bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of a Concasting Technology via a Dynamic Solidification Model of a Slab Caster
Authors: Stetina Josef , Kavička František , Dobrovská Jana , Camek Libor , Masarik Milos
Published: March 2009

Solidification and cooling of a continuously cast steel slab and the heating of the mould is a very complicated problem of transient heat and mass transfer. This original three-dimensional (3D) numerical model is capable of simulating the temperature field of a caster. The numerical computation has to take place simultaneously with the data acquisition—not only to confront it with the actual numerical model, but also to make it more accurate throughout the process. The utilization of the numerical model of solidification and cooling plays an indispensable
role in practice. An important step in this analysis is to determine the necessary quantities in the course of concasting. The software enables data acquisition in real time, which is necessary for optimization. This is ensured by the correct process procedure: real process → input data → numerical analysis → optimization → correction of process. This procedure is necessary for optimization (i.e.
maximization of the quality of the process)—especially when reacting to specific needs and conditions in the operation.
Nanoparticles and Films Formed by Pulsed Laser Irradiation on the CeO2 Target in the Liquid
Authors: Chen Jiwei , Yang Jing , Lian Jian She
Published: March 2009

The irradiation of a Nd-YAG pulsed laser on the CeO2 target in water was investigated. The CeO2 nanoparticles sized of 20-80 nm were formed in water, while the power density was larger than 32 kJ/cm2. The nanocrystalline films with grain sized of 50-150 nm were formed on the target with the energy density of 20 kJ/cm2-25 kJ/cm2. Finally, the amorphous films were formed with the energy
density of 6 kJ/cm2-15 kJ/cm2. The formation mechanisms of the nanoparticles and the films were discussed.
Electrochemical Etching of Aluminum Foil for Electrolytic Capacitors
Authors: Chi C.-S. , Jeong Y. , Kim S.S. , Lee J.H. , Oh H.J.
Published: March 2009

The increase of capacitance on dielectric layer is associated with enlargement of etched surface area of electrodes for aluminum electrolytic capacitors. Etched tunnels extending along [100] directions are formed by crystallographic dissolution of aluminum in a chloride solution. This study has been focused primarily on the effects of addition of inhibitors to hydrochloric acid solution on the increase of the surface area by Electrochemical Impedance Spectroscopy (EIS). The addition of 3 % ethylene glycol was more effective for the enlargement of the surface area comparing with those of 1M sulfuric acid and no additive. And it was observed by TEM that the tunnels were grown straight and parallel to [100] directions.
Spreading Dynamics of Tin, Bismuth and Some Lead-Free Solders over Copper Substrate
Authors: Shang Xiaogang , Mázur Lauricella Christiane , Brandi Sérgio Duarte
Published: March 2009

The spreading of a liquid on a solid surface is very important in a number of practical
applications. Many interesting physical phenomena can be observed when a small drop of a fluid spreads on a solid surface. These phenomena are related to spreading dynamics, which can be classified as spontaneous and forced wetting. In this work spreading dynamics of liquid metals and solders alloys were established to determine the mechanism of spreading. The spreading dynamics of bismuth, tin, 99.3wt%Sn-0.7wt%Cu alloy, 99.8 wt%Bi-0.2wt%Cu alloy and 60wt%Sn-40wt%Pb
were studied by using sessile droplet method. Tests were carried out at a temperature range from 280oC to 350oC over a copper substrate. Results showed a discontinuous decrease of spreading velocity as a function of time. For example, spreading velocity of liquid tin at 320oC decreased from 234.86 mm/s at 0.0025 s to 4.62 mm/s at 0.0225 s, after that increased up to 9.24 mm/s at 0.025 s, then down back to 6.07 mm/s at 0.03 s, and finally reached to the end of spreading after
0.04 s.
Structure and Properties of Ti-Al Intermetallic Layers Produced on Titanium Alloys by a Duplex Treatment
Authors: Wierzchoń Tadeusz , Garbacz Halina , Ossowski M.
Published: March 2009

The rapid progress in engineering enhances the demands set on materials requiring better mechanical properties, resistance to frictional wear, corrosion and erosion etc. These demands can be also satisfied by e.g. applying various surface engineering techniques which permit modifying the microstructure, phase and chemical composition of the surface layers produced on the treated parts. A
prospective line of the development is the production of the intermetallic layers by combining various methods aimed to improve essentially the performance properties and service life of the treated parts. The paper presents properties of the Al2O3+TiAl3+TiAl+Ti3Al type layer produced on titanium alloy Ti6Al2Cr2Mo by duplex method combined with magnetron sputtering process of aluminium coating
with a glow discharge assisted treatment. The results of the examinations: microstructure, chemical and phase composition, frictional wear resistance and mechanical properties are discussed. Produced composite surface layers have the diffusion character and a precisely specified structure, chemical and
phase composition and good wear and corrosion resistance what can widen significantly application range of treated parts.
Annealing Effects on the Structural Properties of Gold Films on Si by the RF Magnetron Sputtering
Authors: Lee Kyung Chul , Kim Nam Ho , O B.H. , Kim Hyoun Woo
Published: March 2009

We have investigated the effect of annealing temperature on the structural property of Au thin films deposited on Si(100) substrate using the radio frequency (RF) magnetron sputtering technique. X-ray diffraction revealed that the relative intensities and FWHM of (111), (200), and (311) peaks increased and decreased, respectively, after thermal annealing at 600°C. Scanning electron microscopy indicated that after annealing at 600-700°C, Au structures agglomerated on Si(100) surfaces. Energy dispersive x-ray spectrometry (EDX) revealed that the agglomerated
structure was composed of pure Au.
Effect of Colloidal Silica Addition and Pre-Coating on the Microstructure Change of Cathode Copper Electrodeposited Film
Authors: Lee Sang Baek , Kim Yung Keun , Kim Byung Il
Published: March 2009

The crystal structure, surface morphology and preferred orientation of copper
electro-deposit were investigated by using sulfate bath with SiO2 suspension and the cathode substrate Au-sputtered. By addition of colloidal silica in copper electrolytic bath and Au pre-coating on substrate, the grains of deposits became fined and uniform and the number of grains were increased. Hardness of copper electrodeposits with colloidal silica increased about 15% in comparison with that of pure copper deposit film. The (111), (200) and (311) planes in the X-ray
diffraction patterns were almost swept away, so preferred orientation of copper deposits change from (111) to (110) plane by co-deposit SiO2 and pre-coating the substrate.
Mechanism of Enhanced Wear-Resistance of the Ti-Mo Modification Layer
Authors: Qin Lin , Qin Yan Mei , Liu Xiao Ping , Tang Bin , Xu Zhong
Published: March 2009

Mo modified layers on Ti-6Al-4V alloy were obtained with plasma surface alloying
technique. The properties of the Mo-diffusion layers were investigated in this paper. Results show that the Mo-diffusion layers obviously enhance the wear resistance of Ti alloys against a polished 2100 steel counterbody ball under ball-on-disc test condition. With a series of experimental results, a wear model of high wear resistance of modified layers is propounded. The noval wear behavior is
a result of absolute elasticity characteristics on the subsurface of Mo modified layers.
FEM Simulation Study on Relationship of Interfacial Morphology and Residual Stress in TBCs
Authors: Chen Li Qiang , Gong Sheng Kai , Xu Hui Bin
Published: March 2009

It is generally believed that the failure of TBCs is attributed to the spallation occurred in the ceramic coat. The spallation is closed linked with sinuate morphology factors, including its amplitude and period, at the TGO/bond coat interface. In this work, dependence of the residual stress distribution on the sinuate morphology in the TBCs has been studied by means of Finite Element Method (FEM) simulation for isothermally annealed specimens. The simulation results indicated that the maximum value of residual stress existed inside the TGO layer. It was also found that the
maximum residual stress occurred at different points, near the TGO/bond coat interface at the peak of the sinuate interface, while near the TGO/ceramic coat interface at the valley, respectively. And the maximum residual stress increased with increasing the ratio of the amplitude to period in the sine morphology, which has been proved by the thermal cycle experimental results.
Characterization and Evaluation of EB-PVD Thermal Barrier Coatings by Impedance Spectroscopy
Authors: Zhang Chun Xia , Liu Fu Shun , Gong Sheng Kai , Xu Hui Bin
Published: March 2009

Two layer thermal barrier coatings (TBCs) were prepared by EB-PVD (Electron
Beam-Physical Vapor Deposition) at different substrate temperatures in the range of 823 to 1123K, and their microstructure was investigated with SEM and AC impedance as a function of substrate temperature and thermal cycling time. YSZ layer of all TBCs samples is in column structure, but the grain size and growth orientation are different with substrate. In this research, impedance spectra (IS)
was measured as a function of thermal cycling between 1323K and 298K for these thermal barrier coatings. Grain boundary and bulk can be distinguished from analysis of AC impedance spectroa to provide information about the relation between microstructure and electric properties.The change in IS until failure was found to be related with the thickness, microcracks and macrocracks of TGO and
the change in the interfacial of TGO/YSZ.
Correlation Exchange Length in Nanocrystalline Soft Magnetic Materials Characterized by Electron Holography
Authors: Gao Youhui , Shindo Daisuke
Published: March 2009

Magnetic ripple structure of Fe84Nb7B9 is studied by electron holography. The correlation exchange length, effective exchange and anisotropy constants are estimated from a field dependence of ripple wavelength. The function of ripple theory is adjusted with a decay constant, which reflects influence of stray field on the ripple structure. A magnetic hardness at elevated temperature is also observed and analyzed.
Study of Bonding of Grain Boundaries in Steels Using EELS
Authors: Zhang X. , Zhang Lina , Qi Jun Jie , Ma Yue
Published: March 2009

A novel EELS technique was developed to study bonding of grain boundary in many kinds of steels. We measured the normalized intensities of Fe white lines and calculated the occupancies of 3d states of iron, and then analyzed the relationship of the occupancies of 3d states of iron and the fracture property of the steels. We found that if the grain boundary has a different occupancy of 3d state of iron from that of the bulk, the steel tends to have an intergranular fracture, whereas if the grain
boundary has almost the same occupancy of 3d state as the bulk, the steel tends to have a transgranular fracture. Our result shows that the difference in the occupancy of 3d state between bulk and grain boundary can be used to study the fracture mode at grain boundary in steel.
Synthesis and Optical Properties of Metal Nanoparticles Embedded in Porous Anodic Alumina Oxide
Authors: Zong Rui Long , Zhou Ji , Shi Shi Kao , Li Long Tu
Published: March 2009

We have improved an electrochemical process in which the alternate current (AC) electrodeposition combined with the etching of substrate to prepare transparent metallic nanoparticles and anodic alumina oxide (AAO) composite films. The new process greatly simplifies the direct current (DC) electrodeposition process to get transparent composite films. Moreover, the
electrocrystallization mechanism has been analyzed. The Ag, Cu and Ag-Cu co-deposited nanoparticles/AAO films have distinct absorption peaks, which can be ascribed to the surface plasmon resonance (SPR) of these noble metal nanoparticles.
Ultrasonic Evaluation of Cyclically Deformed Microstructures of Cu and Cu-35Zn Alloy
Authors: Kim C.S. , Kwun S.I.
Published: March 2009

Ultrasonic nondestructive evaluation (NDE) technique has been applied to investigate the cyclically deformed microstructures of a Cu and Cu-35Zn alloy. These materials, which had different stacking fault energies, were cyclically deformed in order to examine the ultrasonic reaction with different dislocation substructures. The observation of a dislocation structure using TEM and the
measurement of the ultrasonic NDE parameters were performed after various fatigue deformation in order to clarify the relationship between them. The ultrasonic velocity was observed to decrease with increasing fatigue life fraction in both materials, which was attributed to the increasing dislocation density, resulted from the cyclic deformation. The increasing rate of ultrasonic attenuation in Cu with
a cell structure that evolved during cyclic deformation was higher than that in the Cu-35Zn alloy, which had a planar array. This suggests that the dislocation cell structure is more sensitive to the change in the ultrasonic parameters than the planar array structure formed during cyclic deformation.
Application of Monte Carlo Simulation Method to the Nano-Scale Characterization by Scanning Electron Microscopy
Authors: Ding Z.J. , Li H.M. , Sun X.
Published: March 2009

Topographic imaging of materials by a scanning electron microscope (SEM), using the secondary electrons and backscattered electrons escaped from the surface under a primary electron beam bombardment as image signals, has been a very important technique in application to material sciences and the related fields. In this work we have developed a new parallel Monte Carlo simulation program to calculate SEM images especially for an inhomogeneous sample with a complex structure, which may be constructed with some basic geometrical shapes containing
different materials. The ray-tracing arithmetic is employed to obtain the corrected electron flight step length for electrons across the interface of different zones containing distinct elements. We have done simulations for several specimens with artificial structures at the nm level. The results illustrate some new characters of image contrast, demonstrating the applicability of this image simulation technique to the characterization of nano-scale structure.
Wear Mechanism of Nano-Structured Surface Layer under High Impact Energy
Authors: Cen Qihong , Xu Yun Hua , Fang Liang , Zhu Jin Hua
Published: March 2009

Under high impact energy, nano-structured surface layers of Hadfield steel and annealed AISI 1045 steel were investigated in the present paper. It has been observed that a so-called “black layer” for Hadfield steel and “white layer” for AISI 1045 steel has been formed, respectively. That definitely will give rise to a change of wear mechanism. The wear tests showed that the wear weight
loss curve of Hadfield steel will be bent down after some critical impact numbers. The wear curve of the AISI 1045 steel, however, shows a step-like characteristic with increasing impact numbers. It can be found from microstructural examination that high density twin bands of subsurface for Hadfield steel were produced, which have good plastic deformation coordination with bulk material. Cracks are usually initiated in the “black layer” underneath 12 µm in depth, and the worn debris
sizes were also observed in nano-scale. Nano scaled wear controls the whole wear process. For the annealed AISI 1045 steel, cracks are mainly initiated between the interface of the “white layer” and sub-surface deformation layer. Debris is in micron-scale and spalled in the flake-like style. The wear weight loss is, therefore, greater than that of Hadfield steel. The result showed from the wear tests of Hadfield steel and AISI 1045 steel that nanocrystalized process of subsurface becomes one of control factors to affect wear losses and wear mechanism under high impact energy.
Fracture Behavior of a Shape Memory Alloy at High Loading Velocity and High Temperature
Authors: Wang Lei , Kobayashi Toshiro , Harada Y. , Tsuchiya Koichi
Published: March 2009

The fracture behavior under high-loading velocity and at high temperature was
investigated using tensile testing system for a shape memory alloy. Both SEM and X-Ray were used to examined the testing sample before and after tensile testing. It was found that the fracture behavior shows some similar tendency between at high-loading velocity and high-temperature. Based on the results, it can be confirmed that the shape memory alloy can be used to develop high performance intelligent material with high-impact resistance.
Experimental Analysis for the Tubular Hydroformability of Aluminum Alloys at Elevated Temperatures
Authors: Kim B.J. , Park K.S. , Ryu J.S. , Moon Young Hoon
Published: March 2009

Aluminum alloys have a high potential for weight reduction in automotive and other applications, but they have a relatively low tubular hydroformability at room temperature. Hot working processes are commonly used for bulk metal forming, such as forging and rolling, but rare in sheet metal forming like hydroforming. The hydroformability of aluminum alloys can however be enhanced significantly at elevated temperatures. In this study, the hydroformability of aluminum alloys at elevated temperatures has therefore been investigated by using a specially designed induction heating system. The formability characteristics at high temperatures were obtained by a T-fitting forming test as well as a free bulge test. The effects of the process parameters such as an internal pressure and temperature on tubular forming limits have mainly been investigated and the results are presented in this paper
The Influence of Processing Parameters on Mechanical Properties and Microstructure of Welding Zone for Ti3Al-TC4 Dual Alloy
Authors: Yao Ze Kun , Liang Xinmin , Guo Hong Zhen , Wang Bin , Li Guo Hui , Qiao Zh. , Zhang Hui
Published: March 2009

It has been investigated that the influence of processing parameters on mechanical properties of weld zone for Ti-24Al-15Nb-1.5Mo and TC4 dual alloy welded by electron beam in vacuum. The results shows the remarkable influence factors are heat treatment regime and deformation for yield strength of welded dual alloy samples at room temperature tensile test, and the remarkable influence factor is forging temperature for the elongation in tensile test at 500°C. From the combined analysis about other properties at room temperature and 500°C, the microstructure of the weld seam, it can been gotten the optimum parameters of processing dual alloy, i.e. forging at 1020°C, soaking for 12 hour at 700°C, air cooling, about 40% deformation and using billet of rolling state.
Materials and Processing Designs for High-Performance Magnesium Alloys
Authors: Kondoh Katsuyoshi , Tsuzuki Ritsuko , Du Wenbo , Kamado Shigeharu
Published: March 2009

Materials and processing designs for advanced magnesium alloys with fine microstructures and superior properties were established by the combination of the repeated plastic working and the Mg2Si synthesis in solid-state. The grain size was less than 1 μm via RPW process due to its severe plastic working on raw powder. The hot extruded magnesium alloys produced in industries showed high ultimate tensile strength, e.g. 420~450MPa, when employing Mg-Zn-Al-Ca-RE (Rare Earth) alloy coarse powder, having 0.5~2 mm diameter, as input materials.
Phase and Morphological Transformation of Preformed AZ91D Magnesium Alloys in Remelting
Authors: Xia Ming-Xu , Zheng Hong-xing , Yuan Sen , Li Jian Guo
Published: March 2009

The phase and morphological transformation during the remelting process was investigated by isothermal soaking and rapidly quenching of preformed AZ91D magnesium alloys in semisolid state. It was revealed that the morphological transformation of preformed alloys is crucial to obtain homogenously fine spheroidal grains and affect the final forming ability. The transformation is divided into two stages, local remelting of the whole experiment and partial remelting of the respective grains, which behave as liquid bands and liquid cells structures, respectively. In the partial melting, the lower melting point phase, β-Mg17Al12, diffused to the grains boundary and center of the grains and separated to Al2Mg and Mg. The Al2Mg and Mg phases with lower melting points melt into cells structures. The final microstructure of the remelting experiments is composed of cells structures, spheroidal grains and liquid phase.
Study on Microstructure and Properties of Mg-9Al-xZn Alloys
Authors: Zhang Xi Yan , Jiang Feng , Zhou Shi-jie , Jia Chong , Zhao Min , Li Xue Qin
Published: March 2009

Some Zn and a little Ag are added into ZM5 magnesium alloy (one of Mg-9 wt%Al-1
wt%Zn alloys in China), and the differences of the microstructures and properties between the new alloy and ZM5 is investigated. Effects of heat treatment and alloying elements (Zn and Ag) on the microstructure and tensile properties of Mg-9Al-xZn alloys, and relationships between the chemical composition, microstructure and properties are investigated. Zn ad Ag have obvious solid solution strengthening effects on Mg-9Al-xZn alloy, while Ag is detrimental to the corrosion resistance after
being artificial aged. The morphology of pearlite-like secondary γ(Mg17Al12) phase (γII) has close relation with the properties.
Effect of Rolling Conditions on Microstructure and Mechanical Properties of AZ31 Mg Alloy
Authors: Ha Tae Kwon , Sung Hwan Jin , Park Woo Jin , Ahn Sang Ho
Published: March 2009

The effect of warm rolling under various conditions on the microstructure and mechanical property was investigated using an AZ31 Mg alloy sheet. Several processing parameters such as initial thickness, thickness reduction by a single pass rolling, rolling temperature, roll speed, and roll temperature were varied to elicit an optimum condition for the warm rolling process of AZ31 Mg alloy. Microstructure and mechanical properties were measured for specimens subjected to rolling
experiments of various conditions. Warm rolling of 30% thickness reduction per pass was possible without any side-crack at temperatures as low as 200oC under the roll speed of 30 m/min. The initial microstructure before rolling was the mixed one consisting of partially recrystallized and cast structures. Grain refinement was found to occur actively during the warm rolling, producing a very fine grain size of 7 µm after 50% reduction in single pass rolling at 200oC. Yield strength of 204MPa,
tensile strength of 330MPa and uniform elongation of 32% have been obtained in warm rolled sheets.
Mechanical Properties and Texture Evolution of AZ31 Mg Alloy during Equal Channel Angular Pressing
Authors: Jeong Hyo Tae , Kim Woo Jin
Published: March 2009

Microstructure and texture evolution in the AZ31 Mg alloy subject to equal channel
angular pressing (ECAP) have been investigated and correlated with the mechanical properties. When AZ31 Mg alloy was ECAPed up to 8 passes following the route Bc, grain refinement occurred effectively. Texture was also changed during ECAP. The original fiber texture of the extruded AZ31 Mg alloy changed to a new texture component of ] 1 3 2 5 )[ 1 1 01 ( , and the texture of ] 1 3 2 5 )[ 1 1 01 ( orientation was rotated to ] 0 2 5 7 )[ 6 4 13 ( orientation after 6-pass ECAP process. The variation of the strength with the pass number was explained by the texture and grain size. The strength data of AZ31 Mg alloys followed the standard Hall-Petch relationship when the similar texture was retained during the ECAP process. Otherwise the effect of texture on strength was dominant over the strengthening due to grain refinement.
Corrosion Resistance of Si and Al-Bearing Ultrafine Grained Weathering Steel
Authors: Nishimura Toshiyasu
Published: March 2009

The iron rust phase has been analyzed by using EPMA, TEM and EIS after
simulating marine corrosion tests. The ultrafine grained (UFG) weathering steel containing Si and Al showed higher corrosion resistance than carbon steel in the test. Si and Al were identified as Si 2+ and Al 3+ in the complex oxide of inner rust by EPMA and TEM. It was demonstrated by EIS that the resistance at the low frequency region corresponded to that of corrosion reaction of rusted steels (Rt). The Rt value of this steel increased after the continuous formation of inner rust, which implied that Si and Al took part in the conversion of complex oxides into fine structure that prevented the penetration of Cl ions.
Recrystallization in AZ31 Magnesium Alloy during Hot Deformation
Authors: Essadiqi Elhachmi , Liu Wei Jie , Kao V. , Yue Shuang Lin , Verma Ravi
Published: March 2009

In this study, isothermal torsion tests were carried out on magnesium AZ31B alloy under constant strain rate conditions, in the range of 250 to 400oC at 0.01, 0.1, and 1.0 s-1. Alloy flow stress dependence on strain rate and temperature can be described by a power law with activation energy of 130 kJ/mol. Microstructural examination of hot deformed samples shows very fine recrystallized grains decorating grain boundaries of larger gains in the form of a necklace. These fine grains are produced by dynamic recrystallization at the grain boundaries of original grains. Microstructure evolution, based on samples quenched at different strain levels, indicates that increasing deformation strain has little effect on recrystallized grain size but widens the recrystallized region, with full recrystallization achieved at a certain high strain level. Recrystallized grain size increases with increasing deformation temperature and strain rate. The latter suggests recrystallization in AZ31 to be essentially a time dependant phenomenon.
Dislocation Structure for Ambient Temperature Creep in Titanium Metal
Authors: Yamada Tomoyasu , Tanaka Hisamune , Sato Eiichi , Jimbo Itaru
Published: March 2009

The primary creep behavior at ambient temperature of typical h.c.p., b.c.c. and f.c.c. metals and alloys of annealed state was surveyed and the deformation mechanism of CP-Ti was discussed through transmission electron microscopy. Only h.c.p. metals and alloys demonstrated significant creep at ambient temperature. Arrays of straight screw dislocations of b=1/2<2110> and <2110> direction were observed in the crept CP-Ti.
High and Low Cycle Fatigue of Orthorhombic Ti-22Al-27Nb Alloy
Authors: Hagiwara Masuo , Araoka A. , Emura Satoshi
Published: March 2009

The effect of the lamellar morphology on the high cycle fatigue (HCF) and low cycle fatigue (LCF) behavior of the Ti-22Al-27Nb alloy was investigated. The HCF tests were performed in air at an R ratio of 0.1 in the load-control mode, whereas the LCF tests were performed in vacuum at 923 K in the strain-controlled mode. The specimens with fine lamellar microstructure exhibited a better resistance to HCF than those with coarse lamellar microstructure. The microstructure-insensitive behavior was, however, observed in the LCF tests at 923 K. The fatigue
mechanism was discussed based on the concurrent observation of the initiation facet and the underlying microstructure, and the TEM observations.
The Possibility of Cr-Base Alloys for High-Temperature Applications
Authors: Gu Yue Feng , Ro Y. , Harada Hiroshi
Published: March 2009

The mechanical properties of chromium (Cr) and Cr-base alloys are reviewed, with particular emphasis on the ductility at ambient temperature and the strengths at high temperature. Analysis of rather scattered data and our recent results suggest that Cr-base alloy can be ductilized greatly at ambient temperature and is quite capable of being strengthened to high levels at high temperature. New designs on composition would give high possibility to Cr-base alloys as structural materials used in high-temperature applications.
Influence of Microstructural Changes and Grain Boundary Precipitation on the Behavior of 25Ni-15Cr-2Ti Superalloy during High Temperature Creep
Authors: Amer Amer E. , EL-Ghazaly S.A. , Shash Y.S. , Weiss S.
Published: March 2009

Iron-base superalloys are well known materials having excellent high
temperature properties .They are used in turbo superchargers and turbine engines
required for aerospace and power plants. In this investigation precipitation hardenable X5NiCrTi26-15 was used to study the influence of microstructural changes on the creep behavior at different conditions . Different creep cycles were applied for both base alloy and laser beam welded alloy (6kW CO2 ) namely at 600 , 625 and 650C at applied controlled creep stresses of 400 and 450 MPa . The base material sheet was used in as solution annealed state ( 30 min, 960 C, WQ ).The specimens were hardened in two steps (24h,760 C, FC and 16 h, 705 C,AC ) before being investigated . The microstructural changes due to grain boundary sliding, intergranual fracture perpendicular to the metal flow axis , and the type ,morphology of different secondary carbides were measured and discussed . To examine the changes in microstructure Philips EM 400 TEM with an acceleration voltage of 120KV, and SEM as well as light microscopy were used . It was found that , laser beam welded structure investigated after creep deformation at temperatures lower than 650C and at controlled stress of 400 and 450 MPa ,
showed a textured weld metal zone with dendrite having lower hardness combined
with a higher creep resistance than that for base material .It was found also that
creeping at 650C at the same stress values offsets any gain in creep resistance of
welded joints as compared with that for the base material at the same conditions.
Room Temperature Deformation Behavior of Inconel718
Authors: Bian Fang , Su Guoyue , Kong Fan Ya , Yang Ke
Published: March 2009

The deformation behavior of Inconel718 at room temperature was studied by tensile tests. Three kinds of specimens were tested, including cold rolled, heat treated with grain size ASTM5 and heat treated with grain size ASTM7. The true stress-strain curves were obtained based on the tensile test records. The true stress-strain relation can express the room temperature deformation behavior, which can be described by equations similar to the Voce equation. The limit value of the work-hardening rate θ0 is very sensitive to the microstructure of the alloy.
Elastic and Thermal Expansion Anisotropy of Mo-Based 5-3 Silicides
Authors: Hayashi Taisuke , Ito Kazuhiro , Takamoto Misako , Tanaka Katsushi
Published: March 2009

Single crystals of (Mo0.8Nb0.2)5Si3, (Mo0.85W0.15)5Si3 and Mo5Si3 were grown and their thermal expansion along the a- and c-axes and single crystalline elastic property were investigated. An anisotropy ratio of coefficient of thermal expansion (ac/aa) is lower for (Mo0.8Nb0.2)5Si3, and higher for (Mo0.85W0.15)5Si3 at RT than that for Mo5Si3. However, the ac/aa for (Mo0.8Nb0.2)5Si3 increases with increasing temperature and the ac/aa of the three compounds is similar at 800°C. The values of isotropic average Young’s (E), bulk (K) and shear (G) moduli for (Mo0.8Nb0.2)5Si3 is the lowest and those for (Mo0.85W0.15)5Si3 is the highest in the three compounds. On the other hand, the difference of E between [100] and [001] increases when partial substitution of Mo by Nb occurs and it decreases when partial substitution of Mo by W occurs. Simply compared with the results of thermal expansion anisotropy, the result shows opposite tendency.
High Temperature Oxidation in Multicomponent Nb Alloys
Authors: Menon E. Sarath K. , Mendiratta Madan G.
Published: March 2009

Niobium-Silicon alloys offer potential as a new generation of refractory material system that could meet the high-temperature capability envisaged to exceed the application temperatures of Ni base superalloys. A serious concern in the application of Nb based alloys is their poor oxidation resistance at elevated temperatures. The ternary diagram Nb-Ti-Si system exhibits eutectic groves
nearly parallel to the Nb-Ti binary and terminate in a Class II invariant reaction, L+(Nb,Ti)3Si → β+ (Ti,Nb)5Si3. A peretectic ridge from the reaction, L+(Nb,Ti)5Si3 →(Nb,Ti)3Si also exists and these reactions control the microstructures resulting from solidification of these Nb alloys. The microstructures associated with these alloys comprise a distribution of Nb5Si3 in β matrix. The effect of various alloying elements on the resulting microstructures are illustrated The effect of microstructural distribution on oxidation resistance of multiphase alloys are also discussed.
Bonding Character in the Laves-Phases TiCr2 and TiCo2
Authors: Sun Jian , Sun Xue Song , Sun Feng , Jiang Bin , Smith David John
Published: March 2009

The bonding character of Laves phases TiCr2 and TiCo2 has been investigated by electron energy loss spectroscopy and ab-initio calculations. The results revealed the hybridization between the transition-metal atoms in Laves phases. The stronger Cr-Cr (Co-Co) bonding along the Kagome net forms a tetrahedral electronic network in the C15 TiCr2 (TiCo2) structure. This was discussed with the mechanical properties of Laves phases.
Microstructure and Properties of Directionally Solidified NbSi2/ Nb5Si3 Composites
Authors: Li Wei , Yang Hai Bo , Shan Ai Dang , Zhang Lan Ting , Wu Jian Sheng
Published: March 2009

NbSi2 is an attractive material for high temperature applications due to its high melting point, low density and good oxidation resistance. The high-temperature strength of NbSi2 is expected to be further improved by incorporation with Nb5Si3, which performs a high creep resistance and strength at high temperature due to its complex crystal structure. In this paper, directionally solidified NbSi2/ Nb5Si3 in-situ composites have been prepared using an optical floating zone method. Scanning
Electron Microscopes (SEM) and X-ray diffraction (XRD) have been used to investigate the phase constitution and microstructure. The orientation relationship between Nb5Si3 and NbSi2 is investigated by transmission electron microscopy (TEM). High-temperature properties of alloys are tested by compression at the strain rate of 1×10-4/s at 1673K and 1773K. It was found that high temperature strength and phase constitution of directionally solidified alloys depended on the addition of Mo.
Preparation of Nanocrystalline NiAl Compounds and Composites by Mechanical Alloying
Authors: Guo Jian Ting , Du Xing Hao , Zhou Lan Zhang
Published: March 2009

During the past ten years, mechanical alloying/ball milling has been employed to
successfully synthesize nanocrystalline NiAl intermetallic compounds (NiAl, NiAl (Cr,Co,Ti,Fe)) and composites (NiAl-TiC, NiAl-TiB2, NiAl-HfC, NiAl-HfB2) in our group, namely, by means of self-sustained reaction. During the mechanical alloying process, an abrupt temperature rise has been observed. The large heat release from the formation of NiAl, as well as HfC, HfB2, TiC, TiB2 compounds is suggested to be the driven force of the self-sustained reaction. It is interested to
observe that nanocrystalline NiAl exhibits very well microstructure stability during high temperature annealing. The alloying additions can decrease reaction rate and prolong the reaction time. With the increase of alloying additions, supersaturated solid solution even amorphization of NiAl has been formed. The nanocrystalline NiAl compounds show a rise of the compressive strength and the ductility at room temperature compared with that of the cast coarse crystalline compound.
Study on Microstructures and Mechanical Properties of B510L Steel by TMCP
Authors: Li Long , Yang Chun Zheng , Ding Hua , Du Lin Xiu , Liu Xianghua , Wang Guo Dong , Song Hongmei , Zhang Pijun
Published: March 2009

TMCP treatments were carried out on B510L steel followed by using a pilot rolling mill. Effects of finish rolling temperature and coiling temperature on mechanical properties and microstructures of the steel were analyzed. The tensile and impact properties were measured and the microstructures were observed by OM, TEM and SEM. With a proper control of rolling and cooling conditions, the yield strength of 500MPa was obtained, which was much higher than that in normal production. The yield ratio and ductility of the experimental steel were also reasonable. It was revealed that a good combination of ferrite with bainite microstructure was ideal for good mechanical properties. It was also concluded that the strengthening mechanisms included solution hardening, fine ferrite grain hardening, bainite hardening and precipitation hardening. This work can provide an experimental basis for industrial productions.
Electron Beam Welding of Ti-24Al-17Nb-0.5Mo Alloy
Authors: Zou J.Y. , Cui Yu You , Yang Rui
Published: March 2009

Electron beam (EB) welding of Ti-24Al-17Nb-0.5Mo (at.%) alloy and the effects of postweld heat treatments (PWHT) were studied. Through optimizing the welding parameters, defect-free welding joint was obtained. For the as-welded joint, the fusion zone (FZ) consisted of predominant β and occasional α2 within β grains. Microhardness of FZ was higher than that of the base metal (BM) and that of the heat affected zone (HAZ) was between that of BM and FZ. PWHTs greatly modified the microstructures and mechanical properties of the weld zone. PWHTs at both 820oC and 900oC yielded fine acicular laths in FZ leading to severe brittleness of the weld. Appropriate microstructures and phase combination were obtained by PWHT at 1000oC for 2 h, and room-temperature tensile strength reached the value of the base metal after the same thermal cycle.
Phase Constitution and Transformation Behavior of Ni2MnGa-Cu2MnAl Pseudobinary Intermetallic Compounds
Authors: Hosoda Hideki , Higaki Yuji , Miyazaki Shuichi
Published: March 2009

The phase constitution, lattice parameter, martensitic and magnetic transformation
behavior and hardness of the Ni2MnGa-Cu2MnAl pseudobinary alloys designed as
(Ni2MnGa)x(Cu2MnAl)1-x were investigated in order to improve magnetic properties of Ni2MnGa. It was revealed that L21 Ni2MnGa and Cu2MnAl make a continuous solid solution of (Ni,Cu)2Mn(Ga,Al) when heat treated at 1073K, and that the lattice parameter of the L21 phase increases monotonously with increasing the compositional ratio x, that is, the amount of Cu2MnAl. Curie temperature TC also increases with increasing x. On the other hand, the martensitic
transformation temperature of Ni2MnGa seems to decrease rapidly by adding Cu2MnAl. Hardness of the alloys heat-treated at 1073K ranges from HV200 to HV370, and solution hardening was recognized by mixing. When heat treated at 773K, a phase decomposition from L21 phase to Cu9Al4 and b-Mn was confirmed in the Cu2MnAl-rich alloys. The phase decomposition causes a decrease in the lattice parameter of L21 phase and TC and a significant increase in hardness.
High Temperature Oxidation Behavior of TiNi Alloys
Authors: Ko J.H. , Lee Dong Bok
Published: March 2009

The oxidation behavior of the equiatomic TiNi alloy was investigated at 600-900oC. The oxidation resistance of the TiNi alloy was better than the pure Ti alloy, but worse than the pure Ni alloy. The oxide scales consisted of TiO2, with and without embedded particles of TiNiO3 and Ni. The subscale matrix phase was (TiNi3+TiNi) at 600oC, TiNi3 at 700oC, (Ni+TiNi3) at 800oC, and Ni at 900oC. Oxidation was mainly governed by the inward diffusion of oxygen, and the outward diffusion of Ti and a bit of Ni. Detailed microstructures and the oxidation mechanism are proposed.
Effect of Cu Content on Microstructure and Properties of Al2O3-SiO2 Fiber Reinforced Aluminum Matrix Composites
Authors: Xu Hong Yu , Geng Lin , Meng Qing Chang
Published: March 2009

In this paper, pure aluminum and Al-Cu (1%, 3% and 5% mass.) alloy matrix composites reinforced with 40Vol% Al2O3-SiO2 sort fiber were fabricated by Squeeze-casting technique. Microstructure and tensile properties of the composites were investigated by means of SEM, EPMA, TEM and tensile tests. It was found from the experimental results that when pure aluminum, which was added into Cu elements, is used as matrix, chemical reaction occurred at the interface between
amorphous SiO2 and matrix due to the Cu element diffusion and enrichment towards the sort fiber surface. Results indicated that with the increasing of Cu content the ultimate tensile strength decreased firstly then increased continuously.
Hot Compression Behaviour of In-Situ Synthesized (TiB+TiC)/Ti Composites Prepared by Hot-Pressing
Authors: Zheng Zhen Zhu , Geng Lin , Zhang Xue Nan
Published: March 2009

In-situ 5 vol% TiB whisker and TiC particulates reinforced titanium composites were
fabricated by blending Ti powder and B4C particulates followed by reactive hot-pressing. The microstructure of the composites was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Hot compression test was conducted on gleeble-1500 Thermal-Mechanical Simulator. XRD results show that two kinds of reinforcements with different shapes were formed during hot-pressing: TiB short-fiber and equiaxed TiC particles. The true stress-true strain curves is shown as work hardening curves when the compression temperature
below 600°C, and a stable flow stress is seen when the compression temperature above 600°C. Peak flow stress of the composites are much higher than that of the unreinforced alloy.
In Situ Synthesis and Properties of Aluminum Composites with Ultrafine TiB2 and Al2O3 Particulates
Authors: Wakashima Kenji , Shimoyamada T. , Noma H. , Inamura Tomonari , Hosoda Hideki
Published: March 2009

In this paper, we describe our recent work on metal matrix composites (MMCs) with submicron-size TiB2 and Al2O3 particulates that are synthesized in situ from Al-rich Al-Ti-B and Al-TiO2- B powder reactants by reactive sintering. Reaction sequences examined in the two different reactant systems are summarized, and some experimental results on elevated-temperature properties, i.e. thermal expansion, temperature dependence of dynamic tensile modulus and creep behavior, are shown and discussed from micromechanics-based viewpoints.
A Monte Carlo Simulation on the PFZ Microstructures in Al-Based Alloys during Multistep Annealing
Authors: Okuda Hiroshi , Ochiai Shojiro
Published: March 2009

A Monte Carlo simulation using semi grand canonical ensemble method was applied to examine the condition that precipitation free zone (PFZ) appears in an Al-based composite materials under two step aging. The present simulation uses a fcc lattice with a periodic boundary condition for y and z directions, and a grain boundary existing at the end for x direction. A simple grain boundary segregation case gave a nealy parabolic growth law in PFZ width and the volume fraction of
precipitates. Different origin of PFZ, namely, mobility or chemical potential, lead to the opposite effect upon secondary heat treatment.
Influence on Optical Properties of the New-Type Rear Projection Screen by the Content of Additive TiO2 Nano-Particle
Authors: Cui Jing Yi , Guo Liquan , Ma Ju Sheng
Published: March 2009

Adding nano-particles with high refractive index can greatly improve the optical
properties of the PMMA-based composites, which were developed as the new-type rear projection screen. In this paper, the influence on the optical properties, such as gain and view angle, by the content of additive TiO2 nano-particle was studied. Curves of optical properties versus content of nano-particle were obtained and the rational factors were found. Finally the reasons were discussed from the nanostructure point of view and the scattering principle.
Iron/Graphite Core-Shell Structured Nanoparticles Prepared by Annealing of Nanopowder
Authors: David B. , Pizúrová N. , Schneeweiss O. , Bezdička Petr , Morjan I. , Alexandrescu R.
Published: March 2009

We present magnetic and morphological characterization of iron- and iron-carbide- based nanopowder obtained by the laser synthesis from sensitized gas phase mixture containing acetylene and iron pentacarbonyl vapors. The analysis was performed on the as-prepared material and the annealed material. The results of TEM, XRD, Mössbauer and magnetic measurements are reported. Phase transformations taking place during annealing of the nanopowder when core-shell nanoparticles appear are discussed.
Evaluation of p-Type Doping for (1,1,-2,0) Epitaxial Layers Grown on α-Cut (1,1,-2,0) 4H-SiC Substrates
Authors: Blanc Caroline , Zielinski Marcin , Soulière Véronique , Sartel C. , Juillaguet Sandrine , Contreras Sylvie , Camassel Jean , Monteil Yves
Published: March 2009

We report an experimental investigation of the residual (n-type) and intentional (p-type) doping level of <11-20> epitaxial layers grown on a-cut 4H-SiC substrates. Using SIMS, C(V) measurements, low temperature photoluminescence and Hall effect investigations, we show that nitrogen incorporates 3 times more than usually found for <0001> surfaces. Conversely, aluminum incorporates 8 times less. Altogether, this is in excellent agreement with previous results from stepcontrolled epitaxy.
Crystalline Quality Evaluation of 6H-SiC Bulk Crystals Grown from Si-Ti-C Ternary Solution
Authors: Kusunoki Kazuhiko , Kamei Kazuhito , Ueda Y. , Naga S. , Ito Y. , Hasebe Mitsuhiro , Ujihara Toru , Nakajima Kazuo
Published: March 2009

The growth of 6H-SiC crystal from Si-Ti-C ternary solution was conducted under the
temperature gradient and the crystalline quality evaluations of the grown crystals were carried out. 6H-SiC(0001) on-axis pvt-grown crystal was used as a seed crystal. Micropipes in the seed crystal were terminated during the solution growth and 28mm28mm self-standing micropipe-free SiC crystals were obtained. The quality of the grown crystals was investigated by SIMS, high-resolution
x-ray diffraction and molten KOH etching. The content of residual impurities in the SiC were very low. The X-ray -rocking curves of the solution grown SiC showed single peak with high peak intensity ,while that of the seed crystal showed several peaks due to the misoriented domains. Moreover, it was found that the number of etch-pit in the grown crystal is much less than that in the seed crystal and it decreases with the increase of the growth thickness. These results indicate that the
crystalline quality of grown crystal was significantly improved during the solution growth.
Molecular Beam Epitaxy of Semiconductor Nanostructures Based on SiC
Authors: Fissel Andreas
Published: March 2009

The different aspects of molecular beam epitaxy (MBE) for producing two-dimensional (Quantum well), one-dimensional (Quantum wire and rod), and zero-dimensional (Quantum dot) structures based on SiC for functional applications are discussed. Development and implementation
of a suitable MBE growth procedure for fabrication of heteropolytypic layer sequences are demonstrated in context with thermodynamic considerations. Furthermore, the growth of onedimensional structures based on cubic wires and nanorod arrays, also grown on Si(111), is shown. Moreover, the perspectives of quantum dot structures and a novel way to form 3C-SiC-dot structures within α-SiC has been discussed.
A Short Synopsis of the Current Status of Porous SiC and GaN
Authors: Shishkin Y. , Ke Yue , Devaty Robert P. , Choyke Wolfgang J.
Published: March 2009

A brief historical development of porous SiC and GaN is given. SEM images of nine
porous morphologies in 4H, 6H and 3C SiC are shown along with anodization details. Similarly, two porous GaN morphologies are presented. Applications and future prospects are discussed.