bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis on the Structural Reliability of Solid Rocket Motor Grains
Authors: Long Bing , Chang Xin Long , Jian Bin , Lai Jian Wei
Published: April 2012

Based on Integral Stochastic Finite Element Method (ISFEM), the structural reliability of solid propellant grain was analyzed. Viscoelastic finite element method was determined and ISFEM is utilized to improve calculation efficiency. The thermally accelerated aging experiments at 40°C，50°C，60°C and 70°C were carried out, and the mechanical property parameters were investigated. Considering the randomness of Poisson’s ratio and relaxation modulus, structural reliability and its variation tendency solid rocket motor grain under the ignition pressurization case were investigated in combination with failure criterion. The results show that the reliability of SRM grain descends not evidence before twelve years, but quickly descends after 12 years.
FEM Analysis of RSW and LBW Implementation on Side Wall Penal Assembly of Stainless Steel Railway Vehicles
Authors: Wang Wen Quan , Wang Chun Sheng , Tan Fu Xing
Published: April 2012

Comparative finite element method (FEM) analyses of resistant spot welding (RSW) and laser beam welding (LBW) on stainless steel railway vehicles to assembly the framework and the side wall penal were conducted. The stress and strain of RSW joint and LBW lap joint were calculated under the same loading conditions by FEM simulation, respectively. The analyses revealed that not only the stress concentration occurred but also the maximum stress existed in the RSW joint compared with LBW lap joint under the same load. In contrast, LBW technique had more advantages than that of RSW technique in joining the car body framework and side wall penal of railway vehicles in the respects such as smaller deformation, better air tightness, and better appearance of car body and higher efficiency of processing.
Formation and Migration Energy of Native Defects in Silicon Carbide from First Principles: An Overview
Authors: Roma Guido , Bruneval Fabien , Ting Li Ao , Bedoya Martínez Olga Natalia , Crocombette Jean Paul
Published: April 2012

We present here an overview of native point defects calculations in silicon carbide using Density Functional Theory, focusing on defects energetics needed to understand self-diffusion. The goal is to assess the availability of data that are necessary in order to perform kinetic calculations to predict not only diffusion properties but also the evolution of defect populations under or after irradiation. We will discuss the spread of available data, comment on the main defect reactions that should be taken into account, and mention some of the most recent promising developments.
A Reactive Force Field Molecular Dynamics Simulation Study of Corrosion of Nickel
Authors: Assowe O. , Politano Olivier , Vignal Vincent , Arnoux Patrick , Diawara B.
Published: April 2012

The interaction of water molecules on a nickel surface was studied using ReaxFF (reactive force field) molecular dynamics. This approach was originally developed by van Duin et al. to study the hydrocarbon chemistry and the catalytic properties of organic compounds. To our knowledge, this method has not been used to study the corrosion processes of nickel exposed to water, which is what we set out to achieve in the present investigation. To do so, calculations were first performed using ReaxFF in order to reproduce certain well-known properties of pure nickel and nickel-water systems. This allowed us to study the adsorption of a single water molecule interacting with an optimized nickel surface. We also investigated the interaction of 405 molecules of water (ρ=0.99 g.cm-3) on the (100), (110) and (111) surfaces of a single crystal of nickel at 300 K. The results show that a water bilayer is adsorbed on nickel surfaces: the first water layer is directly bonded to the surface, whereas the molecules in the first and second layers are held together by hydrogen bonds.
Grain Boundary Diffusion of Silver in Copper-Iron Alloys
Authors: Vaganov Danil V. , Zhevnenko Sergei , Terentyev Yuri
Published: April 2012

Grain boundary (GB) diffusion of Ag in Cu-based alloys with Fe (0, 0.14, 0.29, 0.43, 0.55 and 0.99 at. % Fe) was investigated. The experiments were performed at 600, 650 and 700 °C, which corresponded to B-regime. It was proved by the presence of diffusion wedges. The triple product of silver GB diffusion was obtained by measuring of angle at the top of isoconcentration profiles which was detected by electrochemical etching. It was shown that iron decreased the triple product at higher temperatures and didnt affect significantly at lower temperatures. SEM investigation showed the presence of small (10-100 nm) precipitates on the copper grain boundaries. Analysis of particles composition by Auger electron spectroscopy indicated higher concentration of iron comparing with the alloy composition.
The Formation of Liquid Metal Channels Network under Grain Boundary Wetting in the Cu-Bi System
Authors: Novikov A. A. , Petelin A.L. , Bokstein Boris S. , Zhevnenko S. N. , Orelkina D. I.
Published: April 2012

Grain boundary liquid grooving process takes place during the contact of solid metal phase with the metal melt. The liquid bismuth network formation along grain boundaries (GB) and triple junctions (TJ) was investigated in copper polycrystalline samples. The experimental observation in situ technique of Bi penetration through the Cu plate was used. Microscopic images of the liquid channels network were obtained. The temperature dependencies of GB and TJ effective penetration depths were determined. The effect of the GB and TJ diffusion on the liquid channels growth mechanism was discussed.
A TEM Study of Bubbles Growth with Temperature in Xenon and Krypton Implanted Uranium Dioxide
Authors: Michel Amélie , Sabathier C. , Carlot G. , Cabié M. , Bouffard S. , Garcia Philippe
Published: April 2012

Transmission electron microscopy (TEM) characterizations were carried out on a set of UO2 thin foils previously implanted at room temperature with 400 keV Xe2+ and 250 keV Kr2+ ions at the fluence 7.1015 at.cm-2 (equivalent to 1 at.%/at. UO2). The experiment was devoted to the study of the evolution of the fission gases bubbles populations with increasing temperature. Annealings were performed in the laboratory furnace at 600°C, 800°C, 1000°C for 12h, 1400°C for 4h and 1500°C for 2h under Ar-5%H2 atmosphere. For each annealing condition and for as-implanted specimens the bubble population has been characterized in size and number density. A comparison between Xe and Kr has been done that showed a similar behaviour. Globally, from the as-implanted sample to the 1500°C annealed, the bubbles growth phenomenon and the microstructure evolution with temperature was put in relieve.
Specific Aspects of Internal Corrosion of Nuclear Clad Made of Zircaloy
Authors: Minne J.B. , Desgranges Lionel , Optasanu Virgil , Largenton N. , Raceanu Laura , Montesin Tony
Published: April 2012

In PWR, the Zircaloy based clad is the first safety barrier of the fuel rod, it must prevent the dispersion of the radioactive elements, which are formed by fission inside the UO2 pellets filling the clad. We focus here on internal corrosion that occurs when the clad is in tight contact with the UO2 pellet. In this situation, with temperature of 400 °C on the internal surface of the clad, a layer of oxidised Zircaloy is formed with a thickness ranging from 5 to 15 µm. In this paper, we will underline the specific behaviour of this internal corrosion layer compared to wet corrosion of Zircaloy. Simulations will underline the differences of stress field and their influences on corresponding dissolved oxygen profiles. The reasons for these differences will be discussed as function of the mechanical state at inner surface of the clad which is highly compressed. Differences between mechanical conditions generated by an inner or outer corrosion of the clad are studied and their influences on the diffusion phenomena are highlighted.
Optimisation of Metallic Interconnects for Hydrogen Production by High Temperature Water Vapour Electrolysis
Authors: Ardigo M.R. , Parry Valérie , Popa Ioana , Chevalier Sébastien , Chandra-Ambhorn Walairat , Phakpeetinan P. , Wouters Yves
Published: April 2012

For economical and environmental reasons, hydrogen is considered as a major energetic vector for the future. Hydrogen production via high temperature water vapour electrolysis (HTE) is a promising technology. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800°C enables the use of metallic materials as interconnects. Chromia forming alloys are among the best candidates. The interconnect material chosen in the present study is a ferritic stainless steel with 18% chromium content. High temperature corrosion resistance and electrical conductivity of the alloy was tested in both cathode (H2/H2O) and anode (O2/H2O) atmospheres. Corrosion products were then characterized by SEM-EDX and XRD. Moreover chromium evaporation measurements were carried out under anode atmosphere.
Diffusion in Internal Oxidation Reactions
Authors: Young David J.
Published: April 2012

When an alloy component is selectively oxidised but cannot reach the surface quickly enough to form a scale, then internal oxidation results. In this process, a gas phase oxidant dissolves in an alloy and diffuses inwards, reacting with a dilute solute metal to precipitate metal oxide or carbide, etc. Penetration kinetics are parabolic, the rate being controlled by oxidant diffusion and the concentration of reacting metal. Rates are predicted from classical oxidation theory on the basis that the reaction product is exceedingly stable, no solute metal remains in the reacted alloy, and oxidant diffusion is via a solvent metal matrix. This paper is concerned with situations where these approximations fail: the development of low stability precipitates and the growth of elongated precipitates which allow interfacial diffusion of the oxidant. Effects on the rates of internal oxidation are discussed.
Initial Aluminizing Steps of Pure Nickel from Al Micro-Particles
Authors: Bonnet G. , Mollard M. , Rannou B. , Balmain J. , Pedraza-Diaz Fernando , Montero X. , Galetz M. , Schütze Michael
Published: April 2012

Novel, unconventional type of high temperature coating systems can be elaborated by depositing Al micro-particles on nickel base substrates, using an appropriate binder, and converting them into a thermal barrier type coating by a two-step heat treatment under argon. Final result is a coating structure consisting of a quasi-foam top coat, constituted by spherical hollow alumina particles, surmounting a β-NiAl diffusion layer able to form during high-temperature oxidation a protective alumina scale. In this work, pure nickel was employed as a model material to evaluate the effects of moderate temperatures (550-700°C), dwelling times and Al particle size on the final characteristics of the coatings. Almost no diffusion occurred below 600°C. In contrast, a Ni2Al3 layer very quickly formed at 650 or 700°C. The rapidity of coating formation was attributed to the appearance of a liquid phase at the coating/substrate interface. The increase of dwelling time did not provide any significant thickness increase as the Al particles got practically emptied after 2h. In addition, the use of different micro-sized particles resulted in similar Al diffusion coatings under the investigated conditions.
Effect of Mn Thickness on the Mn-Ge Phase Formation during Reactions of 50 nm and 210 nm Thick Mn Films Deposited on Ge (111) Substrate
Authors: Abbes Omar , Xu Feng , Portavoce Alain , Girardeaux Christophe , Hoummada Khalid , Le Thanh Vinh
Published: April 2012

An alternative solution for producing logic devices in microelectronics is spintronics (SPIN TRansport electrONICS). It relies on the fact that in a magnetic layer, the electrical current can be spin polarized. To fabricate such components, a material whose electronic properties depend on its magnetic state is needed. The Mn-Ge system presents a lot of phases with different magnetic properties, which can be used for spintronics. The most interesting phase among the Mn-Ge system is Mn5Ge3 because of its stability at high temperatures, its Curie temperature which is close to room temperature and its ability of injecting spin-polarized electrons into semiconductors. In this paper, we have combined Reflection High-Energy Electron Diffraction (RHEED) and X-ray Diffraction (XRD), to study the sequence of formation of MnxGey phases during reactive diffusion of both a 50 nm and a 210 nm thick Mn films deposited by Molecular-Beam Epitaxy (MBE) on Ge (111).
Diffusion in Binary and Pseudo-Binary L12 Indides, Stannides, Gallides and Aluminides of Rare-Earth Elements as Studied Using Perturbed Angular Correlation of 111In/Cd
Authors: Newhouse Randal L. , Minish Justine , Collins Gary Scott
Published: April 2012

Diffusional jumps can produce fluctuating electric field gradients at nuclei of jumping atoms. Using perturbed angular correlation of gamma rays (PAC), jumps of probe atoms cause nuclear quadrupole relaxation that can be fitted to obtain the mean jump frequency. An overview is given of the application of this approach to highly ordered intermetallic compounds having the L12 (Cu3Au) crystal structure. New results are then presented for jump frequencies of 111In/Cd probe atoms in pseudo-binary L12 compounds of the forms In3(La1-xPrx) and (In1-xSnx)3La. For the mixed rare-earth system, jump frequencies are found to scale with composition between jump frequencies of the end-member phases In3La and In3Pr. However, for the mixed sp-element system, a large decrease in jump frequency is observed as Sn atoms substitute for In-atoms. This difference in behavior appears to depend on whether atomic disorder is on the diffusion sublattice (In-Sn substitution), as opposed to a neighboring sublattice (La-Pr substitution), whether or not there is a difference in diffusion mechanism between end-member phases, and/or whether or not there is a valence difference between the mixing atoms. All three conditions apply for only (In1-xSnx)3La.
Diffusion Mechanism in the μ Phase in Nb-X (X= Ni, Co, Fe) Systems
Authors: Balam S.S.K. , Ravi R. , Paul Aloke
Published: April 2012

Nb is one of the common refractory elements added in Ni, Co and Fe based superalloys. This lead to the formation of brittle topological close packed (tcp) μ phase, which is deleterious to the structure. It mainly grows by interdiffusion and in the present article, the interdiffusion process in different Nb-X (X=Ni, Co, Fe) systems is discussed. The activation energy for interdiffusion is lower in the Co-Nb system (173 kJ/mol) than Fe-Nb system (233 kJ/mol), which is again lower than the value found in the Ni-Nb system (319.7 kJ/mol). The mole fraction of Nb in this phase is less than Fe or Co at stoichiometric compositions in the Nb-Fe (that is Fe7Nb6) and Nb-Co (that is Co7Nb6) systems. On the other hand, the mole fraction of Nb is higher than Ni in the same phase (Ni6Nb7) in Ni-Nb system. However, in all the phases, Nb has lower diffusion rate. Possible diffusion mechanism in this phase is discussed with respect to the crystal structure.
Separation in ε-Phase of BiPb Alloy under Mega-Gravity
Authors: Okayasu Satoru , Ono Masao , Nishio Taichiro , Iguchi Yusuke , Mashimo Tsutomu
Published: April 2012

Homogeneous Bi-Pb alloy samples in the ε-phase are treated under mega-gravity centrifugal acceleration field. Atomic sedimentation in solid and associated partial crystallization occurs during the treatment. Small differences of densities in the ε-phase are enhanced under the mega-gravity, and they cause the separation of the ε-phase between fully packed hcp structure of the Bi3Pb7 and partially defected hcp structure of the Bi3Pb7-δ. The compositional graded superconducting alloy is obtained in the latter. Partially melt-growth occurs in the latter and microstructure of Pb is formed along the gravity field associating with the formation of highly oriented the (211) phase of Bi3Pb7-δ. The superconductivity parallel to gravity is Pb, and perpendicular to gravity is Bi3Pb7-δ as the result. Superconducting properties differs between the separated two phases.
Compositionally Gradient Thin Film Deposition by Pulse Laser Ablation under High Gravity
Authors: Nishiyama Takashi , Kajiwara Takashi , Nagayama Kunihito
Published: April 2012

A compositionally graded thin film of Fe/Si was fabricated by a gravity-assisted pulsed laser ablation (GAPLA) system. By this method, a compositionally graded structure along gravity direction was successfully produced under a gravity field of 5,400 G. Systematic experiments were conducted by several parameters, including gravity, distance between target and substrate, and laser fluence in case of typical target material of iron disilicide (FeSi2). We demonstrate that the atomic fraction of Fe, the heavier component of the thin film, showed increasing spatial distribution with the direction of gravity. Relatively high laser fluence as well as a very narrow space between the target and the substrate are found to be essential to the compositionally gradient of thin film.
Study of the Growth Mechanism of some Oxide Scales on Alloy 230 in High Temperature Vapor Electrolysis (HTVE) Conditions
Authors: Guillou Sebastien , Desgranges Clara , Chevalier Sébastien
Published: April 2012

Alloy 230 (also named Haynes® 230) was tested as interconnect for production of hydrogen via High Temperature Vapor Electrolysis (HTVE). Samples were oxidized at 800°C in the both atmospheres representative of the HTVE operating conditions: Ar-1%H2-9%H2O (for cathode side) and air (for anode side). The high temperature oxidation behaviour was studied in both atmospheres together with the electrical conductivity of the thermally grown oxide scales. Oxidation kinetics indicated lower oxidation rate in H2/H2O compared to air (kp = 3.8 .10-15 g2.cm-4.s-1 in H2/H2O and kp = 1.6 .10-14 g2.cm-4.s-1 in air). The corrosion products were characterized by scanning electron microscopy associated with X-ray diffraction analyses and energy dispersive X-ray analyses. The sample electrical behaviour was evaluated by determining the Area Specific Resistance (ASR). The ASR was higher in H2/H2O (ASR = 1 ohm.cm2) than in air (ASR = 0.04 ohm.cm2). The diffusion of proton or hydrogen containing species through the oxide scale is proposed to be responsible for the increase of the electrical conductivity in cathode side.
A Brief Analysis of Domestic Construction and Demolition Waste Recycling Techniques
Authors: Cui Su Ping , Liu Qi Dong , Yan Jian Hua , Du Xin
Published: April 2012

In this paper, the construction and demolition waste (C&D waste) recycling techniques in China is summarized, and proposed the C&D waste recycling suggestions in this foundation. The C&D waste can be divided into construction waste, decorating waste, demolition waste and natural disaster ruin waste. In addition to be buried, domestic C&D waste can be made into landscape material, roadbed material, recycled aggregate, recycled brick, recycled concrete, recycled admixture and so on. The state should establish positive promoting policies, improve the recycling industrial chain, and promote the healthy development of the C&D waste recycling.
Effect of Substitution of Recycled Aggregate by Natural Aggregate on Related Properties of Blended Aggregate and Asphalt Mixture
Authors: Zhu Ji Qing , Wu Shao Peng , Zhong Jin Jun , Wang Dong Ming
Published: April 2012

The effect of substitution of recycled aggregate by natural aggregate on related properties of blended aggregate (without asphalt and mineral filler) and asphalt mixture was investigated in this paper. Demolition waste obtained from Wenchuan earthquake-damaged buildings was used as recycled aggregate in AC-25 asphalt mixture. The absorption, specific gravity and strength of both blended aggregate and asphalt mixture were tested. Results indicate that fine recycled aggregate is not suitable to be used in asphalt mixture because of its high absorption. The substitution of recycled aggregate by natural limestone aggregate can decrease the asphalt absorption and increase the effective specific gravity and indirect tensile strength of asphalt mixture. The quantitative relationship between related properties of blended aggregate and asphalt mixture was obtained. It was concluded that the substitution of recycled aggregate by natural aggregate is a feasible way to use recycled aggregate in asphalt mixture.
Effects of Sasobit on Rheological Properties of Asphalt Binders
Authors: Liu Zhi Fei , Liu Jia Ping , Hong Jin Xiang , Huang Chong
Published: April 2012

Research in the laboratory was carried out to determine if addition of warm mix asphalt additive (Sasobit) has potential to reduce the temperature comparison with control mix. To fulfill this purpose five types of asphalt binders have been produced with a Sasobit additive in concentration range from 0 to 10% by weight of the asphalt. Viscosity test and dynamic shear rheometer test are conducted for the investigation of effects of Sasobit on rheological properties characteristics of binders. Viscosity tests on binders indicated that the Sasobit binders had significantly lower viscosities compared to control binders at the temperature above 100°C, indicating that Sasobit can reduce the mixing and compaction temperatures above the melting point of Sasobit. Sasobit modified binders are more sensitive cracking and had more excellent rutting resistance properties at service temperatures compared with original bitumen. Based on the test results, the suggest content of Sasobit addition is 3% by weight.
Clean Synthesis of Silver-Silica Aerogels via Supercritical Drying and Impregnation
Authors: Li Xiu Yan , Shen Jun , Du Ai , Zhang Zhi Hua , Yang Hui Yu
Published: April 2012

A simple and clean route to synthesize nano-scale mesoporous silver-silica composite aerogels was described here. The composite aerogels were obtained by adding a silver colloid to an about-to-gel silica sol prepared and then dried in supercritical anhydrous ethyl alcohol. The silver colloid and composite aerogels with silver content of 0wt%, 0.5wt%, 1wt% and 3.5wt% were characterized by UV-visible absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and N2 Brunauer-Emmett-Teller (BET). The results show that silver nanoparticles with size about 40nm are successfully impregnated into the spongy porous structure of silica. The surface area decreases from 845 to 443m2/g with the increase of silver content. And the nanoscopic surface and bulk properties of each component are retained in the solid composite.
Finite Element Method on Electromagnetic Shaping for Aluminum Alloy Sheet Parts
Authors: Hu Jian Hua , Du Xue Chao , Song Xue Mei , Cai Heng
Published: April 2012

In this paper, the distribution of magnetic forces of uniform pressure coil and the electromagnetic shaping with die of aluminum alloy 1060 surface parts will be researched using the finite element method. The results show that: Uniform pressure coil can produce a uniform magnetic pressure on the sheet; The springback after electromagnetic aimed stamping is smaller than the springback after normal stamping; Before achieving the best results, with the discharge energy increases, springback will be smaller; with greater punch and die clearance, greater energy will be needed to achieve the best effect; Too large discharge energy will lead sheet bounce after punch, springback increases.
Influence of Fluorine on the Structure and Luminescence Properties of Sm3+ Doped Strontium Titanium Silica Glass
Authors: Hong Li , Qing Ye , Ning Hua
Published: April 2012

Transparent oxide glass is the ideal luminescent host materials used in luminescence, optical communication, fiber optic amplifiers and other areas in the future as its stable physical and chemical properties, high rare-earth ion solubility and easy forming, etc. In this paper, SiO2-TiO2-SrO-SrF2-Sm2O3 glasses with different content of fluorine were prepared by the melting-quenching method. Influence of fluorine on the structure and luminescence properties of the glass were studied by Fourier transform infrared spectroscopy, X-ray fluorescence spectrometer, UV-visible spectrophotometer and fluorescence spectrometer. The results show that there is a new peak at 930 cm-1 in IR spectra because of fluorine, and the intensity of the peak increases with the increases of fluorine content. The glass absorbed ultraviolet rays strongly, and transmitted light well in visible spectra region. The strongest absorption peak is around 403 nm. Fluorine content doesn’t affect the positions and shapes of peaks in excitation and emission spectra, but the luminescent intensity increases with the increase of fluorine content.
Phase Separation and Luminescence of Eu2O3 Doped Boron Silicate Glass
Authors: Tian Pei Jing , Cheng Jin Shu , Zhang Gao Ke , Yang Qin
Published: April 2012

Eu2O3 doped boron silicate glass appearing phase separation have been prepared and characterized. The heat treatment temperature was determined by DTA, the microstructure and optical properties of the glass were studied by SEM and fluorescence spectra. The adding of Eu2O3 restrained the phase separation and crystallization of the glass. Eu ions exist in the glass samples as the Eu3+ ions, rather than the Eu2+ ions. As the heat treatment temperature increases, the phase separation region increased gradually, and the luminescent intensity increases.
Preparation of Polyacrylamide Emulsion Modified Waterproof Desulfurization Building Gypsum
Authors: Wu Qi Sheng , Li Shui Ping , Zhang Chang Sen
Published: April 2012

In this paper the waterproofness of desulfurization building gypsum had been improved by polyacrylamide(PAM) emulsion. The effect of dosage and molecular weight of PAM emulsion on the physical mechanical properties and waterproofness have been investigated and XRD, SEM have been employed to determine the phase compositions of the material. The results showed that softening coefficient of desulfurization building gypsum increased from 0.34 to 0.69, the compressive strength after soaking in water for 24 h increased from 4.9MPa to 6.1 MPa. The effect of PAM emulsion modification prepared by PAM with molecular 3 million weight of on desulfurization building gypsum are better than with molecular weight of 5 million. The effect mechanism of PAM on desulfurization building gypsum was that PAM reacts with the Ca2+ cations produced desulfurization building gypsum hydration to form the ionic compounds acting as a filler and reinforcement in the porosity of desulfurization building gypsum, and also PAM covered the surface of desulfurization building gypsum particles to prevent the crystallization of CaSO4.2H2O.
Combined Effect of Mineral Admixture and Curing Condition on Pore Structure of Concrete
Authors: Shui Zhong He , Geng Hai Ning , Duan Ping
Published: April 2012

The effect of mineral admixture and curing condition in pore structure of concrete was studied in this paper. Concrete samples with different component were prepared firstly, and then they were put into standard condition, fresh water and salt environment that produced artificially respectively at 20 °C. After the experiments of curing at 3, 28 and 180 days pore structure were tested by mercury intrusion porosimetry (MIP). The results obtained reveal that with the increase of the age, the pore structure degradation impact in salt environment of concrete increase dramatically. When at 28 days, total pore volume and porosity of concretes in fresh water is lower by 20% and 5% respectively than the ones with larger mean pore size and critical aperture in salt environment, which represents pore refinement in fresh water had a good effect. Compared to the salt environment erosion, it can be found that the impact of pore refinement in fresh water is more significant.
Thermo-Mechanical Processing in a Synchrotron Beam
Authors: Liss Klaus Dieter
Published: April 2012

Well collimated, high energy X-rays of 90 keV from synchrotron sources have been used to study metals undergoing plastic deformation in-situ, in real time and in the bulk of the materials. The spottiness of poorly illuminated Debye-Scherrer rings showing reflections from individual crystallites is analyzed to obtain grain statistics, mosaic spread and orientation. Upon cold deformation, coarse grained materials show fingerprints of sub-grain formation, grain rotation, grain refinement and the evolution from a single grain into the asymptotic texture. Heating of metals under continuous load drives the observation through the regimes of phase transformation and grain relationships therein, grain coarsening, dynamic recovery and dynamic recrystallization. The paper points out these different phenomena which were observed without precedence.
Stored Energy of Goss Grains in Fe-3%Si Steel after Cold Rolling
Authors: Park Hyung Ki , Kim Se Jong , Han Heung Nam , Han Chan Hee , Hwang Nong Moon
Published: April 2012

According to a sub-boundary enhanced solid-state wetting mechanism, abnormally-growing Goss grains in Fe-3%Si steel are expected to have exclusively sub-boundaries which would be formed during primary recrystallization. This microstructural feature is related with the stored energy of Goss grains after cold rolling. To investigate the possibility of existence of sub-boundary exclusively in Goss grains after primary recrystallization, the deformation feature focused on stored energy of Goss and other specific orientations was analyzed by crystal plasticity finite element method calculations. The calculations indicated that Goss grains stored the lowest energy among the orientations formed after plane strain deformation.
EBSD-Based Techniques for Characterization of Microstructural Restoration Processes during Annealing of Metals Deformed to Large Plastic Strains
Authors: Godfrey Andrew , Mishin O.V. , Yu T.B.
Published: April 2012

Some methods for quantitative characterization of the microstructures deformed to large plastic strains both before and after annealing are discussed and illustrated using examples of samples after equal channel angular extrusion and cold-rolling. It is emphasized that the microstructures in such deformed samples exhibit a heterogeneity in the microstructural refinement by high angle boundaries. Based on this, a new parameter describing the fraction of regions containing predominantly low angle boundaries is introduced. This parameter has some advantages over the simpler high angle boundary fraction parameter, in particular with regard to data collected from electron-backscatter diffraction investigations, where boundaries with very low misorientation angles cannot be reliably detected. It is shown how this parameter can be related to the recrystallization behavior. Another parameter, based on mode of the distribution of dislocation cell sizes is outlined, and it is demonstrated how this parameter can be used to investigate the uniformity, or otherwise, of the restoration processes occurring during annealing of metals deformed to large plastic strains.
Loss of High Angle Boundary Area during Annealing a Cryo-SPD Processed Al-Alloy with a Nano-Scale Lamellar Grain Structure
Authors: Huang Y. , Zahid G.H. , Prangnell Philip B.
Published: April 2012

The grain structure and texture evolution during annealing an Al-0.13%Mg submicron grained alloy, deformed by plane strain compression (PSC) at cryogenic temperatures, has been investigated. On annealing the grain structure coarsened and transformed from lamellar to equiaxed. But, remarkably, the fraction of low angle boundaries (LABs) increased, from less than ~ 25% to ~50% above 300 °C, leading to instability and discontinuous coarsening at higher temperatures. The surprisingly large increase in LAB fraction on annealing is shown to be related to orientation impingement originating from the strong texture present after PSC in liquid nitrogen.
Measuring and Modelling the Microstructures of Two-Phase Aluminium Alloys after Deformation
Authors: Humphreys John F. , Bate Pete S. , Gholinia Ali , Brough Ian
Published: April 2012

The effect of second-phase particles on the deformation and annealing behaviour of metals is re-assessed in the light of some new techniques. Using an EBSD method which provides much improved angular resolution, the effect of small non-deformable particles on the homogeneity of the deformation microstructure has been quantified. The presence of micron sized second-phase particles alters the deformation microstructure adjacent to particles, and a 3-d investigation of the deformation structures associated with large (>1μm) second-phase particles in cold rolled aluminium alloys has been carried out using 3-d FIB sectioning combined with EBSD, and the microstructures compared with the predictions of 3-d CPFEM modelling. The effects of grain orientation, strain and particle size have been investigated, and the results compared with earlier TEM investigations of such microstructures.
Recrystallization in Severely Deformed Aluminum
Authors: Sidor Jurij J. , Petrov Roumen H. , Kestens Leo
Published: April 2012

Qualitative and quantitative texture changes are investigated in a severely deformed 5xxx series aluminum alloy. Unusual recrystallization textures are observed after a rolling strain of more than 97% in thickness reduction. The influence of both strain amplitude and strain mode on the development of the deformation and recrystallization textures is discussed based on experimental data and results of crystal plasticity calculations.
Ultrafine Grain Evolution in Austenitic Stainless Steel during Large Strain Deformation and Subsequent Annealing
Authors: Belyakov Andrey , Tsuzaki Kaneaki , Kaibyshev Rustam
Published: April 2012

The structural changes in a 304-type austenitic stainless steel during large strain cold rolling and subsequent annealing were studied. The severe deformation resulted in the development of highly elongated grains/subgrains aligned along the rolling axis. The transverse grain/subgrain size rapidly decreased to its minimal value of about 50 nm at relatively small strains of ~1 and then hardly changed upon following deformation. Such a structural response on cold working was associated with multiple twinning resulting in fast grain subdivision. The processing was accompanied by a partial martensitic transformation resulting in a decrease of austenite volume fraction to about 0.35 after straining to ε = 4.0. Isochronal annealing for 30 min was characterised by a gradual coarsening of grains, the average size of which increased to about 200 nm after heating to 800°C. The high elongation of ferrite grains facilitated simultaneous homogeneous nucleation of austenite grains throughout the matrix upon heating; and, therefore, promoted the development of ultrafine grained structure with the size of structural elements well below 1 micron.
Predictive Theory for the Grain Boundary Character Distribution
Authors: Barmak Katayun , Eggeling Eva , Emelianenko M. , Epshteyn Y. , Kinderlehrer David , Sharp R. , Ta'asan Shlomo
Published: April 2012

Mesoscale experiment and simulation permit harvesting information about both geometric featuresand texture in material microstructures. The grain boundary character distribution (GBCD) is an em-pirical distribution of the relative length (in 2D) or area (in 3D) of interface with a given lattice misori-entation and grain boundary normal. During the growth process, an initially random texture distribu-tion reaches a steady state that is strongly correlated to the interfacial energy density [9]. In simulation,it is found that if the given energy depends only on lattice misorientation, then the steady state GBCDand the energy are related by a Boltzmann distribution. This is among the simplest non-random dis-tributions, corresponding to independent trials with respect to the energy. Why does such a simpledistribution arise from such a complex system?.
The Effect of Temperature on Microstructure Evolution in a 7055 Aluminum Alloy Subjected to ECAP
Authors: Nikulin Ilya , Kaibyshev Rustam
Published: April 2012

Grain refinement taking place in a commercial 7055 aluminum alloy under equal channel angular pressing (ECAP) was examined in the temperature interval 250375°C. It was shown that the formation of recrystallized grains occurs through continuous dynamic recrystallization (CDRX). At 250°C, a low rate of dynamic recovery and high volume fraction of second phase particles provide the rapid formation of stable three-dimensional arrays of low-angle boundaries and their gradual transformation into high-angle boundaries. Increasing temperature leads an increase in the average crystallite size produced by ECAP from 0.7 μm at 250°C to 1.3 μm at 375°C. The effect of temperature on CDRX kinetic is discussed.
Influence of Annealing Process on Recrystallisation Behaviour of a Heavily Cold Rolled AISI 304L Stainless Steel on Ultrafine Grain Formation
Authors: Ravi Kumar B. , Sahu J.K. , Das S.K.
Published: April 2012

AISI 304L austenitic stainless steel was cold rolled to 90% with and no inter-pass cooling to produced 89% and 43% of deformation induced martensite respectively. The cold rolled specimens were annealed by isothermal and cyclic thermal process. The microstructures of the cold rolled and annealed specimens were studied by the electron microscope. The observed microstructural changes were correlated with the reversion mechanism of martensite to austenite and strain heterogeneity of the microstructure. The results indicated possibility of ultrafine austenite grain formation by cyclic thermal process for austenitic stainless steels those do not readily undergo deformation induced martensite. Keywords: Austenitic stainless steel, Grain refinement, Cyclic thermal process, Ultrafine grain
Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT
Authors: Paul H. , Baudin T. , Kudłacz K. , Morawiec A.
Published: April 2012

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.
Direct Observations of Cube Nucleation from Intergranular Cube Segments in Cold Rolled Al-Mn
Authors: Albou Adeline , Raveendra S. , Karajagikar P. , Samajdar Indradev , Driver Julian H. , Maurice Claire
Published: April 2012

Two major types of Cube bands/segments have been observed in heavily (90%) cold rolled Al-0.1wt %Mn using the EBSD technique with a FEG SEM: i) intergranular transition bands as thin cube segments aligned along RD between S and Cu oriented grains and ii) as transgranular strain localized bands situated in some particular grains. Their evolution is studied by light annealing at 275°C and 300°C and EBSD observations of exactly the same areas to directly correlate local deformation substructure with recrystallization. Only the intergranular cube transition bands give rapid recrystallization nucleation to cube grains of dimension >10µm. In particular the fastest growing cube grains have a near 40°<111> relation with part of their surroundings.
Stored Energy and Annealing Behavior of Heavily Deformed Aluminium
Authors: Kamikawa Naoya , Huang Xiao Xu , Kondo Yuka , Furuhara Tadashi , Hansen Niels
Published: April 2012

t has been demonstrated in previous work that a two-step annealing treatment, including a low-temperature, long-time annealing and a subsequent high-temperature annealing, is a promising route to control the microstructure of a heavily deformed metal. In the present study, structural parameters are quantified such as boundary spacing, misorientation angle and dislocation density for 99.99% aluminium deformed by accumulative roll-bonding to a strain of 4.8. Two different annealing processes have been applied; (i) one-step annealing for 0.5 h at 100-400°C and (ii) two-step annealing for 6 h at 175°C followed by 0.5 h annealing at 200-600°C, where the former treatment leads to discontinuous recrystallization and the latter to uniform structural coarsening. This behavior has been analyzed in terms of the relative change during annealing of energy stored as elastic energy in the dislocation structure and as boundary energy in the high-angle boundaries.
New 3DXRD Results on Recrystallization and Grain Growth
Authors: Jensen Dorte Juul , West S.S. , Poulsen S.O. , Schmidt Søren
Published: April 2012

New in-situ 3DXRD results obtained since the last Rex&GG conference are presented and discussed. This includes: Documentation of the formation of nuclei with new orientations, determination of apparent activation energies for individual bulk grains during recrystallization and evolution in the 3D microstructure during grain growth.
Grain Growth Stagnation Caused by the Grain Boundary Roughening Transition
Authors: Holm Elizabeth A. , Foiles Stephen M.
Published: April 2012

Molecular dynamics simulations of bicrystals show that grain boundaries undergo a thermal roughening transition, and the grain boundary mobility increases abruptly when the boundary roughens. The roughening transition temperature varies widely from boundary to boundary, ranging from less than 0.4 to more than 0.9 of the melting temperature. Thus, at typical annealing temperatures we expect polycrystals to contain both smooth (slow) and rough (fast) boundaries, with the fraction of each type varying with temperature.
Derivation of Statistical Model of Grain Growth Based on 3-D Von Neumann Equation
Authors: Abbruzzese Giuseppe Carlo
Published: April 2012

The derivation of an equivalent 3-D Von Neumann equation and the corresponding kinetics equation in terms of geometrical characteristics of a grain is shown and the formulation is provided in the framework of the statistical theory of grain growth. The topological relationships between number of grain faces, grain size, number of corners and edges and how these can be calculated in a real microstructure with a statistical approach are discussed. A quadratic law for the linkage between number of faces and grain size is found and compared with available experimental results. Inside the above description a basic formulation of the statistical theory will be derived based on simple geometrical and statistical principles without any independent assumption
In Situ Observation of Recovery and Grain Growth in High Purity Aluminum
Authors: Hefferan C. M. , Li S. F. , Lind J. , Lienert Ulrich , Rollett Anthony D. , Suter R.M.
Published: April 2012

We have used high energy x-ray diffraction microscopy (HEDM) to study annealing behavior in high purity aluminum. In-situ measurements were carried out at Sector 1 of the Advanced Photon Source. The microstructure in a small sub-volume of a 1 mm diameter wire was mapped in the as-received state and after two differential anneals. Forward modeling analysis reveals three dimensional grain structures and internal orientation distributions inside grains. The analysis demonstrates increased ordering with annealing as well as persistent low angle internal boundaries. Grains that grow from disordered regions are resolution limited single crystals. Together with this recovery behavior, we observe subtle motions of some grain boundaries due to annealing.
Modeling Recrystallization in Al Alloys: Investigation of Nucleation at Cube Bands
Authors: Sukhopar Olga , Gottstein Günter
Published: April 2012

In the present study, a modified cellular automaton CORe (Cellular Operator for Recrystallization) was used to predict the recrystallization (RX) texture and microstructure of 70% cold rolled commercial AA8079L alloy at 300°C. The nucleation of the Cube orientation is of considerable scientific interest since the Cube texture component influences significantly the anisotropy of material properties. Experimental data collected during this investigation were used for subsequent modeling. By studying the annealed material by EBSD, an average nucleation rate at Cube bands was established and used in the model. The simulated microstructure reveals, in general, good agreement with experiment. The texture prediction shows the right tendency, but the modeled intensity of the Cube texture is about 2 times smaller than in experiment.
The Application of In Situ 3D X-Ray Diffraction in Annealing Experiments: First Interpretation of Substructure Development in Deformed NaCl
Authors: Borthwick Verity , Schmidt Søren , Piazolo Sandra , Gundlach Carsten , Griera Albert , Bons Paul D. , Jessell Mark W.
Published: April 2012

n-situ 3D X-ray diffraction (3DXRD) annealing experiments were conducted at the ID-11 beamline at the European Synchrotron Radiation Facility in Grenoble. This allowed us to non-destructively document and subsequently analyse the development of substructures during heating, without the influence of surface effects. A sample of deformed single crystal halite was heated to between 260-400 °C. Before and after heating a volume of 500 by 500 by 300 μm was mapped using a planar beam, which was translated over the sample volume at intervals of 5-10 µm in the vertical dimension. In the following we present partially reconstructed orientation maps over one layer before and after heating for 240min at 260 °C. Additional small syn-heating maps over a constrained sample rotation of 12-30º. The purpose of this was to illuminate a few reflections from 1 or 2 subgrains and follow their evolution during heating. Preliminary results show that significant changes occurred within the sample volume, for which, surface effects can be excluded. Results show a number of processes, including: i) change in subgrain boundary misorientation angle and ii) subgrain subdivision into areas of similar lattice orientation with new subgrain boundary formation. These results demonstrate that 3DXRD coupled with in-situ heating is a successful non-destructive technique for examining real-time post-deformational annealing in strongly deformed crystalline materials with complicated microstructures.
Deformation and Recrystallization Texture Evolution in Nanocrystalline Nickel
Authors: Madhavan R. , Gurao N. P. , Suwas Satyam
Published: April 2012

Deformation and recrystallization textures in nanocrystalline nickel with average grain size of 20 nm were investigated using X-ray diffraction, electron microscopy and differential scanning calorimetry. The deformation behaviour of nanocrystalline nickel is quite complicated due to intervention of other deformation mechanisms like grain boundary sliding and restoration mechanisms like grain growth and grain rotation to dislocation mediated slip. Recrystallization studies carried out on the deformed nanocrystalline nickel showed that the deformation texture was retained during low temperature annealing (300°C), while at higher temperature (1000°C), the texture got randomised. The exact mechanism of texture formation during deformation and recrystallization has been discussed.