for spintronic device applications.
Origin of Thermal Stability of IrMn Based Specular Spin Valve Type GMR Multilayer
Authors: Yoon S.Y. , Lee D.H. , Jeong K.H. , Yoon D.H. , Suh Su Jeong
Published: March 2009

By using the sputtering process, we made the IrMn based specular spin valve system,
whose nano-oxide layer (NOL) was formed by natural oxidation. After thermal annealing at 305 and
410 °C, the thermal stability of the specular spin valve was observed. We found that the highest
magnetoresistance (MR) ratio of about 12 % MR was produced after optimum annealing at 305 °C
but the sample annealed at 410 °C also had a high MR ratio about 10 %. It is superior to other studies
at this temperature. Based on the AES and XPS results, we could conclude that this enhanced thermal
stability was due to the stable Cu layer between the pinned layer and free layer and to the NOL as a
diffusion barrier for the Mn.
Transformation Behavior and Shape Memory Characteristics of Ti-45Ni-5Cu(at%) Alloy Ribbons Fabricated by Melt Spinning
Authors: Nam Tae Hyun , Lee Jae Hwa , Kim Tae Yeon , Kim Yeon Wook
Published: March 2009

Transformation behaviors and shape memory characteristics of Ti-45Ni-5Cu alloy
ribbons fabricated by melt spinning were investigated by means of optical microscopy,
differential scanning calorimetries(DSC), X-ray diffraction and thermal cycling tests under
constant load. They depended largely on temperatures of liquid metal. The B2-B19-B19
two-step transformation occurred in the ribbons fabricated with the liquid whose temperature
was higher than 1723 K, while the B2-B19 one-step transformation occurred in the ribbons with
the liquid at 1673 K. The stabilization of the B19 martensite in Ti-45Ni-5Cu alloy ribbons was
ascribed to the high density of dislocations which made strong resistance to large lattice
deformation associated with a formation of the B19 martensite.
Microstructure of Cu-TiB2 Nanocomposite during Spark Plasma Sintering
Authors: Kwon Young Soon , Kim Ji Soon , Park Jong Jae , Kim Hwan Tae , Dudina Dina V.
Published: March 2009

Microstructural change of TiB2-Cu nanocomposite during spark plasma sintering (SPS)
was investigated. Under simultaneous action of pressure, temperature and pulse electric current
titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a
interpenetrating phase composite with a fine-grained skeleton. Increase of SPS temperatures and
holding times promotes the densification of sintered compacts due to local melting of copper
matrix.
Effect of Heating Rate on Sintered Microstructure of W-Cu Nanocomposite Powder Produced Using W-CuO Mixture
Authors: Kim Dae Gun , Kim Gil Su , Kim Jin Chun , Oh Sung Tag , Kim Young Do
Published: March 2009

The sintered microstructure homogeneity of W-15wt%Cu nanocomposite powders
prepared from W-CuO mixture was investigated. The increment of heating rate considerably
affected the homogeneity of sintered microstructure. In case of the higher heating rate, the
microstructure was more homogeneous than that of the lower heating rate by reason of Cu-
exudation during heating-up process.
Synthesis of ZnO Nanoparticles Embedded in a Polymeric Matrix; Effect of Curing Temperature
Authors: Jeon Hyung Jun , Chung Yoon , Kim Sun Young , Yoon Chong Seung , Kim Young Ho
Published: March 2009

We studied ZnO nanoparticle formation in a polyimide (PI) film. Polyamic acid (PAA) was
spin-coated onto Zn thin films and PAA/metal films were cured at various temperatures.
Transmission electron microscopy was used to characterize oxide nanoparticles in the polyimide film.
Nanosize ZnO particles were formed in the polyimide film regardless of the curing temperature. The
size and the density of ZnO particles depended on the curing temperature. Th
Effect of Bioactive Grade Surface on In Vivo Behavior and Mechanical Stability in Titanium Based Implant Surface-Modified by Plasma Spray Coating and Chemical Treatments
Authors: Lee Baek Hee , Kim Young Do , Lee Kyu Hwan
Published: March 2009

Geometrical and chemical designs of an implant surface affected the stabilization of
implant and the healing of tissue. In this study, effects of surface designs in implants on in vivo
behavior and mechanical stability were compared by histological and mechanical analyses. The
implants were transversely grafted on dog thighbone and healed for 4 and 8 weeks. The pull-out
strength between living bone and implant was evaluated by universal testing machine (UTM).
Fatigue Performance of Low Rigidity Titanium Alloy for Biomedical Applications
Authors: Akahori Toshikazu , Niinomi Mitsuo , Fukui Hisao , Suzuki Akihiro
Published: March 2009

Microstructures of Ti-29Nb-13Ta-4.6Zr (TNTZ) aged at temperatures between 573 and
723 K after solution treatment at 1063 K have super fine omega phase, or both super fine alpha
and omega phases, respectively in beta phase with an average grain diameter of 20 µm. Plain fatigue
strength of TNTZ aged after solution treatment is much greater than that of as-solutionized TNTZ in
both low cycle fatigue and high cycle fatigue life regions. This is due to the improvement of the
balance of strength and ductility by the precipitation of alpha phase. Fretting fatigue strength of
TNTZ conducted with various heat treatments decreases dramatically as compared with their plain
fatigue strength in both low cycle fatigue and high cycle fatigue life regions. In this case, the
decreasing ratio of fretting fatigue life increases with increasing the small crack propagation area
where both the tangential force and frictional force at the contact plane of pad exist. In fretting
fatigue in air, the ratio of fretting damage (Pf/Ff), where Pf and Ff stand for plain fatigue limit and
fretting fatigue limit, respectively, increases with increasing elastic modulus. In fretting fatigue in
Ringers solution, the passive film on specimen surface is broken by fretting action in TNTZ, which
have excellent corrosion resistance, and, as a result, corrosion pits that lead to decreasing fretting
fatigue strength especially in high cycle fatigue life region, are formed on its surface.
Effect of Tin Addition on Phase Constitution and Heat Treatment Behavior in Ti-40Ta-Sn Alloys
Authors: Ikeda Masahiko , Komatsu S. , Nakamura Yuichiro , Kobayashi Y.
Published: March 2009

Using Ti-40mass%Ta-0, -4, -8 and -12mass%Sn alloys, the effect of Sn addition on phase
constitution in the solution treated and quenched state and isochronal heat treatment behavior is
studied by electrical resistivity and Vickers hardness measurements and X-ray diffactometry. To
confirm shape memory effect of some of these alloys, shape-recovery test was also performed.
Orthorhombic martensite,  was identified in Ti-40Sn-0 to 8Sn alloy quenched from 1173K, while
phase was identified in STQed Ti-40Ta-12Sn alloy. On isochronal heat treatment, increases of
resistivity at LN and resistivity ratio were observed in only 8Sn alloy, because these increases are
due to reverse-transformation of  to phase. From result of shape recovery test, shape memory
effect was observed in Ti-40Ta-4 and 8Sn alloys
Enhanced Modification Process of B.390 Casting Alloy by the Ca Content Control
Authors: Kim H.J , Yoon Eui Pak , Kobayashi Toshiro
Published: March 2009

Primary Si particle size has been refined as Ca content of the melts decreased and cooling rate increased. A control of Ca content by the addition of CuCl2 to the melt was the most efficient in the refinement of primary Si particles. The minimum size of primary Si particles in this study was 15.0um when a residual content of Ca element in the alloy was 5ppm. Primary Si particle size was refined as primary Si crystallization temperature increased, which was attributed to the decrease of
Ca content in the melts.
Grain Refinement of Copper Alloys by Equal Channel Angular Pressing
Authors: Lim Cha Yong , Jung Jae Hyuck , Han S.Z.
Published: March 2009

The equal channel angular pressing (ECAP) is one of the methods to refine the grain size of metallic materials. This study investigates the effect of ECAP process on the formation of the fine grain size in oxygen free Cu and Cu alloys. The average grain size has been refined from 150 µm before ECAP to 300 nm. Microstructure was analyzed by transmission electron micrography (TEM). The diffraction pattern of the selected area confirmed the formation of ultrafine-grained structure with high angle grain boundaries after 8 cycles of ECAP. Mechanical properties such as microhardness and tensile properties of the ultra-fine grained copper materials have been investigated.
Tensile Properties and Fracture Behavior of SiCp/AC4CH Composite at Loading Velocities of up to 10m/s
Authors: Wang Lei , Kobayashi Toshiro , Liu Chun Ming
Published: March 2009

Tensile test at loading velocities up to 10 m·s-1 (strain rate up to 3.2x102 s-1) was carried out forr SiCp/AC4CH composite and AC4CH alloy. The microstructure of the composite before and after tensile deformation was carefully examined with both optical microscope and SEM. The experimental results demonstrated that the ultimate tensile strength (UTS) and yield strength (YS) increase with increasing loading velocity up to 10 m·s-1. Comparing with AC4CH alloy, the fracture elongation of the composite is sensitivity with the increasing strain rate. The YS of both the composite and AC4CH alloy shows more sensitive than that of the UTS with the increasing strain rate, especially in the range of strain rate higher than 102 s-1.
Characteristics of the Compound Layer on the SCM 435 Steel Produced by Plasma Nitrocarburizing
Authors: Lee In Sup
Published: March 2009

Plasma nitrocarburizing treatment was performed for SCM 435 steel by using a pulsed plasma ion nitriding system. The effects of the variation of nitrogen and methan contents upon the hardened layer were investigated. Both the thickness of the compound layer and the amount of ε phase in the compound layer increased with nitrogen content. For an atmosphere containing 90% N2 gas content in the gas mixture, the thickness of the compound layer decreased due to the reduction of the number of nitrogen ion and slow diffusion of nitrogen atoms. The relative amount of ε phase in the compound layer increased with CH4 gas content up to 2%. For CH4 gas content over 2% in the gas mixture, the thickness of the compound layer decreased with CH4 content due to the formation of θ-Fe3C phase.
Fabrication of CdS Thin Film Pattern by CBD Method Using the Self-Assembled Monolayer
Authors: Jung S.-H. , Jeong D.K. , Kim J.Y. , Jung Woo Gwang
Published: March 2009

Microcontact printing of hydrophobic OTS (Octadecyl-Trichloro-Silane) material was made on various substrates, and finely patterned CdS thin film has been fabricated by CBD (Chemical Bath Deposition) method. In the preliminary experiment, it is confirmed that the size of colloid particle and roughness of surface of CdS thin film are increased with increase of pH, fabrication time and temperature. The optimum condition for the selective deposition of CdS film pattern using the SAM with microcontact printing was determined to be pH 10, temperature of 75°C, deposition time of 15 minute. Various patterns of different shape of CdS thin film were
fabricated uniformly and satisfactorily in large area by the conditions determined in the present work. The stoichiometric composition of CdS was confirmed to be 1:1 by EDS and XPS.
Quantitative Analysis of Precipitation Behavior in Ferrite of V Added Microalloyed Steel
Authors: Kang Hun Chul , Lee Sang Hwan , Shin Dong Hyuk , Lee Kyung Jong , Kim Seon Jin , Lee Kyung Sub
Published: March 2009

The quantitative analysis of precipitates in ferrite was investigated using the fact that the formation of precipitates in Nb, V and Ti added steels accelerated austenite/ferrite transformation. The major factors on austenite/ferrite transformation were cooling rate, austenite grain size, and deformation. The slower cooling rate, the smaller austenite grain size and the higher deformation accelerated austenite/ferrite transformation. In 0.34wt%V micro-alloyed steel, the influence of cooling rate and austenite grain size on austenite/ferrite transformation was investigated without
deformation. In addition, the experimental method was set up to measure the amount of precipitates in ferrite by the transformation dilatometer. The amount of precipitates was controlled by the holding temperature and time in ferrite. Then, the specimen was inversely transformed without the formation or dissolution of precipitates. Volume fractions transformed were measured by dilatometer during cooling. Iso-precipitation kinetics was determined by comparing the mean transformation temperatures at various conditions, respectively. The result was compared with the
calculated.
TEM Observations of the Precipitation of A2 Particles in D03 Precipitates in Fe-Si-V Alloy System
Authors: Doi Minoru , Sakai Daisuke , Koyama Toshiyuki , Kozakai Takao , Moritani Tomokazu
Published: March 2009

The present study examined the effects of heat treatment and the addition of Cu-Ni alloy on the corrosion resistance of the matrix of spheroidal graphite cast iron in aqueous environments. Test materials of white cast iron and carbon steel were used for comparison with spheroidal graphite cast iron. The alloy spheroidal graphite cast iron that added Cu and Ni was prepared. The spheroidal graphite cast iron was subjected to three kinds of heat treatment to adjust the matrix: annealing, oil quenching, and austemper heat treatment. In electrochemical tests, measurements of corrosion electrode potential and cathode and anode polarization were used. The following was clarified from the relationship between the electrode potential and current density of each of the materials in each of the solution. The alloy spheroidal graphite cast iron had a high corrosion electrode potential owing to the addition of Cu-Ni, and tended to have a low corrosion current density. This demonstrates that in any of the materials having a matrix adjusted by heat treatment, the addition of Cu-Ni increased the corrosion resistance. The corrosion current density was highest in a sulfuric acid environment.
Low Cycle Fatigue and Fracture Behavior of Nickel-Base Superalloy CM247LC at 760°C
Authors: Seo Seong Moon , Kim In Sup , Jo Chang Yong
Published: March 2009

Low cycle fatigue (LCF) behavior of coarse and fine grained superalloy CM247LC at 760°C has been investigated. Both coarse and fine grained CM247LC showed similar cyclic stress response, however, the fine grained CM247LC specimen exhibited relatively uniform and superior fatigue properties to the coarse grained one. It was found that fatigue crack initiation of the alloy was keen to the applied strain range. Fatigue crack initiated at the surface of the specimen with high strain range (∆εt≥( 0.7%) while the initiation site moved to the internal defects at low strain range (∆εt≤0.6%).
High Temperature Deformation Mechanism Maps of NiAl
Authors: Lee I.G. , Ghosh A.K.
Published: March 2009

In order to analyze high temperature deformation behavior of NiAl alloys, deformation maps were constructed for stoichiometric NiAl materials with grain sizes of 4 and 200 µm. Relevant constitute equations and calculation method will be described in this paper. These maps are particularly useful in identifying the location of testing domains, such as creep and tensile tests, in relation to the stress-temperature-strain rate domains experienced by NiAl.
Effects of Silicon and Chromium on the SCC Properties of Al-Zn-Mg-Cu Cast Alloy
Authors: Kim In Bae , Kim Kwang Nyeon , Kim Kyung Hyun , Kim In Gon
Published: March 2009

Effects of Si and Cr additions and aging treatment on the stress corrosion cracking(SCC) resistance of Al-Zn-Mg-Cu cast alloys were investigated by C-ring test and electrical conductivity measurement. The SCC resistance of Al-Zn-Mg-Cu cast alloys decreased in the order of Cr containing alloy, Si containing alloy and base alloy. The lowest electrical conductivity of Cr containing alloy exhibited the best SCC resistance and this is probably due to an improved corrosion resistance by forming a passive film on the surface. The over-aged alloys showed the better SCC resistance. This is due to the increased distance between coarse particles at grain
boundary. The fracture mode of the alloy was confirmed as intergranular type and showed brittle fracture surface. The SCC mechanism of Al-Zn-Mg-Cu cast alloys was found to be the anodic dissolution model.
Metastable Two-Phase Field(A2+B2) in Co-Al-Fe and Co-Al Alloy Systems
Authors: Kozakai Takao , Shikama Tadaaki , Koyama Toshiyuki , Doi Minoru
Published: March 2009

Precipitation of disordered bcc Co (A2) particles has been investigated in Co-rich B2 ordered Co-Al-Fe and Co-Al alloys by means of a macroscopic composition gradient method using a transmission electron microscope. When Co-Al-Fe ternary and Co-Al binary alloys were annealed at 823-1023K for a relatively short time, bcc disordered particles precipitated within B2 ordered matrix, followed by the formation of equilibrium fcc α-Co (A1) on the phase boundaries. The precipitation limit of metastable A2 phase was evaluated using the binary and ternary specimens with macroscopic compositional gradient. As a result, it was found that the limits are located within the equilibrium A1+B2 two-phase fields in both ternary and binary alloy systems, and that the limit curve on the isothermal section at 923K for Co-Al-Fe system successfully connects with the phase boundary of A2+B2 two-phase field at the Co-Fe binary side of the ternary system.
Structure and Dissolution Properties of Phosphate Glasses for Glass Fertilizer
Authors: Lee Y.S. , Kang Won Ho
Published: March 2009

For usage of glass fertilizer, physical and dissolution properties were investigated
according to variation of the SiO2 and K2O contents in silicate glasses. In glass forming region, K2O/P2O5 0-0.24, SiO2/(SiO2+P2O5) 0-0.29 and CaO/P2O5 0-1.00 were fabricated as clear glass in K2O-CaO-SiO2-P2O5 glass system. The glass transition temperature (Tg) and softening temperature (Ts) were gradually shifted to the higher temperature range according to increase of SiO2 contents. The K2O contents, which could cause the structure change from network structure to polymeric chain structure, have direct proportion with the thermal expansion coefficient and inverse proportion with Tg and Ts. The change of the K2O/P2O5 ratio was a main factor to control chemical durability and physical properties such as density and hardness. In the abnormal glass properties such as fast dissolution in aqueous solution, it was presented that the glass can be a good candidate for agriculture fertilizer.
Relationships between Textures and Surface Roughness, Frictional Behavior, Erosion and Corrosion Properties of TiN Films
Authors: Kim Hee Dong , Kim In Soo , Sung Dong Young , Lee Min Gu , Dost S. , King Hubert W.
Published: March 2009

TiN coated films were prepared by a reactive ion physical vapor deposition method. In this research, we studied the relationships between textures and friction coefficient, erosion-corrosion resistance and corrosion resistance in textured TiN films. The surface roughness of (115) textured TiN films is lower than that of (111) textured TiN films. The friction coefficient of (115) textured surface is similar with that of (111) textured surface of TiN coated films. The erosion-corrosion and corrosion resistance of (115) textured surface is better than that of (111) textured surface of TiN coated films.
Electrical Properties of G4-48azo Dendrimer Containing Azobenzene Functional Groups
Authors: Jung Sang Burm , Yang Ki Sung , Yoo Seung Yeop , Kim Chung Kyun , Lee Burm Jong , Kwon Young Soon
Published: March 2009

In this study, we attempted to fabricate dendrimer Langmuir-Blodgett (LB) films
functionalized with azobenzene groups in their periphery. It is well known that azoenzene-type compounds undergo an efficient and fully reversible photo-isomerization reaction. We investigated monolayer behavior and its characteristics at air-water interface by LB method. Then the molecular behavior shift of the monolayer by 365[nm] light irradiation was also measured because of the isomerization of azobenzene group in periphery. The electrical properties of G4-48Azo dendrimer were compared with between trans form and cis form using metal/dendrimer LB film/metal (MIM)structure and using STM system.
Crystallization Behaviors of the Bulk Amorphous Alloy Ni60Zr25Al8Y7
Authors: Kim W.B. , Ye B.J. , Yi S.
Published: March 2009

The effects of partial replacements of Zr by Y in the alloy Ni60Zr25-xAl8Yx(x=0 and 7 at %) on the crystallization behaviors of amorphous alloys were studied using isothermally heattreated ribbons. With the partial replacement, the supercooled liquid region upon continuous heating was significantly extended indicating that crystallization can be effectively suppressed by the optimum amount of Zr replacement by Y. The first phase appeared during crystallization was identified as the ternary compound AlNi2Zr while the single exothermic event could be observed upon heating the amorphous ribbons. The AlNi2Zr phase was decomposed into binary compounds upon further heating. Therefore, the extended supercooled liquid region of the alloy Ni60Zr25Al8Y7 was attributed to the suppression of AlNi2Zr phase formation by the partial replacement of Zr by Y. The effects of Y on the crystallization behaviors were discussed on the basis of atomic configuration of the supercooled liquid.
Effects of External Electrode and Heat Treatment on Stress Anisotropy and Residual Stress in BaTiO3-Based Ni-MLCCs
Authors: Park Dong Ho , Jung Yeon-Gil , Paik Ung Yu , Kim Jeong Wook , Yu Jin Young
Published: March 2009

Herein, we report the effects of external electrode and heat treatment on stress
anisotropy and residual stress on margins of MLCCs in each direction perpendicular and
parallel to internal electrode at length plane. The residual stresses estimated using an
indentation method are compared in regions with and without the external electrode as a
function of heat treatment. The stress anisotropy is not affected by both heat treatment and
external electrode, showing residual compressive stresses in all directions. However, at the
boundary, the crack length in the perpendicular direction is longer than that in the parallel
direction.
Properties of Tin Oxide Films Prepared by MOCVD
Authors: Choi Gwang Pyo , Park Yong Joo , Noh Whyo Sup , Park Jin Seong
Published: March 2009

Tin oxide thin films were deposited at 375 °C on α-alumina substrate by metal-organic
chemical vapor deposition (MOCVD) process. A number of hillocks on the film were formed after
air annealing at 500 °C for 30 min and few things in N2 annealing. The oxygen content and the
binding energy after air annealing came to close the stoichiometric SnO2. The cauliflower hillocks
of the film seem to be formed by the continuous migration of crystallites from a cauliflower grain
on the substrate to release the stress due to the increase of oxygen content and volume.
Evolving 3D Microstructures Using a Genetic Algorithm
Authors: Basanta David , Miodownik Mark A. , Holm Elizabeth A. , Bentley Peter J.
Published: March 2009

We describe a general approach to obtaining 3D microstructures as input to computer simulations of materials properties. We introduce a program called MicroConstructor, that takes 2D micrographs and generates 3D discrete computer microstructures which are statistically equivalent in terms of the microstructural variables of interest. The basis of the code is a genetic algorithm that evolves the 3D microstructure so that its stereological parameters match the 2D data. Since this approach is not limited by scale it can be used to generate 3D initial multiscale microstructures. This algorithm will enable microstructural modellers to use as their starting point, experimentally based microstructures without having to acquire 3D information experimentally, a very time consuming and expensive process.
Nucleation in Recrystallization
Authors: Humphreys John F.
Published: March 2009

The nucleation of recrystallization in deformed and annealed metals is reviewed. The main mechanisms are thought to involve the growth of subgrains by low angle boundary (LAGB) migration in an orientation gradient or the strain induced boundary migration (SIBM) of existing boundaries. Although these mechanisms are reasonably well understood, the details of the dislocation recovery mechanisms which are often required before migration can occur, particularly in metals in which recovery is slow, are poorly understood. Complete experimental investigation of the nucleation event requires a 3-d in-situ technique which will resolve dislocations, and this is not currently available. Although recrystallized grains of orientations not in the deformed structure have been reported, there is as yet no substantial evidence or theory to suggest the creation of new orientations by mechanisms other than annealing twinning. It is concluded that further understanding of the deformed state is required before adequate models of nucleation can be formulated and verified.
Monte Carlo Modeling of Cube Texture Evolution in Ni-Tapes during Grain Growth
Authors: Lin F. , Godfrey Andrew , Miodownik Mark A. , Liu Qing
Published: March 2009

After primary recrystallization of highly rolled (>98% reduction) high purity Ni (99.999%) tapes the cube texture fraction can range from 45 - 65%. Annealing at temperatures >1000oC leads to cube texture volume fractions of >95% as a result of grain growth. A Monte Carlo Potts model was used to simulate this annealing process. The starting microstructures for the simulations were generated from experimental data taken using electron backscatter pattern analysis. The simulation results suggest that in addition to the grain boundary misorientation and energy functions used, the misorientation texture and grain sizes are also determining factors in the grain growth process. As the grain size after recrystallization is comparable to the tape thickness, the surface energy of the grains may also be an important factor. Simulations were therefore also carried using a surface energy term. If the cube grains have a lower surface energy then a stronger cube texture is predicted.
Dynamic Recrystallisation of Quartz
Authors: Wheeler John , Jiang Zhenting , Prior David J. , Tullis Jan
Published: March 2009

It is generally agreed that the driving force (plastic strain energy) is much too small to allow "classical" nucleation during static and dynamic recrystallisation, and that rotation/growth of subgrains is an alternative. The latter explanation predicts that new grains should begin at low angles to old grains. We have used electron backscatter diffraction on an experimentally deformed quartz polycrystal that has deformed by dislocation creep and partially recrystallised. In a region shortened by about 30% new grains are at high angles (much greater than 15º) to adjacent parent grains. A histogram of misorientation versus number of boundaries shows a gap at 15-20º. In its simple form we expect the subgrain rotation model to predict a spectrum of misorientations but with most of them being low angle. Instead, the histogram suggests that new boundaries began life as high-angle structures, so current models for deformation-induced nucleation require refinement.
Effect of the Strain Reversal on the Microstructure and the Recrystallization Kinetics of the Austenite
Authors: Jorge-Badiola D. , Iza-Mendia Amaia , Gutiérrez Isabel
Published: March 2009

It has been demonstrated recently that when a reversion of the strain is applied during the hot working of a Nb-microalloyed steel, the subsequent static recrystallization kinetics is significantly affected. However, depending on the magnitude of the reversion, the static softening kinetics can be accelerated or delayed. This relates to the substructure dissolution taking place by the effect of the reversal. In the present work, new microstructural results obtained by EBSD on an austenitic stainless steel hot deformed by torsion is used to explain better the observed effect of the reversion of the strain.
Modelling Recovery and Recrystallisation Kinetics after Intercritical Deformation in 0.19 wt% C 1.5 wt% Mn Steel
Authors: Smith A. , Miroux A. , Luo Haiwen , Sietsma Jilt , van der Zwaag Sybrand
Published: March 2009

The softening kinetics of a 0.19 wt% C 1.5 wt% Mn steel deformed at two intercritical temperatures have been characterised using the stress relaxation technique. Recrystallisation of intercritical austenite has been modelled using a single grain model (Chen et al., 2002 [1]), whilst recovery of both intercritical austenite and ferrite has been modelled using a model in the literature [Verdier et
al., 1999 [2]). The models are combined to predict the overall softening kinetics with a rule of mixtures formulation. Comparison of the model with experiment shows significant deviations. The reasons are discussed with reference to the mixture rule and to the local stress-strain distribution which exists in the deformed samples. A simple modification to the model is proposed which takes into account the effect of a local stress distribution in deformed austenite.
Validation of the New Regression Model for the Static Recrystallisation of Hot-Deformed Austenite in Special Steels
Authors: Somani Mahesh C. , Karjalainen L. Pentti
Published: March 2009

A linear regression model consisting of the weighted sums of certain alloying elements has recently been developed to predict the activation energy (Qrex) and kinetics of static recrystallisation (SRX) for hot-deformed austenite based on stress relaxation test results for over 40 different carbon steels. The validity of the model has been further assessed here by determining the Qrex and the kinetics of SRX of certain high-Nb bearing steels, extra-low and low carbon Nb-Mo bainitic and high-Si dual phase and TRIP steels, and Nb-Ti grades with the varying N content. The validity of the model is shown to be fairly good for the Nb-Ti, Nb-Mo and Cr-Mo grades. The approach of maximum effective concentration of Nb and Si and the weight factor for Cr enable reasonable fit for DP, TRIP and Nb-Cr steels, as well. Possible influences of C and N on Qrex and the kinetics of SRX were checked, but none was observed in microalloyed steels.
Using Electron Backscatter Diffraction (EBSD) to Measure Misorientation between ‘Parent’ and ‘Daughter’ Grains. Implications for Recrystallisation and Nucleation
Authors: Halfpenny Angela , Prior David J. , Wheeler John
Published: March 2009

Electron backscatter diffraction (EBSD) is an extremely valuable tool, as it measures full crystallographic orientation information. This technique has been used to measure the statistics of misorientations between original ‘parent’ grains and recrystallised ‘daughter’ grains in a mylonitic quartzite. The angle of misorientation has implications on the controlling recrystallisation mechanism. The sample is a natural mylonitic quartzite collected from the stack of Glencoul, NW Scotland. The sample exhibits a common partially recrystallised microstructure. The data shows the average misorientations between the ‘parent’ and ‘daughter’ grains are 30º, this value seems too high for only subgrain rotation recrystallisation to be taking place. Moreover there is no gradation in the boundary misorientation from the internal substructure of the ‘parent’ grain to the ‘daughter’ grains. The internal substructure size of the ‘parent’ grain is bigger than the size of the ‘daughter’ grains. For subgrain rotation recrystallisation you may expect to see a core and mantle structure and for the ‘daughter’ grains’ to be of similar size to the internal substructure of the ‘parent’ grain. Another mechanism has either controlled the recrystallisation altogether or has become active after subgrain rotation had taken place and modified the microstructure.
Microstructural Evolution of Synthetic Forsterite Aggregates Deformed to High Strain
Authors: Kellermann Slotemaker A. , de Bresser J.H.P. , Spiers C.J. , Drury M.R.
Published: March 2009

Microstructures provide the crucial link between solid state flow of rock materials in the laboratory and large-scale tectonic processes in nature. In this context, microstructural evolution of olivine aggregates is of particular importance, since this material controls the flow of the Earth’s upper mantle and affects the dynamics of the outer Earth. From previous work it has become apparent that if olivine rocks are plastically deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that show grain size reduction through dynamic recrystallization. In the present study we focused on fine-grained (~1 µm) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3), Samples were axially compressed to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. We observed syndeformational grain growth rather than grain size reduction, and relate this to strain hardening seen in the stress-strain curves.