bluuebunny/crossref_metadata_2025 huggingface dataset:
The Metastable Phase Responsible for Peak Hardness and Its Morphology in an Al-Mg-Si Alloy
Authors: Fukui Koichiro , Takeda Mahoto , Endo Takao
Published: March 2009

Precipitation behaviour in an Al-Mg-Si alloy aged at 403 K to 483 K was studied with respect to thermal stability and morphology of the metastable precipitates, using high resolution transmission electron microscopy (HRTEM), Vickers microhardness tests and differential scanning calorimetry (DSC) measurements. The quantitative analysis of the DSC measurements revealed that the change in the first exothermic peak (the peak P) of the metastable phase is proportional to the increases in the Vickers hardness. The HRTEM observations showed the four types of the precipitates in morphology during the isothermal ageing and the change in the peak P was mainly caused by the formation of the precipitates with irregular contrast and the ones with the network interior angle between 65°and 80°
Phase Separation into Nano-Crystalline Nitrides in Ternary Ti-Si-N System via N Implantation
Authors: Muraishi Shinji , Aizawa Tatsuhiko
Published: March 2009

The reaction induced phase separation aimed for the distribution of nano-structured
particles has been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in ternary Ti-Si-N film via N+ implantation. The fabrication of Ti-20at%Si film has made on Si substrates by ion beam sputtering (IBS), and then N+ implantation with 50 keV has been conducted on these films. The selected area electron diffraction (SAED) from as-deposited film shows amorphous Ti-Si. As-deposited Ti-Si film exhibited high stability even for the heat treatment at 773K for 3600s. N+ implantation induced the direct formation of nano crystalline of fcc-TiNx within the Ti-Si film. The XPS depth profiling and chemical shift suggest that the preferential nitriding of Ti accompanied with
the segregation of SiNx occurred during N-implantation.
Infrared Transmission Performance of Gallium Phosphide Thin Films Deposited by RF Magnetron Sputtering
Authors: Li Yang Ping , Liu Zheng Tang
Published: March 2009

Long-wave infrared windows and domes used under harsh conditions always suffer sand abrasion and raindrop erosion. GaP thin film has proved to be effective LWIR protective coating for zinc sulphide window. In this article, the GaP films have been deposited on 5-mm-thick thermo-pressed planar ZnS substrates by RF magnetron sputtering in high pure Ar gas, with a single crystalline GaP disc as the target. The maxima of the GaP/ZnS transmission spectra curve are less than the corresponding transmissivities of ZnS substrates, which indicates that the GaP films are of absorption. SEM results show that the films are very compact and their surfaces are glazed. XPS analysis shows that gallium content is more than phosphor content in the films, and oxygen is the main impurity. The more the gallium content is, the more absorption the film is of. The absorption does not vary greatly with oxygen content. So the absorption of the film is caused mainly by the
overfull metal component, which increases the conductivity and causes the charge carrier absorption. Low absorption GaP film with the thickness more than 10 µm has been deposited, in which the Ga:P ratio is nearly 1:1.
Photoluminescence of SnO2 Films Prepared by APCVD
Authors: Ji Feng , Ma Jin , Wang Yu Heng , Ma Hong-Lei , Yu Xihu , Zong Fu Jian
Published: March 2009

SnO2 films were prepared by atmosphere pressure chemical vapor deposition (APCVD) method. The preparation, structure and photoluminescence (PL) properties of the SnO2 films were investigated. All the obtained films were polycrystalline with the rutile structure. A violet (396 nm) and a blue (446 nm) photoluminescence peaks were observed at room temperatures. The intensity of the PL peaks located at 3.13 eV decreased with increasing the annealing temperature. The emission mechanism of the SnO2 films has been investigated.
Photoinduced Changes in Sn-Doped Sol-Gel Silica Glass Films
Authors: Li Aiwu , Xing Hua , Zhou Cuiling , Shen Jian , Zhang Letian , Zheng Wei , Zhang Yushu
Published: March 2009

Sn-doped SiO2 thin films were fabricated on Si substrates by the Sol-Gel method.
Permanent refractive index change was found using ultraviolet (UV) laser radiation at 248 nm. The photoinduced refractive index change increased after radiation and variety in the contents of Tin. The optical and surface properties of the films were characterized using X-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry (VASE).
Optical Properties of Silica Films Prepared on Sapphire
Authors: Feng Li Ping , Liu Zheng Tang
Published: March 2009

As a coating material with excellent optical and mechanical properties, silica films can be used as anti-reflective and protective layers on the windows and domes of sapphire. In this paper, the designed films of SiO2 have been prepared on sapphire wafers and hemisphere dome of sapphire by radio frequency magnetron reactive sputtering. Compositions and structure of SiO2 films were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The
refractive index of deposited films was measured and effects of the coatings on optical properties of sapphire have been studied. The results express that the refractive index of the films can be varied between 3.4 and 1.4 by changing the gas flow ratio. The deposited films can increase the transmission of sapphire in mid-wave IR greatly. The average transmittance of sapphire wafers
coated with SiO2 films on both sides can be increased to 96.43 % in 3～5 µm.
Analysis of Optical Properties and Structure for CdS Films
Authors: Wang W.L. , Liao K.J. , Zhang Jian , Yu P. , Liu G.B.
Published: March 2009

In this paper, the optical properties and structure of CdS films were investigated by SEM, X-ray diffraction, and x-ray photoelectron spectroscopy. The CdS films in this study were deposited on the plane transparent glass by chemical bath deposition technique. The experimental results have shown that the annealing treatment has an important effect on the optical properties and structure of CdS films. This may be ascribed to decreasing surface contaminations and oxide content in the films.
Deformation Behaviors of 6061 and 7075 Aluminum Tubes at Elevated Temperatures for Warm Hydroforming
Authors: Suh Dong Woo , Sohn Sung Man , Lee Moon Yong , Lee Sang Yong
Published: March 2009

The deformation behaviors of fully annealed or T6-treated 6061 and 7075 aluminum tubes are investigated at elevated temperature using uniaxial tensile test. Fully annealed 6061 and 7075 tube, and T6-treated 7075 tube do not show sharp local necking with an elongation of 50% at tensile temperature of 300oC, accordingly, it is expected that warm hydroforming process can be applied. The increase of tensile temperature does not significantly affect the total elongation of T6-treated 6061 tube.
Magnetic-Transport and Microstructure of FeNi-Cu Nanogranular Films
Authors: Wang Chang Zheng , Guo Zheng Hong , Rong Yong Hua , Hsu T.Y.
Published: March 2009

A series of (Fe50Ni50)xCu1-x granular films were prepared using magnetron controlled sputtering method. The magnetic-transport and microstructure of FeNi-Cu films deposited at room temperature and then annealed at various temperatures were investigated through TEM, XRD and conventional four probes method under room temperature, respectively. The giant magnetoresistence (GMR) as a function of FeNi volume fraction for as-deposited FeNi-Cu films reached a maximum of about 1.8 % at the volume fraction of 32 %. With increasing the annealing temperature, the GMR of films with the volume fraction less than 26 % reaches a peak at certain annealing temperature. While for films with the volume fraction larger than 26 %, the GMR have almost no changes at first and then decrease with increasing the annealing temperature. In addition, the relationship between
magneto-transport and the microstructure, morphology of granular films is discussed.
Numerical Calculation of Kerr Spectra for Magnetic Multilayered and Granular Films
Authors: Huang Zhi Gao , Lin Yingbin , Yang Yan Min , Zhang Feng Ming , Du You Wei
Published: March 2009

In this paper, based on 4×4 matrix method, we present theoretical calculations of the
polar magneto-optical Kerr effect for Co/Pt and MnBi multilayered films, and NixSiO2(1-x) granular films. The calculated results indicate that, (1) the simulated Kerr spectra as a function of photo-energy are in good agreement with experimental ones; (2) the maxima and the periodical and damped oscillation appear in the Kerr spectra curve with the magnetic thickness, which is important for design of the material in the future; (3) the structure of interfacial layer affect greatly the Kerr
spectra, which is significant for the processing of magneto-optical material.
Synthesis of Surface Acoustic Wave Filter with Al/ZnO Thin Film Deposited on Silicon Wafer
Authors: Pan F. , Chen J.J. , Zeng Fei , Gao Y. , Li D.M.
Published: March 2009

ZnO thin film, as a promising piezoelectric material, possesses unique electrical,
acoustical, and optical properties. In this paper, Al/ZnO thin film was deposited on Si wafer by magnetron sputtering. Highly oriented, dense, and fine-grain polycrystalline ZnO films with excellent surface flatness and high resistivities have been obtained, when the sputtered gas pressure was 0.9 Pa, the temperature was 200 °C and the Ar-to-O2 ratio was 1:3. A 780MHz surface acoustic wave filter (SAWF) has been successfully fabricated using the Al/ZnO film on silicon wafer.
Effect of Be Addition on the Precipitation Behaviors and Mechanical Properties in Al-Cu-Li-Mg-Zr-(Ag) Alloys
Authors: Kim J.K. , Chung Dong-Seok , Park H.S. , Enoki Manabu
Published: March 2009

The effect of beryllium (Be) on the precipitation behaviors and mechanical properties of Al–Cu–Li–Mg–Zr–(Ag) alloys was investigated. The results show that adding 0.02%Be to Al–Cu–Li–Mg–Zr–(Ag) alloys, the elongation of the alloy increased without significant decrease in strength and the aging response was accelerated. In a Al–Cu–Li–Mg–Zr–(Ag) alloy, G.P. zone was formed at early aging time (2 h) and T1 and q′ phases were formed at peak-aging and over-aging times, while in Al–Cu–Li–Mg–Zr–(Ag)–Be alloys T1 and q′ phases were formed at early aging time (2 h) and the density of q′ phase was very low and fine T1 phases were homogeneously distributed at peak-aging and over-aging times.
Modification of Electroless Nickel-Plating Coatings with Sol-Gel Film
Authors: Liu Hui Cong , Zhu Liqun , Du Yan Bin
Published: March 2009

Four Sol-Gel films were developed by dip-coating electroless nickel-plated samples in different Sols, followed by heat treatment. The effects of the coating times and heat treatment temperature on the corrosion, oxidation resistance and wearing quality of the modified coating were examined. Results show that, after six coating, Sol-Gel films obtained can provide good corrosion and oxidation resistance, and their anti-corrosion quality remains high even after being oxidized at 500 °C for 60 hours. Addition of inorganic molybdenum salt or chromate into the Ti Sol also makes
the wearing quality of the Sol-Gel film better.
Current-Voltage Characteristic and Grain Boundary Structure in Undoped and Pr and Co Doped ZnO Bicrystals
Authors: Sato Yukio , Oba Fumiyasu , Yodogawa Masatada , Yamamoto Takahisa , Ikuhara Yuichi
Published: March 2009

Our recent studies on current-voltage characteristic and grain boundary structure in ZnO bicrystals are reviewed in this paper. All types of undoped ZnO bicrystals showed Ohmic characteristics. This indicates that nonlinear current-voltage characteristic cannot be generated solely by the atomic disarrangement in undoped ZnO. On the other hand, co-doped ZnO bicrystals showed nonlinear current-voltage characteristics, which depended on the types of grain boundary. It
is considered that the nonlinearity depends on the Pr concentrations at the respective grain boundaries.
Control of Boundary Structure and Grain Growth for Microstructural Design
Authors: Choi Si Young , Kang Suk Joong L.
Published: March 2009

The design of microstructure in materials, ranging from ultrafine, moderately sized, duplex to single crystalline, has long been a challenging subject to material scientists. A basic means to achieve this goal is related to the control of grain growth. Taking BaTiO3 as a model system, this investigation shows that control of grain boundary structure between rough and faceted and control of initial grain size can allow us to achieve the goal. When the grain boundary is rough, normal grain
growth occurs with a moderate rate. On the other hand, for faceted boundaries, either abnormal grain growth or grain growth inhibition occurs resulting in a duplex grain structure or fine-grained structure, respectively. Growth of single crystals is also possible when the boundary is faceted. During crystal growth amorphous films can form and thicken at dry grain boundaries above the eutectic temperature.
As the film thickness increases, the growth rate of the crystals is reduced. This observed growth behavior of grains with boundary structure is explained in terms of the difference in mobility between the two types of boundaries. The results demonstrate the basic principles of obtaining various microstructures from the same material.
Microstructural and Mechanical Properties of TiC, TiB2 and VC with Low Carbon Steel Surface Alloy Fabricated by High Energy Electron Beam Irradiation
Authors: Shin Kee Sam , Yoo Jung Hoon , Lee Sung Hak , Kaneko Kenji , Tomokiyo Yoshitsugu
Published: March 2009

Because of its excellent process advantages such as high energy efficiency, short irradiation time and rapid heating, high energy electron beam (HEEB) irradiation is becoming of interest as a future surface modification technology. In this study, surface alloying of TiC, TiB2 and VC ceramic particles with a low carbon steel substrate was carried out using HEEB of 1.4 MeV. Surface alloyed layers of all
the specimens were about 2 mm thick and consisted of a melted region, an interface region, a heat affected zone (HAZ) and the matrix. In all the specimens, the hardness at the surface was the highest, and then decreased sharply into the interior reaching the lowest values at the matrix. A remarkable increase in the mechanical properties was observed for the VC surface alloyed specimen. Vanadium carbides of large (~ 5 µm) and fine sizes (~ 20 nm) were formed uniformly, which resulted in an increase of hardness to 2-3 times of that of the matrix, and highest wear resistance.
Surface Treatment of Materials with High Current Pulsed Electron Beam
Authors: Hao Sheng Zhi , Gao B. , Wu Ai Min , Zou Jian Xin , Qin Ying , Dong Chuang , Guan Q.F.
Published: March 2009

High current pulsed electron beam (HCPEB) is now becoming a promising energetic source for the surface treatment of materials. When the concentrated electron flux transferring its energy into a very thin surface layer within a short pulse time, superfast processes such as heating, melting, evaporation and consequent solidification, as well as dynamic stress field induced by an
abrupt thermal distribution in the interactive zone impart surface layer with improved
physicochemical and mechanical properties. The present paper reports mainly our experimental research work on this new-style technique. Investigations performed with a variety of constructional materials (aluminum, carbon and mold steel, magnesium alloys) have shown that the most pronounced changes of composition, microstructure and properties occur in the near-surface layers, while the thickness of the modified layer with improved mechanical properties (several hundreds of
micrometers) is significantly greater than that of the heat-affected zone due to the propagation of stress wave. The surfaces treated with either simply several pulses of bombardment or complex techniques, such as rapid alloying by HCPEB can exhibit improved mechanical and physicochemical properties to some extent.
Failure Mechanism of D-Gun Sprayed Thermal Barrier Coatings Subjected to Thermal Shock Cycling
Authors: Ke P.L. , Wang Q.M. , Guo M.H. , Gong Jun , Sun C. , Zhou Yan Chun
Published: March 2009

Thermal barrier coatings (TBCs) with the ceramic coats of hollow spherical
ZrO2-8%Y2O3 powder (HSP-YSZ) were obtained on Ni-base superalloy by detonation gun (D-gun) spraying. Thermal shock cyclic tests were performed by holding samples at 1100°C for 10 min and then water quenching to room temperature repeatedly. The D-gun sprayed TBCs didn’t fail up to 300 cycles and exhibited excellent resistance to thermal shock. Failure mechanism of D-gun sprayed
TBCs subjected to thermal shock cycling was discussed.
Structural and Magnetic Properties of Exchange Spring Type FePt/Fe Multilayers
Authors: Gu You Son , Zhan Xiao Yan , He Jian , Zhang Y. , Ji Zhen , Zhou Cheng
Published: March 2009

A series of [FePt(4min)/Fe(tFe)]10 multilayers were prepared by RF magnetron sputtering and post annealing. The structures, morphology, composition, and magnetic properties were measured by XRD, SEM, EDX and VSM. X-ray diffraction showed that lattice constants of FePt phase changed with Fe layer thickness and annealing temperature. Both a and c are smaller than the
standard values and a decreases as the deposition time of Fe layer increases. The grain sizes of samples annealed at 500°C increase slightly, while those at 600°C increase sharply as Fe layer decreases. The coercivities decrease with the deposition time of Fe layer, and the energy product (BH)max reaches a maximum at Fe layer deposition time of 3 minutes.
Microdiffraction Study of Polycrystalline Copper during Uniaxial Tension Deformation Using a Synchrotron X-Ray Source
Authors: Joo H.D. , Kim J.S. , Bark C.W. , Kim J.Y. , Koo Yang Mo , Tamura Nobumichi
Published: March 2009

In-situ measurement of local orientation and strain Has Been carried out for a copperpolycrystals under a uniaxial loading using a synchrotron x-ray microdiffraction method at the Advanced Light Source. The heterogeneities of deformation-induced microstructure within single grains were observed. There were differences in the selection of simultaneously acting slip systems among neighboring volume elements within a grain.
The Influence of the Stirrer's Shape and Process Parameter on Friction Stir Welded MB3 Magnesium Joining
Authors: Wang Kuaishe , Liu Junshuai , Xu Ke Wei , Shen Yang
Published: March 2009

Friction stir welding (FSW) is a new solid-state plastically joining process developed in the beginning of the 1990’s. The influence of the stirrer’s shape and process parameter on joint quality was studied. The investigation result shows that the microstructure and mechanical property of the joint welded with truncated cone and screw welding pin is better than the joint welded with cylindrical welding pin. When welded with proper stirrer and parameter, maximum joint tensile strength can reach 98% of the parent material. And microhardness of friction stir welded MB3 was
considered with the grain size distribution in the weld zone.
In-Situ Solid-State Synthesis of Mg Composite with Mg2Si Dispersoids
Authors: Tsuzuki Ritsuko , Kondoh Katsuyoshi
Published: March 2009

Super light and high performance Mg2Si/Mg composites, which had excellent mechanical properties, were developed via the combination of solid-state synthesis and hot extrusion process. In this study, cold compacting (CP) and repeated plastic working (RPW) were firstly carried out for the mixture of Mg-Si powders, and the refinement of both Mg grains and dispersoids. Each specimen was
evaluated by observation of microstructure and tensile test. As a result, it was understood that Mg2Si dispersoids were refined and dispersed into Mg matrix, and were flowed along extrusion direction. And their mechanical properties were higher than the conventional die casting alloys. Also the effect of RPW as the improvement of properties and the decrease of synthesis temperature were confirmed.
Research on Semi-Solid Oxidation Behavior of Ti14 Alloy
Authors: Zhao Yong Qing , Ma Xue Dan , Wu Wei Lu , Feng Liang , Yang Hai Ying , Yu Lanlan
Published: March 2009

The semi-solid oxidation behavior of Ti14 alloy was researched. The results show that the weigh gain increases obviously with the increasing of the semi-solid oxidation temperature. After semi-solid oxidation, the oxidation scales are only TiO2 and there are not any oxides of Cu. That is the result of the evaporation of CuO. The evaporation of CuO, which is over 1050°C, makes the weight grain happen to decrease. The oxidation layer consists of five regions. Because of the existence of the low-melting-point-phase (Ti2Cu), the melting grain boundaries become the preference walkway for the oxygen diffusion.
Surface Roughness and Deformation of Grain during Tensile Plastic Deformation of Polycrystalline Titanium
Authors: Li Yan , Abe Takeji
Published: March 2009

The surface folds formed due to plastic deformation and the deformation behaviors of two kinds of polycrystalline titanium with grain sizes of about 30µm and 150µm respectively have been consecutively observed and measured by the scanning probe microscope. The results show that the surface folds in two kinds of specimens were increased with the increase of strain, but their relative position were kept unchanged during deformation. A large amount of twins were formed in each grain when the plastic strain reached about 0.1,which resulted in some new plastic folds. However, these new plastic folds had no influence on the positions of the plastic folds in both specimens as a whole. The roughness, the maximum height difference, and the averaged slope angle of the microscope surface profile increase with the applied tensile strain. But the surface roughness of the specimens with large grains are 1.4 to 4 times higher than that of the specimens with small grains. Two sudden changes in roughness could be observed in the specimens with large grains while the roughness in the specimens with small grains were kept smoothly increased. The influence of grain size on the plastic mechanism and surface roughness were discussed.
An Investigation of Structure Stability and Its Improvement on New Developed Ni-Cr-Co-Mo-Nb-Ti-Al Superalloy
Authors: Xie Xi Shan , Zhao Shuang Qun , Dong Jian Xin , Smith Gaylord D. , Patel Shalesh J.
Published: March 2009

A new nickel-base superalloy Ni-25Cr-20Co-0.5Mo-2Nb-1.7Ti-0.8Al has just developed by Special Metals Corporation in the application to ultra-supercritical boilers with steam temperatures up to 700°C. The structure stability of the alloy was studied in detail in combination of SEM, TEM, XRD and micro-chemical phase analyses. Experimental results show that the most important structure instability is as follows: 1) g¢ coarsening; 2) g¢ to h transformation; 3) G phase formation.
The phase computation by means of Thermo-Calc has been adopted in chemical composition modification for structure stability improvement. Two suggested new modified alloys in adjustment of the Al and Ti contents and in control of Si level were designed and melted for experimental study. These 2 modified new alloys exhibit more stable structure at 760oC long time aging. A bright perspective has been shown for the development of this new alloy in the near future.
Strengthening Mechanisms in Some Single-Crystal Superalloys
Authors: Koizumi Yuichiro , Harada Hiroshi
Published: March 2009

The creep behavior and microstructure of several nickel-base single-crystal superalloys after high-temperature low-stress creep have been investigated. These alloys were designed with varying content of the alloying elements Mo and Ru. At 1100°C and 137 MPa, the large g/g¢ lattice misfit in negative with the addition of Mo leads to the formation of dense interfacial dislocation networks. These dislocation networks are effective to strengthen the alloys during creep by preventing the penetration of the g dislocations into the g¢ phase.
Effect of Grain Size on Mechanical Properties of Single Phase Co-Ni-Cr-Mo Based Superalloy
Authors: Sung Jun Kyung , Kim Mok Soon , Kim Won Yong , Chiba Akihiko
Published: March 2009

A recrystallized Co-Ni-Cr-Mo based superalloy was produced by cold working of 72% and subsequent recrystallization heat treatment. Microstructural observation revealed that a full recrystallization of the cold-worked alloy occured when heat treatment was performed at and above 1273K for 1h. So that, recrystallization heat treatment was carried out in a temperature range from 1273K to 1473K for 1h~24h, by which the average grain size was controlled to 28µm～238µm. Tensile tests were carried out from room temperature (RT) to 1073K in order to understand the effect of grain size on the mechanical properties of the Co-Ni-Cr-Mo based superalloy. At RT and 943K, yield strength, tensile strength and elongation of the recrystallized alloy were improved with decreasing grain size. The alloy having a grain size less than 42µm exhibited a steady-state flow behavior in the true stress-true strain curve at 943K. However, the alloy having a grain size of 28µm showed lower yield strength than that of 42µm at 1073K. It was found that the steady state flow is closely related to the occurrence of {111}<112> deformation twinning in the Co-Ni-Cr-Mo based superalloy.
Roll Bonding and the Application in Making FeCrAl Alloy
Authors: Chen Lichun , Jha Bijendra
Published: March 2009

Fe-21Cr-6Al-0.03(Ce+La) alloy has been made by an innovative method of roll bonding and diffusion alloying for catalytic converter metal foil substrate used for exhaust emission control. During the processes, roll bonding is applied to make a sandwiched Al/Fe22Cr/Al composite material from aluminum and Fe22Cr alloy. Conversion from the composite to the FeCrAl alloy can be accomplished by in-situ diffusion alloying during a thermal process of the converter fabrication.
Interface Morphologies and Microstructure of a Single Crystal Superalloy under High Thermal Gradient Directional Solidification
Authors: Liu Lin , Zhang Jun , Hang Taiwen , Fu Heng Zhi
Published: March 2009

The interface morphologies single crystal superalloys CMSX-2 has been studied over a range of cooling rate with large variations in withdrawal speed in directional solidification. The superfine cellular structure was obtained under both high thermal gradient up to 1000K/cm and fast withdrawal rate up to 1mm/sec. The high rate directional solidification results in reduction in primary and secondary dendrite arm spacing, refinement of λ’ phase, reduced microsegregation of alloying elements and smaller size of γ-γ’ eutectics.
Effect of Chromium on the Oxidation of a Fe-10 Al Alloy at 1000°C
Authors: Zhang Z.G. , Niu Yan
Published: March 2009

The effect of the addition of 5 and 10 at.% Cr on the oxidation of a binary Fe-10 at.% Al alloy (Fe-10Al) was studied in 1 atm O2 at 1000°C. Fe-10Al underwent a very slow initial nearly-parabolic stage followed by a breakaway composed of two subsequent parabolic stages with a smaller rate constant for the final period. The two ternary alloys (Fe-5Cr-10Al and Fe-10Cr-10Al) presented two parabolic stages with final rate constants similar to each other and much lower than that for Fe-10Al. The alumina scale developed initially on Fe-10Al was replaced later by a layered scale containing mixtures of Fe and Al oxides plus many Fe-rich oxide nodules. Fe-5Cr-10Al was mostly covered by a thin alumina layer just above the alloy surface with some Fe-rich nodules formed in the beginning of oxidation, which later on were healed by alumina with a large decrease of the oxidation rate. A continuous alumina layer formed on the whole sample surface without any Fe-rich nodule for Fe-10Cr-10Al. Therefore, the addition of chromium is obviously beneficial for the oxidation resistance of Fe-10Al by inhibiting the formation of fast-growing Fe-containing oxides and promoting the development of an exclusive alumina layer. However, the effect of chromium is different from the classical third-element effect.
Oxidation Behavior of Rh-xTi Refractory Alloys
Authors: Mahapatra Rabindra , Davis A.W.
Published: March 2009

In this paper we report the oxidation behavior of Rh-xTi (x = 15 & 20 atomic percent) alloys isothermally exposed in air between 1000 and 1300 oC up to a period of 312 hours. The weight gain of arc-melted Rh-15Ti and Rh-20Ti alloys as a function of time was monitored. Results indicate that the oxidation resistance of Rh-15Ti and Rh-20Ti alloys at 1000 and 11000 C is similar to that of advanced nickel-base superalloys. However, these alloys show excellent oxidation resistance beyond the operational limit for nickel-base superalloys. Optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) techniques were used to study the microstructure and morphology of the oxides. These alloys oxidize by forming TiO2 and Rh2O3 complex oxides. The Rh-20Ti alloys displayed lower oxidation resistance than Rh-15Ti alloys.
Microstructures and Properties of Refractory Niobium-Silicide-Based Composites
Authors: Qu Shi Yu , Han Ya Fang , Song Liguo
Published: March 2009

The microstructures, mechanical properties and oxidation resistance of the refractory Nb-silicide-based composites have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), compression tests and high-temperature oxidation experiments. The results showed that 1773K/100h heat-treatment was an optimum processing for acquiring equilibrium Nb solid solution and silicides microstructure. In the binary Nb-Si system, the microstructure consisted of
continuous Nb5Si3 equilibrium matrix and dispersed Nb particles, while in the the
Nb-Ti-Cr-Al-Si-(Hf) multicomponent system, there are two typical microstructures, i.e., a two-phase structure of β (Nb solid solution)+D81 Nb5Si3-type silicide in the alloys with the Si+Al content (15at.% and 6at.%, respectively), and a three-phase structure of β+D81 Nb5Si3-type + D88 Ti5Si3-type silicides in the alloys with lower Si+Al content (10at.% and 8at.%, respectively). The results of compression tests showed that all alloys display high strength at both room and high temperatures, only a slight decrease in compression properties occured for Nb-Ti-Cr-Al-Si alloys, comparing to the binary Nb-Si in-situ composites. This type of alloys possesses good high temperature strengths up to at least 1473K. The results of high-temperature oxidation experiments showed that the oxidation rates of the alloys with Ti, Cr, Al and Hf addition were at least one order of magnitude lower than those of the Nb-Si binary alloys.
Oxidation Resistant Silicide Coatings for Nbss/Nb5Si3 In-Situ Composites
Authors: Wang Yong Ping , Li Shu Suo , Zhou Chungen , Qu Shi Yu , Song Liguo , Han Ya Fang
Published: March 2009

Oxidation protective silicide coatings for the new Nbss/Nb5Si3 in-situ composites were prepared by molten salt method at 900°C. The experiment results indicated that the majority phase in the coating was NbSi2. More Nb5Si3 was formed at the interface between the substrate and NbSi2 layer during the oxidation. The oxidation resistance of the composites was improved by the coating, significantly. The improvement in the oxidation resistance of the composites maybe mainly attributed to the formation of large amount of SiO2 and Al2O3 on surface of coating.
Unidirectional Solidification of a Nbss/Nb5Si3 In-Situ Composite
Authors: Guo X.P. , Guan Ping , Ding X. , Zhang Jun , Kusabiraki K. , Fu Heng Zhi
Published: March 2009

The directionally solidified specimens of Nb-13.52 Si-22.60 Ti–6.88 Hf–2.54 Cr–2.24 Al alloy were prepared in an electron beam floating zone melting furnace at the withdrawing rate of 0.1, 0.3, 0.6, 1.0, 2.4 and 6.0 mm/min. All the primary Nb solid solution (Nbss) columns, Nbss + (Nb)3Si/(Nb)5Si3 eutectic colonies and divorced (Nb)3Si/(Nb)5Si3 plates or chains align well along the longitudinal axis of the specimens. With increasing of the withdrawing rate, the microstructure
is gradually refined, and the amount of Nbss + (Nb)3Si/(Nb)5Si3 eutectic colonies increases. Both the room temperature ultimate tensile strength σb and fracture toughness KQ are improved for the directionally solidified specimens. The tensile fracture occurs in a cleavage way.
Microstructure and High-Temperature Creep Behavior of NiAl-25 at.% Cr Intermetallic Compound
Authors: Du Xing Hao , Zhang Guang Ye , Guo Jian Ting
Published: March 2009

The creep behavior and mechanisms of extruded NiAl-25Cr alloy at elevated
temperatures have been studied in the paper. Analysis of the creep data over the temperature range 1073-1123 K reveals two distinct regions of creep behavior present in this material. At lower temperature, the creep characteristics are consistent with mobility-controlled deformation where viscous glide of dislocations controls creep. At higher temperature, the creep characteristics are consistent with a structure controlled creep process where some form of dislocation climb controls
creep deformation.
Microstructure and Tensile Properties of Hot Worked High Nb Containing TiAl Alloy on Industrial Scale
Authors: Lin Jun Pin , Xu Xiang Jun , Gao Jian Feng , Wang Yan Li , Lin Zhi , Chen Guo Liang
Published: March 2009

. A hot working and its effect on the microstructure and tensile properties of Ti-45Al-9 (Nb, W, B, Y) alloy ingot on industrial scale were investigated. The results showed that the alloy has good workability in anα+γphase region. An ingot on industrial scale was successfully extruded followed by multi-step canned forging. The initial microstructure of the alloy is fine full lamellar (FL) microstructure. After hot working a sound pancake exhibiting a fine grain duplex (DP) microstructure with grain size about 20μm was obtained. The as-forged alloy has more balanced tensile properties than the small heats with similar composition and microstructure at both room and high temperatures.
Recent Work on Alloy and Process Development of Ti2AlNb Based Alloys
Authors: Li Shi Qiong , Cheng Yun Jun , Liang Xiao Bo , Zhang Jian Wei
Published: March 2009

Ti2AlNb orthorhombic phase based alloys are the promising high temperature structural materials for aeronautical and aerospace industry because of their low density, high yield strength and excellent high temperature performance. In this paper, the recent work which has been carried out in CISRI on alloy and process of Ti2AlNb based alloys is presented. The work covers the development of the alloy design and microstructure control as well as the processing technology applied for producing good quality alloy ingots and fabricating various components. The progress obtained in application research of the alloys is addressed. The important role that the combination of TMP and the post-TMP treatment affects on the microstructure and thus on the properties of the alloys is emphasized.
Phase Transformation and Synthesis of Ni Substituted CoSb3 Skutterudite Synthesis during Solid State Reaction
Authors: Yang Jun You , Chen Yuehua , Peng Jiangying , Zhu Wen , Song Xin Li
Published: March 2009

Starting from elemental Co (99.9%), Ni (99.9%) and Sb (99.99%) powders, Co4-xNixSb12 powder mixture with different Ni concentration were subjected to mechanical alloying by using a planetary ball mill. Phase transformation during mechanical alloying process of Co-Ni-Sb system was studied in this paper. Ni substituted skutterudite could be synthesized by solid state reaction. With assistance of hot pressing for two hours, the as mechanically alloyed low Ni concentration powders could be completely transformed into skutterudite compound. The lattice parameter of Ni substituted skutterudite compound complies well with Vegard law when x is not more than 0.2. When Ni concentration is larger than the maximum solubility, NiSb2 compound forms and single phase skutterudite compound can not be obtained.
Microstructure and Properties of a 70vol.% SiCp/Al-12Si Composite for Electronic Packaging
Authors: Zhang Q. , Xiu Zi Yang , Song Mei Hui , Wu Gaohui
Published: March 2009

For the purpose of electronic packaging applications, a homogenous and void free 4032Al (Al-12wt.%Si) matrix composite with 70vol.% SiC particles was fabricated by squeeze casting technology. TEM observations indicated that SiC particles acted as heterogeneous nucleation sites for Si phases in the matrix and the SiC-Al interfaces were clean and free from any interfacial reaction products. The composite possessed lower coefficients of thermal expansion (CTEs) and excellent thermal conduction properties, and the CTEs could be further reduced by annealing treatment because of the alteration of original thermal residual stresses within the specimens. The incorporation of high volume fraction of SiC particles also induced enhanced mechanical properties for the composite, and its moduli even exceeded 200GPa. Some diodes were finally produced with nickel plated SiCp/Al
baseplates and the results of thermal cycling tests between -55ı and 150ıfor these diodes were presented.
Effects of Carbon Nanotubes Incorporation on the Grain Growth and Properties of WC/Co Nanocomposites
Authors: Zhang Fa Ming , Sun Jian Fei , Shen Jun
Published: March 2009

Carbon nanotubes (CNTs) combining unique mechanical and physical properties could offer a kind of nanosized reinforcements for composite materials. Incorporating of CNTs to develop advance engineering composites has become an interesting concept, but the cermets based CNTs composites have been less focused. WC-Co-CNTs nanocomposites were consolidated by spark plasma sintering (SPS) to investigate the effects of CNTs incorporation on the grain growth and mechanical properties of WC-Co nanocomposites. Experimental results show that CNTs could preserve their tubular structures in high temperature SPS process, some CNTs are surviving in the WC-Co fracture surfaces featured bridging and pulling out manner. The interaction between the CNTs and the matrix has a retardation effect of grain growth of WC, but CNTs additions could be
resulted in an increase of carbon content in the binder phase that causes enhanced tendency of grain growth, either of which plays the dominated role depending on the CNTs content. The WC-10Co-0.5wt%CNTs nanocomposites possess superior hardness to toughness combinations, which hardness is about 15% and fracture toughness is about 40% higher than that of the pure nano-WC-10Co cermets consolidated under the same process.
Structural Modifications in Thin Films Caused by Gamma Radiation
Authors: Arshak Khalil , Korostynska Olga , Henry John
Published: March 2009

This paper reports on the gamma radiation-induced changes in thin oxide films deposited by thermal vacuum technique. Structures of various oxides thin films, such as In2O3, SiO and TeO2 and their mixtures in different proportions were studied. The influence of gamma radiation on In2O3/SiO films has resulted in significant changes in the microstructure of this film. Some kind of agglomerations with variable sizes in the range 0.5-3 µm has occurred. After a dose of 8160 µSv an
evidence of partial crystallisation was observed with X-ray diffraction. Structural changes in TeO2 thin film were explored by means of Raman spectroscopy. After they have been exposed to g- radiation, a strong peak appeared at 448.83 cm-1, indicating further transformation to g-TeO2 modification.
Biodegradable Polymer Studied by Physical Properties Measurements
Authors: Henry François , Devassine M. , Guerin P. , Costa Luís Cadillon , Briand X.
Published: March 2009

Polylactid acid (PLA), as an aliphatic polyester, is one of the most important and studied biodegradable material. The structure, the morphology, the molar mass regulate that biodegrability. During degradation, the process of chain scission occurs through hydrolysis. In this work we have investigated the water penetration through industrial and purified PLA films, in order to understand that degradability. Using different physical measurements, particularly the activation energy of b relaxation, the crystallinity, the water vapour permeability, the glass transition and the ion selective permeability. The complementary of the techniques permits to obtain results that support the physical model presented.
Analysis of the Creep Behaviour of Polypropylene
Authors: Reinas Dos Santos André José , Pinto José Joaquim Cruz
Published: March 2009

In this work, creep data for a polypropylene (PP) were obtained at different levels of tensile stress and temperature, and were then analysed in the light of a model developed, which is based on physical mechanisms (at the molecular scale) responsible for the material’s behaviour, considering that a minimum retardation time does exist. The model yields very good agreement with the experimental data and physically meaningful theoretical parameter values.
Optical Properties of Sputtered Silver Granular Films
Authors: Paje S.E. , Teran F. , Riveiro J.M. , Llopis J. , García M.A. , Marco de Lucas M.C. , Saviot L.
Published: March 2009

In this research we study optical absorption and morphology of silver films prepared with a sputtering method. Silver granular films are obtained on a glass substrate for films with thickness smaller than about 60 Å. Superficial silver clusters of around 100 nm in diameter are clearly seen in the atomic force micrographs. The absorption of these samples are characterized by plasmon excitation in the 450-650 nm spectral range, which differs from the known excitation of silver nanoparticles fabricated by different techniques. The optical absorption of silver granular films depend on sputtering conditions like substrate temperature or deposition rate and correlates with the surface morphology.
Determination of ZrO2 Thermoluminescence Kinetic Parameters after UV Irradiation Using Peak Shape Methods
Authors: Rivera Montalvo T. , Furetta C. , Azorín Nieto J. , Falcony Guajardo C. , García M. , Martínez Eduardo
Published: March 2009

Various experimental methods are currently employed for the determination of the trap parameters. Methods based on the glow curve shape extract information from a glow peak utilizing the temperature at the maximum emission, TM, the temperature on the ascending part of the peak ,T1, which corresponding to half peak intensity and the temperature on the descending part of the peak, T2, also corresponding to the half peak intensity; as well as, the half width parameters and the symmetry properties. In order to obtain the kinetic order b and the trap parameters, ZrO2 samples were exposed to 260 nm ultraviolet radiation (UVR). The trapping kinetics parameters of the ZrO2 dosimetric peak using the shape of the glow curve were then determined. The order of kinetics followed by the main peak was also determined using the same method. The values of activation energy E and frequency factor ,s, for the main peak of ZrO2 obtained by the above mentioned
methods, showed a good agreement among them.
Characterization of Polyethylene Foams under Compressive Impact Loading
Authors: Ruiz-Herrero J.L. , Rodríguez-Pérez Miguel A. , de Saja Jose A.
Published: March 2009

It has long been recognized that the mechanical behaviour of materials under conditions of rapid loading and impact differs significantly from that under static load application [1].These differences are specially important for those materials as polymeric foams used as low energy impact absorbing materials[2]. An optimum energy absorbing material needs to dissipate the kinetic energy of the impact while
keeping the force on it below some limit, thus resulting in a no-dangerous deceleration of the protected object[3].
The mechanical properties at room temperature of six polyethylene foams with closed cells and different densities have been evaluated in purely compressive impact loading conditions. The energy absorption characteristics have been evaluated through different parameters as the peak of deceleration, the load transmitted, the maximum strain and the impact time. The peak of deceleration is used to obtain the cushion diagrams at five different heights, useful to design energy
absorption structures.
Inhibition Layer Breakdown by a Fast Diffusion Procedure of Zinc in Galvanized Coatings
Authors: Pavlidou Eleni , Pistofidis N. , Vourlias G. , Stergioudis F.
Published: March 2009

Thick sheets of steel were galvanized in a bath containing Al additions. A Fe2Al5
layer is formed at the substrate steel sheet, which leads to a desirable transient inhibition of Fe-Zn reactions. Thus the more protective (eta) phase rich in zinc is favored. However an appreciable intergranular diffusion and a gradual formation of internal and surface oxide particles influence the growth and stability of the inhibition layer. The location of some oxide particles at the Fe2Al5 surface or inside of this layer, led to conclude that oxide particles might cause Fe-Zn outburst growths to form. This is because zinc diffuses along the oxide particle/Fe2Al5 interface. Moreover the mechanism of oxide formation causes a local depletion of the atoms concentration in the bath in the vicinity of the formed oxide. This in turn diminishes the probability of the formation of the Fe2Al5 layer. So the whole mechanism provides a fast diffusion bath for Zn, which reacts with Iron atoms forming Fe-Zn phases. The formation of the phases, were determined by XRD measurements (PHILIPS diffractometer CuKα radiation) while the dispersion of the elements was examined by SEM (20kV JEOL 840A equipped with an OXFORD ISIS 300 EDS analyzer.
Microstructural Characterization by Nondestructive Methods
Authors: Lukáč Pavel , Trojanová Zuzanka , Chmelík František
Published: March 2009

Nondestructive methods may help to detect changes in the internal structure of a material and to explain the behaviour of the material. This paper describes a series of nondestructive tests performed on magnesium composites with a variety of matrices: commercial pure Mg and three magnesium alloys AZ91, ZC63 and ZE41. Short fibres of δ-Al2O3 (Saffil®) were used as the reinforcement. Internal friction measurements and joint dilatation and acoustic emission studies were used to demonstrate how thermal cycling influences the deformation behaviour of Mg based
metal matrix composites. The values of the logarithmic decrement are influenced by the upper temperature of the cycle. The acoustic emission activity and the residual strain increase with increasing upper temperature. The results may be explained assuming that internal thermal stresses are generated.
Criterion of Mechanical Instability in Inhomogeneous Atomic System
Authors: Umeno Yoshitaka , Kitamura Takayuki
Published: March 2009

The mechanical stability of a material is a fundamental issue in strength of atomic systems. Although the criterion of the mechanical stability of homogeneous structures such as perfect crystals have been successfully investigated so far, the criterion has not been able to be precisely evaluated in the cases of non-uniform deformations or bodies of inhomogeneous atomic structures. Now we present an instability criterion of an arbitrary atomic structure based on the energy balance of the whole system. This method gives the mathematically rigorous condition for the onset of an unstable deformation in any inhomogeneous atomic system. Furthermore, the method can be applied to any type of potential field, which means that ab initio evaluations of the mechanical instability of inhomogeneous structure under non-uniform deformation will be possible. The validity of the method is clarified by the application to tension of a cracked body. The onsets of unstable deformations and their deformation modes are precisely evaluated by the method.
Elasticity and Stability of Fe-P Ordered Systems from First Principles
Authors: Černý Miroslav , Pokluda Jaroslav
Published: March 2009

Elastic properties of Fe-P ordered system (the bulk modulus and the theoretical strength under isotropic tension) are computed by means of ab initio computational program code VASP. Different configurations and relative amounts of constituent atoms are considered in the crystal cells of known stable phases as well as of some hypothetical structures. The influence of a relative content of P in the alloy on computed properties is studied. Magnetic ordering is taken into account
by means of collinear spin-polarization. The results of calculations reveal that, somewhat surprisingly, no dramatic changes of elastic moduli are to be expected up to the 67% atomic concentration of P.