bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen Transport in 34CrMo4 Martensitic Steel: Influence of Microstructural Defects on H Diffusion
Authors: Moli-Sanchez L. , Martin F. , Leunis E. , Chêne J. , Wery M.
Published: April 2012

The electrochemical permeation technique was used to evaluate the effect of the microstructure on hydrogen diffusivity and hydrogen trapping at room temperature in martensitic steels. A detailed study of the electrochemical permeation technique was first performed in order to identify the boundary conditions of a permeation test in the selected experimental set-up. The validity of the apparent diffusion coefficient derived from this test is also discussed. A 34CrMo4 quenched steel has been selected and designed at three tempering temperatures (200°C, 540°C and 680°C) in order to obtain three different microstructures. According to permeation measurements, H diffusion strongly depends on the microstructure. The material tempered at 540°C exhibits the smallest diffusion coefficient and the largest fraction of reversible traps at room temperature.
Interdiffusion in Nb-Mo, Nb-Ti and Nb-Zr Systems
Authors: Prasad Soma , Paul Aloke
Published: April 2012

Diffusion couple technique is used to study interdiffusion in Nb-Mo, Nb-Ti and Nb-Zr systems. Interdiffusion coefficients at different temperatures and compositions are determined using the relation developed by Wagner. The change in activation energy for interdiffusion with composition is determined. Further, impurity diffusion coefficient of the species are determined and compared with the available data in literature.
The Solubility of Indium in Liquid Gallium Supercooled to 12 K
Authors: Yin Xiang Yu , Collins Gary Scott
Published: April 2012

The method of perturbed angular correlation (PAC) was used to determine lattice locations of 111In impurity probe atoms present in extreme dilution in the intermetallic compound FeGa3. In slightly Ga-poor samples, probes were found to strongly prefer one of two inequivalent Ga-sites. In slightly Ga-rich samples at room temperature, 293 K, the PAC spectrum exhibited an unperturbed quadrupole interaction signal that is consistent with indium probes dissolved in small liquid pools of the excess Ga. A myriad of such pools are probably located along grain boundaries in the sample. Cooling from 293 K down to 12 K, the site fraction of indium in liquid decreased, being offset by the increase in a signal attributed to indium solutes in precipitates with other impurities at the sides of the Ga pools. However, these changes were completely reversible upon heating, and no crystallization of the liquid gallium pools was observed down to 12 K. This is attributed to the extraordinarily small volumes for the pools, which, while not measured directly, are orders of magnitude smaller than cubic microns. The measured temperature dependence of the site fraction of indium in the liquid was used to extend the metastable solubility curve for indium in liquid gallium down to a temperature of 150 K, much lower than the eutectic temperature of Ga-In at 288.5 K.
Sedimentation in Multicomponent Solids
Authors: Wierzba Bartek
Published: April 2012

The theoretical model describing the sedimentation process, i.e. diffusion induced by the gravity (centrifugal) field in multicomponent system is presented. This procedure starts from the combined mass conservation law, equation of motion, volume continuity equation and Nernst-Planck flux formulae. Two dimensional calculations of sedimentation process in InPb system are presented. Example applications of this theory applied to binary system is evidence of sedimentation in condensed matter via diffusion mechanisms. Keywords: sedimentation, interdiffusion, gravity, pressure, thermodynamics, volume continuity.
Gravitational Annealing of Colloidal Crystals
Authors: Suzuki Yoshihisa , Endoh Jin , Mori Atsushi , Yabutani Tomoki , Tamura Katsuhiro
Published: April 2012

A silica colloidal crystal obtained by centrifugation at 9 G for 2 days in water was annealed by additional stronger centrifugation at 50 G for 5 days. The number of the striations observed in the colloidal crystal under crossed polarized light decreased at some parts in a growth container after the additional centrifugation, while the number also increased at the other parts. The decrease probably shows the shrinkage of the stacking disorders under high gravity, while the increase probably shows the production of new stacking disorders.
Study of the Reactive Dynamics of Nanometric Metallic Multilayers Using Molecular Dynamics : The Al-Ni System
Authors: Linde A. , Politano Olivier , Baras F.
Published: April 2012

A molecular dynamics study of a layered Ni-Al-Ni system is developed using an embedded atom method potential. The specific geometry is designed to model a Ni-Al nanometric metallic multilayer. The system is initially thermalized at the fixed temperature of 600 K. We first observe the interdiffusion of Ni and Al at the interfaces, which is followed by the spontaneous phase formation of B2-NiAl in the Al layer. The solid-state reaction is associated with a rapid system's heating which further enhances the diffusion processes. NiAl phase is organized in small regions separated by grain boundaries. This study confirms the hypothesis of a layer-by-layer development of the new phase. For longer times, the temperature is notably higher (> 1000 K) and the system may partly lose some its B2-NiAl microstructure in favor of the formation of Ni3Al in L12 configuration. This work shows the spontaneous development of a real exothermic solid-state reaction in metallic nanosystems mostly constituted by interfaces.
Morphology and Rheological Analysis of Nanoclay in Polymer Modified Bitumen
Authors: Zhang Ji Zhe , Van de Ven Martin , Wu Shao Peng
Published: April 2012

This paper investigated the influence of nanoclay on the properties of polymer modified bitumen(PMB). The nanoclay-polymer modified bitumen has been produced by mixing a standard 70/100 pen bitumen with polymer at a fixed proportion and then mixed with different amount of nanoclay. The rheological behaviour of the samples have been determined using dynamic shear rheometer. The morphology of the samples as well as the distribution of polymer and nanoclay throughout the bitumen have been characterized with a fluorescence microscopy. The result indicate that the rheological properties of nanoclay-polymer modified bitumens dependent on the percentage nanoclay. The morphology result shows that dispersed polymer particles existed in continuous bitumen phase and the addition of nanoclay does not seem to change the particle size of the polymer.
Research of AC-20 Grading of Conductive Asphalt Concrete Based on Fractal Theory
Authors: Tang Ning , Wu Shao Peng , Sun Chang Jun
Published: April 2012

Aggregate distribution of asphalt mixture had an obvious characteristic of fractal. Based on fractal theory, the distribution function of aggregate of conductive asphalt mixture based on the granular fractal model was deduced. This paper used linear regression analysis to different gradings to get the grading fractal dimension of conductive asphalt mixture and the conductivity of the mixture was tested. Test results indicated that the grading fractal dimension of conductive asphalt mixture was controled by the fine aggregate. On the other hand, the fractal dimension had a congruent relationship with conductivity. The conductive asphalt mixture had good pavement performance and conductive when the fractal dimension of AC-20 grading ranged from 2.43 to 2.53. The fractal dimension can be used as a quantification index of grading evaluation.
Study of High Temperature Performance and Low Temperature Property on Layered Silicate Modified Asphalt Concrete
Authors: Wu Shao Peng , Liu Tian Gui , Pang Ling , Cao Ting Wei , Pan Pan
Published: April 2012

Montmorillonite (MMT), a typical layered silicate, has been widely used to prepare modified asphalt. This paper investigates the high temperature performance and low temperature property on layered silicate modified asphalt concrete. The control concrete is prepared by base asphalt. Meanwhile, three-point bending, conventional and SHRP rutting tests are used to compare the properties of the two types of asphalt concrete. The results of conventional and SHRP rutting tests show that the modified asphalt concrete exhibits a better high temperature performance than the control concrete. And the maximum bending strength of modified asphalt concrete is higher than that of control concrete at the same temperature. It can be concluded that both the high temperature performance and low temperature property of asphalt concrete has been improved efficiently by utilization of layered silicate modified asphalt.
Effects of Gypsum on Cementitious Systems with Different Mineral Mixtures
Authors: Liu Fei , Lan Ming Zhang
Published: April 2012

Gypsum is an indispensable component of ordinary Portland cement. The main function of gypsum is to regulate the setting time of cement. Gypsum has a great influence on water consumption of standard consistence and strength simultaneously. In this article three cementitious systems are prepared by three main mixed materials: limestone, fly ash and slag. The effect of gypsum content and the relation between gypsum quantity and the fluidity of cement with Marsh cone method are studied. Experimental results show that when the gypsum was added in the three kinds of cementitious system, water consumption of standard consistence decreased obviously, and with the quantity of gypsum increased, water demand for normal consistency reduced first, up to a certain extent tended smoothly. With the increase of gypsum quantity, initial and final setting time had different degrees of extension. While a saturation quantity is achieved, setting time will keep steady. The flexural strength and the compressive strength increased gradually and tended to be stable with the increase of gypsum quantity. When gypsum content exceeded a certain range, compressive and flexural strength decreased gradually. But gypsum content and the mobility of systems had little relativity with Marsh cone method.
The Influence of Electrode on Resistivity of Conductive Asphalt Concrete for Self-Monitoring
Authors: Sun Chang Jun , Qin Li Juan , Wu Shao Peng , Sun Guo Liang , Chen Lei
Published: April 2012

This paper focuses on an optimized research about materials and size of electrode of self-monitoring asphalt concrete. It can be easily observed and analyzed the sensitivity of the test and resistivity fluctuations by studying the changes of output resistivity in different electrode embedded in the self-monitoring asphalt concrete. Based on the above method, we can select the proper electrode for the self-monitoring asphalt concrete. The results indicate that the output resistivity of self-monitoring asphalt concrete have much more fluctuation than which used stainless steel mesh as electrode material when choosing the iron mesh as electrode material. Meanwhile, the results demonstrate that the measured output resistivity of self-monitoring asphalt concrete is the most stable when the electrode size is 40~60% of cross-sectional area.
Utilization of Dacite as Alternative Aggregate in Asphalt Mixture
Authors: Wu Shao Peng , Pan Pan , Chen Ming Yu
Published: April 2012

With the widespread application of asphalt mixture, current demand from transportation managers for construction and maintenance of their pavement network consumes large numbers of aggregates. If agencies excessively favor to some certain kinds of excellent aggregates, the cost of construction could be considerably expensive. The major objective of this study is to determine the feasibility of utilizing dacite in asphalt mixtures. By means of Marshall, freeze-thaw, rutting and three-point bending tests, the performances of dacite and basalt asphalt mixture are compared. The results of the testing illustrate that dacite asphalt mixture is more susceptible to gradation and asphalt content than basalt asphalt mixture. Meanwhile it is showed that the performances of dacite asphalt mixture can be improved greatly with the involvement of additives including active mineral powder and cement. Furthermore, it is validated that dacite can be used as alternative aggregate in asphalt mixture.
Crystallization Properties of Ge-Se-Bi Thermoelectric Glasses
Authors: Shangguan Fu Diao , Xie Jun , Wu Zhi Ping , Xing Jin Mei , Zhao Bing , Liu Yin Yao , Chen Guo Rong
Published: April 2012

In the present work, a series of glass samples in Ge-Se-Bi system are prepared. XRD analysis is made on samples for identifying the type of precipitated crystals from glass matrices. Effects of glass matrix composition on crystallization behaviors are discussed. Results show that Ge and Bi content of glasses in the Ge-Se-Bi system are closely related to the precipitation of pure Bi2Se3 thermoelectric crystal phase. The optimal glass-ceramic composition is presented.
Effect of MgO/CuO on the Microstructure and Thermal Properties of Cordierite–Alumina Ceramics
Authors: Tang Li Ying , Cheng Xi , Lu Ping , Yue Fang
Published: April 2012

Abstract: Cordierite–alumina ceramics were prepared with the raw materials of cordierite and α-alumina powder, and TiO2，CuO and MgO were added as composite additives. The effect of MgO/ CuO ratios on the microstructure, thermal conductivity and thermal shock resistance of cordierite–alumina ceramics were researched by X-ray diffraction, scanning electron microscopy and laser flash analyzer; the bulk density and the porosity of cordierite – alumina ceramics were measured. The results show that with increasing of MgO/CuO ratios, the bulk density and thermal conductivity increase firstly and then decrease, and have a minimum with 0.4wt% MgO and 0.667 MgO/CuO; and the porosity of ceramics decreases firstly and then increases and has a maximum with 0.4wt% MgO and 0.667 MgO/CuO;There are little changes in the size of the grain of the ceramics, and a small amount of magnesium aluminate spinel precipitate; the thermal shock resistance performance of the ceramics is developed with the increasing of MgO/CuO ratios.
Facile Fabrication and Efficient Photocatalytic Activity of 3D-Ordered Macroporous ZnO Film
Authors: Xie Hao , Zeng Tao , Wang Xue Lai , Zhao Xiu Jian
Published: April 2012

Three-dimensionally (3D) ordered macroporous ZnO film was fabricated on a glass slide by layer-by-layer depositing and hydrolysis of Zn(CH3COO)2using 3D-ordered latex film as template followed by calcination at 450 °C for 2 h to remove the organic template. The as-prepared 3D-ordered macroporous ZnO film was characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), diffusive reflectance UV-visible absorption spectra (DRUV-VIS), photoluminescence (PL), and photoelectrochemical measurement. Its photocatalytic activity was evaluated by the photocatalytic degradation of crystal violet (CV) aqueous solution at ambient temperature under the irradiation of simulated solar light. It was found that the 3D-ordered ZnO film exhibits efficient photocatalytic activity for photodegradation of CV under the irradiation of simulated solar light.
Preparation and Characterization of Supported H3PW12O40 and Supported Cesium-Substituted Dodecatungstophosphate
Authors: Liu Zi Li , Xu Cui Xia , Dai Qian Wen , Xiang Chao , Zhang Jian Jie
Published: April 2012

Supported H3PW12O40 (HPW) and supported Cesium-Substituted dodecatungsto-phosphate are eco-friendly solid acid catalysts. A series of different loading H3PW12O40/SiO2 and HPW/diatomite were prepared by a typical incipient wetness impregnation of methanol, meanwhile SiO2 and diatomite supported Cs-salt catalysts were prepared via two-step impregnating method. The catalysts were investigated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The results indicate that the Keggin structure of HPW is intact in the SiO2-supported HPW and SiO2-supported CsHPW. HPW and CsHPW are highly dispersed in the SiO2 at the low loading, while the loading is more than 40% the catalyst grains increase and gather on the surface of the carrier. What's more, diatomite is not a suitable support. HPW and CsHPW have better distribution in the SiO2 than in the diatomite. The activity of catalyst was tested in probe experiment of the alkylation of thiopene (TH) with 1-hexene.
Rheological Characteristics of Residue Binder from Low Penetration Grade Bitumen Emulsion
Authors: Xu Guang Ji , Chen Mei Zhu , Wu Shao Peng , Van de Ven Martin , Mookhoek Steven
Published: April 2012

In this study, residue binders from low penetration grade bitumen emulsions were investigated on the basis of rheology and were compared to the neat bitumen binders of which they were produced. The recovery method proposed by EN 13074 (including both recovery and stabilization process at moderate temperatures) was selected to obtain the residue binders used in the analysis, and the corresponding neat binders were treated the same for comparison. The rheological properties of residue binder from low penetration grade bitumen emulsion were evaluated using Dynamic Shear Rheometer (DSR). During the curing process, three stages were divided, and master curves of complex modulus and phase angle were constructed to allow comparison of the residue binder over a large range of frequencies for each stage. The results showed that the complex modulus increases while the phase angle decreases with curing process for the residues, indicating a better performance in terms of elasticity and stiffness.
Influence of Metakaolin on Strength and Microstructure of High-Strength Concrete
Authors: Shui Zhong He , Zeng Jun Jie , Liao Yang , Leng Zheng
Published: April 2012

Concrete with a compressive strength of 100MPa was produced with metakaolin(MK), and the effect of MK replacement levels on compressive strength of concrete with a water to binder ratio of 0.25 was studied in this paper. XRD, microhardness tests, SEM and MIP were used to investigate the influences of MK on the phase composition, microhardness of interfacial transition zone(ITZ), microstructural morphology and pore structure of the high-strength concrete (HSC). The results showed that the incorporation of MK promoted the hydration process and decreased the amount of Ca(OH)2 crystals. Furthermore, MK increased the ITZ microhardness of HSC, enhanced the hydrates and improved the bond performance of aggregate and paste. The weak zone between aggregate and paste became almost disappeared when 10% MK was blended. Meanwhile, refinement of the concrete pore structure was obtained in the presence of MK. The improvement of strength and microstructure became more obvious as the MK replacement level increased to 15%.
The Effect of Al2O3/SiO2 on the Structure and Properties of Na2O-CaO-Al2O3-SiO2 Glasses
Authors: Xie Jun , Xiao Zi Fan , Zheng Wei Hong , Liu Ye , Cheng Jin Shu
Published: April 2012

In the paper, a series of Na2O-CaO-Al2O3-SiO2 system glasses following similar compositions to the soda-lime-silicate float glasses and possessing more excellent physi-chemical properties were prepared with different Al2O3/SiO2 ratio. The structure of glasses have been studied by IR and density tests. The investigation of Al2O3/SiO2 on the performance was carried out by bending strength tests, linear dilatometry and chemical durability tests in aqueous and alkaline environment. The results showed that the number of no bridging oxygens decreased with increasing the Al2O3/SiO2 ratio, the glass network structure and density increased, which leading to enhance the bending strength, thermo-stability and chemical durability of glass.
The Thermodynamic Characteristic of Diesel with 21-30% Oxygen-Enhanced Combustion
Authors: Cheng Jin Shu , Deng Zhen Lu , Wang Jing
Published: April 2012

The study was carried out on the burning test-bed which was controlled by Programmable Logic Controller (PLC) model and diesel was used as the fuel. The thermodynamic characteristic of oxygen-enhanced combustion, including fuel consumption, flue gas volume, flue gas components’ volume concentration, theoretical flame temperature, flame emissivity, energy efficiency and thermal efficiency, etc, were analyzed. The results showed that: with oxygen concentration was increased from 21% to 30%, fuel consumption was decreased by 40.6% and flue gas volume was decreased by 57.5%. Additionally, higher oxygen concentration leaded to higher theoretical temperature and stronger flame blackness because of the decreasing of N2 volume in supporting air. What’s more, the decreasing of energy brought away by flue gas and the thermal efficiency were both increased with the increasing of oxygen concentration.
Study on Hexagonal Mesoporous Silica Film for Antireflective Coating
Authors: Pan Qiang , Shen Jun , Wang Xiao Dong , Zhang Zhi Hua
Published: April 2012

In this paper, ordered mesoporous silica film as a novel antireflective coating was directly synthesized via evaporation induced self-assembly (EISA) process with cetyltrimethylammonium bromide (CTAB) as template surfactant. The mesoporous silica film exhibits ordered 2D hexagonal microstructure as demonstrated by transmission electron microscopy (TEM) and small angle X-ray diffraction (SAXRD). The average transmittance of the coated glass is about 98%, which indicates an increasing transmitted light of 7.5% in the wavelength between 400nm and 800nm. The mechanical performance and hydrophobicity tests prove that the films have excellent scratch resistance and long-time stability. The results of the characterizations and tests show that the film prepared by this convenient method would be very useful and promising for lots of commercial applications.
Study on the Influence of Painting Processes on the Protective Property of Concrete Coating
Authors: Zheng Yan , Mao Qian Jin , Wang Ya Li , Wang Zi Ming , Cui Su Ping
Published: April 2012

With the development of construction project the durability of concrete is becoming more and more prominent, and surface coating is an effective measure to enhance the durability of concrete. Water-based silicone acrylic emulsion coating and water-based fluorocarbon resin coating were chose as prime and topcoat respectively. The impact of the coating’s thickness and viscosity on the durability of concrete and the relationship between the viscosity of the coating and its penetration depth were testified by chloride ion permeability-resistance property of concrete. The results show that thickness is proportional to the protective performance of the coating, and the penetration depth highly depends on viscosity. And the result of coating-4 viscosity method shows that samples with viscosity between 15 and 25 seconds have better chloride permeability resistance.
Characteristics of Dynamic Recrystallization during Hot Deformation for High Nitrogen Stainless Steels
Authors: Luo Hai Wen , Fang Xu Dong , Wang Rui Zhen , Diao Zhan Yin
Published: April 2012

Dynamic recrystallization was studied for the stainless steels with nitrogen contents of 0.56% to 1.08% during hot deformation at temperatures of 900~1200 with strain rates ranging from 0.003 to 42 s-1. It was found that flow stress could increase remarkably with increasing nitrogen content. Flow curves during the deformation by 0.1~42/s at temperatures of 900~1200°C show a single peak, indicating the occurrence of dynamic recrystallization during deformation. The peak strain seems to decrease with increasing N content, suggesting that higher content of N facilitates dynamic recrystallization. The quenched microstructures were analyzed by optical microscopy, EBSD and TEM. The recrystallized grain sizes on the quenched specimens were measured and its dependence on temperature and strain rate was analyzed. At high temperature, continuously dynamically recrystallized microstructures were observed; whilst at low temperature, necklace-like partially recrystallized microstructures were found. Key words: High nitrogen stainless steel; dynamic recrystallization; stress-strain curves
Mechanism of Secondary Recrystallization in Grain-Oriented Si Steel
Authors: Ushigami Yoshiyuki , Nakamura Shuichi
Published: April 2012

On the basis of Hillerts model of grain growth, a new model of Goss secondary recrystallization in silicon steel has been developed in which inhibitor and grain boundary energy are taken into account. An analysis shows that these two parameters synergistically affect secondary recrystallization and Goss grain evolves to a coarse grain as inhibitor intensity increases and statistical grain boundary energy decreases. This model successfully explains Goss secondary recrystallization.
Microstructure Evolution during Recrystallization in Dual-Phase Steels
Authors: Peranio Nicola , Roters Franz , Raabe Dierk
Published: April 2012

The microstructure and texture of rolled and annealed dual-phase steels with 0.147 wt. % C, 1.868 wt. % Mn, and 0.403 wt. % Si were analyzed using SEM, EDX, and EBSD. Hot rolled sheets showed a ferritic-pearlitic microstructure with a pearlite volume fraction of about 40 % and ferrite grain size of about 6 µm. Ferrite and pearlite were heterogeneously distributed at the surface and distributed in bands at the center of the sheets. The hot rolled sheets revealed a through-thickness texture inhomogeneity with a plane-strain texture with strong α-fiber and γ-fiber at the center and a shear texture at the surface. After cold rolling, the ferrite grains showed elongated morphology and larger orientation gradients, the period of the ferrite-pearlite band structure at the center of the sheets was decreased, and the plane-strain texture components were strengthened in the entire sheet. Recrystallization, phase transformation, and the competition of both processes were of particular interest with respect to the annealing experiments. For this purpose, various annealing techniques were applied, i.e., annealing in salt bath, conductive annealing, and industrial hot-dip coating. The sheets were annealed in the ferritic, intercritical, and austenitic temperature regimes in a wide annealing time range including variation of heating and cooling rates.
Monte-Carlo Simulation of Goss Abnormal Grain Growth in Fe-3%Si Steel by Sub-Boundary Enhanced Solid-State Wetting
Authors: Ko K.J. , Rollett A.D. , Hwang N.M.
Published: April 2012

The selective abnormal grain growth (AGG) of Goss grains in Fe-3%Si steel was investigated using a parallel Monte-Carlo (MC) simulation based on the new concept of sub-boundary enhanced solid-state wetting. Goss grains with low angle sub-boundaries will induce solid-state wetting against matrix grains with a moderate variation in grain boundary energy. Three-dimensional MC simulations of microstructure evolution with textures and grain boundary distributions matched to experimental data is using in this study.
Dynamic Recrystallization in Similar 5182 Al/Al and Dissimilar Al/Fe Friction Stir Spot Welds
Authors: Etter Anne Laure , Bozzi Sandrine , Baudin Thierry
Published: April 2012

Dynamic recrystallization mechanisms have been studied after 5182 aluminum Friction Stir Spot Welding (FSSW) and dissimilar friction stir spot welding of 6016 aluminum alloy to IF-steel using EBSD measurements. Moreover, welds have been ice quenched after welding to state on the post-dynamic microstructure evolution after the tool removal. For the Al/Al welds, fine recrystallized grains of the stir zone result from a continuous dynamically recrystallization mechanism followed by a post-dynamic recovery that reduces the low angle boundary fraction in the periphery of the pin. As far as the dissimilar Al/Fe welds are concerned, steel grains of the base metal were fragmented into sub-grains in the thermomechanically affected zone. Nevertheless, recrystallized grains of the stirred zone were about three times larger than these sub-grains. In this case, the continuously recrystallized grains undergo a post-dynamic grain-growth during friction stir welding cooling. In the upper aluminum sheet, the recrystallization mechanisms are the same as in the Al/Al welds.
Evolution of Textures and Microstructures in Low-Reduction Rolled and Annealed Low-Carbon Steels
Authors: Oh Kyu Hwan , Koo Yang Mo , Lee Dong Nyung
Published: April 2012

A study has been made of the evolution of the microstructures and textures in three kinds of low-carbon steel sheets (MAFE, BH and IF) having well developed <111>//ND texture that were rolled by low reductions and annealed at 780 °C in Ar atmosphere. The steel sheets developed different microstructures and textures, even though their initial textures and thermomechanical treatments were similar. MAFE steel showed an unusual behavior that grains with high Taylor factors survived and grew very rapidly. This unusual behavior and the differences in microstructure and texture have been discussed.
Survey of Grain Boundary Energies in Four Elemental Metals
Authors: Olmsted David L. , Holm Elizabeth A. , Foiles Stephen M.
Published: April 2012

Grain boundary properties depend on both composition and structure. To test the relative contributions of composition and structure to the grain boundary energy, we calculated the energy of 388 grain boundaries in four elemental, fcc metals: Ni, Al, Au and Cu. We constructed atomic-scale bicrystals of each boundary and subjected them to a rigorous energy minimization process to determine the lowest energy structure. Typically, several thousand boundary configurations were examined for each boundary in each element.
Stress Induced Grain Boundary Motion in Al Bicrystals
Authors: Molodov Dmitri A. , Gorkaya Tatiana , Gottstein Günter
Published: April 2012

Recent results of experimental research into stress induced grain boundary migration in aluminum bicrystals are briefly reviewed. Boundary migration under a shear stress was observed to be coupled to a lateral translation of the grains for any <100> tilt boundary in the entire misorientation range (0-90°). Measurements of the temperature dependence of coupled boundary migration revealed that there is a specific misorientation dependence of migration activation parameters. Grain boundaries can act during their motion under the applied stress as sources of lattice dislocations that leads to the generation and growth of new grains in the boundary region. The rate of stress induced boundary migration decreases with increasing solute content in aluminum. Both the migration activation enthalpy and the pre-exponential mobility factor were found to increase with rising impurity concentration.
Thermodynamic and Kinetic Properties of Grain Boundary Junctions
Authors: Shvindlerman Lasar S. , Gottstein Günter
Published: April 2012

The results of recent experimental, theoretical and computer simulation studies of the thermodynamics and kinetics of grain boundaries and grain boundary junctions are presented and discussed.
Recrystallization Processes in a Ni-20%Cr Alloy Subjected to High-Pressure Torsion
Authors: Dudova Nadezhda , Belyakov Andrey , Kaibyshev Rustam
Published: April 2012

Microstructure evolution during annealing of a Ni-20%Cr alloy subjected to high-pressure torsion (HPT) at ambient temperature was examined. It was shown that discontinuous static recrystallization (DSRX) occurs in non-uniform manner under subsequent annealing in the alloy strained to ε<4. The material strained to ε6 or higher exhibits continuous grain growth (GG) under subsequent annealing. It is attributed to the fact that HPT led to the formation of nanoscale grains with an average size of 50 nm. Increasing fraction of these grains with strain leads to transition from DSRX to continuous GG under subsequent annealing. It was found that the main feature of recrystallization behavior of the Ni-20%Cr alloy subjected to HPT is simultaneous occurrence of short-range ordering and recrystallization processes under annealing conditions. As a result, despite the formation of recrystallized structure with an average grain size of 340 nm after annealing at 600°C (0.52 Tm), the material exhibits very high microhardness of 3.6 GPa.
Boundary Migration during Recrystallization of Heavily Deformed Pure Nickel
Authors: Zhang Yu Bin , Jensen Dorte Juul , Godfrey Andrew
Published: April 2012

The detailed microstructure in front of recrystallization boundaries and their migration during annealing were traced using ex-situ electron backscatter pattern maps of one and the same surface area taken after annealing. It is observed that many protrusions/detrusions form on the recrystallizing boundaries. During annealing, the recrystallization boundary segments migrate in a stop-go type of fashion, while protrusions and detrusions alternately form and disappear. The correlation between the protrusions/detrusions and the stop-go type of migration are briefly discussed.
Grain Size Control in the Weld Pool and Heat Affected Zone Using Holograms
Authors: Higginson R.L. , Blackmur M. , Gibson M. , Tyrer J.
Published: April 2012

This paper considers the use of Holographic Optical Elements (HOEs) to shape the weld beam and hence control the grain size of the weld bead and the grain growth and phase transformations in the HAZ. Welds have been produced on carbon steel with the introduction of a nickel based filler powder, using different energy densities produced by the HOEs. Cross sections of the welds have been analysed in terms of the weld profile, weld pool shape and grain size in the deposit and the HAZ. Electron BackScatter Diffraction (EBSD) coupled with Energy Dispersive X-ray Spectroscopy (EDS) has been used to study the microstructures developed. The results have shown that by utilising HOEs the grain size within the weld pool can be controlled such that a more equiaxed grain structure is developed when compared with the coarse columnar grains seen with a Gaussian beam.
Warm Forming of FCC Poly Crystals: The Effect of Grain Size under Different Forming Conditions on the Softening Behavior
Authors: Rehrl C. , Kleber Siegfried , Pippan Reinhard
Published: April 2012

Ingot breakdown is the most significant process for achieving high-quality billets in the cogging process. Especially microstructure evolution and grain refinement during the plastic deformation are of technical interest for the metal forming industry. To obtain refined and uniform microstructures after processing, it is necessary to understand deformation mechanisms as well as recovery-and recrystallization phenomena. Polycrystalline pure nickel and cast structured austenitic stainless steels were deformed by a compression test at different warm forming temperatures (800-1200°C) to investigate the influence of initial grain size, strain and strain rate on the structural refinement process. To get rid off static-and postdynamic softening processes the samples were immediately water quenched after deformation. By using the electron back scatter diffraction technique, the microstructural evolution and the crystallographic orientations were captured after deformation.
Simulation of Recrystallization and Recrystallization Textures in Aluminium Alloys
Authors: Engler Olaf
Published: April 2012

The control of the plastic anisotropy during forming of a metallic sheet requires detailed knowledge on its microstructure and, especially, crystallographic texture. During the thermo-mechanical processing of aluminium sheet products in commercial production lines the material experiences a complex history of temperature, time and strain paths, which result in alternating cycles of deformation and recrystallization with the associated changes in texture and microstructure. Thus, computer-based alloy and process development requires integration of models for simulating the evolution of microstructure, microchemistry and crystallographic texture into process models of the thermo-mechanical production of Al sheet. The present study focuses on recent developments in linking softening modules that simulate the progress of recovery and recrystallization with the following texture changes to deformation and microchemistry models.
Laser-Ultrasonic Austenite Grain Size Measurements in Low-Carbon Steels
Authors: Militzer Matthias , Maalekian Mehran , Moreau André
Published: April 2012

Austenite grain size is an important microstructure parameter when processing steels as it provides the initial condition for the austenite decomposition that determines the final microstructure and thus properties of the steel. In low-carbon steels it is frequently difficult if not impossible to quantify the austenite grain size using conventional metallographic techniques. Laser-ultrasonics provides an attractive alternative to quantify the grain size in-situ during thermo-mechanical processing of a steel sample. The attenuation of the laser generated ultrasound wave is a function of the grain size. The present paper gives an overview on the state-of-the-art of this novel measurement technique. Using isothermal and non-isothermal grain growth tests in low-carbon steels the advantages and limitations of laser-ultrasonic measurements will be demonstrated. Further, their application for deformed samples will be presented to quantify austenite grain sizes during and after recrystallization. The in-situ measurements provide significantly new insights into the austenite microstructure evolution during thermo-mechanical processing of low-carbon steels. The implications on expediting the development of improved process models will be discussed.
Simulation of Line Annealing of Type 430 Ferritic Stainless Steel
Authors: Kisko Anna P. , Suikkanen Pasi P. , Garcia C. Isaac , Cho K. , Hua M. , Karjalainen L. Pentti , DeArdo Anthony J.
Published: April 2012

The annealing behavior of cold rolled Type 430 ferritic stainless steel is the subject of this paper. The steel was cold rolled 79%, then heated at 6 °C/s to the soaking temperature of 841 °C, which is just below the Ae1temperature. During heating, specimens were quenched from selected temperatures between 650 and 841 °C and after various times at 841 °C. These quenched samples underwent metallographic examination and micro-hardness determination. The results indicated that under the prevailing experimental conditions, the hardness appeared to correlate strongly with the extent of recrystallization. The kinetics of recrystallization appeared to originate in the cold worked state, where three kinds of grain were found: (i) smooth elongated, featureless of α-fiber orientation {001}<100>; (ii) irregular fishbone grains of the γ-fiber orientations {111}<112> plus {111}<110>; and (iii) twisted grains of the η-fiber orientation {001}<100>. It was found that the twisted grains of the η-fiber were the first to recrystallize, with the fishbone grains of the γ-fiber second, and the smooth elongated, featureless grains of the α-fiber last. It was found that the grains of the α-fiber orientation {001}<100> and the η-fiber orientation {001}<100> were replaced with grains of the γ-fiber orientations as recrystallization progressed. These results are discussed in terms of recrystallization and texture development.
Box-Scan: A Novel 3DXRD Method for Studies of Recrystallization and Grain Growth
Authors: Lyckegaard Allan , Poulsen Henning Friis , Ludwig Wolfgang , Fonda Richard W. , Lauridsen Erik M.
Published: April 2012

Within the last decade a number of x-ray diffraction methods have been presented for non-destructive 3D characterization of polycrystalline materials. 3DXRD [1] and Diffraction Contrast Tomography [2,3,4] are examples of such methods providing full spatial and crystallographic information of the individual grains. Both methods rely on specially designed high-resolution near-field detectors for acquire the shape of the illuminated grains, and therefore the spatial resolution is for both methods limited by the resolution of the detector, currently ~2 micrometers. Applying these methods using conventional far-field detectors provides information on centre of mass, crystallographic orientation and stress state of the individual grains [5], at the expense of high spatial resolution. However, far-field detectors have much higher efficiency than near-field detectors, and as such are suitable for dynamic studies requiring high temporal resolution and set-ups involving bulky sample environments (e.g. furnaces, stress-rigs etc.)
Effect of a Finite Boundary Junction Mobility on the Growth Rate of Two and Three Dimensional Grains
Authors: Barrales Mora Luis A.
Published: April 2012

t has been shown by computer simulations that the MacPherson-Srolovitz relation predicts accurately the growth rate of a grain undergoing ideal grain growth. However, since a finite mobility of the boundary junctions (triple lines and quadruple junctions) affects the evolution of a granular system, it is necessary to modify this equation in order to take into account their effect. In the present contribution, an equation which allows considering these factors is presented and used to modify the von Neumann-Mullins and MacPherson-Srolovitz equations. In order to corroborate these equations two and three dimensional network model simulations were performed. The results showed a very good agreement with the theoretical approaches for both dimensions and all topological classes except those near the classes of zero growth rate in 3D. The reason is that the proposed function is very sensitive to small changes of the finite mobility of the junctions.
Grain Growth during Annealing: Experiments and Modelling
Authors: Candic M. , Tian Bao Hui , Sommitsch Christof
Published: April 2012

In the present work, for the description of grain coarsening, a probabilistic and a deterministic 2D cellular automaton simulation setup were developed. The results of the simulation have been validated by solution annealing experiments of austenitic stainless steel 304L (Fe-18Cr-8Ni) at different temperatures and times. Both cellular automata models show an excellent correlation between the experimental determined data and grain growth kinetics based upon considerations of temperature and second phase particles. Additionally, a two parameter approach of the probabilistic model was implemented, resulting in determining the grain sizes limiting normal and abnormal grains and accurate description of grain growth.
Potts Model Simulation of Grain Boundary Junction Limited Grain Growth
Authors: Zöllner Dana , Streitenberger Peter
Published: April 2012

The standard Monte Carlo (MC) Potts model is modified regarding the mobility of grain boundaries and their junctions allowing the simulation of a size effect observed in nanocrystalline grain growth. In large simulation studies different properties are measured. For initially very small grains the early growth regime corresponds to a separate coarsening state, which is characterised by an average growth law and a self-similar grain size distribution that both show strong deviations from the parabolic normal grain growth behaviour. The simulation results can be described by a theoretical model based on a statistical mean-field theory for nanocrystalline grain growth.
Recrystallization and Roping in a 6000 Series Al Alloy
Authors: Bennett Tricia A. , Petrov Roumen H. , Kestens Leo
Published: April 2012

Recrystallization was investigated in the context of its effect on the roping phenomenon in a 6000 series Al alloy. The findings suggest that, in general, the recrystallized grain size affects the material's susceptibility to roping more than the actual area fraction of specific texture components. For example, bands of Cube grains were typically observed in the final processed samples in cases which had coarse, recrystallized grain sizes from the earlier stages of processing. In contrast, bands were not observed for cases having fine, intermediate recrystallized grain sizes. Although microstructure and texture are highly intertwined, these findings suggest that the microstructural characteristics, such as the recrystallized grain size, are more important than those related to the texture.
Effect of Strain on Recrystallisation during Hot Deformation of Nb-Containing Microalloyed Steel
Authors: Kundu Amrita , Davis Claire L. , Strangwood Martin
Published: April 2012

The Dutta-Sellars equations for predicting recrystallisation and precipitation in microalloyed steels have been assessed for accuracy over a range of strain levels (0.15 to 0.45) during hot deformation (975-1075 °C) of a homogenised 0.045 wt % Nb steel. It has been found that the model predicts the deformation state well at a strain of 0.3 whereas at both lower and higher strains i.e. 0.15 and 0.45, the agreement is less good. The differences between prediction and experimental measurement have been related to solute drag and precipitate potential of Nb.
Sub-Boundary Mobilities during Recovery of Binary Al-Mn Alloys
Authors: Barou Fabrice , Maurice Claire , Feppon Jean Marie , Driver Julian H.
Published: April 2012

Two, high purity, Al-0.1 and 0.3wt%Mn alloys have been cold deformed in plane strain compression to strains of order 1.8 and the kinetics of subsequent recovery by sub-grain coarsening during annealing at 150-300°C measured by high resolution FEG-SEM EBSD. Accurate sub-grain size and misorientation distributions and their evolution with time and temperature have been determined. The average growth rates are then used to estimate the sub-grain boundary mobilities. Growth is analyzed by two well-known growth laws for the average sub-grain size δ (t): i) the standard relation for grain growth: where the exponent n takes values of 2-8 and ii) the relation proposed by Nes for dislocation climb in sub-grain walls: It is shown that the latter relation gives a better fit with the data in terms of the time and temperature dependence of the sub-grain sizes. In particular the activation energies for the logarithmic law are much closer to the values expected for solute-controlled movement of sub-boundaries.
Fabrication of Nanocrystalline Dense Silicon Nitride Ceramics
Authors: Kim Hai Doo , Hong Seong Hyeon
Published: April 2012

Since the properties of the bulk ceramics are dependent on the grain size the ceramic materials with nanoscale grain size is of interest. Sintering of nanosized powder compacts to full density with minimum grain growth is a difficult task to achieve due to its high surface energy. Two step sintering methode was developed to enhance densification with minimum grain growth for silicon nitride ceramics with liquid phase. Starting with nano-sized silicon nitride powder two step sintering methode gives rise to a very fine-grained b-Si3N4 matrix with large agglomerated Si2N2O grains due to its high surface oxygen content. Addition of Y2O3 shifts the composition point to a primary phase field with no Si2N2O, gives rise to b-Si3N4 with nano scale grain size and near full density. Carbothermal reduction method was employed to reduce the oxygen content in nano-sized silicon nitride powder to give nanocrystalline dense silicon nitride ceramics without Si2N2O formation. Use of SPS was effective to suppress the grain growth and to give near full density. Microstructural development and mechanical properties will be reported.
Modelling the Static Recrystallisation Texture of FCC Metals Using a Phase Field Method
Authors: Lan Yong Jun , Pinna C.
Published: April 2012

A three dimensional phase field model has been developed to simulate the texture formed during the static recrystallisation of FCC metals with medium or high stacking fault energy, such as aluminium, copper and nickel. Before recrystallisation the deformation texture as well as the stored energy was simulated using a three dimensional crystal plasticity finite element model. This output calculated on the distorted finite element mesh was first mapped onto the regular grid of the phase field model using a linear interpolation method and then used as initial condition for the subsequent recrystallisation texture modelling. This model has successfully predicted the typical recrystallisation texture components: cube {001}<100>, R {124}<211> in the aluminium alloy. In addition, the softening fraction and three dimensional microstructure produced during static recrystallisation have also been simulated by this model.