bluuebunny/crossref_metadata_2025 huggingface dataset:
WC-8Co-2Al (wt%) Cemented Carbides Prepared by Mechanical Milling and Spark Plasma Sintering
Authors: Li Xiaoqiang , Xiao Zhang Yi , Li Yuan Yuan , Yang Chao , Shao Ming
Published: January 2010

Ultrafine grained WC cemented carbides were manufactured successfully by reaction sintering with Co-Al intermetallic compounds as binder from mixed powders of a nominal composition of WC-8Co-2Al (wt%). The purpose of adding aluminum to the composition is to promote the mechanical properties of hardmetals by the in situ formation of Co-Al intermetallic phase. To manufacture bulk ultrafine WC hardmetals, ultrafine and even nanocrystalline WC powders were prepared as precursors from the mixed commercial powders by mechanical milling. Experimental results show that the transverse rupture strength and hardness of sintered hardmetal reached the maxima, being 1747.8 MPa and 90.2 HRA respectively, when the milling time expands to 55 h. It is affirmed that mechanical milling weakens the thermostability of WC-8Co-2Al powders, and facilitates the formation of Co-Al intermetallic compounds. However, overlong milling results in decreasing of properties and densities of sintered hardmetals, because the powder particles are severely refined and markedly agglomerated.
Recrystallization-Texture Theories in Light of Strain-Energy-Release-Maximization
Authors: Lee Dong Nyung
Published: January 2010

The oriented-nucleation and oriented-growth for recrystallization (Rex) textures of electrodeposits, vapor deposits, and plastically deformed metallic materials have been discussed based on the strain-energy-release-maximization (SERM) model. When the Rex orientation predicted by the SERM model from major components of the deformation texture is the same as a minor component in the deformation texture that is calculated to be thermally stable by the SERM model, the calculated Rex orientation is sure to become the main component of the Rex texture. This implies that the oriented-nucleation and the oriented-growth affect the evolution of the Rex texture. For polycrystalline materials, the Rex orientation predicted by the SERM model is likely to be measured because heterogeneous nucleation can occur in grain boundaries even when shear bands are absent. In other words, the grain boundaries are unlikely to control the Rex texture and the oriented growth dominates the Rex texture.
Mechanically Alloyed and Spark Plasma Sintered Aluminium/Precious Metal Oxide Composite Materials
Authors: Kubota Masahiro , Cizek Pavel
Published: January 2010

Air-atomised pure aluminium powder with additions of 10 at.% of AgO, PtO2 or PdO was mechanically alloyed (MAed) by using a vibrational ball mill, and MAed powders were consolidated into bulk materials by a spark plasma sintering (SPS) process. Mechano-chemical reactions among pure Al, precious metal oxide and stearic acid, added as a process control agent, during the mechanical alloying (MA) process and subsequent heat treatments were investigated by X-ray diffraction. The mechanical properties of MAed powders obtained under various heat treatment conditions and those of the SPS materials were evaluated by hardness tests. Mechano-chemical reactions occurred in Al/precious metal oxide composite powders during 36 ks of the MA process to form AlAg2, Pt and Al3Pd2 for the Al-AgO, Al-PtO2 and Al-PdO systems, respectively. Further solid-state reactions in MAed powders have been observed after heating at 373 K to 873 K for 7.2 ks. The hardness of MAed powders initially increased significantly after heating at 373 K and then generally decreased with increasing heating temperatures. The full density was obtained for the SPS materials under the conditions of an applied pressure of 49 MPa at 873 K for 3.6 ks. All the SPS materials exhibited hardness values of over 200 HV in the as-fabricated state.
Properties of Al-Si-Fe-Cu-Mg Alloy PM Composites Obtained by Closed - Die Forging and Heat Treatment
Authors: Szczepanik Stefan , Wojtaszek Marek
Published: January 2010

Aluminium RAl-1 and its alloy Al17Si5Fe3Cu1.1Mg0.6Zr composite materials were manufactured from powder mixtures by cold pressing, hot closed-die forging at 480oC and heat treatment. Powders ranging in composition in 20 wt.% steps of the alloy were mixed in a Turbula mixer for 1 h. The preforms with alloy concentrations of 80 and 100 % were hot consolidated at 480oC and closed-die forged at the same temperature. The effect of chemical composition on microstructure and mechanical properties in bending and compression was examined. Bend strength ranged from 400 to 540 MPa, compression strength from 415 to 744 MPa and hardness from 32 to 203 HB. Simulated distribution of component materials for a cross-section of the forging and shapes of the materials were analysed using LARSTRAN/Shape finite element program and are qualitatively comparable with the results obtained by forging.
Study on Bending Ultrasonic Fatigue Behavior of Sinter-Hardened Fe-2Cu-2Ni-1Mo-1C Materials Prepared by Warm Compaction
Authors: Xiao Zhi Yu , Zhou Ling , Shen Yuan Xun , Ngai Tungwai Leo , Li Yuan Yuan
Published: January 2010

Bending fatigue behavior of a sinter-hardened high density (7.4 g/cm3) Fe-2Cu-2Ni-1Mo-1C material fabricated by die-wall lubricated warm compaction of partially-diffuse alloyed powder was studied by bending ultrasonic fatigue testing. Results showed that fatigue strength decreases continuously with the increasing number of cycles. The fatigue failure yet occurs in the regime of exceeding 107 cycles and exhibits no traditional horizontal plateau between 106 and 107 cycles. Fatigue strength was 194 MPa, 239 MPa and 293 MPa at 108, 107 and 106 cycles respectively. Scanning electron microscopy revealed that cracks initiated from large pores on the surface and from pore clusters near the sub-surface. The fatigue cracks initiated both at single and multiple sites. Crack propagation was mainly in a trans-crystalline rupture mode. Fatigue striation and cleavage plane were observed in the crack propagation region and dimples were observed in the fracture zones.
Combustion Synthesis of Titanium-Based Cemented Carbides
Authors: Tanaka Tomohiro , Matsuura Kiyotaka , Kojima Keisuke , Ohno Munekazu
Published: January 2010

TiC−Fe system cermets and TiC−SUS310L (TiC−SS) system cermets with fully relative density have been produced from elemental powders via self-propagating high-temperature synthesis (SHS) reaction combined with pseudo-hot isostatic pressing. X-ray diffraction (XRD) analysis showed that the SHS products consist of TiC and the binder phase of Fe or SS. Metallographic analysis revealed TiC particles of several micrometer size were homogeneously dispersed in the binder phase. Regardless of differences in the binders, both cermets have similar tendencies: their relative densities increased and their hardness and compressive strengths decreased with increases in the volume fraction of either Fe or SS. In addition, the cermets used stainless steel as the binder had twice superior corrosion resistance to those used iron and also their hardness and compressive strength showed excellent values.
Investigation of the Mechanical Properties of Lotus-Type Porous Carbon Steel Made by Continuous Zone Melting Technique
Authors: Kujime T. , Nakajima Hideo
Published: January 2010

The lotus-type porous carbon steel with cylindrical pores has been fabricated by continuous zone melting technique in pressurized mixture of hydrogen and helium gases. In order to investigate the mechanical properties, the tensile and compression tests were carried out. The ultimate tensile strength of the specimen with cylindrical pores parallel to the solidification direction is lower than the estimated value assuming that the strength is decreased in proportion to decreasing cross section area of the specimen, while the yield strength is higher than that estimated. The compressive yield strength is also higher than that estimated. The increase in yield strength is attributed to the precipitation strengthening. The tensile strength is increased by quenching and tempering, while the elongation decreases. Such mechanical properties are discussed in terms of microstructureal analysis. Furthermore, simulations of the mechanical properties by FEM analysis were carried out.
Micro-Structural Alterations in MoM Hip Implants
Authors: Pourzal Robin , Theissmann Ralf , Gleising Birgit , Williams Sophie , Fischer Alfons
Published: January 2010

Since the introduction of CoCrMo alloy metal-on-metal hip replacements have shown a great clinical performance. Metal-on-metal couplings produce a much lower wear rate and volume than e.g. metal-on-polyethylene. However, the particle size is significantly smaller within a nm-range.
To evaluate the formation of nano-size wear particles in metal-on-metal hip replacements it is essential to understand the micro-structural changes in the sub-surface region of the CoCrMo alloy.
For this study a MoM hip implant was analyzed by means of TEM. The results revealed that the good wear performance of this CoCrMo alloy is linked to a strain induced fcc  hcp phase transformation and in-situ re-crystallization under high shear stresses. The result is a nano-crystalline surface zone of ~200 to 400 nm thickness which undergoes an ongoing process of mechanical intermixing with componants of the interfacial fluid. The incorporation of organic carbon from proteins in between the nano-crystals could be visualised by EFTEM and EDS. This mechanically mixed nc-zone must be the origin of the wear particle detachment.
An earlier study by Catelas et. al confirms the hypothesis of the location of wear particle detachment by analyzing the shape and chemical composition of emitted wear particles which exhibits the same size and shape of crystals observed in the nc-zone of the implant analyzed in this study.
A Theoretical and Experimental Study on the Dynamic Constitutive Model of Aluminum Foams
Authors: Yu Ji Lin , Wang Er Heng , Guo Liu Wei
Published: January 2010

The phenomenological constitutive framework for compressible elasto-plastic solids presented by Chen and Lu [1] is extended to the dynamic cases by assuming that the material parameter curves in the stress potential depend also on the strain rate. To check the applicability of the extended model, three types of dynamic experiments, i.e., uniaxial compression, lateral-constrained compression and side-constrained compression tests, are conducted for an open-cell aluminum foam at different strain rates. The first two types of dynamic tests are used as characteristic tests to determine the material parameter curves at different strain rates which are then used to construct the stress potential function in the model. The results show that the stress-strain curves under side-constrained compression predicted by the model are in agreement with those obtained experimentally.
Microstructure and Compression Properties of Al-Si Alloy Foams by Spark Plasma Sintering Technique
Authors: Aoyagi Naritoshi , Kamado Shigeharu , Kojima Yo
Published: January 2010

Porous aluminum alloy has been developed by powder metallurgy route using Spark plasma sintering (SPS) technique. Sintered material was produced by SPS system after getting the mixture of Al-12Si alloy and titanium hydride powders. Porous materials are prepared under various process conditions, and the pore morphology was investigated. Compression test is performed at crosshead speed of 1mm/min, 10mm/min and 100mm/min with no lubricant. The compression strength, σC i.e. plateau stress was estimated 12MPa at the density of porous materials, 0.7 Mg/m3. Densification strain εD from compression curve is around 0.6. These properties depend on pore morphology of porous materials, and it is possible to control the morphology under specific condition with this process. Plateau stress and absorbed energy of heat treated porous Al-Si alloy were estimated by measurement of a first peak stress and calculated an area up to 0.5 strain from compressive stress-starin curves. Young’s modulus is measured by starin gauge method under compression test. Porous aluminum alloy filled mold die is also produced successfully.
Modelling Study of Deformation Texture and Plastic Heterogeneity at Grain Boundaries and Triple Junctions
Authors: van Houtte Paul , Kanjarla Anand Krishna , Delannay Laurent
Published: January 2010

A CPFE model was used for an assessment of the assumptions used by the ALAMEL model concerning grain interactions. A finite element mesh was constructed for a multicrystal consisting of four grains. There were 17496 integration points per grain. The main goal was to capture the complex nature of the plastic fields in the vicinity of the grain boundaries. The distribution of strain rates, both along and perpendicular to the grain boundaries, confirms that the basic assumptions of the ALAMEL model are qualitatively correct, except at triple junctions. Splitting of one of the grains was occasionally observed, which has also been observed experimentally.
Recent Development of Equal Channel Angular Rolling (ECAR)
Authors: Chung Young Hoon
Published: January 2010

Equal Channel Angular Rolling (ECAR), the severe plastic deformation process, is suitable for shear deforming long and thin sheet continuously. An interesting issue is that thickness of a sheet is not reduced during ECAR. Although shear texture and fine grain structure in Al alloys are easily obtained by ECAR, yet the ECAR process’s difficulties in terms of technical control still remain, such as surface defect, low ductility and low processing speed. The surface defects and processing speed are partially improved by applying a series deformation of rolling and ECAR. A high-speed solution heat-treatment is developed for restoring the ductility of Al 6061 alloy.
Accumulative Roll Bonding of 7075 Aluminium Alloy at High Temperature
Authors: Hidalgo P. , Cepeda-Jimenez Carmen , Ruano Oscar , Carreño Fernando
Published: January 2010

The 7075 Al alloy was processed by accumulative roll bonding (ARB) at 300, 350 and 400 °C. The microstructure and texture were characterized and the hardness was measured. Cell/(sub)grain sizes less than 500 nm and typical β-fibre rolling texture were observed in the three ARBed samples. At 400 °C, the presence of elements in solid solution leads to a poorly misoriented microstructure and to a homogeneous β-fibre texture. At 300 and 350 °C highly misoriented microstructure and heterogeneous β-fibre rolling texture are observed, especially at 350 °C, wherein the degree of dynamic recovery is higher. Hardness of the ARBed samples is affected by the amount of atoms in solid solution at the different processing temperatures.
Numerical Analysis of the Microstructure and Mechanical Properties Evolution during Equal Channel Angular Pressing
Authors: Trebacz Lechoslaw , Paul Henryk , Madej Łukasz , Pietrzyk Maciej
Published: January 2010

The development of the new technology for manufacturing of multi layer aluminium based materials for heat radiators is the subject of this work. Modern aluminium alloys can be specially processed in a controlled manner to obtain nano(mikro) structures. These ultra fine grained structures play a significant role because they provide a possibility to obtain final product that is characterized by elevated strength properties and, at the same time, good anticorrosion and soldering properties. A detailed understanding of these ultra fined structures using a combination of numerical modelling and experimental analysis is presented in this paper. Particular attention is put on implementation of the microstructure evolution model into the finite element software to simulate Equal Channel Angular Pressing (ECAP) process. Examples of the obtained results are presented and discussed.
Microstructures of Aluminum and Copper Single Crystals Processed by Equal-Channel Angular Pressing
Authors: Furukawa Minoru , Horita Z. , Langdon Terence G.
Published: January 2010

High purity aluminum (Al) and copper (Cu) single crystals of different crystallographic orientations were processed for one pass by equal-channel angular pressing (ECAP). The deformed structures were examined using orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). This paper examines the experimental results in terms of the values of the shear factors based on simple shear theory.
Mechanical Properties of an Al-Mg-Sc Alloy Subjected to Intense Plastic Straining
Authors: Kaibyshev Rustam , Avtokratova Elena , Sitdikov O.S.
Published: January 2010

Effect of intense plastic straining on rollability and service properties of an Al-6%Mg-0.3%Sc alloy was examined. Ultrafine-grained structure (UFG) was produced by equal-channel angular pressing (ECAP) to a strain of 8 at a temperature of 325oC. The formation of UFG structure resulted in increase in the yield stress from 223 MPa to 285 MPa and ultimate stress from 350 MPa to 389 MPa in comparison with initial hot extruded condition. Total elongation slightly decreased from 33% to 29%. After ECAP, the material was subjected to cold and isothermal warm rolling. The formation of UFG structure resulted in enhanced rollability of the present alloy at room temperature. Cold rolling with high reduction provides the development of heavily deformed microstructure with high dislocation density, while the isothermal warm rolling does not remarkably affect the microstructure produced by ECAP. The mechanical properties after ECAP and ECAP with subsequent isothermal rolling were roughly similar. In contrast, cold rolling to the same strain resulted in significant increase of yield stress (495 MPa) and ultimate stress (536 MPa). Total elongation attained was 13%.
Ultrafine Grain Evolution in Copper Alloys Induced by Mechanisms of Continuous Dynamic and Static Recrystallization
Authors: Miura Hiromi , Sakai Taku
Published: January 2010

New thermo-mechanical processes (TMPs) to produce ultrafine-grained copper alloys utilizing continuous recrystallization (cRX) were proposed. These methods stand on our hypothesis that the evolution of ultrafine grains can be evolved by a mechanism of cRX even during severe plastic deformation at ambient temperature. A TMP of warm compression of 10 to 20 % of Cu-1.7mass%Fe alloy followed by annealing was cyclically repeated. The slight reduction, low-temperature annealing and pinning of grain boundaries by precipitates efficiently impeded occurrence of discontinuous recrystallization (dRX). The evolved substructures with nodes of the Fe precipitates gradually changed to new grains surrounded by low- and high-angle boundaries with increasing number of the repeated processes. Ultrafine grains with average size of 0.7 m were successfully evolved. However, the onset of dRX triggered extended grain coarsening accompanied by grain-boundary migration under conditions of insufficient annealing temperature and large pass stain. Another TMP cycles of cold rolling and annealing also induced fine-grained structure of about 0.6 m. The above results improved that ultrafine grain refinement can be realized simply by a mechanism of cRX even in the metallic materials with low stacking fault energy.
Effect of Equal Channel Angular Pressing on the Pitting Corrosion Resistance on the Aluminum Alloys with/without Anodization
Authors: Nakano Hiroaki , Son In Joon , Oue Satoshi , Kobayashi Shigeo , Fukushima Hisaaki , Horita Z.
Published: January 2010

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of Al (AA1100) and Al-Mg (AA5052) alloy with anodization and without was investigated by means of polarization curves in solutions containing 300 ppm or 0.6 mol/L of Cl- and by surface analysis. In Al and Al-Mg alloy without anodization, the potentials for pitting corrosion were evidently shifted to the noble direction by ECAP process, indicating that this process improves resistance to pitting corrosion. SEM observation revealed that the pitting corrosion occurred near the impurity precipitates and the size of impurity precipitated decreased with ECAP process. The time-dependence of corrosion potential and the polarization resistance determined by AC impedance technique suggested that the formation rate of Al oxide films was increased with ECAP process. The improvement in pitting corrosion resistance of Al and Al-Mg by ECAP seems to be attributable to the decrease in the size of impurity precipitates and the increase in the formation rate of Al oxide films.
On the other hand, the time required for initiating pitting corrosion of anodised Al was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. However, the pitting corrosion of anodized Al-Mg alloy occurred earlier with ECAP than without, showing that the corrosion resistance was worse with ECAP than without. In anodized Al-Mg alloy, cracks occurred in the anodic oxide films during initial corrosion and the cracks were larger with ECAP than without. It is assumed that the pitting corrosion was promoted by the cracks due to the higher internal stress resulting from ECAP.
EBSD Characterization of Pure Iron Deformed by ECAE
Authors: Renzetti Reny Angela , Sandim M.J.R. , Sandim Hugo Ricardo Zschommler , Hartwig K.T. , Bernardi Heide H. , Raabe Dierk
Published: January 2010

Polycrystalline iron was deformed by eight ECAE passes using the route Bc to a total strain of 9.2. After deformation the material was annealed at temperatures up to 800oC. Scanning electron microscopy (SEM) and high-resolution electron backscatter diffraction (EBSD) were used to characterize both deformed and annealed structures. In the as-deformed state, the mean grain size is 650 nm and the volume fraction of high angle boundaries (VHAB) is 56%. Upon annealing there is a pronounced softening above 300oC. At the beginning of recrystallization, at about 400oC, the VHAB increases to 71%. The results indicate that discontinuous recrystallization is the main softening mechanism in severely deformed iron.
Structure, Chemical Stability and Properties of NiAl-Al2O3 Interface Modified by hBN and MAX-Phase Interlayers
Authors: Song Jia , Hu Wei Ping , Zhong Yun Long , Chen Hao , Gottstein Günter
Published: January 2010

The interlayers from different materials were used in order to modify the interface structure/property and to improve the mechanical properties of NiAl composites reinforced by continuous single crystal Al2O3 fibers. It was found that the interface without interlayer had a good chemical stability during hot pressing (sample fabricating), resulting in high interface shear strength (about 250 MPa) at RT. But for the composites with interlayers, chemical reactions occurred in the interfacial area during diffusion bonding. The measured interface shear strength for the complete debonding was 70±30 MPa, 110±36 MPa and 32±5 MPa for the composites with hBN, Cr2AlC and V2AlC interlayers respectively. The possible influences by introducing the interlayers on mechanical performance of NiAl composites are discussed.
Solubility Control of αTCP-HAp Functionally Graded Porous Beads in SBF for Biomaterial Use
Authors: Asaoka Teruo , Kajihata Yuji , Furukawa Katsuko , Ushida Takashi , Tateishi Tetsuya
Published: January 2010

As excellent scaffolds for cultivating bone cells, porous beads of bioactive ceramics such as HAp, TCP are considered to be promising. HAp and α-TCP are well known as non-toxic bioceramics to human cells, but their behavior in living body fluid are different. HAp is bioactive material which has both high strength and better tissue-adhesive properties, but that is not readily absorbed by the human body. On the contrary, α-TCP is highly bioabsorbable; it is quickly absorbed by the body, and, therefore, disappears before bone is completely replaced. To realize a composite which has suitable solubility in living body fluid, α-TCP/ HAp functionally graded porous beads were fabricated by the method of spheroidization in liquid nitrogen. This type of composite maintains the function of scaffold with sufficient strength up to growth of new bone, and after the growth, it is expected to absorbed completely in the body.
In the present study, ceramic beads with α-TCP at the center were fabricated and coated with a functionally graded layer of HAp. By controlling the thickness of HAp layer, which could be realized by changing time of hydrolytic reaction, the absorption rate into the body would be easily controlled. In addition, to accelerate the formation of porous structure, some acid solutions were used to dissolve the beads surface and to penetrate pores toward inside of the beads. Observed surface and inner structure by SEM, also the measured change in absorption rate will be presented.
Using Thin Film Stress for Nanoscaled Sensors
Authors: Jebril Seid , Mishra Yogendra K. , Elbahri Mady , Kienle Lorenz , Greve Henry , Quandt Eckhard , Adelung Rainer
Published: January 2010

Thin film stress is often seen as an unwanted effect in micro- and nanostructures. Since recent years, we could employ thin film stress as a useful tool to create nanowires. By creating stress at predetermined breaking points, e.g., in microstructured photo resist thin films, cracks occur on the nanoscale in a well defined and reproducible manner [ ]. By using those as a simple mask for thin film deposition, nanowires can be created. More recently this fabrication scheme could be improved by utilizing delamination of the thin film, in order to obtain suitable shadow masks for thin film deposition in vacuum [ ]. Now, these stress based nanowires can be integrated in microelectronic devices and used as field effect transistors or as hydrogen sensors [ ]. For the functional part of the sensor, it was proposed that thin film stress created by hydrogen adsorption in the nanowire is the driving force. In terms of function, thin films can be also applied on free standing nanoscale whiskers or wires to modify their mechanical features or adding additional functionality. As a second example for the utilization of thin film stress, recent experiments on a piezoelectric and magnetostrictive material combination will be presented. These piezoelectric-magnetostrictive nano-composites are potential candidates for novel magnetic field sensors [ ]. In these composites the magnetostriction will be transferred to the piezoelectric component, resulting in a polarization of the piezoelectric material, that can be used as the sensor signal. The results of two different composite layouts will be presented and discussed with a special focus on the comparison between classical macroscopic composites and the novel nanocomposites.
A Systematic Approach to Performance Evaluation of Shape Memory Alloys as Actuator Material
Authors: Brailovski Vladimir , Terriault Patrick
Published: January 2010

This work presents a combined performance evaluation approach for SMAs as actuator material – an approach based on the combination of three testing modes: a) stress-free thermal recovery mode, b) fixed-support stress generation mode and c) constant (or variable) bias-stress recovery mode. Based on this testing, a so-called “design diagram” can be constructed. This diagram demonstrates the mechanical work generation potential of an SMA and therefore represents a must-have tool for the application engineer. Given that the working envelope depends on the material composition, microstructure and number of actuation cycles, this approach allows the selection of an appropriate material and the processing technique that will meet the functional requirements of a specific application. To illustrate the proposed performance evaluation technique, we show how it can be applied to the design of an SMA actuator for a morphing wing.
Recent Advances in Microwave, Millimeter-Wave and Plasma-Assisted Processing of Materials
Authors: Imam M. Ashraf , Fliflet Arne W. , Bruce Ralph W. , Feng C.R. , Stephenson Chad , Kinkead A.K. , Gold Steven H.
Published: January 2010

We present results on microwave, millimeter-wave, and millimeter-wave-driven plasma-assisted processing of materials. The research is primarily based on two systems- a 2.45 GHz, 6 kW S-band system and an 83 GHz, 15 kW gyrotron-based quasi-optical system. The S-Band system is used to synthesize nanophase metals, metal mixtures, and metal oxides by our patented continuous microwave polyol process, which has potential for large scale and low cost production. This system is also being investigated to develop techniques for titanium melting and sintering. The 83-GHz system is used for rapid sintering of ceramic powder compacts to produce polycrystalline materials with limited grain growth. An important application is to the development of polycrystalline laser host materials for high power solid-state lasers, where the requirement is for transparency with high optical quality and good lasing efficiency. We are currently investigating solid-state reactive sintering of Nd-doped YAG (Yttrium Aluminum Garnet) from commercial oxide powders. This has thus far yielded translucent samples with good fluorescence lifetime of the lasing state. Techniques for further reducing light scattering by residual pores are being investigated. Finally, the millimeter-wave system is being used in the development of millimeter-wave plasma-assisted diamond deposition, as the quasi-optical system has significant advantages over conventional microwave plasma-assisted diamond deposition systems. The results and implications of this wide range of materials processing experiments are presented and discussed.
Stress Amplitude Dependence of Internal Friction in TiNbAl Shape Memory Alloy
Authors: Inamura Tomonari , Yamamoto Y. , Kim Hee Young , Wakashima Kenji , Miyazaki Shuichi , Hosoda Hideki
Published: January 2010

Stress amplitude dependence of internal friction (tanδ) of a Ti-base shape memory alloy, Ti-24mol%Nb-3mol%Al, with a well developed texture is investigated by a dynamic mechanical analyzer (DMA) in a tensile mode. In the martensite (C-orthorhombic) phase, tan was 0.01~0.05 and was much higher than that of the parent phase in all the test conditions. This means that the martensite/martensite interfaces move under the external sinusoidal stress. In addition to this high background, tanδ-peak appeared at around 153K. The tanδ-peak height clearly depended also on the stress amplitude (10~50MPa). In addition, a threshold stress for the appearance of the tanδ-peak existed in the DMA test and it was in good agreement with the yield stress (0.2% proof stress) in a tensile test at 153K. These results mean that a long-range motion of twin-boundaries is necessary for the appearance of the tanδ-peak.
Shape Memory Behavior of Ti-Ni-X (X= Pd, Cu) Ternary Alloy Thin Films Prepared by Triple-Source DC Magnetron Sputtering
Authors: Inoue Shozo , Hori K. , Sawada N. , Nakamoto N. , Namazu T.
Published: January 2010

We have deposited the Ti-Ni-X films having various compositions while keeping the Ti content to be ~50at% by means of triple-source dc magnetron sputtering. All of the annealed films showed thermoelastic martensitic transformation. Ms temperature of the Ti-Ni-Pd films increased with increasing Pd content, and the highest Ms temperature of ~180°C was attained for the Ti-23%Ni-27%Pd film. On the other hand, Ms temperature of Ti-Ni-Cu films slightly increases as Cu content increases. The transformation hysteresis is decreased rapidly down to 15~20°C by adding Pd or Cu more than 10at%. Both ternary alloy films showed shape memory behavior during thermal cycling tests under various constant stresses. The critical stress against plastic deformation, c, of the Ti-Ni-Cu films is higher than that of the Ti-Ni-Pd films. The recoverable strain of these ternary alloy films is found to be ~2%. Actuation response by Joule's heat induced shape memory effect of Ti-Ni shape memory alloy films was slightly improved by the addition of Pd or Cu into the alloy.
Closed Cellular Materials for Smart Materials
Authors: Kishimoto Satoshi
Published: January 2010

New methods to fabricate a metallic closed cellular material for smart materials using an isostatic pressing and penetrating method are introduced. Powder particles of polymer or ceramics coated with a metal layer using electro-less plating were pressed into pellets and sintered at high temperature. These powder particles were sintered by spark plasma sintering (SPS) method. Closed cellular materials including polymer were fabricated by penetrating polymer into metallic foams. Many kinds of metallic closed cellular materials including different materials from that of cell walls were tried to fabricate. The physical and mechanical properties of these materials were measured. The results of the compressive tests show that this material has high-energy absorption and the result of measuring the internal friction show that the internal friction of these materials is larger than that of pure aluminum.
Laser Sintering of Silver Nanoparticles for Electronic Use
Authors: Maekawa Katsuhiro , Yamasaki Kazuhiko , Niizeki Tomotake , Mita Mamoru , Matsuba Yorishige , Terada Nobuto , Saito Hiroshi
Published: January 2010

The silver NanoPaste® having silver nanoparticles with 5 nm in average diameter, coated either on a polyimide substrate or a copper one, is successfully sintered with CW lasers. A rapid metallization from the paste surface with the visible laser makes the evaporation of solvent and dispersant difficult, resulting in an insufficient sintering with large pores. In contrast, the near-infrared laser with a little absorption in the paste heats the substrate first, and then develops metallization up to the paste surface, so that an easy evaporation makes the structure denser. No peeling was observed at the interface of the laser-sintered Ag film and the substrates. Its adhesive strength is nearly equal to that of the furnace-sintered sample.
Synthesis of New Structural and Functional Materials by SPS Processing
Authors: Makino Yukio , Mizuuchi Kiyoshi , Tokita Masao , Agari Yasuyuki , Kawahara Masakazu , Inoue Kanryu
Published: January 2010

Capabilities of synthesizing new structural and functional materials by SPS processing were indicated by exemplifying the synthesis of nano-structured alumina with high bending strength or high transparency, Al/diamond composites with high thermal conductivity and zirconia(3Y)/ SUS410L FGM. In the synthesis of alumina, the bending strength of more than 720MPa was attained by choosing suitable SPS conditions. It was also indicated that SPS processing could easily synthesize Al/diamond composites with high thermal conductivity of more than 400W/(m･K), suggesting elaborate control of interface between Al and diamond in SPS consolidation. Further, zirconia(3Y)/SUS410L FGM could easily be fabricated by SPS. Mechanical weakness in the zirconia(3Y)-rich layers of the FGM was shown from the analysis of stress state based on Raman scattering method. It is suggested that the designing of the layer staking in FGM based on the Raman scattering analysis is effective for the improvement of the weakness in the FGM.
Metal-Containing Diamond-Like Carbon Coating as a Smart Sensor
Authors: Takagi Toshiyuki , Takeno Takanori , Miki Hiroyuki
Published: January 2010

A new type of smart sensor based on metal-containing diamond-like carbon (DLC) coatings is presented. DLC coatings are widely used as protective coatings to improve the surface properties of objective materials; for example, to increase hardness and chemical stability. With the addition of metal clusters into DLC coatings, electrical conduction appears to depend on the microstructure. Such coatings can be used in fabricating resistive sensors. In this paper, we present tungsten-containing DLC (W-DLC) as a possible strain sensor. The strain sensitivity is greatly affected by the deposition condition. We also fabricate a double-layered DLC/W-DLC coating. The double-layered structure is expected to be used as a smart coating having functionality as a sensor with a protective DLC overcoat.
Thermal Properties of Diamond-Particle-Dispersed Cu-Matrix-Composites Fabricated by Spark Plasma Sintering (SPS)
Authors: Mizuuchi Kiyoshi , Inoue Kanryu , Agari Yasuyuki , Yamada Shinji , Tanaka Motohiro , Sugioka Masami , Takeuchi Takashi , Tani Junichi , Kawahara Masakazu , Lee Jun Hee , Makino Yukio
Published: January 2010

Diamond-particle-dispersed copper (Cu) matrix composites were fabricated from Cu-coated diamond particles by spark plasma sintering (SPS) process, and the microstructure and thermal properties of the composites fabricated were examined. These composites can well be consolidated in a temperature range between 973K and 1173K and scanning electron microscopy detects no reaction at the interface between the diamond particle and the Cu matrix. The relative packing density of the diamond-Cu composite increases with increasing sintering temperature and holding time, reaching 99.2% when sintered at a temperature of 1173K for a holding time of 2.1ks. Thermal conductivity of the diamond-Cu composite containing 43.2 vol. % diamond increases with increasing relative packing density, reaching a maximum (654W/mK) at a relative packing density of 99.2%. This thermal conductivity is 83% the theoretical value estimated by Maxwell-Eucken equation. The coefficient of thermal expansion of the composites falls in the upper line of Kerner’s model, indicating strong bonding between the diamond particle and the Cu matrix in the composite.
Electron Beam Surface Modification of Cobalt Chrome Molybdenum Alloy Formed by a Laminate Molding Method
Authors: Nagae Takekazu , Kakiuchi Shigeki , Himi Kiyokazu , Tomida Shogo , Yamaguchi Emi , Yoneda Takashi
Published: January 2010

We used electron beam irradiation on a laminate molded Co-Cr-Mo bulk alloy to reduce the surface roughness and increase hardness. The accelerating voltage and beam current were 40 kV and 0.5~5.0 mA, respectively. Irradiation time for each dot was 0.1 ms and the distance between dots (dot pitch) was either 0.2 or 0.4 mm, which corresponded to a scanning speed of 200 or 400 mm/s, respectively. The roughness value, Ra, decreased to 0.3~0.45 m for a beam current of 1 mA and a dot pitch of 0.02 mm. The coarse grains present in the base alloy were refined to sizes of less than 1m by rapid solidification. An increase in the Knoop hardness from 470 HK for the base metal to about 550 HK was achieved by this technique.
Second Step Approach for Self Healing Ceramics
Authors: Nakao Wataru
Published: January 2010

Self healing of surface cracks is the most effective function to ensure the structural integrity for ceramic components, because even minute surface crack give rise to a large strength decrease because of its high sensitivity to flaws. The present author and coworkers succeeded that the degraded strength due to cracking can be completely recovered by self crack healing ability driven by the high temperature oxidation of silicon carbide. Then, the mechanism and the effect of the self-healing were investigated. The most attractive feature of the self healing is to be able to respond to the damage caused during service. Thus, enhancement in self healing velocity has been necessary to actualize the self healing ceramics. In the present study, nanometer sizing the disperse silicon carbide particle was attempted to achieve the purpose. Alumina composites containing various shapes of silicon carbide nanometer sized particles were synthesized from mullite, aluminum and carbon powders. From the strength recovery behaviors of these alumina/ silicon carbide composites, the following aspects were derived. Silicon carbide particles nanometer sizing can heal completely the surface cracks at lower temperature and shorter time.
Microstructure and Mechanical Properties of Dissimilar Joints of AZ31 MG Alloy to Aluminium Alloys
Authors: Chang Woong Seong , Kim Heung Ju , Kim Sung Wook
Published: January 2010

In attempts to improve the performance of dissimilar joints between AZ31 Mg alloy and different Al alloys, solid state joining processes such as Magnetic Pulse Welding (MPW) and Friction Stir Welding (FSW) were applied for minimizing the formation of brittle intermetallic phases. MPW process has been concentrated mainly on round section tube to tube and tube to bar welds. Mg alloy AZ31 has been successfully welded to pure Al A1070 as well as to Al alloy A3003. Tensile test clearly showed the MPW welds were stronger than the weaker of the base metal so failure occurred in aluminum base metal. While FSW process for the dissimilar joint between AZ31B/A6061 alloys with a thickness of 2mm revealed optimum weldability under the conditions of travel speed of 0.8mm/sec and tool rotation speed of 850rpm. For the sound dissimilar joint, the maximum tensile strength of 179 MPa, which was about 80 % of the Mg base metal tensile strength, has been obtained.
High-Temperature Oxidation Resistance and Crack-Healing Function of Ni/Al2O3 Nano-Hybrid Materials
Authors: Nanko Makoto
Published: January 2010

High-temperature oxidation resistance of Ni/Al2O3 nano-hybrid materials was described in this paper. Y2O3 doping and SiC co-dispersion in Ni/Al2O3 nano-hybrid materials are useful techniques to improve high-temperature oxidation resistance. On the other hand, nano-Ni/Al2O3 has the crack healing function by high-temperature annealing in air. SiC-Ni/Al2O3 nano-hybrid materials have similar crack healing performance with better oxidation resistance at high temperatures than Ni/Al2O3 nano-hybrid materials.
Microstructure and Thermoelectric Properties of Al-Doped ZnO Sintered Body
Authors: Shikatani Noburo , Misawa Tatsuya , Kawakami Yuji , Ohta Michihiro
Published: January 2010

ZnO is heat-resistant and inexpensive, and the raw material of which is abundant, it is considered to be a good candidate thermoelectric material. Usually, a low-resistance n-type ZnO sintered body is obtained by doping 0.5-5 mol% Al2O3 followed by burning at a high temperature of approximately 1673K. However, this high-temperature burning has drawbacks, such as high power consumption and an increase in thermal conductivity with grain growth. Under these circumstances, we attempted to address these disadvantages. When ZnO was burned with Al as a dopant in an electric furnace at a temperature as low as approximately 1473K, ZnO with relatively good thermoelectric properties was obtained. In addition, the Al-doped sample showed lower electric resistance (332 K: 6.85×10-4Ωcm) than the Al2O3-doped sample, as determined on the basis of the resistance temperature characteristics of these samples. The causes of this low resistance may be as follows: 1) the metal-Al-mediated sample was densified by burning at a low temperature of approximately 1473K and 2) the Al distribution to the entire region of the ZnO bulk, resulting in the spread of Al solid-solution regions in the ZnO. We also found that the thermal conductivity decreased (973 K: 3.66 Wm-1K-1) in the Al-doped sample.
Electrochemical Characteristics of Pure Titanium Produced by MIM (Metal Injection Molding) Process
Authors: Sunada Satoshi , Nunomura Norio , Majima Kazuhiko
Published: January 2010

Two kinds of pure titanium specimens, i.e., the first one is prepared by the ingot metallurgy (I/M) process and the second one is prepared by the metal injection molding (MIM) process were used in this experiment, and their corrosion behavior under stress has been investigated in several aqueous solutions by Slow Strain Rate Tensile (SSRT) test. Ti MIM specimen showed the larger maximum stress and the lower maximum stain than I/M Ti specimen in the deionized water. Both Ti I/M and MIM specimens indicated good corrosion resistance in the aqueous solution of 2.5 kmol/m3 H2SO4 + 0.2 kmol/m3 NaCl in which SUS304 stainless steel showed SCC, and showed the decrease of the maximum stress and the maximum strain in the aqueous solutions of CH3OH + 0.1 kmol/m3 HCl, where the brittle fracture appearance was more remarkable with an decrease of H2O in the solution.
Preparation of Lithium Sulfide-Carbon Composites Using Spark-Plasma-Sintering Process and their Electrochemical Properties
Authors: Takeuchi Tomonari , Sakaebe Hikari , Sakai Tetsuo , Tatsumi Kuniaki
Published: January 2010

Lithium sulfide (Li2S)-carbon composite positive electrodes were prepared by the spark-plasma-sintering (SPS) process for use in rechargeable lithium batteries. By the SPS treatment of Li2S and acetylene black (AB) blended powder, the strong binding between the active materials and the carbon powders were formed. Such contact effect improved the electrochemical performance of the cells with liquid electrolytes (1M LiFP6/(EC+DMC)), probably due to the increase in conductivity of the positive electrodes, though the samples prepared by the ball-milling process showed no significant capacity in the electrochemical tests.
Investigation of Lattice Contraction in Mn3XN(X=Zn, Cu, Sn)
Authors: Wang Cong , Sun Ying , Wen Yong Chun , Chu Li Hua , Nie Man
Published: January 2010

The Mn3XN(X=Zn, Cu, Sn) compounds and their solid solutions with anti-perovskite structure were prepared by solid state reaction. Their magnetic transition and simultaneous abnormal thermal expansion behaviors were studied by SQUID and variable temperature X-ray diffraction. The lattice contraction was found in Mn3Cu0.5Sn0.5N and Mn3Zn0.5Sn0.5N during the magnetic transition process, however not in pure Mn3XN(X=Zn, Cu, Sn). The mechanism is discussed, combined with the different doping effects. It seems that the lattice contraction behavior is sensitive to the number of valence electrons at the X site in Mn3XN series.
Training Effects on Damping Capacity in Fe-Mn and Fe-Mn-Cr Alloys
Authors: Watanabe Yoshimi , Sato Hisashi , Nishino Yoichi , Kim Ick Soo
Published: January 2010

Training effect in the Fe-Mn-Si shape memory alloy is known as useful method to improve the shape memory effect. In this study, the training effects on damping capacity in Fe-20mass%Mn and Fe-20.5mass%Mn-12.5mass%Cr alloys have been investigated. As training treatments, the thermal training (only thermal cycling) and the thermo-mechanical training (thermal cycling with rolling deformation) are carried out. Internal friction was measured at room temperature using a free-decay method. Moreover, the behavior of dislocations was observed by TEM. Both training treatments improve the damping capacity of the Fe-Mn alloys with increasing the number of treatment. Strong training effect was found for the specimens trained by the thermo-mechanical training. The main training effect by thermal cycles is concluded to be due to size effects, while the size effects and volume fractional effects of martensite phase affect the damping capacity of the thermo-mechanically trained alloys. These training methods can improve both damping capacity and strength of Fe-Mn alloys.
Virtual Jet Engine System
Authors: Fukuda Masafumi , Harada Hiroshi , Yokokawa Tadaharu , Kitashima Tomonori
Published: January 2010

In 1999, we proposed the concept of a virtual gas turbine system which is a combination of turbine design and material design programs. Using this system, it has become possible to design a gas turbine engine and a combined cycle automatically, by inputting some basic information such as power output, turbine inlet temperature and material specifications. The derived outputs are turbine gas path dimensions, gas and cooling air flow rates, thermal efficiency, CO2 emissions, etc. We use the system to evaluate the potential improvement if a newly developed material is to be used in building the engine. Based on the virtual gas turbine system we have begun developing the virtual jet engine system, which can simulate the operation of a jet engine or a gas turbine engine to predict the degradation of materials used in the high temperature parts of the engine. The system consists of a thermal and aerodynamic analysis of the engine, a thermal and stress analysis of hot parts, and a material degradation analysis. Actual engine dimensions, operation data and material specifications are used to perform the analyses. In this paper, we will show some of the results of the use of the virtual gas turbine system, and then describe the development plan and the preliminary output of the virtual jet engine system.