bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Stress Mapping in Railway Rails
Authors: Kelleher Joe F. , Buttle David J. , Mummery Paul M. , Withers Philip J.
Published: March 2009

Residual stress has been mapped in the heads of three normal grade and one heat treated (350HT) ex-service railway rails. Transverse, vertical and in-plane shear stresses were deduced using energy dispersive synchrotron X-ray, magnetic permeability and laboratory X-ray measurements. Differences were found between samples both in the distribution of compressive stress introduced at the running surface, and in the locations of the balancing tensile stress below this. The heat treated rail was found to have a thinner layer of surface compression than the normal
grade rails, with tensile stress being closer to the active gauge corner. The thinner layer of surface compression in the heat treated rail may reduce the protective benefits for rail integrity that surface compression is thought to confer.
Comparative Neutron and Synchrotron X-Ray Diffraction Studies to Determine Residual Stress on an As-Welded AA2024 Plate
Authors: Ganguly S. , Fitzpatrick Michael E. , Edwards Lyndon
Published: March 2009

The residual stress field in a VPPA welded AA2024 coupon sample was measured by
neutron diffraction. A similar sample was measured using synchrotron X-rays to determine the inplane strain directions. The macrostrain obtained from both sources compares well in spite of the significant difference in gauge volume and diffraction geometry. The result confirms the repeatability of the weld process and also shows good correspondence between the two diffraction processes.
Residual Stress in a Quenched Gear Shaft Treated by Water Cavitation Peening
Authors: Tsuda H. , Ju Dong Ying , Uchiyama T. , Sunayama Y. , Oba R.
Published: March 2009

Water cavitation technique can be applied to modify the surface strength of materials as an attractive new peening route. By inducing cavitation of ultrahigh speed water due to water-jet, the numerous impacts induced by the cavitation bubbles impact can produce compressive residual stress on material surface in the similar way as that by shot peening. In the present paper, an automobile part of steel gear shaft with complex shape is processed by water peening process. Compressive residual
stress induced by water peening was measured to investigate the surface strengthening effect as a quantitative factor. The residual stresses on the tooth surface of the gear are measured by X-ray diffraction method. The effect of process conditions such as water outlet pressure, standoff distance of the nozzle, and peening time are discussed. To investigate the effect of heat treatment, carburizing-quenching is implemented to the gear shaft. By comparing the residual stresses of the tooth before and after water peening, the effectiveness of water peening process on surface strengthening is verified for a quenched gear shaft.
A Study on Residual Stress Relaxation under Quasi-Static Load
Authors: Qin M. , Ji Vincent , Ma S.Y. , Li J.B.
Published: March 2009

Investigation on the quasi-static residual stress relaxation is an important aspect of
component design and life management. After taking into account the influence of transverse stress and strength distribution, this paper proposes a new criterion of residual stress relaxation under quasi-static load as follow: the surface residual stress tends to relax as long as the Mises effective stress anywhere exceeds the local yield point. In addition, by X-ray tensile test, a method of determining superficial yield strength based on the Von Mises hypothesis was applied at the shot-peened surface of a martensitic stainless steel 0Cr13Ni4Mo. The experimental results show
that the yield strength of superficial layer is larger than that of core material. According to the experimental results, a simplified ladder-shaped model of the depth distribution of yield strength is proposed. On the basis of the above-mentioned relaxation criterion and the strength distribution model, a new method is presented to calculate the relaxation amount. The calculated results coincide with the experimental results.
Internal Stress Effects on Mechanical Properties of TiCp Particle Reinforced Titanium Composites
Authors: Mao Xiao Nan , Ji Vincent , Zhou Lian , Zhou Y.G. , Zhang P.S. , Yu L.L.
Published: March 2009

In this paper the internal stresses had been measured on Ti-6Al-4V/7TiC, Ti-3Al-2.5V/7TiC and TP650 composite using the XRD method, the results show no other phases separate out besides the alpha(major phase, for over 90 percent), bate and TiC in the course of heating treatment. Compared the internal stress between prior of heat-treatment and latters, the internal stress was induced in Ti matrix and reinforcement (TiC particles). With temperature of heat-treatment enhancing, internal stress increases gradually, respectively. The relation between the internal stress and strength properties shows the static tensile strength of T64,T32 and T650 developed gradually with compressive internal stress increasing on TiC particle. The compressive stress induced in reinforcement relieved the stress intensity on surface of particle and develops the fracture toughening.
Thermal Stress Relief in 7050 Aluminum Forgings by Uphill Quenching
Authors: Wang Q.C. , Wang Li Tao , Peng Wei
Published: March 2009

A novel deep cryogenic treatment is presented to relieve residual stresses in 7050
aluminum alloy parts, in which the parts are submerged in liquid nitrogen and uphill quenched in proprietary QCW-01 quenchant. The optimum parameters of uphill quenching process were concluded in an attempt to combine maximum stress relief with the required levels of mechanical properties. The experimental results show that this novel deep cryogenic treatment can relieve as much as roughly 71% of residual stresses, higher than the traditional treatment uphill quenched in boiling water. An application example is highlighted, in which this uphill quench treatment has resulted in lower levels of residual stresses and machining distortions for an aircraft bulkhead
forging.
Thermoelectric Properties of Poly(3-Alkylthiophenes)
Authors: Shinohara Yoshikazu , Ohara K. , Nakanishi Hachiro , Imai Yoshio , Isoda Yukihiro
Published: March 2009

Typical conductive polymers of poly(3-alkylthiophenes) were synthesized by oxidative polymerization. Alkyl side chains were CnH2n+1 with n=4, 6, 8, 12. The regioregularity with the HT linkage was larger than 99% based on NMR analysis. Completely regioregular head-to-tail (HT) poly(3-alkylthiophenes) were obtained. We have evaluated the effect of side chain size on the thermoelectric properties of Seebeck coefficient and electrical conductivity. The results were as follows: 1) Seebeck coefficient decreased with an increasing electrical conductivity. 2) High Seebeck coefficient >1mV/K was observed at low electrical conductivity <10-2S/cm. 3) The small side chain caused the higher electrical conductivity in the range of electrical conductivity <10- 1S/cm.
Multifunctional Applications of Thin Film Li Polymer Battery Cells
Authors: Qidwai Muhammad A. , Baucom Jared N. , Thomas James P. , Horner David M.
Published: March 2009

Commercial off-the-shelf (COTS) thin-film solid-polymer Li-ion battery cells appear to posses the requisite physical characteristics for dual use as both electrical energy-storage devices and structural members under a finite load. One realistic application could be small electric unmanned vehicles where the power requirements are in the range of 10 to 100 watts and the mechanical loads are relatively small. We tested the multifunctional feasibility of COTS battery cells by designing a specific mechanical testing protocol based on realistic use in unmanned vehicles. Our characterization protocol included randomized bending and shear testing and generation of energy-power relation (Ragone) plots of the COTS cells. The results indicate that multifunction applications of COTS Li polymer battery cells are feasible; however, battery packaging geometry and bonding are critical design issues.
Effects of the Thermal Residual Stress Field on the Crack Propagation in Graded Alumina/Zirconia Ceramics
Authors: Vena P. , Gastaldi D. , Contro R.
Published: March 2009

A numerical approach to study the crack propagation in symmetric step-wise graded
Alumina/Zirconia composites subjected to a residual stress field is presented in this work. The finite element method is used to calculate the stress intensity factor for cracks developing from the surface and to determine the effects of the thermal residual stresses. The results show that a suitably conceived stacking sequence induces in the laminate a residual stress field able to provide increased toughness and reliability of the structure by making the crack propagation stable below a given threshold stress. Moreover a lower bound on stress, below which no crack propagation occurs, can be identified.
The Use of Functionally Graded Poly-SiGe Layers for MEMS Applications
Authors: Witvrouw A. , Mehta A.
Published: March 2009

It is difficult to meet all the different material and economical requirements posed to a MEMS structural layer that can be integrated with the electronics on the same substrate using a single layer process. Therefore a multilayer process, which uses a combination of a CVD crystallization layer and a high-growth rate PECVD bulk layer was developed. High-quality films with excellent electrical and mechanical properties can be obtained at low temperature (#450°C) and high deposition rates (~100 nm/min). Fine-tuning of the stress gradient is accomplished by the use of a top stress compensation layer, whose optimal thickness was estimated from an evaluation of the stress gradient profile over thickness. These layers have been used for processing a 10 µm thick poly-SiGe gyroscope on top of a standard 0.35 µm CMOS process.
Synthesis and Characterization of NaX Molecular Sieve Zeolite Films on Ceramic Paper for Membranes
Authors: Lee Hae Jin , Kim Hyung Chul , Kim Ik Jin
Published: March 2009

NaX molecular sieve films on ceramic paper prepared by in-situ hydrothermal method were investigated. The NaX zeolite seed crystals of a uniform size of 5 µm were synthesized by hydrothermal method in a mother solution having a composition of 3.5Na2O : Al2O3 : 2.1SiO2 : 500~1000 H2O. These dip-coated NaX seed crystal on ceramic paper lead to further the thickness (20 ~ 100 µm) of NaX film on the substrate at 90°C for longer 3~7 days in autoclave. Pure zeolite films consisting of a continuous intergrown of 5~ 20 µm NaX crystal have been prepared on the substrates. The zeolite films were characterized by XRD, SEM, BET and XRF.
Wear Mechanisms in Functionally Graded Aluminium Matrix Composites: Effect of the Presence of an Aqueous Solution
Authors: Gomes J.R. , Ribeiro A.R. , Vieira A.C. , Miranda A.S. , Rocha L.A.
Published: March 2009

Functionally graded aluminium matrix composites reinforced with SiC particles are
attractive materials for a broad range of engineering applications whenever a superior combination of surface and bulk mechanical properties is required. In general, these materials are developed for the production of high wear resistant components. Also, often this kind of mechanical part operates in the presence of aggressive environments, such as marine atmospheres. In this work, aluminium
composites with functionally graded properties, obtained by centrifugal cast, are characterised by reciprocating pin-on-plate sliding wear tests against nodular cast iron. Three different volume fractions of SiC reinforcing particles in each functionally graded material were considered. Sliding experiments were performed with and without the presence of a lubricant (3% NaCl aqueous solution). In the case of the lubricated tests, electrochemical parameters (corrosion potential) were monitored during sliding. Friction values were in the order of 0.42 for unlubricated conditions, but varied between 0.22 and 0.37 when the aqueous solution was present. For all test conditions, relatively high wear rates (over 1×10-6 gm-1) were obtained, particularly for the cast iron pin. The volume fraction of SiC particles
exerted a net effect on the tribological response of the composites, although conditioned by the presence or absence of the aqueous solution. The worn surface morphology of the composites indicated that the presence of the aqueous solution modifies the protective action promoted by the combined effect of the presence of reinforcing particles as load bearing elements and the formation of adherent iron-rich tribolayers. The evolution of the corrosion potential during the sliding action is in
accordance to the degradation mechanisms proposed for these systems.
Design of Functionally Graded Structures Using Topology Optimization
Authors: Paulino Glaucio H. , Silva Emílio Carlos Nelli
Published: March 2009

The concept of functionally graded materials (FGMs) is closely related to the concept of topology optimization, which consists in a design method that seeks a continuum optimum material distribution in a design domain. Thus, in this work, topology optimization is applied to design FGM structures considering a minimum compliance criterion. The present approach applies the so-called “continuous topology optimization” formulation where a continuous change of material properties is considered inside the design domain by using the graded finite element concept. A new design is obtained where distribution of the graded material itself is considered in the design domain, and the material properties change in a certain direction according to a specified variation, leading to a structure with asymmetric stiffness properties.
Electrodeposition of Gradient Layers for Improved Impact Load Resistance
Authors: Fauser Heidi , Poizat Christophe , Grimm Markus , Knoll Heiko , Schmitt Winfried , Freudenberger Renate
Published: March 2009

The aim of the research project described here is to increase the durability of components under cavitation erosion by electrodeposition of gradient layers. Parallel to the material development, a simulation tool is elaborated to determine the optimal gradient layers for improved load resistance. This helps in minimising the number of prototype layer systems to be manufactured within the project. The initial experiments were executed with the nickel-phosphorus system, which is well-known for its favourable properties regarding hardness, corrosion resistance and tribology.
Single and gradient layers are characterised and evaluated in view of the following properties: hardness, internal stresses, ductility, coefficient of friction, wear resistance, elastic modulus and tensile strength.
Combustion Synthesis of Dense Functionally Graded B4C Reinforced Composites
Authors: Zlotnikov I. , Gotman I. , Klinger Leonid , Gutmanas Elazar Y.
Published: March 2009

Dense FGMs with gradually changing fraction of very hard and light-weight B4C particles were fabricated employing an original Reactive Forging (RF) combustion synthesis method. In RF, a self-sustained reaction (thermal explosion, TE) is ignited by placing a powder blend between preheated press rams and the high temperature achieved is utilized for consolidation of the combustion product. The reported FGMs were prepared by stacking layers of highly exothermic Ti-C-Ni powder blend diluted with varying fractions of non-reacting B4C particles. Only a limited amount of B4C could be added as its diluting action reduces the overall exothermicity of the blend. In some cases, B4C particles were precoated in order to prevent their interaction with Ti during combustion. Temperature evolution in (Ti-Ni-C)-B4C powder compacts corresponding to different FGM layers was measured separately and in the stacked form. The better understanding of combustion process in B4C-diluted blends coupled with well-devised geometrical design allowed us to fabricate FGMs with high volume fractions of B4C in the surface layer.
Formation of Compositional Gradient during Fabrication of FGMs by a Centrifugal In Situ Method
Authors: Watanabe Yoshimi , Oike Shin , Kim Ick Soo
Published: March 2009

The purpose of the present work is to study the formation of the compositional gradient during the fabrication of FGMs by a centrifugal in-situ method. Al-Al2Cu FGMs were fabricated by the centrifugal in-situ method using eutectic Al-33mass%Cu alloy, and the microstructures of fabricated FGMs were studied. It was found that the Al-Al2Cu FGMs could be fabricated by the centrifugal in-situ method from eutectic alloy. Based on the experimental results, the formation mechanism of the compositional gradient during the fabrication of FGM by the centrifugal in-situ method in the A-B alloy could be summarized as follows; 1) Partial separation of A and B elements in the liquid state occurs due to the density difference. 2) A compositional gradient is formed before the crystallization of the primary crystal. 3) The primary crystals in the matrix appear to depend on local chemical composition. 4) The primary crystals migrate according to density difference, and a further compositional gradient is formed.
Toughness Enhancement of Al2O3/Ce-TZP Functionally Graded Materials by Annealing in Inert Atmosphere
Authors: Vleugels Jef , Zhao Chao , Van der Biest Omer
Published: March 2009

CeO2-stabilised ZrO2-based functionally graded materials (FGMs) can be successfully produced using electrophoretic deposition and pressureless sintering in air. A cylindrical Al2O3/ZrO2 FGM, for instance, shows an ideal structure for applications such as drill blanks. It has a central hole with a diameter less than 0.5 mm, a tough Ce-ZrO2 core with a diameter of about 3 mm, a gradient layer of about 1 mm, and a hard Al2O3-rich surface layer. The Ce-ZrO2 core shows a Vickers hardness between 10 and 11 GPa and an excellent toughness (>10 MPa m1/2). In the gradient layer, hardness and toughness vary continuously along the radius. The Al2O3-rich surface layer has a hardness of 15.2 GPa but a modest toughness of 2 MPa m1/2. Annealing experiments of the air-sintered FGM in inert atmosphere (Ar + 5 vol % N2) allows a significant toughness enhancement, especially in the surface layer (up to 8 MPa m1/2). The experimental results indicate that a proper controlled reduction of the Ce-TZP phase allows a modification of the toughness of the Ce-TZP phase. The influence of the annealing cycle on the properties of the FGM are reported and elucidated.
Preparing 3D Functional Gradients for SLS
Authors: Yang Shou Feng , Evans Julian R.G.
Published: March 2009

The creation of three dimensional functional graded materials by powder processing
methods requires the capability to arrange a sequence of two dimensional images that can be presented to a solid freeforming device. Planar stacking methods can only achieve a one dimensional gradient. We describe the acoustic control of powder metering and dispensing valves in which the flow rate and switching of powders from a capillary can be controlled using the frequency and amplitude of acoustic vibration from a computer sound card. An orchestra of such valves can be used to pattern layers of powder on the building platform which forms part of a 3-axis
table in the Selective Laser Sintering (SLS) process. Patterns and gradients were prepared using copper and steel powders.
Influence of Al2O3 Addition on the Microstructure and Mechanical Properties of Pressureless Sintered Ce-TZP
Authors: Huang Shui Gen , Li Lin , Vleugels Jef , Wang Pei Ling , Van der Biest Omer
Published: March 2009

Mixtures of 12 mol% CeO2-stabilised ZrO2 with 5 to 20 wt % Al2O3 were prepared and densified through pressureless sintering in air at 1450° C for 1 to 4 h. The influence of the Al2O3 content and sintering time on the phase constitution, microstructure and mechanical properties of the as-sintered composites were investigated. Fully dense Ce-TZP/Al2O3 ceramics with a good combination of hardness and fracture toughness can be obtained by pressureless sintering in air for only 1 h. The addition of Al2O3 to Ce-TZP improves the mechanical properties and suppresses ZrO2 grain growth. The average ZrO2 grain size increases with increasing sintering time and decreasing Al2O3 content. This leads to an increase in toughness. An excellent fracture toughness of 14.3 MPam1/2 in combination with a Vickers hardness of 9.14 GPa was obtained for 12 mol % CeO2-TZP with 5 wt % Al2O3, sintered for 4 h.
Low Pressure RF Capacitively Coupled Plasma Reactor for Modification of Seeds, Polymers and Textile Fabrics
Authors: Puač N. , Petrović Z.Lj. , Radetić M. , Djordjević A.
Published: March 2009

Plasma reactor operating at low pressures (0.2-1 Torr) at 13.56 MHz has been developed with an idea to optimize the treatment of polymers, biological and textile materials. The reactor proved very effective in treatment of polymer surfaces and wool fabrics in order to improve wettability, efficiency of dyeing and printing as well as to reduce the felting shrinkage. It also gave good results in improving germination of seeds. The basic conditions that the reactor has to satisfy are: the energy of ions that hit the surface has to be low and the reactor should be efficient in production of active radicals. Two systems with different geometries were studied, both capacitively coupled plasma reactors operating at 13.56 MHz. Cylindrical geometry was selected in order to minimize the energy of ions reaching the surface. Modeling of the discharge was performed with an aim to verify the energy distribution function of ions. As a critical diagnostic test of the system, voltage and current probes were developed to check the operation mode of the discharge. Oxygen, air and argon were used with different results.
Formation of Solid TiC from Thermal Plasma: Thermodynamic Consideration
Authors: Radić-Perić J.
Published: March 2009

The synthesis process of solid TiC in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixture containing titanium and chlorine (titanium as a reactant is assumed to be in the form of titanium tetrachloride) with argon, hydrogen and carbon (carbon as a reactant is assumed to be in the form of methane). The calculation was performed for the temperature range between 500 and 6000 K and the total pressure in the system of 1 bar. The fact that thermal plasma is plasma in (local) thermodynamic equilibrium made possible the theoretical determination (by employing the Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state) of its equilibrium composition. From the calculated compositions of the investigated gas systems the temperature zones with saturated and/or oversaturated vapor of Ti, TiC and C were determined and the mechanism of the formation of TiC in solid state was proposed.
Structural Characterization of Poly(o-Tolidine)
Authors: Ćirić-Marjanović G. , Marjanović B. , Trchová M. , Holler P.
Published: March 2009

A new polymer of o-tolidine was synthesized by chemical and electrochemical methods from its aqueous solutions in 1M HCl. Chemical oxidative polymerization was performed using ammonium peroxydisulfate as an oxidant. Electrochemical polymerization was carried out using two steps which were successively repeated in a continual process: first, holding the working platinum electrode under a constant anodic potential of +1.6 V, and second, the voltammetric cycle between +0.3 and +1.6 V. During this procedure a polymeric film was formed on the working electrode. Polymerization of o-tolidine was exactly proved by gel permeation chromatography evidencing the chains of molar masses in the range of 1000 – 12600 g mol─1. The structure of poly(o-tolidines) obtained by both chemical and electrochemical procedures was studied by IR spectroscopy. Coupling pathway N–C during polymerization, existence of quinonoid rings and hydrogen bonding involving NH group in polymeric products are revealed by IR spectroscopic analysis. The mechanism of o-tolidine oxidative polymerization is proposed.
Examinations of Cross-Linked Polyvinylpyridine in Open Reactor
Authors: Milošević M. , Pejić N. , Čupić Ž. , Anić S. , Kolar-Anić Lj.
Published: March 2009

Macroporous cross-linked copolymer of 4-vinylpyridine and 25% (4:1) divinylbenzene is analyzed under open conditions, that is in a continuous well-stirred tank reactor (CSTR). With this aim the appropriate bifurcation diagram is found and the behavior of the system with and without polymer in the vicinity of the bifurcation point is used for the polymer examinations. Two different granulations of polymer are considered. Moreover, some physicochemical characteristics of the polymer, such as specific surface area, skeletal and particle density, are determined.
Adsorption of Tiron onto Alumina
Authors: Roćen J.J. , Čerović Lj.S. , Milonjić S.K.
Published: March 2009

It has been shown recently that small organic molecules, used as dispersants in the
colloidal processing of ceramic powders to adjust the forces between the particles, are quite efficient in preparing aqueous suspensions of high solid loadings and low viscosity. One of them is 4,5-dihydroxy-1,3-benzenedisulfonic acid, disodium salt monohydrate, ((OH)2C6H2(SO3Na)2·H2O), commercially known as Tiron. The adsorption of Tiron, as a function of its concentration and solution pH, onto alumina was investigated by the solution depletion method, applying UV spectrophotometry. KNO3 (10-2 mol/l) was used as the background electrolyte. The obtained results indicate an increase in the amount of adsorbed Tiron with its increasing concentration. The maximum adsorption was recorded at pH≈7 when the Tiron molecule was uncharged, i.e. undissociated (pKa1=7.6). The experimental data were fitted with different adsorption isotherm models. The maximum amount of Tiron adsorbed, as well as the constants of adsorption process were calculated.
Nature of Magnetism in the HfCo2 Laves Phase
Authors: Belošević-Čavor J. , Novaković N. , Cekić Bozidar , Koteski V.
Published: March 2009

Despite the fact that the magnetic properties of the intermetallic compounds with C15- type Laves phase structure have so far been studied intensively, the nature of magnetism in some of them is still a matter of controversy. In order to establish and understand the magnetism in the HfCo2 Laves phase with C15 (MgCu2-type) structure, calculations using FP-LAPW WIEN 97 program package for non-polarized and spin-polarized cases were made. They have shown that the spin-polarized case is more stable, i. e. the energy of its ground state is lower by about 0.15 eV. This is in collision with the measured TDPAC spectra, which show no sign of magnetic interaction, as well as with the earlier reported magnetization and susceptibility measurements, which claim that HfCo2 is Pauli paramagnet. Probable explanation for the obtained contradiction is the deviation of the real structure from the ideal one.
A Dislocation Density Based Constitutive Model for Crystal Plasticity FEM
Authors: Ma A. , Roters Franz , Raabe Dierk
Published: March 2009

Crystallographic slip, i.e. movement of dislocations on distinct slip planes, is the main source of plastic deformation of most metals. Therefore, it was an obvious idea to build a constitutive model based on dislocation densities as internal state variables in the crystal plasticity. In this paper the dislocation model recently proposed by Ma and Roters (Ma A. and Roters F., Acta Materialia, 52, 3603-3612, 2004) has been extended to a nonlocal model through separating the statistically stored dislocation and geometrically necessary dislocation densities. A nonlocal integration algorithm is proposed, which can be more easily used in conjunction with commercial software such as MARC and ABAQUS than the model proposed in the work of Evers(Evers L.P., Brekelmans W.A.M., Geers M.G.D., Journal of the Mechanics and Physics of Solids, 52, 2379-2401, 2004).
Dynamic Twin Nucleation at Triple Junctions in Fe-32%Ni Stainless Steel
Authors: Miura Hiromi , Andiarwanto Sutandyo , Sakai Tetsuo , Jonas John J.
Published: March 2009

The preferential initiation of dynamic recrystallization (DRX) at triple junctions (TJs) in stainless steel polycrystals was investigated in compression at 1123 K to 1323 K at a strain rate of 2 x 10-4 s-1. Nucleation appeared at TJs at strains as low as 0.1. This strain is only about 1/5 to 1/2 of the peak strain at which DRX is conventionally believed to occur extensively. Furthermore, DRX nucleation was not observed to take place at grain boundaries or in the matrix at this strain. The probability of DRX nucleation at TJs increased monotonically with strain and temperature. It also depended on the angle, y, between the compression axis and the sliding boundary. That is, when the angle, y, approaches 45 degrees, the probability of DRX nucleation at TJs is higher. These results reveal the important role of grain-boundary sliding (GBS) on DRX nucleation at TJs. It should also be noted that more than 90% of the grains nucleated at TJs were twins. Such dynamic twinning suggests that the essential DRX nucleation mechanism is twinning.
The Effect of Grain Orientation on Micro Frictional of Medium Carbon Steel
Authors: Reza Bateni M. , Azzi Marwan , Szpunar Jerzy A. , Wang X. , Li Dong Yang
Published: March 2009

The mechanical processing of metals results often in development of preferred orientation of grains or texture. On the other hand, the orientations of grains have a significant effect on the friction and wear behaviour of materials in contact. The objective of this investigation was to determine the crystallographic anisotropy of the coefficient of friction. Medium carbon steel AISI 1045 were selected as the substrate material. Automated orientation imaging analysis system (OIM) was used to identify orientations of grains in polycrystalline specimens. Micro-friction tests were
carried out using a Tribocope, a combination of nano-mechanical probe and atomic force microscope with an electrochemical cell. The micro friction tests were performed along different crystallographic directions inside different grains.The obtained results have shown that the coefficient of friction for individual grains depends on crystallographic orientation, and that the coefficient of friction for higher atomic density planes is lower than that for lower atomic density planes.
The Influence of Errors of X-Ray Texture Measurements on ODF Calculation with Central Normal Distribution Approximation
Authors: Ivanova T.M. , Lubman H.U. , Savyolova T.I. , Serebryany Vladimir
Published: March 2009

Experimental pole figures are measured by x-ray method for materials with hexagonal
symmetry (Ti and Mg alloys). The Orientation Distribution Function is calculated by approximation method with central normal distribution. Texture inhomogeneities and effects of defocusing are the main sources of pole density errors. The measurement errors depend on crystal direction {hkl} and are different for maximum and minimum regions on pole figure. The influence of texture measurement errors on accuracy of the ODF calculation is investigated.
The Application of Multiscale Modelling for the Prediction of Plastic Anisotropy and Deformation Textures
Authors: van Houtte Paul , Van Bael Albert , Seefeldt Marc , Delannay Laurent
Published: March 2009

The paper focuses on the multi-level character of existing or currently developed models for polycrystal deformation. A general multilevel frame is presented, which can be applied to models for the simulation of plastic anisotropy to be implemented in FE codes for the simulation of metal forming processes, or to models for the simulation of deformation textures. A short overview is presented of two-level models ranging from the full-constraints Taylor model to the crystalplasticity finite element models, including the description of a few recent and efficient models (GIA and ALAMEL). Validation efforts based on experimental cold rolling textures obtained for steel and aluminium alloys are discussed. Finally a recent three-level model which also takes the microscopic level (dislocation substructure) is discussed.
The ODF-Spectrum a New and Comprehensive Characterization of the Degree of Anisotropy of Orientation Distributions
Authors: Matthies Siegfried
Published: March 2009

The texture index F2 (1£ < F2 £ ¥ , F2 = 1 – random distribution) is up to now the only parameter used in a global way to characterize the degree of anisotropy of a given ODF – the foremost question to be answered in applied TA. However, one number is a quite poor characteristic, and a concrete F2-value can hardly be interpreted. It depends on many parameters and may belong to very different orientation distributions. Introducing so-called ODF-channels a one-dimensional ODFchannel histogram can be got for any ODF. Its form and spectral properties provide a comprehensive characterization of the character of anisotropy of a given ODF.
Multiscale Characterisation of the Transformation Texture in a High Performance Steel
Authors: Godet Stéphane , He You Liang , Jonas John J. , Jacques Pascal J.
Published: March 2009

The orientation relationships operating during the austenite (FCC) to BCC phase transformation were investigated in a high performance steel using X-ray and electron diffraction techniques and employing several length scales. These steels contain some retained austenite that permits the direct comparison of the textures of the parent (austenite) and product (ferrite, bainite, martensite) phases. X-ray diffraction allowed the global texture of the rolled parent austenite phase to be determined as well as that of its transformation product. EBSD techniques permitted study of the orientation relationships on a local scale. The observed correspondence relations are expressed in Rodrigues-Frank space. The exact Kurdjumov-Sachs relation was never found. The local spread of orientation in the parent austenite (due to deformation) is seen to be inherited by the bainite. This is attributed to the displacive mode of transformation to bainite. The influence of prior deformation of the austenite on the occurrence of variant selection was also studied. It appears that a critical strain is necessary to produce a significant amount of variant selection.
The Study of Texture Development of High Temperature Oxide Scales on Steel Substrates Using Electron Backscatter Diffraction
Authors: Higginson R.L. , West G.D.
Published: March 2009

Low silicon carbon steel has been oxidised at varying temperatures in free flowing air
using a thermomechanical simulator to control heating and cooling rates. The resultant oxide scales have been studies using Electron Backscatter Diffraction (EBSD) and the phases identified by the differences in the diffraction patterns. The crystallographic textures were calculated from the EBSD data. There is a correlation between the textures of the different phase layers within the scale, which depends on the formation mechanism of the individual phases.
Comparison between the Growth Behaviour of the Small Goss Grains and that of the Large Matrix Grains in Silicon Steels. Influence of the Textured Cluster Presence
Authors: Afer H. , Rouag N. , Penelle Richard
Published: March 2009

In the Fe-3%Si alloys, grade Hi-B with AlN and MnS as inhibitors, the Goss grains that abnormally grow have not a size greater than the average size of the primary matrix. In such a heterogeneous microstructure, the size factor is not a required condition for the secondary recrystallization. The abnormal growth onset of the small Goss grains appears to be related to a particular behaviour of their grain boundaries and therefore to the local texture so as the distribution of the inhibitors. The presence and the evolution of textured clusters ensure to the small Goss grains
a favourable neighbourhood to grow. In this study, their growth ability is compared with that of the largest grains of the matrix. The modified Monte-Carlo approach, performed in the present study, considers the local environment of each grain, so that the growth rate is dependent of its real spatial position, the matrix heterogeneity is then taken into account.
Recrystallization Texture and r-Value of Rolled and T4-Treated Al-Mg-Si Alloy Sheets
Authors: Inoue Hirofumi , Yamasaki Tohru , Gottstein Günter , van Houtte Paul , Takasugi Takayuki
Published: March 2009

In order to improve deep drawability of Al-Mg-Si alloy sheets for automotive body panel by texture control, the effects of Mn addition and warm rolling on recrystallization texture were investigated for rolled and T4 treated sheets and the r-value was related to overall texture through thickness. Recrystallization texture after T4 treatment varied significantly depending on alloy composition and rolling condition. Planar anisotropy of r-value could be predicted relatively exactly from recrystallization texture by the Taylor full constraints model for all specimens. Mn addition led to an increase of average r-value in both cold and warm rolled materials, while warm rolling resulted in a decrease of average r-value in spite of relatively high predicted r-values in the surface layer.
Joint Inclination Effect on Strength, Stress-Strain Curve and Strain Localization of Rock in Plane Strain Compression
Authors: Wang X.B.
Published: March 2009

Peak strength, mechanical behavior, and shear band (SB) of anisotropic jointed rock (JR) were modeled by Fast Lagrangian Analysis of Continua (FLAC). The failure criterion of rock was a composite Mohr-Coulomb criterion with tension cut-off and the post-peak constitutive relation was linear strain-softening. An inclined joint was treated as square elements of ideal plastic material beyond the peak strength. A FISH function was written to find automatically elements in the joint. For the lower or higher joint inclination (JI), the higher peak strength and more apparent strain-softening behavior are observed; the failure of JR is due to the slip along the joint and the new generated SBs initiated at joint’s two ends. For the lower JI, the slope of softening branch of stress-strain curve is not concerned with JI since the new and longer SBs’s inclination is not dependent on JI, as can be qualitatively explained by previous analytical solution of post-peak slope of stress-strain curve for rock specimen subjected to shear failure in uniaxial compression based on gradient-dependent plasticity. For the higher JI, the post-peak stress-strain curve becomes steeper as JI increases since the contribution of the new SBs undergoing strain-softening behavior to axial strain of JR increases with JI. For the moderate JI, the lower strength and ideal plastic behavior beyond the elastic stage are found, reflecting that the inclined joint governs the deformation of JR. The present numerical prediction on anisotropic peak strength in plane strain compression qualitatively agrees with triaxial experimental tests of many kinds of rocks. Comparison of the present numerical prediction on JI corresponding to the minimum peak strength of JR and the oversimplified theoretical result by Jaeger shows that Jaeger’s formula has overestimated the value of JI.
The Role of Crystallographic Texture of Ti-6Al-4V Alloy on Cell Attachment and Proliferation
Authors: Faghihi S. , Bateni M.R. , Azari Fereshteh , Szpunar Jerzy A. , Vali H. , Tabrizian M.
Published: March 2009

Owing to their lower modulus, great corrosion resistance and superior biocompatibility, titanium alloys are increasingly used as artificial joint replacements. However bone bonding capability of these materials needs to be improved. Many studies are currently conducted to improve the osseo-integration of titanium based implants. In the present study, the role of crystallographic texture of titanium alloy Ti-6Al-4V on bone bonding capability was investigated in vitro systems. X-ray diffraction analysis was used to determine preferred orientation in each substrate. These substrates were seeded with preosteoblast cells to examine cell attachment and proliferation. Attachment of cells was assessed by counting the number of adhered cells within 30-240 min. The proliferation rate of cells was measured between the 3rd-11th days of incubation. The results suggest that the substrate with (100) orientation shows better osteoblastic cell adhesion and proliferation rate than the (110).
Development of Nonuniform Substructure and Microstrain Distribution by Texture Formation in Metal Materials
Authors: Perlovich Yuriy , Isaenkova Margarita , Fesenko Vladimir , Bunge Hans Joachim
Published: March 2009

The substructure nonuniformity of metal materials with developed deformation texture
was studied by use of the X-ray method of Generalized Pole Figures. Main regularities of substructure nonuniformity were revealed for the first time. Substructure conditions of grains in rolled material form an extremely wide spectrum and vary by passing from texture maxima to texture minima, where residual deformation effects are most significant. The distribution of residual elastic microstrains in the orientational space of rolled material shows the distinct cross-wise
system, consisting in alternation of quadrants with predominant microstrains of opposite signs.
Texture Development in Interstitial Free (IF) Steel Subjected to Two Cycles of Equal Channel Angular Extrusion
Authors: Pereloma Elena V. , Gazder Azdiar A. , Davies Chris H.J.
Published: March 2009

Texture development and grain refinement of interstitial-free (IF) steel as a function of ideal simple shear or torsion was undertaken for up to 8 pressings, Route BC. Dominant texture components evolved after a single pass and remained correspondent for all subsequent passes. End-cycle (4 and 8 pass) orientation distribution functions (ODFs) showed an increased spread of contour levels and the re-appearance of texture components similar to the 0-pass condition. Rotation of torsion components away from their ideal pole figure (PF) orientations increased at mid-cycle and decreased to almost equivalent levels after end-cycle passes. This is attributed to the principle slip directions of BCC structures aligning with the shear direction.
A Texture Evolution Study Using the Texture Component Crystal Plasticity FEM
Authors: Roters Franz , Jeon-Haurand Heyon S. , Raabe Dierk
Published: March 2009

Crystal plasticity FEM simulations of plane strain compression were performed. The
Texture Component Crystal Plasticity-FEM was used for the texture mapping. Two different starting textures (random and hot rolling texture) were studied using four different FE meshes and two different sets of boundary conditions. While for the random starting texture the evolution of the texture with deformation was found to be rather similar in all cases studied, the simulations using an experimental hot rolling texture as staring texture are much more sensitive to the boundary conditions and probably also to changes in the mesh geometry.
Improving the Self-Consistent Predictions of Texture Development of Polycrystals Incorporating Intragranular Field Fluctuations
Authors: Lebensohn Ricardo A. , Tomé Carlos , Ponte Castañeda Pedro
Published: March 2009

In this contribution we present how to implement the calculation of average field
fluctuations inside the grains of a thermoelastic aggregate in terms of the derivatives of the stress potential given by the standard linear self-consistent (SC) model, and how this statistical information can be used to generate second-order estimates for the mechanical behavior of nonlinear viscoplastic polycrystals, by means of a rigorous non-linear homogenization procedure. To illustrate the differences between this second-order (SO) self-consistent approach and the classical first-order SC approximations, we compare them in terms of their predictions of the effective
behavior of random fcc polycrystals as a function of their rate-sensitivity, and of the texture evolution in hcp ice polycrystals under uniaxial compression. In the latter case, the SO approximation is the only one able to predict a substantial accommodation of deformation by basal slip, even when the basal poles become strongly aligned with the compression direction and the basal slip systems became unfavorably oriented.
High-Speed Steels Produced by Conventional Casting, Spray Forming and Powder Metallurgy
Authors: Mesquita Rafael Agnelli , Barbosa Celso Antonio
Published: March 2009

Powder metallurgy (PM) and spray forming (SF) have been reported as important alternative routes for tool steel production. The ability to promote refined and more uniform microstructures is their main advantages, leading to improved properties and larger isotropy. While PM application is a completely established technology, the SF process may be considered as a not totally explored field. Therefore, the present work aimed to study the potential of both processes, focusing at high-speed steel (HSS) production. AISI M3:2 highspeed steel was produced by conventional casting, spray forming and powder metallurgy. Conventional ingots and a 400 mm diameter SF billet were rolled to small diameter bars, with cross section around 110 mm. The PM material was evaluated in the as-HIPed condition, in comparative diameters. Large diameter HSS bars are used mainly in cutting tools, but are also applied in cold work tooling when high wear resistance is required. In the present characterisation, microstructures and bend test analysis were used, both in transverse and longitudinal directions. The results show that the as-HIPed PM material presents finer and more uniform carbide distribution, leading to a complete isotropy and higher toughness than conventional steel. In the SF material, carbides are also finer, have good distribution and the isotropy is considerably higher than that for conventional HSS.
Evaluation of the Effect of Heavy Rare Earth Elements on Electrical Resistivity of Zirconia-Yttria Ceramics
Authors: Lazar Dolores Ribeiro Ricci , Ussui Valter , Muccillo E.N.S. , Bressiani Ana Helena A. , Pascoal José Octavio A.
Published: March 2009

The use of yttria concentrates was investigated in this study for synthesis and processing of zirconia based ceramics applied as solid electrolyte materials. Terbium, dysprosium, holmium, erbium and ytterbium are the chemical elements, classified as heavy rare earths, that can be found in those concentrates due to their association with yttrium ores. The ceramic characteristics were compared to zirconia-yttria and zirconia-yttria-heavy rare earth oxide systems, containing 3 and 9 mol% of dopant. Powders were prepared by the coprecipitation route and ceramic processing conditions were established to attain relative densities up to 95%. The characterization of assintered pellets was performed by apparent density measurement by Archimedes method, X-ray diffraction, scanning electron microscopy and electrical resistivity measurement by impedance spectroscopy. It was observed that the presence of heavy rare earths in a concentrate containing 85 wt% of yttria has no significant influence on the total ionic resistivity of zirconia based ceramics.
Ceramic Composites Derived from Polysiloxane/Al/Nb by AFCOP Process
Authors: Schiavon Marco Antônio , Yoshida I.V.P. , Bressiani José Carlos , Acchar Wilson
Published: March 2009

In this work, ceramic matrix composites (CMC) were prepared by AFCOP process, using a polysiloxane network filled with metallic niobium and aluminum powders as active fillers. The liquid polysiloxane precursor was loaded with a suitable polymer/filler ratio in relation to stoichiometric Nb : C and Al : O molar ratios. Changing Al for a-Al2O3, which acted as an inert filler, non-stoichiometric conditions were obtained. The mixtures were blended, uniaxially warm pressed, and pyrolysed in flowing argon at 800, 1000 and 1200 °C. Thermogravimetry was used to follow the weight changes during the pyrolysis process. X-ray diffraction was used to identify the formation of new crystalline phases, such as Al2O3, NbC, Nb2C and Al3Nb in the composites. Sintered specimens were also characterized by SEM and EDS. The results indicated good potential for this system to obtain multiphasic composite material in the Al-Nb system at lower temperatures.