bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Assisted Turning of Sintered Silicon Nitride
Authors: Wu Xue Feng , Zhang Hong Zhi , Wang Yang
Published: December 2010

Laser assisted turning is an effective method machining difficult-to-machine materials such as ceramics, which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. A transient, three-dimensional heat transfer model was developed for laser assisted turning of silicon nitride using Finite Element Method to understand the thermal process of laser heating and to optimize the operating parameters. A laser assisted turning experiment system was set up to investigate the thermal conditions and cutting process of laser assisted turning of sintered silicon nitride and the experiments were conducted on the system using selected parameters. Effects of cutting parameters on cutting forces and specific cutting energy were investigated. Forces on the chip and SEM micrographs of chip morphology were studied to discuss the material removal mechanism of laser assisted turning of silicon nitride. Tool wear, surface roughness of the machined surface and the quality of subsurface were investigated. The results showed that the heat transfer model could be used to optimize the cutting parameters and laser assisted turning method could increase the machining efficiency while maintaining machining quality and reasonable levels of tool wear. A method of optimizing LAM based on the thermal model was presented.
Micro-ECM of Maze Flow Channel on Bipolar Plates of Fuel Cell
Authors: Chen Yuan Long , Zhan H.B. , Lee Shuo Jen , Zhu S.M
Published: December 2010

A lot of flow channels should be processed on stainless steel bipolar plates of fuel cell. In
order to increase contact area of gas with electrode and ensure the gas flowing smoothly, the flow
channels will be multichannel maze. It is difficult to be machined by conventional methods, because
the width and depth of the flow channels are very small (about 300μm). When using micro
electrochemical machining, flow channels with low surface roughness and good machining accuracy
could be produced efficiently. The machining cathode tool, fixture, μ-second grade pulse power
supply and machining parameters are introduced. Using microsecond pulse current processing, the
maze-shaped flow channel on bipolar plates of fuel cell can be processed seccessfully, with high
efficiency and good quality. Thus graphite bipolar plates may be replaced by metal bipolar plates. It
may promote the technology advancing for fuel cell, and reducing its cost. Key factors for influencing
electrochemical machining process of flow Channels on bipolar plates include the design of cathode
and fixture , microsecond pulse current, and suited technical parameters
A Capillary Model for Gasesas Coolant and Lubricant in Metal Cutting
Authors: Zhang Yue , Sun Tai Li , Li Qi Dong , Zhang Xi Chuan
Published: December 2010

The gases of nitrogen, oxygen, argon and carbon dioxide were employed as coolant and
lubricant in metal cutting. Therefore, the smaller kinetic diameter of gas, the lower cutting forces can
be obtained. A conical capillary model is proposed, based on the experimental results and the theory
analysis of stress distributions at the tool-chip interface. According to the boundary-layer theory, the
kinetics equations of gas flow were solute. The velocity and flux of gas molecule are presented. In the
capillary, the adsorption of tool-chip interface results in boundary lubricating film; the conical shape
of capillary limits the depth of coolant and lubricant penetrating; and the negative press is the motility
for coolant and lubricant penetrating. The study results show the molecule size of the coolant and
lubricant could effect on its performances, and the coolant and lubricant with a relatively small
molecule may have the particularly effective nature, in metal cutting.
Modeling and Simulation of Flexible Band Based on the Muti-Body Dynamics
Authors: Wu Bing Hui , Pang Bao Jun , Deng Zong Quan
Published: December 2010

To provide theory and technique support for the research on dynamic properties of flexible lock-unlock technology, dynamic equation of band is built up based on the muti-body dynamics. Simulation based on modal neutral file and mixed model with rigid and flexible properties are accomplished in the software of ADAMS. The result reveals that the later one is much closed to the actual movement.
Study on Frictional Wear Property of the High Vanadium High Speed Steel
Authors: Chen Hui Min , Xu Liu Jie
Published: December 2010

The frictional resistance and abrasion mechanism of high vanadium high speed steel were
studied by the self-made friction wear testing machine under the conditions of 10% slip-roll ratio.
Results show that the frictional resistance increases with the increase of carbon content and is optimal
when the carbon content is 2.92%. The carbon content affect the wear resistance by changing the
amount of the retained austenite and the shapes of carbides, the moderate quantities of retained
austenite makes the matrix have better impact toughness and hardness; The spherical VC can prevent
the initiation and expansion of cracks forming and make the frictional resistance increase. The
abrasion mechanism is fatigue flake under the condition of rolling and sliding.
Finite Element Analysis of the Influence of Cutting Edge Radius on Mechanical-Thermal Distribution in High-Speed Cutting TiAl6v4
Authors: Fan Yi Hang , Zheng Min Li , Yang Shu Cai , Zhang Wei , Zhang De Qiang
Published: December 2010

On the basis of analyzing the cutting edge structure and cutting edge radius measurement of high-speed insert, thermal - mechanical coupling finite element method (FEM) is used in this paper, to obtain the effect law of different cutting edge radius on the mechanical-thermal distribution of high-speed cutting TiAl6V4. At last, cutting experiments are carried out to verify FEM results. There is a clear exposition of the intrinsic reason why the cutting edge radius has influence on the mechanical -thermal distribution of high-speed cutting process. The results indicate that the experimental results have a good agreement with FEM; with the cutting edge radius increases, cutting force increases; cutting temperature is not monotonic, but there exists an optimum edge radius that makes temperature lowest; cutting edge changes the plastic flow of materials around tool tip and broaden plastic deformation zone. The cutting edge radius has a greater impact on equivalent stress.
Research on NC Electrochemical Mechanical Complex Machining Stainless Steel
Authors: Gan Wei Min , Xie Xi Lian , Xu Bo , Huang W.B.
Published: December 2010

For hard machining metal materials with high rigidity，high strength or high toughness, the method of electrochemical mechanical complex machining is proposed. A NC high-speed machine tool for carving and milling is transformed into a NC electrochemical mechanical complex machine tool in which complex tool-electrodes, particular tool holders, a new rotary table, a protective flume for electrolyte and pipelines are made and assembled, so that machine tool can achieve a series of machining, such as milling, drilling, grinding and polishing by utilizing complex tool-electrode motion generated by NC. For 304 stainless steel orthogonal experiment is carried out, and five principal process parameters that are spindle rev, feed speed, voltage, pressure of electrolyte and depth of cut, are investigating in the method of NC Electrochemical Mechanical complex machining. The optimization process parameters are obtained.
Design of Straw Reuse & Soil Levelling Compound Machine in Paddy Field
Authors: Yang Xin Chun , Wang H.J.
Published: December 2010

The parameters of paddy field straw reuse and leveling machine, such as the rotating angle
of leveling board, the force and placement angle of the ascend cylinder, were optimized in design.
The machine integrated the function of rotary tilling, breaking soil, cutting straw, burying straw and
leveling soil. It is applied to leveling soil and returning straw to field in paddy field mechanized
harvest, and it has many merits such as small working resistance, good burying straw, and leveling
soil effect etc. Experiment shows that it can directly return straw such as rice straw, wheat straw, and
high stubble to field in one time. It has strong ability to carry soil and slurry with no interference. It
ascends freely, and acts to respond quickly. It integrates three processes such as cutting straw,
breaking soil and leveling soil, which is an efficient technology to return straw in paddy field.
Effect of Temperature on the Impact Performance of Short Fiber Reinforced Composites
Authors: Wang Fu You , Zhang Guo Li , Li Jia Lu , Zhang Yu Feng , Chen L. , Zhang Ming
Published: December 2010

In order to test the impact performance of short glass fiber reinforced composite materials
in different temperature, on the basis of molding process, the specimens of polypropylene modified
resin based glass fiber reinforced composites were made, the impact performance of the materials
with the different temperature of -35°C, 23°C and 80°C were tested. Results show that the maximum
load of specimen can bear is gradually increased with the temperature increase, and the maximum
impact load of specimen is 0.8722kN at -35°C, while the maximum impact load which is improved
38% is 1.2024kN at 80°C. Also the energy absorbed by composite materials increase with the
temperature increase. Results also show that the composite materials manifest as plastic fracture in
high temperatures and brittle fracture in low temperatures.
The Hydrophobicity of Micro Water Pool and the Interfacial Fluidity of PC-Based W/O Microemulsion Droplet Involved with Reactivity of Phospholipase A2
Authors: Yamazaki Keiju , Imai Masanao
Published: December 2010

The impact of physicochemical character of the W/O microemulsion droplet on the reactivity of phospholipase A2 (PLA2) was investigated for optimal design of the micro-reactor. Hydrophobicity of micro water pool and fluidity of micro-scaled interface of W/O microemulsion droplet were dominant factors to determine the appearance of maximum reactivity. Phosphatidylcholine (PC) in this system performed not only as a substrate for PLA2 but also as an amphiphilic molecule to form W/O microemulsion droplet. The organic phase was composed by isooctane (C8*) as a main solvent and 1-butanol (C4) as a co-solvent. The molar ratio was fixed as isooctane:1-butanol =11:1. The water content in the W/O microemulsion was indicated by the molar ratio of H2O moles to PC moles presented by Wsoln [-](≡[mol-H2Osoln]/[mol-PC]). By the increasing of the water content from 1 to 5, the reactivity of PLA2 was remarkably increased from 0.01 to 0.03 [mM･s-1･mg-PLA2-1]. Over 5 of Wsoln range, the reactivity was decreased. The optimal water content was indicated as Wsoln=5 [-]. The hydrophilicity of micro water pool and the interfacial fluidity of the water pool were detected by the signal of the fluorescence probes, Coumarin 343 and TMA-DPH, respectively. The hydrophobicity was decayed with the increasing of the water content. More than 10 of Wsoln, the hydrophobicity was fully decayed and achieved to bulk aqueous one. The interfacial fluidity was decreased with the increasing of the water content. In more than Wsoln of 5, the reactivity was decreased by the decline of the collision frequency between PLA2 and PC molecule due to lower fluidity of micro-scaled interface.
Large Resistance Ratio for High Reliability of Multi-Level Storage in Phase-Change Memory
Authors: Yin You , Noguchi Tomoyuki , Ohno Hiroki , Hosaka Sumio
Published: December 2010

Reliability (or stability) of multi-level storage (MLS) is the critical characteristics for multi-level cells. In order to improve reliability of MLS of phase-change memory, there are two effective approaches, (i) enlargement of the ratio between resistance levels and (ii) reduction of scattering of resistance level. On the basis of our experimental results, it is demonstrated that the Ge2Sb2Te5-based double-layered cell has a high ratio of highest to lowest levels up to two-to-three orders of magnitude, implying high reliability. The cells exhibit the possibility of stable switching for four-level storage.
Theoretical Analysis of Photonic Band Gaps and Defect Modes of Novel Photonic Crystal Waveguides Consisting of Si-Ion Implanted SiO2 Using the Finite-Difference Time-Domain Method
Authors: Umenyi Amarachukwu Valentine , Kawashiri Shinya , Miura Kenta , Hanaizumi Osamu
Published: December 2010

In this paper, photonic crystals (PC) based on 2-D periodic arrays of air holes were investigated on Si-ion implanted SiO2using finite-difference time-domain (FDTD) simulations. The PC design parameters based on the telecommunication wavelength (λ=1.55 µm) were obtained by varying the radius to lattice constant ratio (r/a) from 0.2 to 0.45. We analyzed both transverse electric (TE) and transverse magnetic (TM) mode propagation in triangular-lattice PCs. The result obtained shows that a PC bandgap (PBG) exists for TE-mode propagation in the Si-ion implanted SiO2patterned 2-D triangular lattice of air holes. We have also calculated the dispersion relations for the TE mode of a line defect in the structure and shown a fabricated sample. These analyses are obviously important for fabricating novel PC waveguides, which can easily be integrated into the existing silicon technology for directing light from one part of a chip to the other.
Demonstration of Light-Emitting Two-Dimensional Photonic Crystals Composed of Silicon-Rich Silicon-Dioxide Thin Films
Authors: Miura Kenta , Hanaizumi Osamu
Published: December 2010

A light-emitting, two-dimensional photonic crystal composed of silicon-rich silicon-dioxide thin film was fabricated by using radio-frequency magnetron sputtering, simple interference exposure, and plasma etching. An enhanced photoluminescence spectrum was observed from the photonic crystal. We found that the photoluminescence peak was located around a wavelength of 830 nm and that the peak intensity was 1.5 times stronger than that from a silicon-rich silicon-dioxide thin film without a periodic structure.
A Design Method for Two-Degree-of-Freedom Multi-Period Repetitive Control Systems
Authors: Yamada Kou , Nakazawa Nobuaki , Murakami Iwanori , Ando Yoshinori , Hagiwara Takaaki , Yamamoto Shun , Nguyen Nhan Luong Thanh , Sakanushi Tatsuya
Published: December 2010

Multi-period repetitive controllers improve the disturbance attenuation characteristic of the modified repetitive control system that follows the periodic reference input with a small steady state error. Recently, the parameterization of all stabilizing multi-period repetitive controllers was studied. However, when the parameterization of all stabilizing multi-period repetitive controllers is used, the input-output characteristic and the feedback characteristic cannot be specified separately. From the practical point of view, it is desirable to specify the input-output characteristic and the feedback characteristic separately. In addition, the parameterization is useful to design stabilizing controllers. Therefore, the problem of obtaining the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers that can specify the input-output characteristic and the disturbance attenuation characteristic separately is important to solve. In this paper, we propose the parameterization of all stabilizing two-degree-of-freedom multi-period repetitive controllers.
A Design Method for Stabilizing Modified Smith Predictors for Multiple-Input/Multiple-Output Time-Delay Plants
Authors: Yamada Kou , Mai Nghia Thi , Ando Yoshinori , Hagiwara Takaaki , Murakami Iwanori , Hoshikawa Tatsuya
Published: December 2010

The modified Smith predictor is well known as an effective time-delay compensator for a plant with large time-delays, and several papers on the modified Smith predictor have been published. The parameterization of all stabilizing modified Smith predictors for single-input/single-output time-delay plants is obtained by Yamada et al. However, they do not examine the parameterization of all stabilizing modified Smith predictors for multiple-input/multiple-output time-delay plants. The purpose of this paper is to expand the result by Yamada et al. and to propose the parameterization of all stabilizing modified Smith predictors for multiple-input/multiple-output time-delay plants. Control characteristics of the control system using obtained parameterization of all stabilizing modified Smith predictors are also given. Finally, a numerical example is illustrated to show the effectiveness of proposed parameterization of all stabilizing modified Smith predictors.
Spin and Orbital Magnetic Moment of Pd3Co Evaluated by X-Ray Magnetic Diffraction Experiment
Authors: Ito Masahisa , Oba Yoshiaki , Sato Ayako , Suzuki Kosuke , Tadenuma Tatsuki , Nagayasu Ryota , Sakurai Hiroshi , Adachi Hiromichi
Published: December 2010

We have measured spin and orbital magnetic form factors of Pd3Co for various reciprocal lattice points by the X-ray magnetic diffraction. Observed spin and orbital magnetic form factors are fitted by theoretical curves of the isolated atomic model under the dipole approximation. By the fitting analysis we have evaluated separately the spin and orbital component of the magnetic moment of Pd3Co alloy as 2.19 µB/f.u. and 0.83 µB/f.u., respectively. The total magnetic moment 3.02 µB/f.u. is comparable to the value of 2.93 µB/f.u. obtained by the magnetization measurement.
Preparation of CaTiO3:Pr Phosphor by Using CaB2O4 as a Flux
Authors: Kyomen Toru , Hirozumi Kouki , Hanaya Minoru
Published: December 2010

Powder of Pr-doped CaTiO3 phosphor was prepared with addition of CaB2O4 to the starting materials. The primary particle size was increased and the photoluminescence intensity was enhanced by the addition when prepared at 1373 K. The remarkable effects were not observed when prepared at 1273 K.
Solvent-Free Synthesis of Siloxanes and their Usage as Potential Cross-Coupling Reagents
Authors: Unno Masafumi , Tanaka Ryoji , Obinata Daisuke , Endo Mayuko , Sakurai Tomoyuki , Ojima Satoshi , Katayama Takako , Fugami Keigo
Published: December 2010

Hexaarylcyclotrisiloxanes were selectively prepared by solvent-free synthesis from diarylsilanediol. These well-known stable compounds were found to undergo palladium-catalyzed cross-coupling reaction with aryl halides in good yields. All of attached aryl groups on silicon atom could be utilized. Furthermore, base-sensitive functionality such as acetyl and nitro groups survived the reaction.
Synthesis and Properties of Fluorescent Biological Molecules Labeled with Novel Silylated Perylene Derivative
Authors: Sato Yuzuru , Ozaki Akiko , Hosaka Masahiro , Moriguchi Tomohisa , Shinozuka Kazuo
Published: December 2010

We have synthesized novel perylene derivatives bearing a silyl function with modifiable functional groups as a feasible material for visualizing biological substances. The fluorescent perylene derivative was coupled to C-5 position of pyrimidine nucleotide and the nucleotide was subsequently incorporated to the middle position of oligoDNA using an automated DNA synthesizer. Also, the derivative was coupled with a cholesterol analog with different length of linking alkyl function. The resulting modified fluorescent oligoDNA exhibited a small change in its fluorescent signal upon hybridization with the complementary oligoDNA. While the cholesterol analogs bearing the silylated perylene exhibited marked fluorescent signal in living cells. The signal is stronger in the analog having longer linker function compared to the analog having shorter linker function. In each case, however, the signal was much prominent compared to that of dehydroergosterol (DHE), a fluorescent cholesterol analog widely used in biological study.
A Key Factor for the Actual Application of a Vapor Feed Passive DMFC Operated with High Concentration of Methanol
Authors: Abdelkareem Mohammad Ali , Nakagawa Nobuyoshi
Published: December 2010

The supply of water to the anode from the cathode through the electrolyte membrane is a critical factor for the operation of vapor feed DMFC at high methanol concentrations. A comparative study in a passive vapor feed DMFC employing a PCP on the anode surface had been carried out with and without a hydrophobic cathode filter. Compact and a noncompact cells were fabricated and used. The noncompact cell could be operated with high methanol concentrations of even 100 wt%, while the compact one could not be operated with 90 wt% methanol. This was related to the deficiency of water at the anode surface in the compact cell design, where heat dissipation was not enhanced. For the supply of water to the anode surface, the employment of a hydrophobic filter on the cathode surface was necessary, especially for the compact cell.
Influence of Atmospheric Gases Present in the Pores of MCM-41 on Lifetime of Ortho-Positronium
Authors: Zaleski Radosław , Sokół Michał
Published: December 2010

The modification of the extended Tao-Eldrup model accounting ortho-positronium quenching in air is presented. Taking into account quenching by oxygen molecules adsorbed on the surface of porous material gives reasonable agreement between results of the model and the experimental positron annihilation lifetime spectroscopy data. Pore size distributions calculated using this model from the spectra for MCM 41 mesoporous sieve obtained in air, oxygen or vacuum are compared and discussed taking into account effect of ortho-positronium migration from small open pores to the larger ones. The rates of ortho-positronium quenching by air (47.2 µs-1 MPa 1), oxygen (220 µs-1 MPa-1) or nitrogen (1.7 µs-1 MPa-1) obtained from pressure dependences of the lifetimes observed in MCM 41 agree reasonably with the experimental results of other authors, if the correction for oxygen adsorbed on the surface is applied.
What Else for Improvement of Reconstructed Densities?
Authors: Biasini M. , Kontrym-Sznajd G.
Published: December 2010

Reconstruction techniques, belonging to two different categories (series expansion and transform methods), are compared with regard to their applicability to line projections of a model density. It is demonstrated that in the case of this model the algebraic technique gives much better results than the filtered back projection (FBP) algorithm. However, it could not be a case for real data where a region of densities to be considered is very large comparing to the modelled one. In this connection we propose a new way of dealing with two-dimensional (2D) angular correlation of annihilation radiation (ACAR) data. Such a treatment, proposed for all reconstruction techniques, allows to improve reconstructed densities and filters the experimental noise.
Calculation of Gamma Spectra for Positron Annihilation on Molecules
Authors: Green D.G. , Saha S. , Wang F. , Gribakin G.F. , Surko C.M.
Published: December 2010

Calculations of gamma spectra for positron annihilation for a selection of molecules, including methane and its fluoro-substitutes, ethane, propane, butane and benzene are presented. The contribution to the -spectra from individual molecular orbitals is obtained from electron momentum distributions calculated using the density functional theory (DFT) based B3LYP/TZVP model. For positrons thermalised to room temperature, the calculation, in its simplest form, effectively treats the positron as a plane wave and gives positron annihilation  spectra linewidths that are broader (30–40%) than experiment, although the main chemical trends are reproduced. The main physical reason for this is the neglect of positron repulsion from the nuclei. We show that this effect can be incorporated through momentum-dependent correction factors, determined from positron-atom calculations, e.g., many-body perturbation theory. Inclusion of these factors in the calculation gives linewidths that are in improved agreement with experiment.
Similarity of Primary Processes in Tracks of Fast Electrons, Positrons, Muons and in Blobs of Moessbauer Atoms. Common Model of early Chemical Reactions for Radiation, Positron, Muon Chemistry and Moessbauer Spectroscopy
Authors: Byakov Vsevolod , Kulikov Leonid A. , Perfil'ev Yurii D. , Stepanov Sergey V.
Published: December 2010

A unified mechanism describing formation of Ps and Mu atoms in condensed matter, radiolytic hydrogen in water and products of Auger ionization in Moessbauer atoms is presented. All these processes are similar to the Ps formation mechanism in a condensed molecular milieu.
Localization of Positronium in Polymers
Authors: Kobayashi Yoshinori , Ichikawa T.
Published: December 2010

A good correlation is found between ortho-positronium (o-Ps) pick-off annihilation lifetimes and surface tensions of molecular liquids and polymers. Systematic shortening of the o-Ps lifetime with increasing surface tension suggests that the hole for Ps localization in polymers may be that subjected to considerable expansion as in liquids. The driving force of this hole expansion is the large quantum mechanical zero-point energy of a light particle confined in an angstrom size space. The hole expansion is insignificant in a larger nm scale pore, where the zero-point energy is much lowered.
Effect of Post Annealing Treatment on Nano-Structured Low Carbon Steel Sheets Processed by Constrained Groove Pressing
Authors: Khodabakhshi Farzad , Kazeminezhad Mohsen , Azarnush Mohammad , Miran Seyyed Hossein
Published: December 2010

There are many works on annealing process of SPDed bulk metals but there are limited works on annealing process of SPDed sheets. Therefore, in this study the annealing response after constrained groove pressing (CGP) of low carbon steel sheets has been investigated. These sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100 to 600 °C for 20 min. The microstructural changes after deformation and annealing are studied by optical microscopy. The effects of CGP strain and annealing temperature on microstructure, strength and hardness evolutions of the nano-scale grained low carbon steel are examined. The results show that annealing phenomena can effectively improve the elongation of process sheets with preserving the hardness and mechanical strength. Also, a thermal stability of microstructure can be observed with annealing at a temperature range of 375–425 °C and 400 °C is achieved as an optimum annealing temperature. Microstructure after post-annealing at temperatures of higher than 600 °C shows abnormal grain growth.
Phase Transformations and Functional Properties of NiTi Alloy with Ultrafine-Grained Structure
Authors: Prokofiev Egor , Burow Juri , Frenzel Jan , Gunderov Dmitriy , Eggeler Gunther Friedrich , Valiev Ruslan
Published: December 2010

Severe plastic deformation (SPD) processes, are successfully employed to produce ultra fine grain (UFG) and nanocrystalline (NC) microstructures in Ni50.7Ti49.3 shape memory alloy. The effect of grain size on phase transformations during annealing is investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results of comparative studies of phase transformations in coarse-grained, UFG and NC alloys after SPD and subsequent long-term (up to 100 hours) annealing at 400С is presented. The functional properties and the innovation potential of UFG NiTi alloys is considered and discussed.
Microstructure and Properties of T2 Copper Tube Produced by Severe Hot Rolling
Authors: Wang Ya Li , Liu Ying , Wang Jing Tao , Tian Fu Sheng
Published: December 2010

In this study, the microstructure evolution as well as mechanical properties of T2 copper tube during severe hot rolling has been investigated. Owing to the severe hot rolling deformation and high rolling temperature, the microstructure of T2 copper tube evolved from initial cast structure into relatively homogenous and equiaxed grains during the process, which was testified through the results of optical microscope observation. Besides, the microhardness measurements were taken, from which the results gained were in correspondence to the microstructure transformation.
Annealing Behavior of Solution Treated and Aged Al-0.2wt% Sc Deformed by ARB
Authors: Borhani Ehsan , Jafarian Hamidreza , Adachi Hiroki , Terada Daisuke , Tsuji Nobuhiro
Published: December 2010

The effect of prior and subsequent precipitation on recrystallization behavior during the isothermal annealing of an Al-0.2%wt.Sc alloy heavily deformed by accumulative roll bonding (ARB) up to 10 cycles at ambient temperature was investigated. Three kind of different microstructures, i.e., solution treated one, 300°C pre-aged one and 400°C pre-aged one, were prepared as the starting structures for the ARB process. It is found that precipitation pinning effect of Al3Sc suppresses recrystallization and especially the 400°C pre-aging was effective to stabilize the ultrafine grained structure of the matrix. Dissolution of pre-aging Al3Sc precipitates was suggested by re-precipitation during annealing of the ARB processed specimens at around 300°C.
Microstructure and Mechanical Properties of Accumulative Roll Bonded AA6014/AA5754 Aluminium Laminates
Authors: Hausöl Tina , Höppel Heinz Werner , Göken Matthias
Published: December 2010

Among the well-known methods of severe plastic deformation the accumulative roll bonding (ARB) process is most promising for producing ultrafine-grained (UFG) materials with extraordinary mechanical properties at an industrial scale. Besides, it has also been shown that the ARB process can be successfully used to produce multi-component materials with tailored properties by reinforcement or grading, respectively. In this work, laminates with alternating layers of the high strength aluminium alloy AA5754 and the AA6014 alloy, well-known for good formability and high surface quality, were produced by ARB at 230 °C. Microstructural and mechanical investigations were performed after 2, 4 and 6 ARB cycles by means of light and electron microscopy, nanoindentation experiments and tensile testing. After ARB processing an ultrafine-grained microstructure is obtained. The UFG microstructure as well as the local mechanical properties alter with the layer composition. With increasing number of ARB cycles the interfaces between the layers become more and more wavy by shear band formation. Compared to the pure accumulative roll bonded AA6014 the yield and ultimate tensile strength of the multi-component laminates are considerably higher and are only slightly reduced in comparison to the high strength AA5754. In terms of elongation to failure no reduction in ductility is found. The serrated yielding effect, clearly visible in AA5754, is shifted to higher strains or fully disappears, respectively, whereas in AA5754 the magnitude of serrations increases with increasing number of ARB cycles. Combining AA5754 and AA6014 sheets by ARB results in well bonded ultrafine-grained laminates which exhibit a combination of the beneficial properties of the single-component materials: high strength of AA5754 and good surface quality of AA6014.
Severe Plastic Deformation Processes with Friction Induced Shear
Authors: Lapovok Rimma , Estrin Yuri , Djugum Richard , Lerk Andre
Published: December 2010

Among the known severe plastic deformation (SPD) techniques, there is a special group of processes involving friction-induced shear. One of the sample or work-piece dimensions used in such processes, namely the thickness, is much smaller than the other two dimensions. The well-known process of High Pressure Torsion (HPT) and the relatively new Cone-Cone (CC) method applied to thin conical samples fall into this category of SPD techniques. Wrought aluminium alloy 2124 was used to study the effect of CC processing on microstructure and mechanical properties. The influence of the processing parameters, including the rotation speed and thickness of the conical strip specimens on the microstructure and the mechanical properties of the CC-processed material was investigated.
The Evolution of Structure and Mechanical Properties of Fe-Mn-V-Ti-0,1C Low-Carbon Steel Subjected to Severe Plastic Deformation and Subsequent Annealing
Authors: Maier Galina G. , Astafurova Elena G. , Naydenkin Evgeny V. , Raab Georgy I. , Dobatkin Sergey V.
Published: December 2010

The present work deals with the evolution of mechanical properties and structure of low-carbon Fe-1,12Mn-0,08V-0,07Ti-0,1C (wt.%) steel after severe plastic deformation (SPD) and high-temperature annealing. Steel in initial ferritic-pearlitic state was deformed by equal channel angular pressing (ECAP) at T=200°C and high pressure torsion (HPT) at room temperature. The evolution of ultrafine grained structure and its thermal stability were investigated after annealing at 400-700°C for 1 hour. The results shown that SPD leads to formation of structure with an average size of (sub-) grain of 260 nm after ECAP and 90 nm after HPT. Ultrafine grained structures produced by SPD reveal a high thermal stability up to 500°C after ECAP and 400°C after HPT. At higher annealing temperatures a growth of structural elements and a decrease in microhardness were observed.
Equal-Channel Angular Pressing of NiAl
Authors: Skrotzki Werner , Chulist Robert , Beausir Benoît , Hockauf Matthias
Published: December 2010

Equal-channel angular pressing (ECAP) was applied to polycrystalline NiAl at temperatures around the brittle-to-ductile transition temperature (BDTT). NiAl rods encapsulated in a steel jacket were ECAP-processed in a die with a channel angle of 120°. The microstructure and texture were characterized by electron backscatter diffraction with a scanning electron microscope. The volume fraction of the texture components typical for simple shear in the intersection plane of the channels changes in the range of the BDTT.
The Formation of Submicrometer Scale Grains in a Super304H Steel during Multiple Compressions at 700°C
Authors: Tikhonova Marina , Dudko Valeriy , Belyakov Andrey , Kaibyshev Rustam
Published: December 2010

The deformation behavior and the microstructure evolution in a 304-type austenitic stainless steel were studied in multiple forging tests at temperature of 700°C. The flow stresses increased to its maximum value with straining to about 1 and, then, slightly decreased resulting in a steady state deformation behavior at strains above 3. The structural changes were characterized by the development of a spatial net of deformation subboundaries, the misorientations of which increased to the values typical of conventional grain boundaries. The number of ultrafine grains increased with straining, leading to development of submicrocrystalline structure. The fraction of submicrocrystalline structure composed of ultrafine grains with an average size of about 300 nm exceeded 0.7 after straining to 2.
Production of Bulk Ultrafine Grained Steel through Severe Plastic Deformation
Authors: Ghazani Mehdi Shaban , Eghbali Beitallah
Published: December 2010

In the present research, a combined forward extrusion-equal channel angular pressing (FE-ECAP) was developed and used for production of bulk ultrafine grained steel in the high temperature conditions. In this method, two different deformation steps including forward extrusion and equal channel angular pressing takes place successively in a single die. The deformation process was performed at different deformation start temperatures (800, 930, and 1100 °C). In addition, 3D finite element simulation was used to predict the hot/warm deformation parameters such as strain and temperature variations within the samples during deformation. The results show that the EF-ECAP process is effective in refining the grains from initial size of 32 m to final size of 0.9 m after executing of extrusion and ECAP on as received samples. The main mechanisms of grain refinement were considered to be strain assisted transformation, dynamic strain-induced transformation, and continuous dynamic recrystallization.
Grain Refinement in AZ61 Mg Alloy during Hot Cyclic Bending
Authors: Jiang Yu Pei , Yang Xu Yue , Zhang Lei
Published: December 2010

Strain-induced grain refinement in magnesium alloy AZ61 was studied by means of cyclic bending carried out at a temperature 623K. The deformed microstructures were investigated by optical and SEM/EBSD metallographic observation. The results show that the grain size of the surface layer can be significant refined to about 3 μm by dynamic recrystallization. The volume fraction of new grains increases with strain and reaches a value of 0.8 after 8 passes. Most of the new grains are separated by high angle boundaries. Hardness distribution through thickness for the cyclic bended sheet exhibits “V” shape with the marked difference between the surface and the inside, the hardness is critically increased in surface layer, i.e. ~82 Hv, which is about 1.39 times than the as-received AZ61.
Evidence of Bulk Nanostructuring in Zr-Based Alloys under Deformation at Temperatures of α↔β Phase Transformations
Authors: Isaenkova Margarita , Perlovich Yuriy , Fesenko Vladimir , Krymskaya Olga , Zavodchikov Alexander
Published: December 2010

The deformation behavior of commercial Zr alloys with 1% and 2,5%Nb under compression at temperatures of the (α+β)-region of Zr-Nb phase diagram is considered on the basis of experimental data obtained by X-ray texture study of deformed samples. Mechanisms, responsible for plastic deformation of alloys by different temperature-rate regimes were determined on the basis of resulting textures. Among these mechanisms there are crystallographic slip and mutual displacements of crystallites along interphase boundaries. The latter mechanism sharply intensifies by grain fragmentation down to nanostructuring under conditions of α«β phase transformations. Texture features of deformed samples testify about interaction of plastic deformation with phase transformations and indicate that due to this interaction compression by optimal regimes promotes the utmost refinement of structure elements.
Cooperative Grain Boundary Sliding and Shear Banding at High Strains in Ultrafine Grained and Nanocrystalline Pd Alloys
Authors: Ivanisenko Yulia , Fecht Hans Jörg
Published: December 2010

Instrumented high pressure torsion, i.e. mechanical test in a torsion mode under high pressure, allows interesting possibility of materials testing, because materials mechanical response can be studied in a practically unlimited shear strain range. We have studied microstructures formed in initially coarse crystalline and nanocrystalline (nc) Pd and its alloys after instrumented HPT up to shear strain 300, and revealed signatures of similar processes occurring in all these materials. In particular, we found traces of cooperative grain boundary sliding in the form of aligned in parallel segments of boundaries of several grains with straightened triple points. Fracture surfaces contained shear bands. Texture measurements revealed lower dislocation activity in nanocrystalline state as compared with coarse crystalline one. Therefore we argue that cooperative grain boundary sliding is an important deformation mechanism at large strain which develops in both ultrafine grained (ufg) and nanocrystalline materials. In nc and ufg materials planes of cooperative grain boundary sliding act as precursors of shear bands and shear occurs along planes formed by numerous grain boundaries.
The Effect of Grain Boundary Sliding and Strain Rate Sensitivity on the Ductility of Ultrafine-Grained Materials
Authors: Nguyen Quang Chinh , Csanádi Tamás , Gubicza Jenő , Valiev Ruslan , Straumal Boris , Langdon Terence G.
Published: December 2010

Most ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) exibit only limited ductility which is correlated with the low strain rate sensitivity (SRS) of these materials. Recently, it was demonstrated that SPD is capable of increasing the room temperature ductility of aluminum-based alloys attaining elongations up to 150%, together with relatively high strain rate sensitivity. In the present work, additional results and discussions are presented on the effect of grain boundary sliding (GBS) and SRS on the ductility of some UFG metals and alloys. The characteristics of constitutive equations describing the steady-state deformation process are quantitatively analyzed for a better understanding of the effects of grain boundaries and strain rate sensitivity.
Mechanical Properties of Al-6061 and an Al-6061 Metal Matrix Composite Processed by High-Pressure Torsion
Authors: Xu Cheng , Horita Z. , Langdon Terence G.
Published: December 2010

It is now well established that the application of high-pressure torsion (HPT) leads to exceptionally small grain sizes in bulk solids, usually in the nanometer scale. The HPT method thus attracts considerable attention and has been utilized in processing many materials such as pure metals, alloys and even ceramics. This paper describes experiments conducted on samples of an Al-6061 alloy and an Al-6061 metal matrix composite, reinforced with 20 vol.% Al2O3 particulates, in order to evaluate the mechanical properties of the alloy and its composite processed by HPT. The tensile properties of the materials were obtained both at room temperature and at 773 K and representative microstructures were observed using transmission electron microscopy.
Application of High-Pressure Torsion to Al-Si Alloys with and without Scandium Additions
Authors: Venkateswarlu K. , Rajinikanth V. , Sen Mani Kuntal , Alhajeri Saleh N. , Langdon Terence G.
Published: December 2010

Al-2 wt. % Si alloys with and without 0.25 wt. % scandium additions were processed by high-pressure torsion up to five turns at room temperature under a pressure of 6.0 GPa. Microstructural examination of the as-cast Al-2Si-0.25Sc alloy revealed the presence of Al3Sc precipitates which refined the Al grain structure, whereas no major changes were observed in the morphology of the Si particles. Processing by HPT of both experimental alloys revealed submicrometer grains with uniformly distributed Si particles. The mechanical properties were obtained using hardness measurements and the ball-indentation technique. The results show the hardness increased in the first turn of HPT and further increased with increasing numbers of turns. In addition, the hardness values were lower at the centers and continuously increased towards the edges of the disks. The difference in hardness values between the centre and the edge decreased with increasing turns, thereby suggesting an increasing homogeneity with increasing processing. The scandium addition and HPT processing of the Al-2Si alloy strongly influences the grain refinement and mechanical properties. The grain size reduction in the Al-2Si alloy was similar to Al whereas the presence of Sc in Al-2Si during HPT processing was responsible for large precipitation networks and a submicrometer grain formation.
Prediction of the Tension/Compression Asymmetry of ECAP Processed FCC Material Using an Integrated Model Based on Dislocation and Back-Stress
Authors: Chen En Ze , Duchêne Laurent , Habraken Anne Marie , Verlinden Bert
Published: December 2010

In our recent work, a new integrated model was proposed to describe the back-stress evolution based on the dislocation substructure and texture. By relating the back-stress to the dislocation density in cell walls and in the cell interior, this model is able to capture the back-stress evolution of ECAP processed pure aluminium. In this paper, the model is used for another FCC material, namely copper. The aim is to check whether this model is able to predict the tension/compression asymmetry (due to the back-stress) of copper. The results show that this is indeed the case and it is also found that the strain rate ratio proposed in our previous work [1] is a function of the dislocation density ratio.
Mechanical Properties and Microstructure of a Duplex Nanostructure
Authors: Chen L. , Jiang Ping , Wu Xiao Lei , Yang Mu Xin , Wang Chang , Yang Gang
Published: December 2010

The nanostructure was obtained in a duplex stainless steel (DSS) by means of equal channel angular pressing. The mechanical properties were characterized by uniaxial tensile tests, while the microstructure was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that the yield strength in a deformed nanostructure increased significantly from 402 MPa to 1461 MPa as compared to its coarse-grained counterpart. In contrast, the uniform elongation decreased significant to only 2% together with elongation to failure of 9.8%, much lower than those of 25.4% and 42.6%. After annealing at 700°C for 10 minute, however, uniform elongation increases to 5.3% with the yield strength of 1200 MPa. TEM observation exhibited that deformation twins prevail in the austenite phase whereas the dislocations of high density present in ferrite. The plastic behavior in both phases was analyzed based on the deformation twinning and the presence of dislocation. Finally, the effect of the microstructure on mechanical properties was discussed.
Nanostructure Formation in Silicon Photovoltaic Cells by Femtosecond Laser Pulses
Authors: Taleb A.M. , Al-Naimee K.A. , Abdalah S.F. , Meucci Riccardo , Arecchi F.T.
Published: December 2010

The experimental evidence of the effect of femtosecond laser pulses on the spectral response of a Silicon photovoltaic cell is demonstrated and investigated. The response of this device is covering the visible to near infrared spectral region. The responsivity of the photovoltaic cell is enhanced from 0.18A/W (0.5A/W to 0.85 A/W) to 0.25A/W, this means that the conversion efficiency increases from about 9% to about 14% due to irradiation effect. All treatments and measurements have been done at room temperature. The observed enhancement is related to the appearing of nano-structured groves in the 700-900 nm range.
Measurements of Magnetic Properties of Fe-Mn-Cr-Si-Sm-B Ferromagnetic Shape Memory Ribbons Depending on Stress and Temperature
Authors: Todaka Takashi , Yamamichi D. , Enokizono Masato
Published: December 2010

This paper presents measured magnetic and shape memory properties of Fe-Mn-Cr-Si-Sm-B ferromagnetic shape memory ribbons depending on tensile stress and temperature. The samples were produced with the melt spinning method in air and the magnetic properties were measured with an open solenoid type measurement system under controlling their temperature and tensile load. The alloys are multi-functional materials, which have both the ferromagnetic property and shape memory property. The measured results show applicability of the produced ribbon in applications for magnetic sensors and actuators.
Oblique Ion Etching for Copper at Elevated Temperature
Authors: Hino Tomoaki , Kobayashi T. , Yamauchi Y. , Nobuta Y. , Nishikawa M.
Published: December 2010

In order to smooth the uneven surface of polycrystalline copper, argon ion etching at the elevated temperature was conducted. The polycrystalline copper was obliquely irradiated by argon ion beam with ion energy of 1 keV and an incident angle of 70°. The substrate temperatures during argon ion irradiation were room temperature (RT), 473 K and 573 K. Before and after the irradiation, the surface morphology was observed using an atomic force microscope (AFM). After the irradiation at 473 K and 573 K, the surface was significantly smoothed compared with that at RT. In addition, the fluence required to obtain the smooth surface can be very low, compared with the case at RT. The present study shows that the oblique ion etching at elevated temperature is quite useful to obtain the smooth surface.