bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study on 3D Forming of Sheet Metal Using Plasma Arc
Authors: Xu Wen Ji , Fang Jian Cheng , Liu F. , Pang Gui Bing
Published: March 2009

For the development of flexible forming using plasma arc (FFUPA), it is extremely
necessary to investigate the forming rules of curvilinear scanning and multipath combined scanning. In this paper, the difference between circular scanning and linear scanning and the influence of sheet metal geometry on forming effect have been discussed. In the experiments, circle, ring and rectangle mild steel sheets with thickness of 0.8mm are taken as workpieces and the experimental results show
that nonlinear prolonged surface can be obtained by curvilinear scanning and there exists the obvious difference between circular scanning and linear scanning. Afterwards, the reason of the difference mentioned above is concisely analyzed. Finally, some suggestions are presented for the future investigation.
Magnetron Co-Sputtering of Nanostructured Chromium Aluminium Nitride Coatings
Authors: Wuhrer Richard , Yeung Wing Yiu
Published: March 2009

Ternary chromium aluminium nitride (Cr,Al)N coatings were produced by reactive
magnetron co-sputtering technique at different nitrogen deposition pressures. Densified nanostructured coatings with grain size below 100 nm were obtained under critically controlled deposition conditions at low nitrogen partial pressures. The nanostructured coatings were generally of improved surface roughness and properties. Microhardness measurements showed that the coatings had much higher hardness than those of coarser grain sizes. It is believed that the
refinement of the coating structure at low nitrogen pressures is associated with a larger number of atoms/molecules depositing on the substrate with higher energies, thus enhancing the adatom mobility and nucleated cluster formation in the coatings. The relationship between the grain size reduction and the deposition rate of the coatings was analysed.
Effect of Solution Chemistry and Electroplating Conditions on the Deposition Rate and Wear Resistance of Eco-Friendly Trivalent Chromium Layers
Authors: Choi Min Young , Choi Y. , Choe J.I. , Kim Man , Kwon Sik Chol
Published: March 2009

Chromium chloride (CrCl3) or chromium sulfate(Cr2(SO4)3) content increased trivalent chrome deposition rate. The addition of formic acid and the relative content change of potassium hydroxide decreased the trivalent chrome deposition rate. Industrially applicable trivalent chromium layers with more than 200 µm thick were well prepared at the conditions of pH with the range of 1.3-1.8, electrical current density of 5.0-5.6 A/cm2 and applied voltage of 4.0-5.9V. Average
microhardnesses of the chromium layers prepared in the chromium chloride and chromium sulfate solutions are about 803-820 and 700-712 Hv, respectivevly. The wear resistance of the trivalent chromium layers was improved by plating voltage which was related to residual compressive stress on the chomium layer.
Crystallization under 1 MeV Electron Beam Irradiation of Nanometer-Sized W-Dendrites Fabricated on Alumina Substrates with Electron-Beam-Induced Deposition
Authors: Song Ming Hui , Mitsuishi Kazutaka , Furuya Kazuo
Published: March 2009

Nanometer-sized W-dendritic form structure was fabricated with electron-beam-induced deposition (EBID) in a 200 kV transmission electron microscope. The as-prepared nanodendrites are composed of W-nanocrystals and amorphous. The as-prepared nanodendrites were then irradiated with 1 MeV electron beam in a high voltage transmission electron microscope. The effect of the irradiation is investigated. The irradiation transformed effectively almost all the amorphous
part to crystalline state. Morphology of the nanodendrite also changes. The irradiation induced crystallization and morphology change are discussed.
Effect of Hydrogen on Dislocation Behavior in Ni-Cr Alloys
Authors: Miyata Kaori
Published: March 2009

The effects of hydrogen on dislocations in Ni-Cr alloys have been investigated by TEM observations using single crystals. The deformation mode of Ni-Cr alloys is characterized by planar dislocations in the absence of hydrogen. However, hydrogen charging changed the dislocation configurations to promote curved dislocations, where the Shockley partials frequently constrict to make nodes and cross-slip. The hydrogen-affected dislocations are enhanced with increasing Ni
content. The effect of hydrogen on superdislocations of Ni2Cr superstructure has been also investigated using an aged alloy. While the deformation mode in Ni2Cr superlattice is classified as 5 variants of superdislocation triplets and one variant of ordinary dislocations, the hydrogen charging has preferred the ordinary dislocations. The results suggest that the charged hydrogen changes the
local plasticity to affect the deformation dynamics in Ni-Cr alloys.
HVEM Study of Crack Tip Dislocations in Silicon Crystals
Authors: Higashida Kenji , Tanaka Masaki , Onodera Ryuta
Published: March 2009

The present paper describes the nature of crack tip plasticity in silicon crystals examined by high voltage electron microscopy (HVEM) and atomic force microscopy (AFM). Firstly, AFM images around a crack tip are presented, where the formation of fine slip bands with the step heights of one or two nanometers is demonstrated. Secondly, crack-tip dislocations observed by HVEM are
exhibited, where it is emphasized that dislocation characterization is essential to consider the relief mechanism of crack-tip stress concentration.
Microstructures after Processing by Aging and ECAP for Al-Mg2Si Alloys Containing Excess Si or Mg
Authors: Fujita Kazuko , Fujita Takeshi , Oh-ishi Keiichiro , Kaneko Kenji , Horita Z. , Langdon Terence G.
Published: March 2009

In this study, severe plastic straining through equal-channel angular pressing (ECAP) is imposed on age-hardenable Al-Mg-Si alloys having two different compositions of excess Si or Mg in the Al-Mg2Si pusedo-binary system. Thereafter, the alloys are subjected to aging and the microstructures are examined using transmission electron microscopy. It is shown that the precipitation behavior is significantly changed through application of ECAP.
Surface Cleaning Effects of Silicon Substrates by ECR Hydrogen Plasma on Subsequent Homoepitaxial Growth
Authors: Kim Hyoun Woo
Published: March 2009

We have demonstrated the preparation of the almost defect-free homoepitaxial layer and the defective layer, respectively, with and without applying the in-situ cleaning of the silicon substrate surface using electron cyclotron resonance hydrogen plasma. Secondary ion mass spectroscopy indicated that the interfacial oxygen and carbon concentrations, respectively, decreased and increased with the in-situ cleaning. We have investigated the effect of process parameters such as microwave
power, d.c bias, and cleaning time, on the epitaxial growth, by evaluating the cross-sectional transmission electron microscopy images of the subsequently deposited Si homoepitaxial film.
Wetting and Contact Properties Studied Using the Nanoprobe System
Authors: Chen Qing , Wang Sheng , Peng Lian Mao
Published: March 2009

Using a nanoprobe system, we have studied the wetting and the contact properties of Ga with Au, TiN on Al, SiO2 and carbon nanotubes in micro and nano meter scale. Some new phenomena have been observed.
The Effect of Electromagnetic Vibration on the Silicon Size at Hypoeutectic Al-Si Alloy
Authors: Choi Jung Pyung , Kim Ki Bae , Park Joon Pyo , Yoon Eui Pak , Nam T.W.
Published: March 2009

In this study, the electromagnetic vibration process is adopted for modifying the eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration (EMV), the finer the size of the eutectic Si phase. The tensile strength and elongation of EMVed alloys were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000Hz was approximately six times as high as that of the normal alloy and half of that of Sr
modified alloy. The mechanism for the increase in twin density due to EMV during solidification could be suggested from the fact that the preferential growth along <112> in silicon was suppressed by preventing the Si atom from attaching to the growing interface of the Si phase and by changing the solid/liquid interfacial energy of silicon.
Direct Tensile Tests of Individual WS2 Nanotubes
Authors: Kaplan-Ashiri I. , Cohen S.R. , Gartsman K. , Rosentsveig R. , Ivanovskaya V. , Heine T. , Seifert G. , Wagner H.D. , Tenne R.
Published: March 2009

The Young’s modulus of WS2 nanotubes is an important property for various
applications. Measurements of the mechanical properties of individual nanotubes are challenging because of the small size of the tubes. Lately, measurements of the Young’s modulus by buckling of an individual nanotube using an atomic force microscope1 resulted in an average value of 171GPa. Tensile tests of individual WS2 nanotubes were performed experimentally using a scanning electron
microscope and simulated tensile tests of MoS2 nanotubes were performed by means of a densityfunctional tight-binding (DFTB) based molecular dynamics (MD) scheme. Preliminary results for WS2 nanotubes show Young’s modulus value of ca.162GPa, tensile strength value of ca. 13GPa and average elongation of ca. 12%. MD simulations resulted in elongation of 19% for zigzag and 17%
for armchair MoS2 single wall nanotubes. Since MoS2 and WS2 nanotubes have similar structures the same behavior is expected for both, hence there is a good agreement regarding the elongation of WS2 nanotubes between experiment and simulation.
Effects of Microstructure on the Fatigue Resistance of Steel Tire Cords
Authors: Yang Yo Sep , Park S.Y. , Jun Hyun Jo , Park Chan Gyung , Lim S.H. , Ban D.Y.
Published: March 2009

Effects of microstructural parameters on fatigue resistance (σFL) of the steel tire cords have been investigated experimentally from microscopic points of view. At first, microstructural parameters depending on carbon content have been identified by using transmission electron microscopy (TEM). The fatigue resistance of the steel tire cords depending on carbon content has been measured by using the Hunter rotating beam tester under the bending stress of 900 to 1500 MPa.
The fatigue resistance was improved with increasing the carbon content from 0.7, 0.8 to 0.9 wt. % C, due to variations of microstructural parameters, such as lamellar spacing (λp), cementite thickness (tc), and volume fraction (Vc) of cementite. As the carbon content increased, the lamellar spacing and the
cementite thickness decreased, while the volume fraction of cementites increased. The effects of microstructure on fatigue resistance have been discussed in terms of the microstructural parameters mentioned above.
Formation of Single Crystal Nanowires of GaN on the Si Substrates
Authors: Xue Cheng Shan , Dong Zhi Hua , Zhuang Hui Zhao , Gao Haiyong , Liu Yi'an , Wu Yu Xin
Published: March 2009

An extreme thin SiC buffer and Ga2O3 layer were deposited on silicon substrate
sequentially with a r.f. magnetron sputtering system. Then the sample was annealed in the ambiance of ammonia at high temperature. Nanowires were found when the sample was tested with scanning electron microscopy (SEM). The composition of the nanowires is found to be GaN when the sample was tested with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). A nanowire
was observed with transmission electron microscopy and it was even and uniform, with diameter of about 60nm. And the nanowire can be testified of wurtzite single crystal structure by electron diffraction (ED) analysis attached to the TEM. The high-resolution transmission electron microscopy (HRTEM) analysis to the nanowire indicates that the nanowire was single crystal with very good quality.
The Orientation Characterization of Single Crystal Superconductor Film with 2-Dimensional X-Ray Diffraction
Authors: Rao Q.L. , Lu Qing Hua , Yao X. , Hu J.
Published: March 2009

With area detector X-ray diffraction system, the orientation of superconductor films and their relationships with substrates can be easily examined. For YBCO high temperature superconductor films having complex crystalline orientation relationship fore and after melting process, 2-dimesional X-ray diffraction provides us much more information than common X-ray diffraction. This is very helpful for understanding the peritectic reaction during melting process because the growth mechanism of Y211 crystalline can be explained from its orientation information. Y211 phrase in the film and its orientation relationship with YBCO phase and MgO
substrate have been analyzed at first. It is found that Y211 crystalline is well match with both MgO substrate and YBCO parent phase. Then the melting process of YBCO has been discussed from the view of the orientation relationship between each phase.
Characterization of Submicron Mechanical Properties of Al-Alloy Foam Using Nanoindentation Technique
Authors: Kim Am Kee , Hasan Md Anwarul , Lee Hak Joo , Cho Seong Seock
Published: March 2009

Nanoindentation test has been performed to characterize the mechanical properties of aluminium alloy foam cell wall. Two of the mechanical properties: hardness and Young’s modulus of cell wall material were evaluated using the stiffness of contact during both loading and unloading. Properties obtained from unloading stiffness were in better agreement with the conventional test result than those obtained from loading stiffness. The finite element analysis using nonlinear finite element code ABAQUS was performed to characterize the yield strength and the stress-strain curve of the cell wall material of the foam. Properties of foam cell wall material were found to be substantially different from the properties of the material before foaming. The methodology used in this paper can be effectively used to characterize the mechanical properties of cell wall of any cellular material.
Deformation Characteristics in Radially Extruded Tubular Parts
Authors: Choi Hyoung Jin , Kim S.H. , Hwang Beong Bok
Published: March 2009

Radially extruded tubular components are adopted for the deformation analysis by
rigid-plastic finite element method. FE Simulations were conducted to investigate the influence of different geometric parameters and process condition, such as the ratio between inner and outer diameter of tubular components, gap height, die corner radius and friction factor, on metal flow into radial direction. The results of the simulations are discussed in terms of separation length, defined as the length that the material flow is separated away from the die in gap height, and maximum force
requirements for the radial forming process. Furthermore the pressure distributions exerted on the die-wall interfaces and deformation pattern was shown to obtain the features in producing sound radial extruded components. Finally some guidelines for basic design data in the radial extrusion process due to this simulation work might be drawn up.
Corrosion Behavior of 316L Stainless Steel in Supercritical Water Environment
Authors: Yoon Jae Hong , Son K.S. , Kim H.S. , Mitton B. , Latanision R.M. , Yoo Y.R. , Kim Young Sik
Published: March 2009

There is a need to destroy both military and civilian hazardous waste and urgency,
mandated by public concern over traditional waste handling methodologies, to safe and efficient alternative technologies. One very effective process for the destruction of such waste is supercritical water oxidation (SCWO). Nevertheless, corrosion of the materials of fabrication is a serious concern. This work intends to obtain the fundamental data for developing the corrosion resistant steel for the construction of SCWO system. The effects of various factors on the corrosion resistance of flat, welded, and U-bend 316L stainless steels in Trimsol solution were studied.
Corroded product on surface was composed of multi-layer with oxides and salts, and dealloying was observed. Major corrosion phenomena of 316L stainless steel under SCWO condition were intergranular corrosion, pitting corrosion, SCC, and erosion corrosion. This work focused on the elucidation of corrosion mechanism of 316L stainless steel in SCWO environment.
Effect of Creep Holding Time on the Fatigue Behavior in P92 Steel Weldment at High Temperature
Authors: Kim Bum Joon , Lim Byeong Soo
Published: March 2009

In this study, the crack growth behavior in P92 steel (9%Cr-2%W) weldment was
investigated at 600ı under the load of trapezoidal wave shape with various holding times. The relationship between the crack growth behavior and holding time was studied and it was characterized using the ΔK and (Ct)avg parameters. The number of micro-voids/cavities at the crack tip and fracture modes were examined and the relationship between crack growth rate and holding time was investigated.
Finite Element Analysis of the Compaction Processes for Hollow Three-Level (Class IV) Components
Authors: Ham B.S. , Hwang Beong Bok , Jang D.H.
Published: March 2009

The yield criterion describing asymmetric behavior of powdered metal compacts in tension and compression is introduced by modifying that used for sintered powdered metals. The plasticity theory related to the modified yield criterion is reviewed and summarized for a powdered metal compact. The constitutive equation is applied to the variational principle and its discritization is also introduced. Axisymmetric die pressings with copper powders were performed to see the deformation mechanics of hollow three-level parts. The simulation includes two different types of multiple-motion tooling compaction of a Class IV part of hollow three-level component. Predictions are made for density distributions, load-stroke relationships, average density as function of height, pressure distributions along the die-walls and punches, average compact densities at each level, and energy
consumption for each pressing. The information from simulation can be used to synthesize the various punch motions in a multiple action tooling system.
Nano-Structured Thin Films: A Lorentz Transmission Electron Microscopy and Electron Holography Study
Authors: de Hosson Jeff T.M. , De Raedt Hans A.
Published: March 2009

This paper aims at applying advanced transmission electron microscopy (TEM) to functional materials, such as ultra-soft magnetic films for high-frequency inductors, to reveal the structure-property relationship. The ultimate goal is to delineate a more quantitative way to obtain information of the magnetic induction and local magnetization. Nano-crystalline Fe-Zr-N films have been prepared by DC magnetron reactive sputtering with a thickness between 50 and 500 nm. Conventional TEM and selected area diffraction (SAD), reveal crystallites of sizes ranging between 2 and 30 nm. The films showed a granular or hillock type of roughness with an rms amplitude of 5 nm. In particular this paper concentrates on an analysis of phase maps in electron holography and intensity maps in Lorentz transmission electron microscopy including the thickness variation over the sample. For a particular statistical description of the roughness and values for the roughness it is shown that analytical expressions can be obtained. We demonstrate that starting from the concept of the vector potential in classical electrodynamics these results can be achieved assuming independent stationary Gaussian distributions for the height correlation functions.
Closed-Cell Metal Foams Manufactured from Bulk Metal and Alloy Sheets through ARB Process
Authors: Kitazono Koichi , Sato Eiichi
Published: March 2009

Aluminum foams having extremely low densities offer a large potential for lightweight
structural materials. New manufacturing process without expensive aluminum alloy powder has been developed using conventional bulk aluminum alloy sheets. Preform plate containing blowing agent particles is first manufactured through accumulative roll-bonding (ARB) process. By heating the preform plate, closed-cell aluminum foams having various porosity and cell morphology are produced. It was revealed that ARB processing condition is significantly important to produce suitable aluminum foam with high porosity and uniform pore distribution. Present manufacturing process also possesses a potential to apply to many other metal and alloy foams.
Wear and Corrosion Behaviour of In-Situ Al-TiB2 Metal Matrix Composites
Authors: Sekhawat D.S. , Chakraborty M. , Chatterjee U.K.
Published: March 2009

In-situ Al-TiB2 metal matrix composites containing 5 wt% and 10 wt% TiB2 have been synthesized through master alloy and mixed salt routes. The composites have shown five times increase in wear resistance compared to commercially pure aluminium. Corrosion evaluation by polarization technique carried out in NaCl, H2SO4 and NaOH solutions indicates a lower corrosion resistance of the composites than the corresponding base metals. The composites produced through mixed salt route suffered higher corrosion than those prepared by master alloy route. The results have been explained from the physical and electrochemical effects of TiB2 in the matrix.
Development of Mg Alloy Sheets via Strip Casting
Authors: Park Sung S. , Kim Young Min , Kang Dae H. , Kim Nack
Published: March 2009

AZ31 and experimental ZMA611 alloys were strip cast into 2 mm thick strips. The as-cast AZ31 alloy strip consists of columnar dendrites. On the other hand, as-cast ZMA611 alloy strip shows equiaxed dendritic structure through the thickness of strip. These alloys were subjected to various thermomechanical treatments and their tensile properties were evaluated. Strip cast AZ31 alloy in H24 condition has equivalent yield and tensile strengths with similar ductility compared to commercial ingot cast AZ31-H24 alloy, indicating that strip casting is a viable process for the fabrication of Mg alloy strips. The ZMA611 alloy has a large volume fraction of fine dispersoid particles in the microstructure, resulting from the beneficial effect of strip casting on microstructural refinement. It has been shown that the ZMA611 alloy has superior tensile properties compared to commercial ingot cast AZ31-H24 alloy, suggesting the possibility of the development of new wrought Mg alloy sheets by strip casting.
Microstructure and Tensile Properties of Magnesium Alloy Containing Quasicrystallines Processed by Equal-Channel-Angular-Extrusion
Authors: Zheng Ming Yi , Qiao Xiao Guang , Xu Shi Wei , Wu Kun , Kamado Shigeharu , Kojima Yo
Published: March 2009

Equal channel angular extrusion (ECAE) was performed on as-cast ZW1101 (Mg-11wt%Zn- 0.9wt%Y) Mg alloy containing quasicrystallines. The grain size of α-Mg was effectively refined, and coarse eutectic quasicrystalline phases were broken and dispersed in the alloy by ECAE. The alloy processed by ECAE exhibited a good combination of high strength and high ductility, which is due to the grain refinement and fine dispersed quasicrystallines in the alloy.
Effects of Rolling Condition on Warm Deep Drawability of Magnesium Alloy Sheets Produced by Twin-Roll Strip Casting
Authors: Watari Hisaki , Davey Keith , Rasgado M.T. Alonso , Clark L.D. , Nakamura Ryoji , Koga Nobuhio
Published: March 2009

Effects of rolling conditions on warm deep drawability of cast magnesium alloy that were hot rolled after roll strip casting were investigated to ascertain the feasibility of twin-roll strip casting process of AZ31B magnesium alloy. Hot rolling and heat treatment conditions were changed to examine which conditions were appropriate for producing AZ31B wrought magnesium alloys after strip casting process. Microscopic observation of the crystals of the manufactured wrought magnesium alloys was performed. It has been found that a limiting drawing ratio of 2.7 was possible in a warm deep drawing test of the cast magnesium alloy sheets after being hot rolled.
Characteristics of Deformation-Enhanced Transformation in Plain Low Carbon Steel
Authors: Sun Zu Qing , Yang Wang Yue , Qi Jun Jie
Published: March 2009

The concept of deformation-enhanced transformation of ferrite in plain low carbon steel is introduced. The characteristics are presented. Systematic works conclude that deformation significantly enhances the ferrite transformation of undercooled austenite in plain low carbon steel. Nucleation is the dominant process of the transformation. Until the completion of the transformation, nucleation is always repeated, especially at the zone in front of the newly formed ferrite grains, which restrict the grain growth and lead to formation of very fine ferrite grains. Three stages of kinetics are clearly shown from the experimental measurement, which correspond to nucleation at grain boundaries, at the zone in front of newly formed ferrite grains and within residual austenite.
The Forming Process of Magnesium Alloy for Japanese Home Electric Components
Authors: Takara Akira , Higashi Kenji
Published: March 2009

Magnesium alloys have replaced resins as a material for the components of electronic products such as cell phone and notebook personal computer mainly, because of their lightness and rigidity. Thin walls, a complicated shape, and high appearance quality are all needed in the external parts. Die-casting and injection molding are the main method of manufacturing magnesium alloy parts. The optimal cast conditions and mold design have been investigated in order that a few defects
such as surface cracks and mold cavities in casting parts would be reduced. Instead of cast, plastic forming technologies such as warm drawing and hot forging have been developed to form thinner walls and less defects. Plastic formability of magnesium alloy in hot working is dependent on a grain size of material. The material with fine grains has advantage of being formed at high strain rate. The characteristics of forming processes of magnesium parts for Japanese home electric appliances are compared in the viewpoint of quality, cost, and productivity.
Vacuum Distillation Refining and Extrusion Process of Magnesium
Authors: Inoue Makoto , Doi T. , Aida Tetsuo , Matsuki Kenji , Kamado Shigeharu , Kojima Yo
Published: March 2009

In this study, it refined by the vacuum distilling refining and the billet was produced for the obtained 99.99% or more of purity magnesium deposit by compression forming, extrusion process was performed and the corrosion resistance of extrusions and the tensile characteristic which were acquired were investigated. The specimen showed good corrosion resistance rather than commercial AZ91D magnesium alloy die-castings. The specimen has high ductility and it is good, and compared with 99.9% of purity magnesium.
Effects of Grain Refinement on Rollability of AZ31 Mg Alloy
Authors: Jin Qinglin , Lim Su Gun , You Bong Sun
Published: March 2009

The initial coarse grain size of 400㎛ of a as-cast AZ31 alloy was refined to 130㎛ by
carbon addition method. The microstructural evolution, recrystallization, edge cracking phenomena of the coarse grained AZ31 alloy during hot rolling were investigated and compared with those of grain refined AZ31 alloy.
Fluxless Recycling of Die-Cast AZ91 Magnesium Alloy Scrap
Authors: Jung Hwa Chul , Lee Young Cheol , Shin Kwang Seon
Published: March 2009

Magnesium die-casting has experienced dramatic growth over the past decade and the recycling of magnesium scrap has become increasingly important due to the generation of substantial quantities of scrap in the die-casting process. Magnesium is a readily recyclable material and the recycling of magnesium scrap is crucial in making magnesium more competitive. The main concern associated with using the secondary magnesium is the high level of Fe content and oxide inclusions that are detrimental to the corrosion and mechanical properties of the secondary alloy. In this study, the die-cast specimens were produced using the recycled class 1 scrap which is refined by means of Ar bubbling and Mn addition without using refining fluxes, and their mechanical properties and corrosion characteristics were investigated. The results showed that the tensile properties of the secondary AZ91 alloy were equivalent to those of the primary magnesium alloy after appropriate
treatments. The corrosion resistance of the recycled magnesium was also found to increase by Ar bubbling and Mn addition.
Effects of Contact Pressure on Fretting Fatigue Characteristics of Ti-4.5Al-3V-2Mo-2Fe with Acicular Alpha Structure
Authors: Takeda Junji , Niinomi Mitsuo , Akahori Toshikazu
Published: March 2009

The effects of microstructure and contact pressure on fretting fatigue characteristics of Ti-4.5Al-3V-2Mo-2Fe conducted with annealing at 1123 K and 1223 K were investigated in this study. Fretting fatigue tests in low and high cycle fatigue life regions of the alloys with equiaxed α and acicular α structures were carried out at each contact pressure of 10, 15, 30, 45, 75, 105 and 153 MPa. In the alloy with equiaxed α structure, fretting fatigue strength tends to be very low at contact pressures of 10 MPa and 15 MPa in low and high cycle fatigue life regions, respectively. Furthermore, fretting fatigue strength tends to be nearly constant at the contact pressure over 45 MPa in each fatigue life region. On the other hand, in the alloy with acicular α structure, fretting fatigue strength tends to be very low at contact pressures of 15 MPa and 30 MPa in low and high cycle fatigue life regions, respectively. Furthermore, fretting fatigue strength tends to be nearly constant at contact pressures of 45 MPa and over 30 MPa in low and high fatigue life regions, respectively.
Effects of Microstructure and Environment on Fatigue Properties of Investment Cast Ti-6Al-4V Alloy Welds
Authors: Lee Hak Cheol , Choi Jin Won , Oh Jin Keun , Kim Nack
Published: March 2009

Effects of microstructural and environmental factors on fatigue crack propagation behavior of welded regions of cast Ti-6Al-4V alloy were investigated. Fatigue crack propagation tests were conducted for the welded regions, which were processed by two different welding methods: gas tungsten arc (GTA) welding and electron beam (EB) welding, under various load ratios (R=0.1, 0.9) and atmosphere (air, seawater). EB weld consisting of very thin α platelets had the faster crack
propagation rate than the base metal and GTA weld, regardless of load ratio and atmosphere. Fatigue crack propagation rates at high load ratio (R=0.9) were faster than those obtained at low load ratio (R=0.1) and there was no crack closure at high load ratio (R=0.9), indicating that fatigue crack propagation at high load ratio was mainly controlled by intrinsic factors such as microstructure. Fatigue crack growth resistances in seawater atmosphere were slightly lower than those in air, but showed the similar trend with variation of specimen conditions. The degrees of crack closure were almost same regardless of specimen conditions in seawater atmosphere, suggesting that the fatigue crack propagation in seawater was mainly controlled by intrinsic factors such as microstructure.
The Size Range of Volume Change of Melting
Authors: Lu H.M. , Jiang Qing
Published: March 2009

Through considering the packing density and the lattice contraction, volume changes of elements with different structures DV on melting are modeled. An agreement between the model predictions and the experimental as well as theoretical data is found. Moreover, the alloy design principle for GFA of bulk metallic glasses (BMG) based on the size of DV is also suggested that amorphous metallic alloys will have the best GFA when its packing density approaches that of A2 crystal.
Tensile Properties of HIP/DB'ed Ni-Base Superalloys
Authors: Park Nho Kwang , Yeom Jong Taek
Published: March 2009

Hot isostatic pressing(HIP)/diffusion bonding(DB) was employed for cast superalloy MM247 and P/M superalloy Udimet720. The effects of P/M Udimet720 particle size, holding time for HIP/DB and post heat-treatment on the microstructure and tensile properties were investigated. Tensile properties of HIP/DB’ed MM247/Udimet720 were improved at room temperature and 650°C with decreasing powder size from –140mesh to –270mesh, and with increasing HIP/DB time from 2h to 3h. Post-HIP heat-treatments, which strengthen the soft MM247 with cuboidal ’ precipitation, are proposed to enhance the mechanical properties of the HIP/DB’ed MM247/Udimet720.
Mechanical Behaviour of a Single Crystal Superalloy DD32 - A Comparison with the Alloy SRR99
Authors: Yu Jin Jiang , Sun Xiao Feng , Jin Tao , Guan Heng Rong , Hu Zhuang Qi
Published: March 2009

Stress rupture and tensile properties of a single crystal superalloy DD32 are investigated comparing with the alloy SRR99. It is shown that the alloy DD32 offers an improved creep temperature capability of more than 60°C at higher stresses. The g¢ precipitates in the stress ruptured samples were rafted to P-N type directional coarsening. The fracture mechanism of the stress ruptured samples was initiated from the micropores.
Control of Martensitic Morphology in Thermal-Mechanical Processing of Ferrous Alloys
Authors: Meng Q.P. , Rong Yong Hua , Hsu T.Y.
Published: March 2009

The quantitative relationships are suggested that the applied stress decreases the
nucleation barrier and activation energy of nucleation of martensitic transformation, and strain increases the nucleus sites. Taking Fe-20Ni-0.5C and Fe-25Ni-0.66C alloys as examples, their different martensitic morphologies in thermal-mechanical processing can be explained and the origin of such a difference may be revealed based on the above theoretical analysis. Accordingly, the control of martensitic morphologies in thermal-mechanical processing of ferrous alloys will become possible.
Microstructure and Mechanical Property of MoSi2 Based Composites
Authors: Lee Sang Ll , Lee Jin Kyung , Min Byeong Hyeon , Shin Yun Seok , Bae Dong Su , Park Jun Young , Sasaki Gen
Published: March 2009

This study dealt with both the strengthening of matrix and the suppression of interfacial reaction for the development of high toughness Nb/MoSi2 laminate composites. The impact values of Nb/MoSi2, Nb/MoSi2-SiC, Nb/MoSi2-ZrO2 laminate composites were investigated at the room temperature. The flexural strength of MoSi2 based composites containing SiC or ZrO2 particles were also evaluated at elevated temperatures. The reduction of reaction layer by the addition of ZrO2 particles led to the sufficient improvement in the impact value of Nb/MoSi2 laminate composites. The flexural strength of MoSi2-SiC and MoSi2-ZrO2 materials decreased at temperatures higher than 800 °C.
Powder Injection Molding of Niobium
Authors: Smid Ivi , Aggarwal Gaurav
Published: March 2009

Niobium and niobium-based alloys are used in a variety of high temperature applications ranging from light bulbs to rocket engines. Niobium has excellent formability and the lowest specific weight among refractory metals (Nb, Ta, Mo, W, and Re). Powder injection molding of niobium powder was investigated for efficiency of the process. The sintering of injection molded bars was conducted up to 2000°C in vacuum and low oxygen partial pressure atmosphere. This paper investigates the effect of sintering time, temperature and atmosphere on processing of pure niobium.
Characterization of Kinetics of Deformation-Enhanced Transformation in a Low Carbon Steel
Authors: Qi Jun Jie , Yang Wang Yue , Sun Zu Qing , Zhang X.
Published: March 2009

Quantitative characterization of microstructural development during deformation
enhanced transformation in a low carbon steel was investigated on a Gleeble 1500 machine. General conclusions of the features of austenite transformation kinetics during deformation-enhanced transformation were formulated. It was shown that the process of deformation-enhanced transformation can be divided into three stages according to the characteristics of transformation kinetics: The kinetics equations of two early stages fitted well in J-M-A equation. The kinetics of the first stage obeys Cahn’s site saturation mechanism, with the value of kinetics parameter n of 4. Ferrite nucleates at austenite grain boundaries and triple points during the first stage. Kinetics of the second stage doesn’t obey Cahn’s theory, with the value of kinetics parameter n of 1-1.5, corresponding to ferrite nucleation repeatedly at areas with high stored energy in front of the ferrite/austenite interface. The kinetics doesn’t obey the law of J-M-A equation any more in the final stage, and only few
nucleation sites left at this moment.
Effect of Y Ion Implantation on Oxidation Behavior of IC6 Alloy at 1100°C
Authors: Song Jin Xia , Han Ya Fang , Xiao Cheng Bo
Published: March 2009

The effect of ion implantation of yttrium on the oxidation behavior of Ni3Al base alloy
IC6 at 1100°C was investigated by SEM/EDS, TEM and XRD methods. The results indicated that after Y ion implantation, the surface of IC6 alloy changed from large column crystals to fine distributed nano-crystals, and the density of dislocations in distorted region increased with the implanted ions dose, which can act as high-diffusivity path and oxide core. Comparing to un-implanted IC6 alloy, Y-implantation increased the oxidation rate of IC6 alloy in initial 25 h at 1100°C, but decreased the maximum weight gain and the oxidation rate in final period. Moreover, the oxide scales of Y-implanted IC6 alloy were more continuous and compact due to the benefit effect of yttrium, and had better coherence to substrate through reduction of oxide grain size resulting in oxide scale plasticity improvement. Hence the proper amount of implanted Y could improve the oxidation resistance of IC6 alloy at 1100°C in air slightly.
Selection of Can and Insulating Materials for Controlled-Dwell Extrusion of Gamma-TiAl
Authors: Bai C.G. , Liu Dong , Xu D.S. , Cui Yu You , Hao Yu Lin , Yang Rui
Published: March 2009

Finite element method (FEM) simulation is carried out to analyze temperature
distribution of the workpiece for the controlled-dwell extrusion of gamma-TiAl. We focused on the selection of can and insulating materials and concluded that silica fabric is a better insulating material than ZrO2 powders. 304SS, Ti6Al4V, 1Cr18Ni9Ti and pure Ti can be selected as can material if the dwell time and in-container time are well controlled. Thermo-mechanical coupled analysis is performed to investigate flow uniformity and temperature homogeneity for different can and insulating materials. Extrusion experiment was conducted and the results basically agree well with those of the simulation.
Investigation on a Fabrication Technique of TiAl Sheet
Authors: Su Yan Qing , Zhang Guo Xiong , Guo Jing Jie , Jia Jun , Fu Heng Zhi
Published: March 2009

A TiAl sheet fabrication technique from Ti/Al foils was studied experimentally. Firstly, the reaction sequence between Ti and Al foils were studied with DSC and then a three stage solid transformations processing was carried out. At the first stage, Al diffused into Ti foils and formed Al3Ti. The heating temperature was selected based on a ruler that the pure Al was consumed by solid diffusion with a short time and avoiding the melting of Al. The resulted microstructure consists of pure Ti and Al3Ti. At the second stage, part of Al in Al3Ti diffused into pure Ti and formed the high temperature phase. At the third stage, the sample was heated into the high temperature -phase zone and hold a given time and then cooling with the furnace. A full density γ-TiAl based alloy sheet with lamellar microstructure was successfully fabricated under above processing. The lamellar orientations are aligned around 0-45o compared to the longitudinal direction of the sheet.
Microstructural Evolution and Mechanical Properties of Modified 9%Cr-1%Mo Steel upon Isothermal Heat-Treatment
Authors: Hur Sung Kang , Shin Kee Sam , Yoo Jung Hoon , Koo Ja Min , Lee Soo , Jung Yeon-Gil , Bae Chang Wan
Published: March 2009

The evolution of microstructure and its effects on the mechanical properties of modified 9%Cr-1%Mo steel during heat-treating at 1050°C for 15 min and then isothermal heat treatment at 380~760°C with subsequent air-cooling have been investigated. For the microstructural and mechanical property analyses, OM, SEM, EDS, XRD, hardness and impact tests were used. In accordance with the severity of the heat-treatment, the microstructure evolved from the untransformed martensite to the partially transformed dual phases of martensite and ferrite, and then fully transformed to ferrite. Impact values at ambient temperature for specimens isothermally heat-treated at 320 - 380°C, predominantly at about 350°C were lower than others’ with similar martensitic structure. The partially transformed specimens with dual phases of martensite and ferrite also showed lower impact values than samples with untransformed with martensitic, and transformed with ferritic structures.
Finite Element Simulation of Canned Forging on TiAl Alloy Containing High Nb
Authors: Lin Hao Zhuan , Li Shu Suo , Su Xikong , Han Ya Fang
Published: March 2009

A rigid plastic finite element simulation method on canned forging was introduced to explain and optimize the large ingot deformation of TiAl alloy containing high content of Nb. By this method the process of deformation and the distribution of stress and strain especially on the interface can be obtained, thus the influence of capsule on the deformation and final shape of ingot can be easily explained and an appropriate processing of canned forging was ingot.
The Effect of Temperature on Microstructure and Mechanical Behavior of the Vacuum Brazed Joint of Ti-46.5Al-5Nb Alloy and 42CrMo Steel
Authors: Liu W. , Gao Q. , Cong W. , Guo Jian Ting
Published: March 2009

： In this work, the effect of temperature on the microstructure evolution of vacuum brazed joint of TiAl alloy and 42CrMo was studied. The results have shown when the brazing temperature is under 870°C, no compound is formed at the boundary on the 42CrMo side. But when brazing temperature is over 870°C, a very narrow TiC compound film is found at the homologous site., while on the TiAl side, there always exists a Ti(Cu,Al)2 intermetallic compound layer at any brazing temperature. The elemental diffusion and reaction is the predominant factor of joint forming. The tensile fracture strength of brazed joint increases with the brazing temperature, the increase of the tensile strength of joint is due to the variation of the joint structure.
Precipitation Behavior and Phase Stability of Intermetallic Phases in Fe-Cr-W-Co Ferritic Alloys
Authors: Yamamoto Keisuke , Kimura Yoshisato , Mishima Yoshinao
Published: March 2009

Precipitation behavior of intermetallic phases in ferrite matrix is investigated by
transmission electron microscopy (TEM) in Fe-10Cr-1.4W-4.5Co (at%) alloys with and without 0.3at%Si. It is intended to provide basic information for the alloy design of ferritic heat resistant alloys strengthened by intermetallic compounds. In the alloy containing Si, icosahedral quasicrytalline phase (I-phase) is found to precipitate during aging at 873K. It is confirmed that selected area diffraction (SAD) patterns of the precipitates exhibit two-, three- and five-fold symmetry and have diffraction spots in the positions related to the golden section. In the Si-free
alloy, the R-phase precipitates instead of I-phase at 873K, and the Laves phase precipitates in both alloys during aging at higher temperature, 973K. The Laves phase formed at 973K transforms to the I-phase in the Si-added alloy but to the R-phase in the Si-free alloy during subsequent aging at 873K. The factors in controlling the phase stability of I-phase, R-phase and Laves phase precipitates
in Fe-based alloys are discussed by the atomic size ratio and electron concentration factor (e/a).
RCu1+xSb2 (R = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y) Phases with Defect CaBe2Ge2-Type Structure
Authors: Yang Xin Xin , Lu Y.M. , Zhou S.K. , Mao S.Y. , Mi J.X. , Man Z.Y. , Zhao J.T.
Published: March 2009

Ten new title compounds were synthesized and their crystal structures refined from X-ray powder diffraction data. For the light rare earth (R = La, Ce, Pr, Nd, Sm) compounds, one of the copper sites is only partially occupied while the occupancies of this position are almost ignorable for the rare earth metals heavier than Gd including Y. The unit cell parameters show normal lanthanide contraction. The bonding energy and density of states of the La compounds are calculated. The results show that the La compound with partial Cu occupancy is more stable than
that without the extra Cu.
Investigation on Microstructure Transformation and Failure Behavior of Cu-Cd-Nb-CP Electrical Contact Material
Authors: Cui Yu Sheng , Shao Wen Zhu , Zhen L. , Ivanov V.V.
Published: March 2009

Dependence of microstructure upon transfer stability of the powder-metallurgy copperdiamond electrical contact material with Cr and Nb addition during type-test process is investigated by optical microscope and SEM observation. During making and breaking process, micro-cracks occurred along grain boundaries under electrical and mechanical forces. Addition of cadmium into the composite increases oxidizable capability of this material, and also leads to oxide accumulation along grain boundaries. These factors reduce the reliability of electrical contacts in practice. Arc erosion quantities during commutation operation processes relates with grain size of matrix and particle size of the second metallic phase. The optimal grain size is 20~50µm and 10~20 µm for niobium particles in these tests.
Influence of Strain Rate and Temperature on the Compressive Deformation of a Eutectic Al-Si Alloy Based Composite Reinforced with -Si3N4 Whisker
Authors: Feng A.H. , Geng Lin , Qu Shou Jiang
Published: March 2009

The compressive properties characterized as a function of the true stress-strain response of -Si3N4 whisker reinforced 4032 aluminum alloy composite were examined at strain rates ranging from 10-3 to 100s-1 in the temperature interval 500~620oC. The effect of compressive deformation parameters such as strain rate and temperature on the mechanical behavior was systematically investigated. The strain rate sensitivity exponent and activation energy were calculated. The activation energy is 126 KJmol-1 at 500oC to 540oC, close to that for lattice self-diffusion in aluminum (142KJmol-1), and is 210 KJmol-1 at 540oC to 580oC ( =0.37s-1). The compressive deformation behavior of the composite can be described quantified by the Zener-Hollomon parameters (Z) for the solid state and the Non Newton-fluid for the semi-solid state of the composite. It is demonstrated that a linear equation of the logarithmic Z fits the flow stress of the composite at elevated temperatures. The compressive deformation mechanisms of the -Si3N4w/4032Al composite were discussed preliminarily.
Microstructure and Mechanical Properties of B/Al Composite after Thermal-Mechanical Cycling
Authors: Qin Yao Chun , He Shi Yu , Dezhua
Published: March 2009

The mechanical properties of B/Al composite were measured at room temperature before and after thermal-mechanical cycling (TMC) in the temperature interval from –125°C to 125°C under constant stress of 30 MPa. The effects of TMC on microstructure and tensile fracture behavior of B/Al composite were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The fiber / matrix interfaces were degraded during TMC, the extent of
which was enhanced with increasing the cycles, causing a measurable decrease of stageⅠmodulus of the B/Al composite. The TMC induced the dislocation generation in the aluminum matrix and the dislocation density increased with increasing the cycles. The tensile strength of the composites increased with the cycles in the early stage of TMC, but subsequently decreased after further TMC. The interfaces in the B/Al composite changed from the strongly-bonded toward the appropriately-bonded, and then to the weakly–bonded ones with increasing the cycles.