bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Fe86Zr5.5Nb5.5B3 Nanocrystalline Bulk Alloy under High Pressure
Authors: Lu Bin , Yi Dan Qing , Yan Biao , Yin Jun Lin , Liu Yan , Liu Hui Qun , Wu Biao Li , Chen Xiao Li
Published: March 2009

Mechanical alloying(MA) technique and single-roller melt spinning technique were used to prepare Fe86Zr5.5Nb5.5B3 nanocrystalline and amorphous powders, bulk alloys were prepared by cryogenically high-pressure quick sintering. The results showed that: (1) after MA process for 15 hours, the grain size of α-Fe phase was ≤10nm; (2) melt spinning powders were fragmented by ball milling, but remained amorphous state. The crystallization temperature of this amorphous
powder was about 500°C. Apparent activation energy of the amorphous crystallization was E=294.1KJ/mol; (3) under the quick sintering conditions of P=5.5GPa/t=3min/Pw≥1050W, single phaseα-Fe nanocrystalline(8～15nm) bulk alloys with relative density≥98.7% can be obtained.
On Structural Stability of Nanostructured Aluminium
Authors: Van Der Kolff E.J. , Berkahn M. , Wuhrer Richard , Yeung Wing Yiu
Published: March 2009

Nano- and submicron-structured aluminium was produced by equal channel angular
extrusion with a total strain of ~17. Large residual stress and strain energy were built up in the extruded metal and subsequent heat treatments were applied to investigate the stability of the nanostructures. X-ray diffractometry and transmission electron microscopy were performed to evaluate the microstructural changes in the nanograin metal. It was found that the nanostructures remained stable at temperatures up to 250oC. Above 250oC, changes in the major x-ray peak
reflections became evident, suggesting substantial grain growth had occurred. Electron microscopy confirmed that at low annealing temperatures, the fine grain structures were stable and indeed became more equiaxed and well defined.
Structure Changes in Stainless Steels Used in Nuclear Reactors and Turbo Generators after Minor Low Cycle Fatigue Deformation
Authors: Eterashvili Tamaz , Dzigrashvili T. , Vardosanidze M.
Published: March 2009

The structure of austenitic steel before and after 25% of total number of cycles of low cycle fatigue tests conducted at room temperature is studied using TEM. It is shown that the cyclic deformation of the steel proceeds heterogeneously. The microstructure of the steel is investigated in the area between the deformed and undistorted parts of the samples. The crystallography of the observed
twins and the slip bands is specified. The value of local plastic deformation within a micro area of a grain is measured, and the influence of microstructure on crack initiation is discussed.
Quasicrystal Formation in the System Zr75-xTixCu25-yNiy
Authors: Soubeyroux Jean Louis , PELLETIER Jean-Marc
Published: March 2009

During the crystallization study of the bulk metallic glass 46.8Ti8.2Cu7.5Ni10Be27.5 (Vit4) we have demonstrated that the primary crystals appearing during isothermal annealing in the glass region, above Tg and before Tx, were of quasicrystalline nature and beryllium free. The formula of the quasicrystalline phase so obtained and determined by electron techniques (EDX and EELS) was
Zr63Ti14.4Ni12.4Cu10.2. We have synthesized phases in the system Zr75-xTixCu25-yNiy by melt spinning and obtained either amorphous or quasicrystalline phases. For the amorphous phases, we have studied the crystallization by in-situ neutron diffraction and obtained quasicrystals as primary crystals. Neutron and X-ray diffraction, DSC studies are presented.
Mechano-Synthesis and Characterization of Fe-Co Based Nanocrystalline Magnetic Materials
Authors: Mujahid M. , Sim S.H. , Zhu J.
Published: March 2009

Nanostructured Fe-Co based alloys are believed to be good candidates for imparting
improved magnetic behavior in terms of higher permeability, lower coercivity, reduced hysteresis loss and higher Curie temperatures. In the present work, Fe-Co alloys with Ni additions were prepared using mechanical alloying (MA). Grain size and internal strain in the MA powders was measured using X-ray diffraction. It has been shown that the grain size could be reduced down to less than 5 nm
in these alloys. Nanocrystalline materials thus obtained were also evaluated for magnetic behavior and the influence of grain size and internal strain on the magnetic properties has been discussed.
Rapid Synthesis of Zinc Oxide and Lead Oxide Nanorods by One-Step Solid-State Reaction Methods at Ambient Conditions
Authors: Cao Yali , Liu Lang , Jia Dienzeng , Xiao Ding Quan
Published: March 2009

A simple and facilitate method was reported to synthesize zinc oxide and lead oxide nanorods. Two metal oxides nanorods were directly obtained from grinding solid metallic salts and sodium hydroxide in agate mortar with the assistance of a suitable surfactant in only one step, which is different from the results of hydroxides in solution. The as-prepared products were characterized by XRD, TEM and SEM. An explanation describing possible mechanism for the rod-formation is given.
Field Electron Emission from Carbon Nanotube Films on Diamond Films
Authors: Liao K.J. , Wang W.L. , Wang Y.T. , Lu J.W. , Sun X.L.
Published: March 2009

The field electron emission from carbon nanotube films on polycrystalline diamond films was investigated. The carbon nanotubes and diamond films on Si substrates were prepared by a conventional hot filament chemical vapour deposition. The films obtained were characterized by scanning electron microscopy and Raman spectroscopy. The field emission properties of the samples were measured in an ion-pumped vacuum chamber at a pressure of 10-6 Pa.. The experimental results showed that the field emission behaviours of carbon nanotubes/diomond films
structure have greatly been improved as compared with carbon nanotubes and diamond films, respectively. A turn-on field of 1.0 V/µm and a maximum current of 500 µA at 1.5 V/µm were observed, which were lower than those of carbon nanotubes and polycrystalline diamond films, respectively. This improvement was attributed to the tip shape of sample surface, which provided an additional local increase in electric field at the tube ends.
Analysis of Interface between Free-Standing Diamond Films and Mo Substrates
Authors: Li Hui Qing , Li Cheng Ming , Chen Guang Chao , Lu Fan Xiu , Tong Yu Mei
Published: March 2009

Interfaces between Mo substrate and free-standing diamond films prepared by DC arc plasma jet operated at gas recycling mode were investigated, including for the first time used and multi-time used substrate. The morphology, phase composition and bonding state of elements in the interface between substrates and diamond films were examined by optical microscopy, XRD and XPS. The profiles of carbon concentration of Mo substrates were measured by GDOES. It showed
that Mo2C and MoC were formed on the first time used Mo substrate, and MoC was found on diamond films nucleation side after detachment. It suggested that MoC was peeled off from Mo substrate. The stable Mo2C on Mo substrate was formed after multi-time use of Mo substrate. However, MoC has not been found on it. The thickness of carburizing layer on the first time used Mo substrate is up to 30µm, and the carburizing layer on the multi-time used substrate is much thicker
than that on the first used. The amorphous carbon in the surface of the substrate and nucleation side of diamond films was found by XPS, including for the first time used and multi-time used substrate.
A Novel Efficient Blue Organic Light Emitting Structure
Authors: Jiang Wen Long , Duan Yu , Zhao Yi , Hou Jingying , Liu Shi Yong
Published: March 2009

In this paper, we describe the performance of an organic light emitting devices〔OLEDs〕 with ITO /4,4’,4“-tris{N,- （ 3-methylphenyl ） -N-phenylamino}triphenylamine (m-MTDATA) /N,N-diphenyl-N,N-bis1-naphthyl-1,1-biphenyl-4,4-diamine (NPB) /copper phthalocyanine (CuPc) / NPB / Bathocuproine(BCP) / tris-8-hydroxyquinoline Aluminum (Alq3) / LiF/ AL structure, the
CuPc inserted between the two layers of NPB as a hole-consuming layer (HCL), and the BCP as a hole-blocking layer (HBL) . The EL spectrum peak is at 430 nm, indicating that the carrier recombination is confined in the NPB layer, in additional light emission originates from NPB. Compared with the luminous efficiency of the conventional diode without CuPc layer, that of the diode with HCL has been sharply increased up to 2.62 cd /A. It suggested that the CuPc and BCP
exactly function as hole-consuming and hole-blocking layers, respectively, which enhance the efficiency of carrier，s recombination and confine the excitation in the EL layer.
The Morphology and Optical Characterizations of AlGaN/GaN Based on Al2O3 Prepared by MOCVD
Authors: Li M.C. , Zhao Lian Cheng , Li H.M.
Published: March 2009

The microstructure, optical absorption properties and luminescence function of GaN thin films grown on the sapphire substrate with the buffer layer of GaN by metal-organic chemical vapor deposition (MOCVD) have been studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared transmission spectrum, ultraviolet-visible absorption spectrum and photoluminescence. XRD results show that the crystal structure of GaN is hexagonal wurtzite structure. The thin films have preferred orientation in c axis with very high quality. TEM images of the cross-sectional specimen show that the thickness of every layer in the superlattice are uniform with the average period of 13.3 nm, but there are high-density dislocations in the superlattices
region. From related optical experimental data, it is found that optical absorption edge is at about 370 nm. The theory calculation indicates that the five samples are direct transition semiconductor and band-gaps are about 3.4 eV. The refractive indexes of the samples increase with photon energy enhancing and decrease with the wavelength increasing. The results show that the extinction coefficients reach the lowest point at 370 nm. Photoluminescence test results show that superlattice
has preferable luminescence property. In addition, the yellow luminescence is found in all samples.
The Temperature Dependence of In Desorption during InN Growth and Annealing
Authors: Bi Z.X. , Zhang Rong , Xie Zi Li , Xiu Xiang Qian , Ye Yu Da , Liu B. , Gu Shu Lin , Shi Y. , Zheng Y.D.
Published: March 2009

The MOCVD-growth and annealing of InN films have been studied in this work. The
XRD spectra of InN films grown at 350 °C~500 °C indicate that the diffraction of In increases with increasing the growth temperature to 425 °C and the temperature higher than 425 °C causes the decrease of In diffraction. The corresponding SEM images show that In grains disappear from the surface as the growth temperature is higher than 425 °C. These are attributed to the increase of the desorption of In with the growth temperature. In addition, the SEM images of the annealed InN
films also show that the In grains decrease gradually as the annealing temperature is higher than 425 °C. Thus, it is concluded that the desorption of In is the main process as the temperature is higher than 425 °C.
TbFe2/α-Fe Nanocrystalline Exchange Coupling Magnetostrictive Films
Authors: Zhang Wan Li , Jiang Hong Chuan , Peng Bin , Zhang Wen Xu , Yang Shi Qing
Published: March 2009

In this paper, the influences of annealing temperature on TbFe magnetostrictive film
magnetic and magnetostrictive characteristics were discussed. TbFe films were prepared by RF magnetron sputtering. XRD patterns indicate that polycrystalline films consisting mainly of a-Fe and TbFe2 Laves phase could be obtained through rapid cycle annealing process (RCAP) at higher annealing temperature. Grain sizes could be controlled through varying annealing temperature. From
film hysteresis loops measured by VSM, it has been found that the annealing treatment can improve TbFe film in-plane magnetization at 1600 kA.m-1 external field, and decrease in-plane coercivity. Magnetostriction of annealed TbFe films measured by optical cantilever deflectometer is better than as-deposited films at 40 kA.m-1 external magnetic field.
Microstructure and Electronic Properties of Al/Zr/LiNbO3 Multilayers
Authors: Li D.M. , Pan F. , Wang X.B. , Niu J.B. , Liu M.
Published: March 2009

To obtain both high power durability and fine-dimensional control in high-frequency
surface acoustic wave devices, a highly oriented (111) texture was developed in electronic beam evaporated Al films on Zr underlayer. In this paper, the effects of Zr underlayer on the microstructure and resistivity of Al/Zr/LiNbO3 films were investigated. The films show an extremely smooth surface. The optimum annealing temperature is 200 °C to obtain low resistivity. For Al films with Zr underlayer, reactive ion etching with gases containing BCl3 can be more easily
performed than that for Al films with Cu underlayer.
Effect of Pt Interlayer on Thermal Stability of NiSi Films
Authors: He Ying , Feng Jia You , Wu Q.L.
Published: March 2009

In this paper, the effect of a thin interlayer of Pt on thermal stability of NiSi films on
Si(111) has been studied. The Ni/Pt/Si(111) bilayered samples with the same film thickness were annealed by rapid thermal annealing at 640 °C-900 °C. Both the X-ray diffraction analysis and four-probe measurements show a remarkable improvement in the thermal stability NiSi as a result of Pt interlayer. The possible reason for the enhanced NiSi thermal stability is attributed to the formation of the Ni(Pt)Si solid solution and its preferred orientation, leading to the decrease in the
driving force of NiSi2 nucleation and the increase in the interfacial energy change respectively. The experimental results are explained in terms of Miedema’s Model and Thomas-Fermi-Dirac (TFD) equations in detail.
Surface Morphology, Structure and Transport Property of NaxCoO2 Thin Films Grown by Pulsed Laser Deposition
Authors: Zhang X.P. , Xiao Y.S. , Zhou H. , Xie B.T. , Yang C.X. , Zhao Y.G.
Published: March 2009

In this paper, we report the growth of NaxCoO2 thin films by pulsed-laser deposition
(PLD). It is shown that the concentration of sodium is very sensitive to the substrate temperature and the target-substrate distance due to the evaporation of sodium during the deposition. α'-phase Na0.75CoO2 and γ-phase Na0.71CoO2 thin films can be obtained with different conditions. Correspondingly, the surface morphology of the films changes from flake-like to particle-like. The
temperature dependence of resistivity for the films prepared with the optimal condition shows metallic behavior, consistent with the data of NaxCoO2 single crystals. This work demonstrates that PLD is a promising technique to get high quality NaxCoO2 thin films.
Study of Microwave-Absorbing Property of Nanometer Multi-Layer
Authors: Bi Yun Fei , Ye Tao , Liu Pei Ying
Published: March 2009

Ferromagnetic layer and dielectric layer of nanometer thickness were deposited
alternatively on quartz glass plates to compose nanometer multiple-layers with microwave absorbing function by electrostatic self-assembly. The thickness of a double-layer composed of a ferromagnetic layer and a dielectric layer is 6~8 nm measured by UV-VS spectrophotometer. The nanometer multi-layer with total thickness of 100~200 nm exhibits obvious microwave-absorbing effect in the wave range of 8~18 GHz and the maximum attenuation reaches -16.85 dB. The
wave-absorbing mechanism of nanometer multiple-layers was discussed based on the quantum theory
The Investigation of Microstructure of Pt/Ti Explosive Clad Interface
Authors: Wei Shi Zhong , Li Yan , Zhu Jin Hua
Published: March 2009

Microstructure in anchoring site of Pt/Ti explosive clad Plate was observed, tested and analyzed by analytical and high resolution transmission electron microscope, X-ray diffractometer, scanning electron microscope and energy-dispersive spectrometer. An intermittent micro-crystal layer was observed in anchoring area, with thickness of 2 um. The inner crystal size was from some nanometer. to hundreds of nanometer. Some crystal had defects in it, such as staggered layer. The layer was composed of metal compound, like PtTi，Pt5Ti3，Pt3Ti，Ti3Pt and etc. The direct Pt—Ti anchoring area, hexagonal Ti variation-orthorhombic crystal system, α″-Ti metastable martensite phase and bicrystals with partial deformation were also observed. The research of microstructure in anchoring area revealed the nature of explosive compound in metallurgical anchoring.
The Use of Trimethylaluminum for Producing Surface Layers by the PACVD Method
Authors: Sobiecki Jerzy Robert , Sitek R. , Wierzchoń Tadeusz
Published: March 2009

The paper presents the use of trimethylaluminum in PACVD method to obtain the
surface layers like alumina or aluminum nitride on Inconel nickel alloy. The glow discharge nitriding at a temperature of 750°C leads to the formation of aluminum oxynitride in the layer, whereas annealing in argon plasma at a temperature of 1050°C – to the formation of nickel and aluminum based intermetallic phases of the NiAl or Ni3Al type with aluminum oxide present within the outer zone of the coating. The presence of the surface layer of the Al2O3+NiAl+Ni3Al type formed on nickel alloys may be significant from the point of view of the applications that require a
high heat resistance.
Development of Wear Resistant Zirconium Oxide Thin Films on Stainless Steel Substrates
Authors: Then I.K. , Mujahid M. , Zhang B.
Published: March 2009

The present work deals specifically with the development of zirconium oxide thin film
coatings on the stainless steel orthodontic bracket system by sputtering technique. Thin films of zirconium oxide have been deposited on injection molded stainless steel substrates using sputtering under controlled temperature and environment conditions. The deposited films, 1.5 µm in thickness, were found to have a predominantly tetragonal structure with grain size of about 5 nm. The grain size
was found to increase only slightly with increasing heat treatment time at 650°C. It has been shown that thin-film zirconia coatings with stable structure and good adhesion along with very low friction coefficient could be produced.
A Control of the Nanopore Regularity in Alumina Layer
Authors: Oh H.J. , Lee J.H. , Jeong Y. , Suh Su Jeong , Chi C.-S.
Published: March 2009

This study placed a focus on fabrication factors and surface morphology characteristics to obtain anodic alumina layers with ordered nanopore arrays using two-step anodization process. The regularity of nanopore arrangement in anodic alumina was prepared in oxalic acid at 40 V. The regular array was shown to be more strongly dependent on the time of first anodization than that of
second anodization. The widening process of oxide surface in H3PO4 solution clearly exhibits that the nanopore diameter of the alumina layer subjected to widening time increased linearly at a rate of 0.6 nm/min at 30°C, and 0.8 nm/min at 40°C. The pore arrays in anodic alumina were analyzed by SEM.
High Temperature Deformation Behavior of Pre-Sintered Al-10Si-5Fe Based Alloy
Authors: Lee Dong  Suk , Shim Gyu-Sam , Kim Mok Soon , Kim Won Yong , Yamagata Hiroshi
Published: March 2009

Compressive deformation behavior of pre-sintered Al-10Si-5Fe-1Cu-0.5Mg-1Zr (wt%) alloy containing 15% of porosity was investigated in the temperature range from 753 K to 793 K and at strain rates from 10-4 to 100 s-1. From the microstructural observation, it was revealed that the occurrence of grain boundary sliding accomodated by dynamic recrystallization during the compressive deformation was closely associated with the considerable decrease in the porosity of the pre-sintered alloy. In the specimens deformed at 793 K with 10-4~100 s-1 and at 773 K with 10- 4~10-2 s-1, we have found an evidence of the occurrence of a liquid phase during compressive deformation in the microstructure. The liquid phase was considered to promote particle boundary sliding and hinder the reduction of the pore.
Surface Modification of Superfine Aluminum Oxide Powders
Authors: Cui Hai Ping , Yan Jun , Liu J.Z.
Published: March 2009

The effects of two silane coupling agents (KH550, KH570) and three coupling agents of organic titanate (JSC, CT136 and NTC401) on the surface modification of superfine Al2O3 powders were tested and compared. The results showed that three coupling agents of organic titanate succeeded in modify the surface of Al2O3 particle from hydrophilic property to lipophilicity, while two silane coupling agents failed. The group changes of the surface were confirmed by IR spectrum,
which also indicated that chemical absorption occurred between NTC401 and the powders surface, but for JSC and CT136 mainly occurred physical absorption. SEM photos of the powders showed that agglomeration-free particles could be obtained when the powders were treaded by NTC401. However, when treated by JSC or CT136 the powders tended to be secondly agglomerated. The proper coupling mechanism was analyzed, and it was thought that space structure of octahedral complex of titanium ion with six ligands could effectively impede agglomeration.
Microstructural Characterization of Rheology Material Fabricated by Rotational Barrel Type
Authors: Seo P.K. , Kang Chung Gil
Published: March 2009

The new rheology fabrication process has been developed to rheo die casting and rheo forming process. The barrel type equipment, which could continuously fabricate the rheology material, was specially designed to have a function to control cooling rate, shear rate and temperature. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed. The barrel surface has both the induction heating system and the cooling system to
control the temperature of molten metal. By using this system, the effect of the rotation speed and the rotation time on the microstructure was widely examined. The possibility for the rheoforming process was investigated with microstructural characteristic.
Sliding Wear Characteristics of Ultrafine-Grained Non-Strain-Hardening Aluminum-Magnesium Alloys
Authors: Kim Yong Suk , Ha J.S. , Shin Dong Hyuk
Published: March 2009

Coarse grains of commercial 5052 Al and 5083 Al alloys were refined by the accumulative roll bonding (ARB) process. Average grain size of the refined microstructure was 200 nm. The 5083 Al alloy that has higher Mg content required more deformation for the refinement. Dry sliding wear behavior of the ultra-fine grained (UFG) Al alloys was investigated using a pin-on-disk wear tester at
room temperature. The UFG microstructure of the processed alloys hardly increased the wear resistance of the Al alloys in spite of the increased strength and hardness. Wear rate of the UFG Al alloys was higher than that of the non processed coarse-grained starting alloys. The SEM observation of worn surfaces revealed that surface deformation controlled the wear. The low wear resistance of
the UFG Al alloys was attributed to non-equilibrium and unstable grain boundaries and low strain hardening capability of the alloys.
On the Stability of Defects and Grain Size in Ultrafine-Grained Copper during Cyclic Deformation and Subsequent Ageing at Room Temperature
Authors: Huang Cun Xin , Wang S.C. , Wu Shi Ding , Jiang Cheng Bao , Li G.Y. , Li Shou Xin
Published: March 2009

Ultrafine-grained (UFG) pure Cu processed by equal channel angular pressing (ECAP) was subjected to cyclic deformation and subsequent ageing treatment at room temperature (RT) in order to investigate the stability of defects and grain size. Cyclic deformation for 1000 cycles at RT leads to a large decrease of internal stress. X-ray diffraction (XRD) shows that the stability of defects and grain size at RT in as-cyclic deformed sample is lower than that in as-processed sample
and that a reduction of internal stress takes place prior to grain growth. TEM observations show that the microstructural evolution during ageing is characterized by normal grain growth accompanied with recovery within grain interior.
A New Scheme for the Exit-Wave Reconstruction from a Small Set of Focus Series of HREM Images
Authors: Lin F. , Chen Qing , Peng Lian Mao
Published: March 2009

A new procedure is proposed for the exit electron wave reconstruction using a small set of high-resolution electron microscopy (HREM) images. This procedure is similar to that proposed by van Dyck and coworkers, but the relative shifts between different HREM images are obtained via the genetic algorithm instead of the more widely used cross-correlation function (XCF) method. The new procedure is demonstrated using simulated HREM images with added noise, and shown to
be able to deal with situation where the scheme based on the method of XCF is not applicable.
Niobium Doped Potassium Titanate Nanowires and Nanobelts
Authors: Wang Bo Lu , Chen Qing , Hu Y.F.
Published: March 2009

The nanowires and nanobelts longer than several micrometers have been synthesized through simple KOH treatment. The nanowires and the nanobelts were found to contain K, Ti, Nb and O. The structures of the nanowires and the nanobelts were analyzed. The bandgap of the nanobelts was calculated from the absorbance spectrum to be about 3.3eV.
Water Vapor Oxidation Behavior under High-Temperature and Pressure Conditions of the Nitrided Alloys for Steam Turbine Valve System Parts
Authors: Yoon J.H. , Kim I.S. , Kim H.S. , Hur I.C. , Son K.S. , Lee Je Hyun , Kim H.S.
Published: March 2009

Mechanical and corrosion properties were evaluated in the nitrided and non-nitrided
specimens of ASTM 355 and SUS422 steels. The oxides formed on the specimen were analyzed using by XRD and the weight change was measured after oxidation test at high temperature, high pressure, and steam conditions. The oxidation behaviors and rates between two alloys and nitrided/non-nitrided specimens were clearly different. XRD analysis showed that the nitrides formed on the nitrided specimen were composed of CrN, Fe4N, and Fe2-3N. Also, it was found that
the hardness on the nitrided specimen at 283°C decreased from Hv 1150 of room temperature to Hv 425.
Effect of Heat Treatment Conditions on Tube Hydroformability
Authors: Park K.S. , Kim B.J. , Moon Young Hoon
Published: March 2009

Tube hydroforming provides a number of advantages over conventional stamping process, including fewer secondary operations, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength and stiffness. It can produce wide range of products such as sub-frame, engine cradle, and exhaust manifold. In this study, the effect of heat treatment conditions, such as post seam annealing(PSA) and bright annealing(BA), on the ovality and hydro-formability of steel tubes has been investigated. Hydroformability has been estimated as the bulging height obtained depending on the various process parameters such as an internal pressure, axial feeding, and heat treatment conditions. The ovality and forming height were found to strongly depend on material properties after heat treatments.
Inspection of Creep Defects and Degraded Zone Using Ultrasound
Authors: Lim Byeong Soo , Jeong C.S. , Bae Si Yon , Ryu Seog Hyeon , Kim Jeong Tae , Keum Y.T.
Published: March 2009

The initiation and growth of internal defects usually cause the failure of long term operated structural components at high temperature. Therefore, by investigating the internal defects of material, the integrity of the system can be maintained and the unexpected failure can be prevented. The main purpose of this study is to investigate the possibility of the application of ultrasound to the measurement and estimation of the creep damage. In this study, the phased array ultrasound and
backward ultrasound were employed to detect the internal defects caused by creep. Using the newly developed P92 steel, both creep and NDE ultrasound tests were performed. The results of defect inspection were checked by microstructure examination. Reliable information on the size and position of crack were obtained and successful estimation of the amount of micro-voids and their distribution proved to be obtainable by the ultrasound inspection technique. The width of the creep
degraded zone was confirmed by the width of ultrasonic signal, and the severity of degradation was confirmed by ultrasonic amplitude.
Fatigue Microcrack Plastic Zone Size Determination
Authors: Eterashvili Tamaz , Vardosanidze M.
Published: March 2009

The microcrack tip plastic zone sizes in austenitic steels are measured using REM and interference microscope. It is shown that the plastic zone size varies from 300µm to 350µm. The importance of determining this parameter is discussed. Based on the analysis of the conventional continuum equations of linear-elastic approach a simple formula is derived for calculation of plastic zone size, R=d E/2π σF, establishing relation between the plastic zone radius (R), microcrack width (d), elasticity modulus (E) and the yield strength of the material (σF). The
measured values of plastic zone size are in a good agreement with those reported in literature, and calculated by the above formula.
A Comparative Study on Preparation of TiO2 Pellets as Photocatalysts Based on Different Precursors
Authors: Luo Yong Gang , Zou Linda , Hu Eric
Published: March 2009

The porous TiO2 pellets were prepared based on pigment grade titaina, P25 titania
powder and titanium(IV) butoxide. The characterization was done with X-Ray diffraction, scanning electron microscopy and BET measurements. The result shows that TiO2 pellets by using titanium(IV) butoxide with some addictive have the best surface porosity, with specific surface area of 196.9m2/g. For pigment grade titania and P25 titania powder, it is still effective to enhance the
surface area after reassembling. The surface area increased from 11.6 to 29.2 m2/g for pigment grade titania and from 50 to 84.4 m2/g for P25 titania powder. Furthermore, it has been investigated on how to optimize and get the highest surface area by controlling the sintering temperature, reaction temperature, pH of solution, and the amount of alcohol and addictive of surfactant during
preparation. The experimental photocatalytic degradation of acetone and toluene was performed using titania pellets made from P25 titania powder.
The Texture of 1050 Al Sheet Produced by Equal Channel Angular Pressing
Authors: Akramov Saidmurod , Lee Min Gu , Kim In Soo , Sung Dong Young , Park Byung Hyun
Published: March 2009

. Equal channel angular pressing (ECAP) is useful method to obtain the ultra-fine grained and the high hardened metal. The microstructure, the hardness, and the texture of the 1050 Al sheets by ECAP are changed by a severe shear deformation. The change of the microstructure, the hardness, and the texture were investigated on the 1050 Al sheets that were prepared by ECAP and annealing.
High Pressure Wear Characteristics of Alloyed Ductile Cast Iron - Effect of Cu, Mn, Si and Mo
Authors: Bang Woong Ho , Kang C.S. , Park J.H. , Oh Kyu Hwan
Published: March 2009

Under a high-pressure condition, the wear characteristics of alloyed and unalloyed ductile cast iron were investigated. Mn, Cu, Si and Mo were chosen as alloying elements, and their effects on mechanical properties of hardness and toughness were correlated with wear properties. In most cases, high-pressure wear of alloyed and unalloyed DCI were sequentially developed by mild wear region followed by severe wear. The transition of wear mode was indicated by the drastic increase of friction coefficient and wear rate. The observation of worn surface at mild-wear region suggested that wear had been concentrated at graphite phases, whereas severe wear mode damaged both of graphite and matrix. It was found that DCI alloyed with Si-Mo exhibited the most prominent resistance to the beginning of severe wear while the toughness of DCI was also a crucial factor.
Oxide Growth Mechanism and Oxidation Resistance in Mechanically Alloyed Ni-20Cr-20Fe-5Nb-1Y2O3 Alloy
Authors: Kim Il Ho , Kwun S.I.
Published: March 2009

The oxidation characteristics of a Ni-20Cr-20Fe-5Nb-1Y2O3 alloy and a Ni-20Cr-
20Fe-5Nb alloy both with ultra-fine grains were compared with those of commercial Inconel 718 and PM1000 alloys. The oxidation resistance of the Ni-20Cr-20Fe-5Nb-1Y2O3 alloy was superior to that of both the Ni-20Cr-20Fe-5Nb and commercial Inconel 718 alloys. This was attributed to the suppression of successive oxidation via the oxide formed during the oxidation of the ODS (oxide dispersion strengthening) alloy. It was confirmed that the prior powder boundary is the site where the oxide grows continuously during ODS alloy oxidation.
Structure Centric Education in Materials Engineering
Authors: Upadhyaya Gopal S. , Fellow Emeritus
Published: March 2009

The detailed knowledge of structure of materials whether crystalline or noncrystalline, is essential in fully understanding its impact on materials engineering. By structure, we mean structure at any scale from electronic to macro. The properties, processing and performance of materials are directly interwoven with the structure. In the present paper the whole strategy of materials engineering education keeping in view structure in the centre has been developed. Pedagogically such a treatment is most sound.
Segregation Effects on the Metal-Carbide Interface
Authors: Liu L.M. , Wang Shao Qing , Ye Heng Qiang
Published: March 2009

We employ density functional calculations to investigate the doped Al/TiC interfaces. The effects of different segregation atoms are discussed. The results show that the different transition metal atoms have different effects on the adhesion. Results of analysis of atom size and electronic structure have shown that both atom size and activity of the doped atom influence on the adhesion. Our results are consistent with other results of doped metal-oxide interface.
A Low Environmental Load Modifying and Refining Treatment of Casting Al Alloys with RE
Authors: Mao Xie Min , Ouyang Zhi Ying , Zhang Jin Long
Published: March 2009

Melt treatment is one of the most important processes in the production of casting Al
alloys. It is also a source of environmental pollution. A green and effective melt treatment with low environmental load (EI), which added with RE (Rare Earth) elements, was investigated in the paper. The research results show that this new treatment can modify, refine and purify the casting Al alloys simultaneously. Compared with the conventional treatment, the process is simplified, the metallurgic quality and mechanical properties are improved, and the environmental pollution which existed in the conventional treatment is solved thoroughly, so represented its wide applicative values.
Enhanced Mechanical Properties of A206 Aluminum Casting Alloy by Addition of Rare Earth Elements
Authors: Jun Joong Hwan , Kim Jeong Min , Seong Ki Duk , Kim Ki Tae , Jung Woon Jae
Published: March 2009

Changes in tensile properties of A206 Al-Cu-Mg casting alloys containing trace amount of rare earth(RE) elements up to 0.2% were investigated and discussed in relation to the microstructural evolution. The A206 alloy with 0.1%RE shows higher values of ultimate tensile strength(UTS) and yield strength(YS) than A206 alloy at room and elevated temperatures up to 300oC, whereas no remarkable
change is found in elongation with respect to RE addition. In view of X-ray diffractometry(XRD) and transmission electron microscopy(TEM), the improvement of tensile strength in the A206 alloy with 0.1%RE would be caused by higher number density of Al2Cu(q¢) strengthening precipitates.
Continuous Casting of Magnesium Billets for Semi-Solid Processing
Authors: Jung Hwa Chul , Shin Kwang Seon
Published: March 2009

Semi-solid processing is recognized as an attractive alternative method for the near
net-shape production of engineering components. Although there has been a significant progress in semi-solid processing of aluminum alloys, very limited information is available on semi-solid processing of magnesium alloys, except for the thixomolding process. Continuous casting process has been utilized to produce the billets with the desirable cross-section at a reduced production cost for many metals, such as steel, copper and aluminum alloys. It has also been commercially utilized to produce the aluminum billets with non-dendritic microstructure for subsequent thixocasting process. However, continuous casting of magnesium billets for semi-solid processing has not yet been commercialized due to the difficulties involved in casting of magnesium alloys. In the present study, a continuous casting process has been developed for the production of the cylindrical billets of magnesium alloys for the subsequent thixocasting process. In order to obtain the desired non-dendritic microstructure with an excellent degree of homogeneity both in microstructure and composition, an electromagnetic stirring system has been utilized. A continuous casting process has been proven to be an efficient way to produce the high quality billets of magnesium alloys for semi-solid processing. A prototype air conditioner cover was produced using the continuously cast billets of AZ91 alloy.
Development of Mg-Al-Zn Based Diecasting Alloys for Elevated Temperature Applications
Authors: Kim Jeong Min , Park Bong Koo , Shin Kee Sam , Jun Joong Hwan , Kim Ki Tae , Jung Woon Jae
Published: March 2009

Effort has been devoted to develop new heat resistant diecasting alloys based on Mg-Al- Zn system in this research. Small amounts of cerium-rich misch metal and antimony additions to AZ91 alloy could enhance the tensile strength at an elevated temperature while keeping the good castability. The increase of Zn content in Mg-8(wt%)Al-xZn-0.5RE-0.5Sb alloys, was observed to significantly increase the yield strength at 175oC although the castability such as fluidity and hot cracking resistance was slightly decreased. Intensive microstructural investigation on the new Mg- Al-Zn diecasting alloys was also carried out.
Effects of Precipitates and Alloying Element on Microstructure and High Temperature Properties of Mg-Al Alloys
Authors: Chung Yeon Jun , Shin Kwang Seon
Published: March 2009

The effects of precipitates and alloying element on the high temperature tensile properties of Mg-Al alloys were investigated in this study. In order to modify the precipitation behavior and microstructure of Mg-Al alloys, Sr and/or Mm (Misch metal) were added to the Mg-9Al and AZ91 alloys. All test specimens used in this study were die-cast on a 320 ton cold chamber high-pressure die-casting machine and the microstructures of the specimens were examined by optical and scanning
electron microscopy. Tensile tests were carried out at room temperature, 150oC and 200oC at a strain rate of 2×10-4/sec. The microstructure analyses revealed that thermally stable MgAlSr and AlMm compounds were precipitated in the Sr and/or Mm added alloys and these compounds suppressed the precipitation of the discontinuous Mg17Al12 phase at grain boundaries. The high temperature
mechanical properties of the Mg-Al alloys were found to increase with the addition of Sr and/or Mm. It was concluded that the addition of Sr and/or Mm improved high temperature tensile properties of the Mg-Al alloys by the formation of thermally stable precipitates.
Effect of Heat Treatment on Microstructure and Mechanical Property of 45XD and 47XD TiAl Alloys
Authors: Zhu H. , Seo Dongyi , Maruyama Kouichi
Published: March 2009

The effect of heat treatment on microstructure and property of Ti-45 and
47Al-2Nb-2Mn+0.8%vol.%TiB2 alloys (45XD and 47XD) has been studied. Annealing and subsequent oil quench produced fine-grained fully lamellar structure (FGFL) in both alloys. For microstructural stabilization, the FGFL structures were subjected to different aging treatments. Microstructural examination showed that degradation of the FGFL structure, such as coarsening of γ lamellae, recrystallization of γ grains and break-up of a2 lamellae, presented to varying degrees after different aging treatments. Hardness values in the aged alloys decreased due to the degradation.
The creep resistances were improved in the aged alloys though the degradation occurred, indicating
that the aging treatments stabilized the FGFL structures effectively. The differences in the changes
of properties caused by different aging treatments and compositions were compared in combination
with the microstructural variants.
Low Cycle Fatigue Behavior of a Near-α Ti Alloy Containing Rare Earth Nd
Authors: Zhu Zhi Shou , Cao Chun Xiao , Yan Ming Gao
Published: March 2009

Low cyclic behavior of a new type near-α titanium alloy containing rare earth Nd (Ti60) with and without dwell time introduced at maximum tensile strain has been investigated at ambient temperature and 600°C. The results show that, Ti60 alloy exhibits a cyclic softening behavior at almost all strain levels being investigated. The cyclic processes show good agreement with predictions based on the fatigue crack
propagation model. At 600°C, the LCF life of Nd-bearing near-α titanium alloy is superior to that at room temperature within the investigated strain range, which indicates that Ti60 alloy is a good candidate for high temperature component under complicated load and temperature conditions. The results also show that the creep-fatigue interaction is related to the strain range applied. The creep-fatigue fracture is characterized by transgranular fracture mode due to the formation of matrix voids induced by Nd-bearing particles.
Evolution of Internal Stress Field in Ni-Base Superalloy through Creep Deformation
Authors: Tanaka Katsushi , Kajikawa T. , Ichitsubo T. , Osawa M. , Yokokawa Tadaharu , Harada Hiroshi
Published: March 2009

Internal elastic strain, and its change accompanied with the raft formation during creep deformation in the Ni-based single crystal superalloy (TMS-26) have been investigated by X-ray diffractometry. The elastic strain caused by the lattice misfit between g and g' phases has markedly been changed by creep deformation especially in the directions perpendicular to the [001] tensile axis. The change in the elastic strain can be explained by the effect of creep dislocations stacked at g/g' interfaces. The evolution of the elastic stress field estimated from the elastic strain has explained well the transition from primary creep stage to the second one.
Continuous Cooling Transformation Temperatures and Microstructures of Niobium Bearing Microalloyed Steels
Authors: Lee Young-Kook , Hong Jin-Myung , Choi Chong Sool , Lee Jae Kon
Published: March 2009

Effects of niobium content and cooling rate on ferrite and bainite start temperatures (Ar3, Bs) and microstructural features have been studied in niobium bearing ultralow carbon microalloyed steels. The Ar3 and Bs temperatures decrease as niobium content or cooling rate is increased. The dependence of Ar3 on cooling rate is greater than that of Bs in all niobium contents. The bainitic ferrite laths become longer and narrower with increasing niobium content and cooling rate, and niobium also shows a tendency to decrease polygonal ferrite grain size.
New Phases in a Multicomponent High Ruthenium Single Crystal Superalloy
Authors: Feng Q. , Rowland L.J. , Pollock T.M.
Published: March 2009

Three unusual Ru-rich phases have been identified in a multicomponent Ni-base single crystal superalloy, including a L21 Ru2AlTa Heusler phase, a B2 RuAl phase and a hcp Re(Ru)-rich δ phase. These phases have their own preferential precipitation location within the dendritic structure. No conventional topologically-close-packed (TCP) phases have been observed with thermal exposure at 950oC for 1500 hours.
Effect of Ta on the Oxidation Resistance of a Cast Nickel-Base Die Material with Low Cr and High W Content
Authors: Li Qing , Xiao Cheng Bo , Song Jin Xia , Wang Ding Gang , Han Ya Fang
Published: March 2009

A conventional cast nickel-base superalloy with the chemical composition of Ni-16W-2Mo-1.5Cr-6Al wt % has been recently developed as isothermal forging die material operating at temperatures above 1000°C. The oxidation test results showed that the oxide scale spalled heavily after exposure in air at 1050°C for 100 h, which is unacceptable for the process of isothermal forging. To improve the high temperature oxidation resistance, 3 wt% Ta was added into the alloy. Specimens after oxidation test were analyzed by the scanning electron microscope (SEM) and the X-ray diffraction analysis (XRD). The results showed that the oxides were mainly NiO, NiWO4, and NiAl2O4 for all the samples. The oxidation resistance of the alloy with 3wt%Ta was fairly good at 1050°C with the mass gain rate of around 0.016g/m2•h and spallation of oxides less than 2g/m2 within 100h.The SEM results showed that a continuous protective layer of Al2O3 has been formed under the layer of NiO for the alloy containing Ta.
The Control of Microstructures in (Mo1-x, Nbx) Si2 Intermetallics
Authors: Yang Hai Bo , Li Wei , Shan Ai Dang , Wu Jian Sheng
Published: March 2009

The intermetallics of (Mo1-xNbx) Si2 consisted of C11b phase and C40 phase when x is equal to 0.05, 0.10 and 0.15, and consisted of only C40 phase when x is equal to 0.20. Systemic heat treatments were conducted on the alloys. The evolution of microstructure was investigated with varying annealing temperature and time. Through the appropriate heat-treated processing, the microstructures of the alloys can be controlled to form full lamellar structure
Catalytic Properties of Ni3Al for Hydrogen Production Reactions
Authors: Xu Ya , Kameoka Satoshi , Kishida Kyosuke , Demura Masahiko , Tsai An Pong , Hirano Toshiyuki
Published: March 2009

Ni3Al has attractive high temperature properties, such as high strength and good
oxidation/corrosion resistance, and is possible to be used for high temperature chemical processing and manufacture. Until now, the catalytic properties of Ni3Al were rarely investigated since the leaching of aluminum from Ni3Al is difficult to obtain a porous Raney-Ni compared to NiAl3 and Ni2Al3. In the present work, the catalytic properties of Ni3Al were examined for hydrogen production reactions from methanol. It was found that alkali-leached Ni3Al showed high activity for methanol decomposition (CH3OH→ 2H2+CO). Furthermore, Ni3Al catalysts suppress the formation of methane, i.e. they show higher selectivity for the methanol decomposition reaction than Ni catalyst. These results indicate a possibility for Ni3Al used as a catalyst for hydrogen production reaction.
Oxidation of Four NiAl-Ag Alloys at 900°C in 1 Atm O2
Authors: Zhang X.J. , Niu Yan
Published: March 2009

Small amounts of silver have been added to the intermetallic compound β-NiAl for the
purpose of improving its mechanical properties. Four ternary NiAl-Ag alloys NiAl-0.5Ag, NiAl-1Ag, NiAl-5Ag and NiAl-10Ag (at.%), and an Ag-free β-NiAl have been oxidized at 900oC for 24 h in 1 atm O2 to study the effect of the presence of silver on the oxidation of β-NiAl. The kinetics of all the alloys were generally composed of two main parabolic stages with slightly larger parabolic rate constants for the second stage, except for NiAl-10Ag, which has an instantaneous parabolic rate constant decreasing with time. A continuous external layer of Al2O3 formed on all the alloys. In particular, the scales formed on NiAl-5Ag and NiAl-10Ag contained a thin and discontinuous layer of silver at the alloy/Al2O3 interface. Furthermore, NiAl-10Ag formed also isolated Ag particles or even a discontinuous Ag layer occasionally surmounting the Al2O3 scale. The addition of minor amounts of silver does not affect significantly the oxidation of β-NiAl, because silver is essentially present as a second phase due to its very small solubility in this intermetallic compound.
Advances in Ambient Temperature Creep Deformation Behavior of Two-Phase Titanium Alloys
Authors: Jaworski A. , Ankem Sreeramamurthy
Published: March 2009

In recent years, significant advances have been made in regard to the creep deformation behavior of two phase titanium alloys. It has been shown that the creep resistance depends on a number of factors, including the shape of the component phases, the strength difference between the phases, and the stability of the beta phase. For example, in two-phase materials with a similar volume fraction and morphology of phases, if the beta phase is less stable, then the creep resistance is lower. These developments will be reviewed and the reasons for such effects will be suggested.