bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation on the Process of Jet Electrochemical Machining and Guided Laser Beam Machining
Authors: Yuan Li Xin , Xu Jia Wen , Zhao Jian She
Published: December 2010

Laser beam machining is often associated with the metallurgical defects related with spatter, recast layer and heat-affected zone. In order to overcome the defects, this paper presents a process of jet electrochemical machining and guided laser beam machining (JECM-GLBM). On the explain of experimental principle and apparatus, jet electrochemical machining and laser beam machining(JECM-LBM) and JECM-GLBM experiments have been performed on 0.5mm thick 321S20 stainless steel under the same experimental condition respectively. The experimental results show that the entry circularity, repeatability and the surface quality of JECM-GLBM are significantly better than JECM-LBM, and the spatter and the recast layer of hole-wall has been mostly removed in JECM-GLBM. In addition, increasing the IEG leads that the taper and overcut are decreased in JECM-GLBM. By analyzing the experimental results, the best IEG is 10mm, which is unusually beneficial for the design of equipment in engineering application.
A Parametric Curve Interpolation Algorithm for High Speed Machining
Authors: Liu Q.J. , Yue J.H. , Wang Y.F. , Dong J.C. , Wang Tai Yong
Published: December 2010

This paper proposed a new and effective parametric curve interpolation algorithm with error compensation capability for high speed machining. The proposed algorithm is developed from the first-order Taylor expansion interpolation algorithm and the speed-controlled interpolation algorithm. It is also incorporated the geometry features of the machined curves, the dynamic characteristics of machine tools and the adaptive error control. The proposed algorithm achieves high surface accuracy and avoids feedrate fluctuations. Simulation results have demonstrated the effectiveness and satisfactory performance of the proposed algorithm.
The Development of an Economic Model for the Milling of Titanium Alloys
Authors: Ding Song Lin , Izamshah R.A. R. , Mo John , Zhu Yong Wei
Published: December 2010

This paper presents a model for the determination of optimal cutting parameters in the
milling of Titanium alloys based on real manufacturing data collected from cutting tests. The
objective of the optimal function is to achieve the lowest overall costs. Design of Experiment and
Taguchi methods are applied in the design of cutting tests. Optimal cutting parameters such as
cutting speed, feed, depths of cut are obtained by solving the economic model which is developed
according to workshop-specific data.
The Confined Chord Error Algorithmfor Machining Complex Parametric Curve
Authors: Hao Yong Jiang , Zhang Zhi Qiang , Wang Tai Yong , Liu Q.J. , Qiao Zhi Feng
Published: December 2010

The part’s precision-machined quality of NC machining is influenced by the chord error
greatly during precision machining. The confined chord error Algorithm for Machining Complex
Parametric Curve is proposed for the complexity of the chord error. The information of the arc length
error is utilized to control the chord error of the interpolated point indirectly. The arc length error of
interpolated point is computed by Simpson expressions, the information of coordinate and the first
order derivative of interpolated point is computed by the interpolation algorithm, so the computed
difficulty is not increased greatly. The computed error of the algorithm is discussed and the
simulation example of NURBS curve proves that the destined precision of the chord error can be
satisfied by this algorithm.
Studied on the Microfluidic Chip Based on the Kapton by Excimer Laser Ablation
Authors: Sun S.J. , Zhu Ji Jun , Yung Winco K.C.
Published: December 2010

This work has been undertaken to study the microfluidic chip made by the excimer laser ablation. A Kind of Micro electrophoresis chip, Micro polymer chain reaction (PCR) and combined with electrochemical detection and micro blood separator are made using the commercial Polyimide film (Kapton from Dupont). The surface characterization of the excimer-ablated polymide is studied by using the Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM) and X-ray photoelectronic spectroscopy (XPS). The surface roughness is also measured by white light interference microscope (Wyco NT8000, Vecco. Com, USA). A kind of heat transfer equation is also given in this paper.
Self-Assembled Nanodot Fabrication by Using Diblock Copolymer
Authors: Huda Miftakhul , Yin You , Hosaka Sumio
Published: December 2010

In this study, we investigate self-assembled large-area nanodot fabrication on a silicon substrate using poly(styrene)-poly(dimethyl-siloxane) (PS-PDMS) for the application to quantum dot solar cell. By optimizing the PS-PDMS concentration by 2% and the volume of PS-PDMS solutions by 20 μL/cm2 dropped to silicon substrate, nanodots with a pitch size of 33 nm and a diameter of 23 nm are achieved with the molecular weight of 30,000-7,500. It is found that the dropped volume of PS-PDMS solution correlated to the thickness of spin-coated PS-PDMS layer has a great effect on the size and the pattern morphology.
A Design Method for Modified PID Control Systems to Attenuate Unknown Disturbances
Authors: Hagiwara Takaaki , Yamada Kou , Murakami Iwanori , Ando Yoshinori , Matsuura Shun
Published: December 2010

PID(Proportional-Integral-Derivative) controller structure is the most widely used one in industrial applications. Yamada and Hagiwara proposed a design method for modified PID controllers such that modified PID controllers make the control system for unstable plants stable and the admissible sets of P-parameter, I-parameter and D-parameter are independent from each other. When modified PID control systems are applied to real plants, the influence of disturbance in the plant must be considered. In many cases, disturbance in the plant is unknown. It is comparatively easy to attenuate known disturbance, but it is difficult to attenuate unknown disturbances. From a practical viewpoint, it is desirable to design a modified PID control system to attenuate unknown disturbances. However, no paper examines a design method for modified PID control systems to attenuate unknown disturbances. In this paper, we propose a design method for modified PID control systems to attenuate unknown disturbances.
Architecture of Wideband High-Efficiency Envelope Tracking Power Amplifier for Base Station
Authors: Kaneta Masato , Kanbe Akihiro , Hirata Hitoshi , Shimura Tatsuhiro , Yamagishi Kentarou , Kobayashi Haruo
Published: December 2010

This paper proposes new architectures for envelope-tracking power supplies for base stations. (1) The proposed multiphase DC-DC converter circuit uses multiple switching circuits with hysteresis comparators (as well as a voltage follower circuit), each optimized for a different envelope frequency, to realize both high efficiency and wide bandwidth. (2) We also propose the one using interleaved PWM switching circuits. The operation of the circuits, and simulation results, are described.
Ionic Conductivity of Polycrystalline Li2GexSi1-xO3 (x = 0.0~1.0)
Authors: Furusawa Shinichi , Enokida Shun
Published: December 2010

Polycrystalline Li2GexSi1-xO3 (x = 0.0~1.0) was synthesized by solid state reaction, and its ionic conductivity was studied as a function of x in a temperature range of 500–700 K. The ionic conductivity was found to depend on x and was enhanced at x = 0.2–0.7. Furthermore, the pre-exponential factor and activation energy in the Arrhenius equation were also found to depend on x. These results suggest that lithium ionic conduction in Li2GexSi1-xO3 is strongly influenced by the structure of the framework.
Nano-Platelet Structure of Clay Materials Observed by Atomic Force Microscope
Authors: Kakiage Masaki , Takamatsu Rie , Uehara Hiroki , Yamanobe Takeshi , Suzuki Keizo
Published: December 2010

In this study, we investigated the nano-platelet structures of original and organically modified montmorillonite clays. Atomic force microscope observation gave accurate width and thickness of the nano-platelet clays. The organically modified clays could not be homogeneously dispersed even in organic solvent. Ultrasonication of the solution resulted in the destruction of the layered structure of the clays. In contrast, the supernatant solution before ultrasonication contained the mono-layered nano-platelets of the organically modified clays whose surface was rough in the angstrom level due to the adsorbed molecules.
Application of Micro-Metal Textile for Flexible Dye-Sensitized Solar Cell
Authors: Kakiage Kenji , Fujimura Emi , Abe Masayuki , Shinoda Hajime , Kyomen Toru , Hanaya Minoru
Published: December 2010

As a means to make a flexible dye-sensitized solar cell (DSSC), we prepared a TiO2 electrode by using a micro-metal textile made from Sn-plated Cu wires, and examined applicability of the micro-metal textile as a substrate for the electrode. The TiO2 electrodes were prepared successfully by painting a TiO2 paste to the textile using a squeegee method followed by sintering at 500 °C, and the electrodes showed no exfoliation of the TiO2 layer from the textile even when the electrode was bent to a cylindrical shape with 10-mm diameter. The solar cells constructed with these electrodes, on which N3 dye was adsorbed as a sensitizer, exhibited actually a photovoltaic performance. The results indicated the applicability of the micro-metal textile as the flexible substrate for the TiO2 electrode producing an efficient flexible DSSC.
Positron Annihilation in Undercooled Water and Ice
Authors: Šauša Ondrej , Iskrová Martina , Sláviková Barbora , Majerník Viktor , Krištiak Jozef
Published: December 2010

Positron lifetime and Doppler broadened annihilation line at wide temperature range 15-300 K was measured. The phase transition at melting temperature and its temperature shift in undercooled water was observed. The change in temperature dependence of long lifetime component in region 150 K was observed. The lifetime distributions (by program MELT) were calculated in full temperature range with an accent for the phase transition temperature range.
New Experiment for the First Direct Measurement of Positronium Hyperfine Splitting with Sub-THz Light
Authors: Miyazaki Akira , Yamazaki Takayuki , Suehara Taikan , Namba Toshio , Asai Shoji , Kobayashi Tomio , Saito Hruo , Idehara Toshitaka , Ogawa Isamu , Urushizaki Yuichi , Sabchevski Svilen
Published: December 2010

Positronium is an ideal system for the research of Quantum Electrodynamics (QED), especially for QED in bound state. The discrepancy of 3.9σ was found recently between the measured HFS values and the QED prediction of O(α3). It might be due to the contribution of unknown new physics or systematic problems in the all previous measurements. We propose a new method to measure HFS directly and precisely. A gyrotron, a novel sub-THz light source is adopted with a Fabry-Pérot cavity with high finesse and an efficient transportation system in order to obtain sufficient radiation power at 203 GHz. The present status of the optimization studies and the current design of the experiment are described.
A Computational Model for Nano Scale Cavities in the Atomic Structure of Polymer Melt and Comparisons to PALS
Authors: Račko Dušan
Published: December 2010

In the Present Contribution the Atomistic Structure of the Polymer Melt at 300 K Is Simulated by Means of Molecular Dynamics. the Agreement with an Experimental Density Is Obtained with a Deviation Lower than 1%. the Free Volume Is Analyzed in 1,000 Structures and 6.5 X 108 Cubic Å of Molecular Space. a Model for the Free Volume Cavities Is Proposed. in the Model the Size and Number of the Cavities Can Be Scaled by Three Parameters: Probe Radius, Cavity Depth and Cavity Threshold Volume. the Experimental Values of the Nano-Sized Cavity Volumes as Well as Ortho-Positronium Lifetimes Are Obtained, as Compared to Models with Cylindrical and Spherical Geometry. a Typical Value of the Number Density of Free Volume Cavities at 0.001 Å-3 Is Obtained. the Cavities Have Typically Elongated Shape with a Side-to-Length Ratio 1:2.
Investigation of Resonances in the Scattering of a Heavy ‘Positron’ by H2 that Involve Vibrationally Excited Quasi-Bound States
Authors: Armour Edward A.G.
Published: December 2010

There is currently great interest in the very large values of the positron annihilation rate that have been observed in low-energy positron scattering by some molecules. The annihilation rate is proportional to , the effective number of electrons in the target available to the positron for annihilation. These very high rates and associated values of have been observed experimentally to occur at energies just below the energies of excited vibrational states of the molecule concerned. This has been explained by Gribakin [Phys. Rev. A Vol. 61 (2000), p. 022720] and Gribakin and Lee [Phys. Rev. Lett. Vol. 97 (2006), p. 193201] as being due to Feshbach resonances involving excited quasi-bound vibrational states. Their explanation is partly phenomenological. In this paper, I describe the results of an ab initio treatment of this resonant behaviour in the case of the scattering of a heavy ‘positron’ by , using the Kohn variational method.
Point Defect Study in Fe72Al28 Alloy as a Function of Thermal Treatment by Positron Lifetime Spectroscopy
Authors: Kansy Jerzy , Hanc Aneta , Jabłońska Magdalena , Bernstock-Kopaczyńska E. , Giebel Dawid
Published: December 2010

The defect structure of Fe28Al samples is examined with the Positron Annihilation Lifetime Spectroscopy. The studies are carried out for samples in as-cast state and after heat treatments: annealing for 24 hours at 900°C (or 1050°C) and either slow cooling with furnace or quenching to oil. The PALS spectra are analyzed using two-state trapping model. Only one type of defects is detected. The positron lifetime in these defects (V) suggests that they are quenched-in Fe-monovacancies (VFe). The vacancy concentration strongly depends on the rate of cooling. Besides, V also depends slightly on the rate of cooling of the material. This fact suggests, according to the predictions of latest theoretical calculations, that V is sensitive to the atomic configuration in the nearest neighborhood of VFe, which give hope to estimate the degree of atomic ordering in alloys by the PALS technique.
Study of the e+ Distribution in a Layered Stack Sample Using Positron Lifetime Spectroscopy
Authors: Dryzek Jerzy , Horodek Paweł
Published: December 2010

The results of the Monte Carlo (MC) simulations, using GEANT4 codes, indicate the enhancement of the fraction of the e+ in the denser regions of the sample embedded by the less dense environment. The positron lifetime measurements, performed for two stacks of layers consisting of pure aluminum and silver do not seem to reveal this effect. Some features of the e+ distribution detected in the experiments are not reproduced by the MC simulations.
Phase Transitions in Polymers Containing Long Self-Assembled CH2 Sequences in the Side Chain: A Positron Lifetime Study
Authors: Yu Yang , Dlubek Günter , Krause-Rehberg Reinhard , Beiner Mario , Hempel Elke
Published: December 2010

Positron lifetime annihilation spectroscopy (PALS) was used to study the temperature- dependence of sub-nanometer size local free volumes in two atactic poly(n-octadecyl methacrylate)s (PODMA) with different molecular weight. These materials exhibit short range layered structure with a self-assembly and crystallization of side chains. From the ortho-positronium (o-Ps) lifetime the size of free volume holes and its distribution are calculated. At a temperature Tm=311 ± 5 K, the mean hole volume  shows an abrupt and strong increase from 0.15 nm3 to 0.2 nm3, which comes from the melting of side-chains. The reverse effect, attributed to side chain crystallization, was observed during cooling the samples at slightly lower temperatures. The lifetime result of PODMA is compared with semifluorinated polyesters in which the side chain has an oxydecylperfluorodecyl structure (-O-(CH2)10-(CF2)9-CF3). Long chain polymers without side-chains such as polyethylene and short side-chain poly(n-alkyl methacrylate)s: poly(methyl methacrylate) (PMMA) and poly(n-hexyl methacrylate) (PHMA) are also compared with these polymers.
Positron Annihilation Studies in Gamma Irradiated Polyesters
Authors: Consolati Giovanni , Mariani Mario , Quasso Fiorenza
Published: December 2010

Polymerisation and polymer modification are often carried out by means of radiation methods, since irradiation can modify the structure of materials and improve their performance. On the other hand, combined action of ionising radiation and oxygen may induce a degradation of the polymer. Physical changes of different polyesters subjected to gamma irradiation up to 1 MGy are discussed and evidenced by various techniques, mainly viscometry, differential scanning calorimetry and positron annihilation lifetime spectroscopy (PALS). Viscometry monitors variations in the molecular weight. Calorimetric measurements allow one to detect crystallinity changes. PALS evidences possible irradiation effects on the free volume; furthermore, it supplies information on the chemical modifications induced by oxygen. The results can be explained in terms of the main mechanisms induced by gamma irradiation (chain scission, crosslinking and oxydative degradation), although their importance depends on the dose.
Influence of Stacking Fault Energy on the Mechanical Properties and Work Hardening Behavior of Ultra-Fine (UF) Grained Cu and Cu Alloys
Authors: Yang Peng , Yang Hao , Tao Jing Mei , Li Cai Ju , Shen Li , Zhu Xin Kun
Published: December 2010

Ultrafine-grained (UFG) pure Cu and Cu–Zn alloys samples were prepared using cold-rolling under liquid nitrogen temperature to investigate the influence of stacking fault energy (SFE) on the mechanical properties and microstructure. The tensile tests were performed at room temperature with the strain rate of 10-4/s, and the strain hardening rate (SHR) was computed from the engineering stress-strain curves. A decrease in SFE simultaneously improves strength and ductility. The average grain sizes, microstrain, dislocation density and twin density were examined using X-ray diffraction (XRD). X-ray diffraction measurements indicate that grain size decreased and microstrain, dislocation and twin densities increased with decreasing SFE.
Overview on the Corrosion Behavior of Ultra-Fine Grained Materials Fabricated by Equal-Channel Angular Pressing
Authors: Song Dan , Ma Aibin , Jiang Jing Hua , Lin Ping Hua
Published: December 2010

With the development of the ECAP technology, the corrosion behavior of the UFG materials has been investigated in some degree. Two categories of corrosion behaviors of UFG material were discussed in this paper. The large proportion of the non-equilibrium grain boundaries and high residual stress inside of the grain were regarded as the key to affect the corrosion behavior of the UFG materials. The corrosion behavior was also affected by the ECAP factors especially the press pass number and the pressing temperature. Finally some prospects of making UFG materials combined with high mechanical property and good corrosion resistance by ECAP technology were expounded.
Evolution of Microstructure and Mechanical Properties of Titanium Grade 4 with the Increase of the ECAP-Conform Passes
Authors: Polyakov Alexander V. , Gunderov Dmitriy , Raab Georgy I.
Published: December 2010

This work reports on the results of investigation of microstructure change of commercially pure titanium Grade 4 with the increase of the number of ECAP-Conform passes. There has been investigated influence of continuous equal-channel angular pressing by the scheme “Conform” (ECAP-C) on the structure and properties of commercially pure titanium Grade 4. It has been demonstrated that as a result of first two ECAP-C cycles titanium structure is strongly fragmented and deformation bands are formed. With the further increase of ECAP-C passes to 6 the band structure is transformed into ultrafine-grained (UFG) structure with the grain size of about 250 nm. The strength of titanium regularly grows with the increase of the number of ECAP-C passes, while ductility, which settles after first cycle on the level of 12%, is almost not changed with the further strain degree increase. As a result of the subsequent drawing of titanium after ECAP-C its strength additionally increases to 1300 MPa, with retention of ductility about 11%.
Recycling of Aluminum Scrap by Severe Plastic Deformation
Authors: Cui Ji Rang , Guo Wei , Roven Hans Jørgen , Wang Qu Dong , Chen Yong Jun , Peng Tao
Published: December 2010

The production of primary aluminum is an energy costly process. With the global warming being of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive due to its economic and environmental benefits. Recycling of aluminum by new solid state recycling techniques instead of conventional remelting and subsequent refining processing can result in significant energy savings. Severe Plastic Deformation (SPD) techniques have been applied for consolidating nano particles into fully dense materials with good mechanical properties. However, solid state recycling of scraps by SPD is only in the beginning. In the present study, degreasing of aluminum chips from the machine workshop was investigated by a thermal method and chemical treatment. Thereafter, the decoated chips were recycled by Cyclic Extrusion Compression (CEC) at deformation temperatures between 400 and 500 °C. The microstructure and mechanical properties of the recycled aluminum scrap processed by SPD were subsequently investigated. The results show that SPD technology provides a promising alternative for recycling of aluminum scrap. Thermal degreasing of aluminum scrap resulted in more oxidization of aluminum scrap particles. Visible interfaces between chips were observed even at a low magnification.
Development of Textured Coated Superconductor Substrate Tapes by Severe Plastic Deformation Processing
Authors: Bhattacharjee Pinaki Prasad , Tsuji Nobuhiro
Published: December 2010

An attempt has been made to fabricate highly cube textured ({001}<100>) polycrystalline nickel substrate tapes for coated superconductor applications using severe plastic deformation route. For this purpose high purity Ni (~99.97%) plates with widely different average grain size (28 µm or fine grained starting material and 650 µm or coarse grained starting material, respectively) are severely deformed by Accumulative Roll Bonding (ARB) up to an equivalent strain level of (εeq = 6.4) and annealed at various temperatures between 300° to 800°C for one hour. Upon annealing at different temperatures, the fine grained starting material developed a much stronger cube texture than the coarse grained starting material. By suitable annealing treatment near 100% cube textured tape could be obtained in the SPD processed fine grained nickel tapes having a predominantly low angle boundary network. The observed difference in the strength of cube texture in the two materials could be explained based on the oriented nucleation mechanism of formation of cube texture. The present results indicate that SPD processing route such as ARB is very effective in fabricating high purity Ni or Ni alloys intended for coated superconductor substrate applications.
Current Practice and Future Opportunities for Two-Turn ECAP
Authors: Rosochowski Andrzej , Olejnik Lech
Published: December 2010

Equal channel angular pressing (ECAP) is the most popular severe plastic deformation process used to refine grain structure of metals. However, its application exhibits inherent problems of low productivity and poor utilization of material. In order to address these problems, the ECAP channel with two-turns can be used. Historical examples and current applications of this configuration are provided including route BC version of the process. Route C version of two-turn ECAP is illustrated with a scaled-up process used for processing square inch cross section aluminium billets. To address another problem, that of short billets, it is suggested that future applications of two-turn ECAP are based on the new process of incremental ECAP; it enables decoupling feeding of the material and its deformation and thus reduces dramatically the feeding force for billets, plates and sheets.
Ag Powders Consolidated by Reciprocating Extrusion (CEC)
Authors: Richert Maria W. , Richert Jan , Hotloś Agnieszka , Pałka Paweł , Pachla Wacław , Perek-Nowak Małgorzata
Published: December 2010

CEC has unique characteristic. These are applicability of very large strain and deformation under high hydrostatic pressure. Due to these abilities of CEC, several unique phenomena have been observed. One of them is the possibility of consolidation of metallic powders in room temperature to the form of bulk material. In the present paper the consolidation of AgSnBi and AgNi to bulk composites was presented. Applying the deformation of  = 0.42 in the single cycle of CEC, under high hydrostatic pressure, the samples without pores and discontinuities were fabricated. The microstructure observations were performed by optical microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). They show refinement of microstructure at all levels of observation. The nanometric-size subgrains/grains were found inside consolidated granules. The microhardness level of AgSnBi in average achieved level 110 μHV100, and AgNi of about 90 μHV100. The AgSnBi samples consolidated by CEC and additional hydrostatically extruded to wires with 3 mm in diameter average showed 500 MPa yield point.
Obtaining a Homogeneous Fe-C Nanostructure from a Ferritic-Pearlitic Dual-Phase Steel by High Pressure Torsion
Authors: Ning Jiang Li , Ivanisenko Yulia , Wang D. , Murashkin Maxim Yu. , Fecht Hans Jorg
Published: December 2010

We processed a ferritic-pearlitic dual-phase steel under high pressure torsion for three and five rotations at room temperature, the results shew the concurrent processes of the grain refinement of ferrite phase and the decomposition of the cementite lamellae. After three rotations, a non-homogeneous structure was observed. The ferrite structure contained both cellular structure and banded nano-granular structure. The cementite was fragmented to fine particles, aligned along the longitudinal direction of the banded ferrite structure in the local region. After five rotations, a homogeneous mixture of nanoscaled equiaxed ferrite crystallites and cementite particles was obtained, without any visible trace of the former lamellar-type structure or particle alignment. The size distribution of the remaining cementite particles turned to a more narrow distribution skewed to finer sizes especially smaller than 10 nm, since the torsion increased from three to five rotations.
On the Theoretical Limits of Microstructure Evolution in Severe Plastic Deformation
Authors: Divinski Sergiy V. , Padmanabhan K. Anantha , Wilde Gerhard
Published: December 2010

Systematic radiotracer diffusion studies on metals present in severely deformed, ultra-fine grained (UFG) states have revealed the existence of ultra-fast transport paths, which include the so-called “non-equilibrium” grain boundaries and other defects including excess free volume. Under certain experimental conditions percolating porosity is produced even in a ductile metal like pure copper. This result indicates the importance of the cavitation phenomena in severe plastic deformation under those conditions. It is well known that micro-cracking can take place in metals rather early, if the local maximum shear stress equals or exceeds the shear yield stress of the material. However, the growth and propagation of these cracks will be postponed till very late in the deformation process because of the intrinsic ductility of metals, the effect of the superimposed hydrostatic component of the stress system and/ or concurrent dynamic recovery/ recrystallization, when the latter two are present (which is likely to be the case, if the severe plastic deformation operation is successful). That is, the stage in which crack growth and propagation is present represents a material state in which the scope for further deformation is exhausted and fracture processes have taken over. Using these and similar ideas, the load required for equal channel angular pressing, the change in the slope of the Hall-Petch plot with decreasing grain size and the theoretical limit for the smallest grain size attainable in a metal subjected to a severe plastic deformation (SPD) process are predicted and checked against experimental results.
Structure and Properties of Ultrafine-Grained Cu-Cr Alloys after High Pressure Torsion
Authors: Shangina D.V. , Bochvar N.R. , Dobatkin Sergey V.
Published: December 2010

The effect of chromium content (0.75, 9.85, 27%) and initial state on the thermal stability of copper-chromium alloys after severe plastic deformation has been studied by microhardness and electrical resistivity measurements. The stability of the structures is established to depend on the initial state of the alloys and on the content of chromium phase. In the low-alloy bronze, quenching before HPT substantially increases the thermal stability of the alloy relative to that observed after annealing. The softening temperature increases with increasing chromium phase content and reaches 450°C for the alloy with 27% Cr.
Microstructures and Mechanical Properties of Pure Titanium by Dynamic Plastic Deformation
Authors: Sun Jing Li , Wang Jing Tao
Published: December 2010

Dynamic plastic deformation of commercially pure titanium in the temperature range of -100-18°C at the strain rates of 3.0×102-2.5×103, as well as at quasi-static compression were carried out by a Split Hopkinson Pressure Bar technique and conventional compression testing machine respectively. The formation of deformation twins plays a key role on the accommodation of a large amount of strain produced by plastic deformation. Grain orientation has a great influence on the formation of twins. Temperature has smaller effects than strain rate on the evolutions of the microstructures and mechanical properties. The area fraction of twins and their intersections increase with the increasing strain rate and the deformation strain, resulting in refined microstructures and higher hardness values. Strain rate also leads to the change of twin shape (type). While more lenticular twins are observed in samples after quasi-static deformation, there are lots of needle-like twins with straight and long boundaries in samples processed via dynamic plastic deformation. This may imply that different twin systems operate at different strain rate. For the needle-like twins in samples after dynamic plastic deformation, the twin area fraction approaches saturation beyond the true strain of about 0.13, which is significant turning point for twinning rate. This saturated trend is not observed in quasi-static deformation.
Microstructure and Properties of Nanostructured Zirconium Processed by High Pressure Torsion
Authors: Podolskiy Aleksey V. , Bonarski Bartlomiej J. , Setman Daria , Mangler Clemens , Schafler Erhard , Tabachnikova Elena D. , Zehetbauer Michael J.
Published: December 2010

Several structural states of nanostructured zirconium were achieved by high pressure torsion (HPT) at pressures of 2 and 4 GPa with and without subsequent low temperature annealing. The nanostructured Zr was studied by X-Ray Diffraction, Transmission Electron Microscopy and Differential Scanning Calorimetry to reveal the microstructure, phase composition and the thermal stability of this material. The fine grained structure being achieved by HPT had an average grain size of 100-200 nm. It was shown that HPT at 4 GPa leads to a phase transformation from α-Zr to ω-Zr, which has been demonstrated to be reversible by annealing at 300 °C without considerable change of the grain size. The evaluation of texture evolution in Zr during HPT exhibits activity of prismatic slip systems. DSC curves confirm the presence of HPT deformation induced lattice defects and the occurrence of the ω-α phase transition in Zr.
Strain Compatibility and Nanostructuring of Bulk Metallic Materials via Severe Plastic Deformation
Authors: Utyashev Farid Z.
Published: December 2010

Nanostructured (NS) metallic materials can exhibit high strength at room temperature and superplastic properties at elevated temperatures. This enables to enhance their technological and structural properties, when producing various parts from them. For producing NS materials by severe plastic deformation (SPD), the development of effective SPD techniques for practical use is an urgent task. It is shown that solution of such a task should take into account strain compatibility on the macro-, meso- and micro-levels. Not only shear but also rotational deformation mode should be considered. Properties of NS materials and possibilities of their structural applications are considered from this point of view.
TEM and DSC Investigation of the Recovery of a Recycled Aluminum Processed by Equal Channel Angular Extrusion
Authors: Rebhi Atef , Makhlouf Thabet , Couzine Jean Philippe , Champion Yannick , Njah Nabil
Published: December 2010

TEM investigation was performed on a recycled aluminum processed by Equal Channel Angular Extrusion. The aluminum contains many inclusions which were identified to be rich in iron and silicon.This has a substantial effect in dragging recovery. ECAE was performed via routes B and C using a die formed by two channels characterized by the well defined angles =90° and  = 90°. The evolution of the microstructure seems to be similar whether using route B or C. a high dislocation density was introduced since the first passage together with a high density of Frank dislocation loops. The latter are due to a by-passing of inclusions by cross-slip mechanism. Weak beam experiments enable us to investigate the early stages of recovery consisting in the formation of dislocation walls and few dislocation cells. A partial arrangement of dislocations was observed since the first passage through the die. The formation of dislocation cells began already before annealing and progresses at more elevated temperatures. The substantive recovery seems to push recrystallization process to high temperatures. By contrast, DSC investigations show a significant difference: The amount of energy deduced from the area of the peak relative to recrystallization is higher when using route C.
High-Pressure Torsion for Ring Samples in Different Thicknesses
Authors: Iwaoka Hideaki , Harai Yosuke , Horita Z.
Published: December 2010

High-pressure torsion (HPT) was conducted with ring samples of pure Al (99.99%) having different thicknesses. They were cut from an Al plate with 10 mm thickness to dimensions having inner and outer diameters of 23 and 30 mm with thicknesses of 2 mm or 4 mm. HPT was conducted at room temperature under a pressure of 1 GPa at a rotation speed of 1 rpm. It is shown that the strain was introduced more intensely in the mid part on the cross section. This strained region extended with increasing number of revolution and covered throughout the cross section in the 2 mm thickness ring after 30 revolutions. The intense-strained region extended to ~3 mm in the 4 mm thickness ring after 30 revolutions but remains almost the same even after 100 revolutions. The thickness of ~3 mm may be an upper limit to achieve homogeneous introduction of the strained region throughout the cross section.
Processing and Characterization of Pure Nickel Sheets by Constrained Groove Pressing (CGP) Technique
Authors: Kumar S.S. Satheesh , Raghu T.
Published: December 2010

Pure nickel sheets are severe plastically deformed by constrained groove pressing technique at room temperature up to three passes. A total strain magnitude of 3.48 is imparted to the sheets and further processing is limited by initiation of surface microcracks. The grain size evolution studied by optical microscopy reveals significant grain refinement at the end of third pass evidently illustrating the effectiveness of groove pressing technique for grain refinement in sheet materials. Vickers microhardness measured during different stages of groove pressing process clearly describes the deformation behaviour in different segments of slant and flat regions. The change in mechanical properties of constrained groove pressed sheet is evaluated by room temperature tensile and microhardness tests. Results showed considerable increase in strength and hardness during initial passes followed by slight drop during third pass.
The Evolution of Texture in AA 1050 Alloy Deformed by Equal-Channel Angular Pressing
Authors: Kliauga Andrea Madeira , Ferrante Maurizio , Bolmaro R.E.
Published: December 2010

The aim of the present work is to analyze the evolution of texture after ECAP and post deformation heat treatment of an AA1050 alloy produced by roll casting. The initial plate exhibited a weak cube texture at the surface, decreasing in its intensity toward the sheet center, where the deformation texture consisted of Brass and Copper components. ECAP-deformation employed one to four passes at room temperature, following route A in a = 120o die. Texture evaluation was performed by x-ray analysis and by EBSD, using transverse cross section scans. Only the central part of the plate was studied. Results were analyzed by regular texture and orientation distribution function calculations. After 1, 2 and 4 passes the texture changed to a strong {111}// TD and after recrystallization at 350oC for 1 h this main orientation was maintained.
Anomalous Property Evolution during Annealing in HPTed SUS 304 Austenitic Stainless Steel
Authors: Shuro Innocent , Umemoto Minoru , Todaka Yoshikazu , Kuo Ho Hung , Wang Hong Cai
Published: December 2010

SUS 304 austenitic stainless steel (ASS) was deformed by high pressure torsion (HPT) to obtain 100% volume fraction of martensite (α') from a fully austenitic (γ) matrix. Deformation caused an increase in hardness (Hv) from 1.6 GPa in the as annealed state to 6.4 GPa　after HPT. Deformed samples were then annealed in the range 200 – 600oC and peak hardness of 7.8 GPa was observed after annealing at 400oC for 1 hour. Differential scanning calorimetry (DSC) and electrical resistivity tests showed that the deformed alloy undergoes a two stage phase transformation on heating from room temperature up to 700oC. The first stage of transformation was associated with hardening behavior while the second one which is reverse α' → γ transformation resulted in a reduction in hardness. Annealing at 400oC after deformation was found to increase the magnetization saturation (Msat) values.
Research on Temperature Change and Microstructure Evolution of Bore in Steel Target Penetrated by Copper Jets
Authors: Chen Hao , Tao Gang
Published: December 2010

Copper fragments are found to adhere on penetration channel wall after copper jets penetrate steel target, and the research on it is helpful to know microstructure evolution of jets in the process of penetration and cooling time. This paper is based on the observation of bore in steel target penetrated by copper jets, and uses numerical simulation to study the process of copper jets penetration, then the change of temperature and grain size of jets adhered on penetration channel wall can be gotten, and the results agree with the observation of penetration channel wall taken by SEM. From the observations of copper and steel, we can get the conclusion that copper jets are not melted but have dynamic recrystallization in the process of penetration, then copper grain size increases obviously in cooling time, and twins are formed at the same time.
Effect of a Special ECAP Die Configuration on Microhardness Distributions in Pure Aluminum
Authors: Duan Zhi Chao , Langdon Terence G.
Published: December 2010

Experiments were conducted to evaluate the feasibility of using a new ECAP die configuration in which there are arcs of curvature at the intersection of the two channels at both the outer and inner points. The experiments used a configuration in which the radii of curvature were identical at both the outer and inner points since calculations suggest this corresponds to an optimum configuration. High-purity aluminum was pressed using this special die and hardness measurements were taken on cross-sectional planes after pressing. The results show the new die configuration leads to less homogeneity than with conventional ECAP dies.
Contribution of Twins to the Strengthening of Commercial Purity Titanium after Equal-Channel Angular Pressing
Authors: Zhang Yue , Alhajeri Saleh N. , Figueiredo Roberto B. , Gao Nong , Wang Jing Tao , Langdon Terence G.
Published: December 2010

Room temperature equal-channel angular pressing (ECAP) was employed on commercial purity titanium in the present work. Mechanical twining was observed in ~90% grains while the grains were not significantly refined (~10 μm) after ECAP. TEM observations showed that the twins observed under OM are usually composed of a serial of parallel twin bands with a width of ~1 μm. Microhardness and tensile tests showed that such a coarse-grained microstructure combined with a high fraction of mechanical twins has a microhardness of ~ 240 Hv, yield strength of ~ 730 MPa, tensile strength of ~ 740 MPa and elongation to failure of ~ 16%. This yield strength is much higher than 620-640 MPa, the yield strength of ultrafine-grained titanium by 8~12 passes of ECAP at 450 oC with a grain size of 200-300 nm, and is close to ~ 790 MPa, the yield strength of commercial Ti-6Al-4V alloys.
Finite Element Simulation of Die Design for Warm Equal Channel Angular Extrusion Process of AZ31 Alloy and its Experimental Investigation
Authors: Xu Shu Bo , Jing Cai Nian , Ren Guo Cheng , Liu Peng
Published: December 2010

In this paper, a systematic investigation of equal channel angular extrusion/Pressing (ECAE, ECAP) process on the AZ31 alloy and die design is performed by using numerical simulation. The stress distributions on the die were obtained, and general consideration of the die during the whole pressing process was given. The numerical results revealed that effective stress distribution at the corner of the cavity and the extruded load during extrusion processes was effect by channel angles and friction factor. From the simulations, it was found that the closer the die corner is, the higher stress value results can be acquired. And the effective stress concentration in ECAP die cavity corner. The extruding load fell rapidly when the angular angle increasing. With the increase of friction factor, extruding load also increased significantly. The proposed method can serve as preconditions to analyze the abrasion and fatigue of ECA Pressing die. Besides, this method also provides a feasible way for other die stress analysis.
High Strength and Electrical Conductivity of UFG Copper Alloys
Authors: Champion Yannick , Couzine Jean Philippe , Tusseau Nenez S. , Bréchet Yves , Islamgaliev Rinat K. , Valiev Ruslan
Published: December 2010

Copper based materials are still the most attractive low resistivity materials for microelectronics and electrotechnics applications, though, all variants developed to combine strength and conductivity, such as solid solutions and composites, suffer from decay in electric conductivity while strength is increased . In a addition, linear decay was also conjectured for pure copper when grain size is refined below the UFG and nanostructured domains (except when grain boundaries are pure twins). Copper alloys with low content of silver and chromium were prepared by high pressure torsion (HPT) with various annealing conditions. Vickers hardness and electric resistivity in the temperature range of 4K-340K, were measured as well as microstructural characterizations were performed using quantitative X-ray diffraction. Depending on the annealing conditions the alloys exhibit from 25% to 75% of IACS electric conductivity at room temperature and hardness in the range of 200 Hv. Origins of both high strength and high electric conductivity were investigated from microstructures analysis, using transmission electron microscopy and mechanical testing.
Microstructure Stability and Creep Behaviour of a Cu-0.2wt.%Zr Alloy Processed by Equal-Channel Angular Pressing
Authors: Dvořák Jiří , Král Petr , Kvapilová Marie , Svoboda Milan , Sklenička Václav
Published: December 2010

A dispersion-strengthened Cu-0.2 wt.% Zr alloy was subjected to equal-channel angular pressing (ECAP) at room temperature for up to 12 passes through route BC using a die having a channel angle of 90°. The microstructural investigations were performed using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Tensile creep tests were conducted at temperature 673 K and at the applied stress in the range from 80 to 180 MPa. The migration of boundaries and subsequent grain growth were restricted by Cu9Zr2 precipitates. The study was performed in order to evaluate the effects of severe plastic deformation and precipitation on creep behaviour and microstructure of the pressed alloy. It was found that creep behaviour is strongly dependent on number of ECAP passes. The pressed alloy after up to 4 ECAP passes exhibited a considerable improvement in creep properties in comparison with the unpressed alloy.
Enhancing Strength and Maintaining Ductility of Mg-3%Li-1%Sc Alloy by Equal Channel Angular Pressing
Authors: Yang Hua Jie , Shao Xiao Hong , Li S.X. , Wu Shi Ding , Zhang Zhe Feng
Published: December 2010

Equal channel angular pressing (ECAP) has been conducted on as-cast Mg-3%Li-1%Sc alloy for four-passes to study the microstructure uniformity and tensile properties. After ECAP, the microstructure become muddled, contains about 65% of deformed coarse grains with abundant low angle grain boundaries and about 35% of recrystallized small grains. Meanwhile, a strong basal texture is formed in the ECAP sample. The texture type of the recrystallized grains and the deformed grains are the same, however, the texture strength of the recrystallized grains is much lower than the deformed ones. Tensile strength is improved effectively and the elongation is maintained after ECAP. The increment of strength results from the microstructure refinement and residual dislocations produced by ECAP, while the recovery of ductility may be attributed to a shear type texture formed in the alloy during ECAP.
Processing by Severe Plastic Deformation: Historical Developments and Current Impact
Authors: Langdon Terence G.
Published: December 2010

It is well established that processing through the application of severe plastic deformation (SPD) provides opportunities for achieving exceptional grain refinement to the submicrometer or even the nanometer level. This paper provides a brief summary of the developments in SPD processing from the earliest days in ancient China to research at the present time. It is shown that SPD research and bulk nanostructured materials have had a significant impact on the field of Materials Science. Using citation data and examining the publication records for five major journals, the analysis shows research in these areas accounts for a large fraction of the top ten all-time most cited papers in these journals.
Influence of Annealing on the Structure and Mechanical Properties of Ultrafine-Grained Alloy Ti-6Al-7Nb, Processed by Severe Plastic Deformation
Authors: Polyakova Veronika , Semenova Irina P. , Valiev Ruslan
Published: December 2010

This work is devoted to enhancement of strength and ductility of the Ti-6Al-7Nb ELI alloy, which is less harmful from medical point of view for human body in comparison to Ti-6Al-4V. It has been demonstrated that formation of an ultrafine-grained structure in the alloy with the help of equal-channel angular pressing in combination with heat and deformation treatments allows reaching high strength (UTS = 1400 MPa) and sufficient ductility (elongation 10 %).