bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the Master Sintering Curve Theory to Non-Isothermal Sintering of BaTiO3 Ceramics
Authors: Nikolić Maria V. , Pavlović Vera P. , Pavlović Vladimir B. , Labus Nebojsa , Stojanović B.D.
Published: March 2009

In this paper a practical approach to the analysis of sintering of BaTiO3 using the Master Sintering Curve concept has been presented. Non-isothermal sintering of high-purity non-doped BaTiO3 ceramics was monitored using a sensitive dilatometer at three different heating rates (10, 20 and 30 oC/min) up to 1380oC. Densification of BaTiO3 during sintering was analyzed using the Master Curve Sintering Theory. A MSC was defined characterizing the sintering behavior of barium-titanate regardless of the heating rate. Construction of the MSC enabled estimation of the process activation energy. Using defined MSC, densification behavior of BaTiO3 ceramics during sintering can be predicted for arbitrary temperature-time excursions and these predictions can be used in controlling and planning the sintering process of this material.
SiC/SiC Composites Prepared with a BN Interphase Processed by LP-CVD from Molecular Precursor
Authors: Jacques Sylvain , Berthet Marie Paule , Bonnetot B.
Published: March 2009

A BN interphase has been deposited by infiltration of a Hi-Nicalon fibre tow in a Low Pressure Chemical Vapour Deposition reactor using a boron nitride molecular precursor: the tris(dimethylamino)borane (TDMAB), an halogen-free precursor. This precursor prevents fibre and CVD apparatus from chemical damage. Then SiC/BN/SiC 1D mini-composites were produced by classical CVD of SiC from hydrogen and methyltrichlorosilane mixture. The interphase composition was characterised using FT-IR and XPS analyses and the presence of carbon in the BN has be related to surface pollution and not from carbon bounded to the coating. The tensile properties of the mini-composites were tested with unload-reload cycles and have shown very good mechanical properties corresponding to a high interfacial shear stress. The observations of the interphase using TEM reveal that it is made of an anisotropic turbostratic BN. The fibre/matrix debounding, which occurs during mechanical loading, was shown to be located within the BN interphase.
Biopolymer Chain Folding and Biomolecular Recognition: A Quantum Decoherence Theory Approach
Authors: Raković D. , Dugić M. , Plavšić M.B.
Published: March 2009

In this paper we describe the biopolymer chain folding problem in the framework of the so-called quantum decoherence theory. As we propose a rather qualitative scenario yet bearing generality, it seems this provides promising basis for the solution-in-principle of the (semi) classically hard kinetic problem of biopolymer chain folding from coiled to native conformation in highly selective ligand proteins/target-receptors biomolecular recognition processes, implying underlying macroscopic quantum nonlocality on the level of biological cell.
Theoretical and Experimental Exploration of the Energy Landscape of LiI
Authors: Čančarević Ž.P. , Schön J.C. , Fischer D. , Jansen Martin
Published: March 2009

The prediction of the existence and stability of (meta)-stable phases in a chemical system is realized via a two-step process: identification of structure candidates through global exploration of the classical empirical energy landscape, followed by a local optimization of the candidates on ab-initio level employing a heuristic algorithm. From the computed energy/volume curves, one can then calculate the thermodynamically stable phase at a given pressure and the transition pressures
among the phases. In order to gain insight into the kinetic stability of the structure candidates, one computes estimates of the energy and enthalpy barriers around the structures with the so-called threshold algorithm, yielding a tree graph representation of the chemical system. In this work we perform a theoretical and experimental study of the LiI energy landscape. We determine the structure candidates, construct the tree graph representation and compute the abinitio
energy/volume curves for the hypothetical structures. We find that the thermodynamically preferred modifications at standard pressure should exhibit the rock salt and the wurtzite structure, respectively. In order to validate our predictions by experiments, we have employed the newly developed ´Low-Temperature - Atomic Beam Deposition` (LT-ABD) technique, which allows to disperse the components of the desired product at an atomic level and in an appropriate ratio. After depositing
LiI at T = 77 K, the first crystallization occurs at T » 173 K in the wurtzite-type structure followed by a transition to the more stable rock salt-type structure at T » 273 K. At room temperature only the cubic phase remains.
Application of In Situ HREM to Study Crystallization in Materials
Authors: Sinclair R. , Min Kyung Hoon , Kwon U.
Published: March 2009

A review is given of the application of in situ transmission electron microscopy to study various processes associated with the crystallization of amorphous thin films. Solid phase epitaxial regrowth of ion-implanted silicon is compared with nucleation and growth in deposited thin films. The mechanism of metal-mediated crystallization is deduced directly from high resolution recordings, and the kinetics of tantalum oxide devitrefication are obtained. The advantages of direct in situ observation are described
Lowest Energy Structures and Electronic Properties of Small Molybdenum Clusters
Authors: Koteski V. , Cekić Bozidar , Novaković N. , Belošević-Čavor J.
Published: March 2009

The structural and geometric properties of small Mo clusters are studied by means of first principles density functional theory (DFT) calculations with planewaves and pseudopotentials. The lowest energy structures of Mon (n=2-6) clusters are determined. The evolution of electronic properties with increasing cluster size is discussed. The geometric structure, average bond lengths, and binding energies of the lowest energy isomers are reported and the results are compared with the available experimental and theoretical data.
Experimental Study on the Influence of Grain Boundaries on the Subdivision Behaviour of Al-3%Mg Polycrystals during Cold Deformation Using Electron Backscatter Diffraction
Authors: Van Boxel Steven , Seefeldt Marc , Verlinden Bert , van Houtte Paul
Published: March 2009

The substructure of a single grain in an electron backscatter diffraction (EBSD) data map is studied, focusing on the influence of the grain boundary configuration on the misorientation to the average grain orientation of data points close to the grain boundary. For most grain boundary segments a certain degree of linking between the misorientations to the average orientation of the grain exists and large deviations from the average orientation of the grain are observed close to the triple junctions of the boundary segments. Changes of the misorientation over one boundary segment are analysed and possible explanations for these variations are discussed. It is suggested that the variations of the misorientation over the boundary segment can be attributed to the requirements of stress equilibrium and strain compatibility. Also the tendency of the grain boundary to lower its surface energy might have a significant influence on the misorientation profile and therefore on the subdivision behaviour of the grains.
The Role of Texture, Temperature and Strain Rate in the Activity of Deformation Twinning
Authors: Brown Donald W. , Agnew Sean R. , Abeln S.P. , Blumenthal W.R. , Bourke Mark A.M. , Mataya M.C. , Tomé Carlos , Vogel Sven C.
Published: March 2009

Plastic deformation in cubic metals is relatively simple due to the high crystallographic
symmetry of the underlying structure. Typically, one unique slip mode can provide arbitrary deformation. This is not true in lower symmetry hexagonal metals, where prismatic and basal slip (the usual favored modes) are insufficient to provide arbitrary deformation. Often, either pyramidal slip and/or deformation twinning must be activated to accommodate imposed plastic deformation. The varied difficulty of activating each of these deformation mechanisms results in a highly anisotropic yield surface and subsequent mechanical properties. Further, the relative activity of each
deformation mode may be manipulated through control of the initial crystallographic texture, opening new opportunities for the optimization of mechanical properties for a given application.
Study and Modelling of Some Variant Selections in bcc to hcp Phase Transformations
Authors: Humbert Michel , Gey Nathalie , Germain Lionel
Published: March 2009

One very often observes that the texture inheritance in BCC to HCP phase transformation shows variant selections, even though no external stress field is applied. These variant selections are related to the metallurgical state, the microstructure and the texture of the parent phase. From our own investigations, we came to the conclusion that the variant selections we observed in some phase transformations of various materials were influenced at different degrees by the elastic behaviour of the parent phase. Considering the transformation strain of each variant and the elastic anisotropy of the parent, we have build variant selection models based on energy minimum of elastic strain and assuming different types of interactions. The simulation results of texture transformation of a zircalloy sample show that the elastic characteristics of the parent phases are key parameters involved in the variant selection.
The Control of Texture and Grain Boundary Microstructure by Magnetic Annealing
Authors: Watanabe Tadao , Tsurekawa Sadahiro , Fujii H. , Kanno T.
Published: March 2009

This paper gives an overview of our recent works on the effect of magnetic
annealing, i.e. annealing in a magnetic field, on the evolution of texture and grain
boundary microstructure in ultra-fine grained and nanocrystalline magnetic materials
differently produced; rapidly solidified Fe-6.5mass%Si ribbons, electrodeposited
nanocrystalline nickel, and nanocrystalline Fe78Si9B13 alloy ribbon crystallized from the amorphous state. It was found that the effect of magnetic annealing was powerful and useful for controlling grain growth resulting in the evolution of different types of texture and grain boundary microstructure, depending on the condition of magnetic annealing. In particular, the magnetic crystallization of amorphous Fe78Si9B13 alloy was found to be powerful for producing a nanocrystalline material with a sharp texture and a special grain boundary microstructure.
Orientations of Recrystallization Nuclei Studied by 3DXRD
Authors: Juul Jensen Dorte , Larsen A.W.
Published: March 2009

A critical point in the understanding of recrystallization textures is the development of crystallographic orientations of the nuclei. Here an issue, which has been debated much recently [eg. 1], is if nuclei have orientations identical to those of the deformation microstructures from which they originate or not. Traditional nucleation mechanisms like strain induced boundary migration [2] and particle stimulated nucleation [3] operate with nuclei orientations identical to the “parent”deformation microstructure. This is also what is commonly incorporated in recrystallization modeling. However, a number of studies have found recrystallization nuclei in orientations that were not expected from measurements on deformed structures. Some of these results are reviewed and discussed in this paper, and new in-situ results obtained by the 3 dimensional X-ray diffraction (3DXR) method are presented.
In-Line Phase and Texture Control in Microelectronics Industry
Authors: Kozaczek Kris J.
Published: March 2009

We present the principles of operation and a summary of results from in-fab automated X-ray diffraction (XRD) metrology in support of copper damascene roduction. The automated XRD tools (an example is shown in Figure 1) are capable of rapid mapping of 300 mm wafers (with a throughput rate of 40 wafers/hour) of quantitative information about the film crystallographic composition, texture and thickness with a spatial resolution down to 30 microns. Microstructure control plays an increasingly important role in improving the performance and reliability of ULSI devices that use the damascene copper technology at 130 nm node and below. The problems related to delamination, stress voiding, and electromigration failures could be mitigated by the selection of proper materials, processing methods, and manufacturing tools. The optimum process would result in a tailored microstructure of barrier/seed/electroplated copper aggregate. At the same time, the microstructure could be used as an internal sensor, sensitive to process excursions and providing guidance for corrective actions. The texture and crystallographic phase data can be used as a direct measure of the deposition process in terms of film quality, reproducibility, and stability over time. The spatial distribution of crystallographic texture and phase can be measured on a single wafer in order to check wafer uniformity. More importantly, the same measurements can be carried out at predetermined intervals on wafers from a single deposition tool, and the results used to create a database that can be applied to trend charting and tool qualification. Examples of microstructure control in damascene copper processing include: process development and qualification, process control and stability, process excursion and post maintenance stability, deposition tool qualification, and on-line R&D. The examples of texture control will refer to materials and processes typical of damascene copper technology for ULSI. A typical processing route includes the PVD deposition of a barrier layer and copper seed layer, followed by copper electroplate, anneal and chemical- mechanical planarization. All the processing steps affect the texture of annealed copper, and therefore affect directly the performance of interconnects. We will also present examples of application to processing of metal gates (NiSi films) and ferroelectric non-volatile memory (PZT films).
Texture of Alumina by Neutron Diffraction and SEM-EBSD
Authors: Guilmeau E. , Henrist Catherine , Suzuki Tohru , Sakka Yoshio , Chateigner Daniel , Grossin D. , Ouladdiaf B.
Published: March 2009

The orientation distributions of α-Al2O3 textured ceramics are determined from neutron diffraction and SEM-EBSD. A curved position-sensitive detector coupled to a tilt angle (χ) scan allowed the whole neutron diffraction pattern treatment in the combined Rietveld-WIMV-Popa algorithm. Analyses from neutron and electron diffraction data gave similar results if EBSD data are smoothed to account for grain statistics. Four textured alumina ceramics were prepared by slipcasting under a high magnetic field and sintered at 800°C, 1300°C, 1400°C and 1600°C. The inverse pole figures and EBSD-mapping highlights the influence of the magnetic field and sintering temperature on the texture development. The inverse pole figures calculated for the fiber direction show a major (001) component for all the samples. With the increasing sintering temperature, the texture strength is enhanced and the c-axis distribution is sharper. The effectiveness of the combined approach for determining the crystallite size is also evident. As a global trend, the calculated crystallite size and observed grain size are similar and increase with the increasing sintering temperature. The mechanism of the texture development in the sintered specimens is certainly initiated from the preferred orientation of the green body after slip-casting under a high magnetic field. The basal texture is enhanced during sintering by selective anisotropic grain growth. We evidenced here the powerfulness of the Rietveld texture analysis correlated to SEM-EBSD calculation to provide a basis for the correlation of texture, microstructural parameters and anisotropic properties.
Product and Component Grain and Domain Textures in Ferroelectric Ceramics
Authors: Jones Jacob L. , Slamovich Elliott B. , Bowman Keith J.
Published: March 2009

Ferroelectric/ferroelastic structures exhibit systematic crystallographic distortions below certain phase transition temperatures. Domains, or regions of spatial continuity in such distortions, form in a self-compensating pattern when cooled in the absence of an applied field, forming equal volume fractions of all possible states by uniform selection of crystallographic variants. An applied field (poling) can alter the volume fraction of domains within the ferroelectric phase by switching of the non-preferred orientations, a form of ferroelectric domain texture. When ceramics possess a crystallographic texture prior to inducing domain texture, the two component textures combine multiplicatively to form the complete product texture. Using tape cast bismuth titanate (Na0.5Bi4.5Ti4O15) with an initial crystallographic texture, this paper establishes the quantitative approach for resolving both the component grain and domain textures and describing the complete product texture.
Orientation and Microstructure Dependence of Electromigration Damage in Damascene Cu Interconnect Lines
Authors: Mirpuri Kabir Kumar , Szpunar Jerzy A.
Published: March 2009

In the present paper we report the texture and microstructure dependence of electromigration damage in Cu interconnects. This was made possible by ncorporating a sophisticated set of instrumentation within the SEM which enabled in-situ monitoring of the electromigration defects. The electron backscatter diffraction (EBSD) maps were obtained before and after the completion of the electromigration tests. Thus, by comparing the maps before and after the failure it was possible to associate the texture and microstructure with both failure sites - voids and hillocks. Results from lines down to 130 nm are included and orientation dependence of the defects is discussed.
New Interpretation of the Influence of Various Parameters on Texture Evolution in Damascene Cu Interconnect Lines
Authors: Mirpuri Kabir Kumar , Szpunar Jerzy A.
Published: March 2009

The article takes into account various factors which effect the texture evolution in the Cu lines. We propose here an explanation for the formation of {111}<110> and {111}<112> texture in the Cu lines. The explicit role of principal stresses, shear stresses and dislocations is discussed. The influence of line spacing on strength of the {111}<110> and {111}<112> texture components is also demonstrated in relation to the dislocation density.
The Texture Evolutions of Mg Alloy, AZ31, under Uni-Axial Loading
Authors: Yi Sang Bong , Brokmeier Heinz Günter , Bolmaro R. , Kainer Karl Ulrich , Homeyer Jens
Published: March 2009

The texture influence on the mechanical behavior during uniaxial tension was studied in AZ31 (Mg – 3 Al – 1 Zn in wt.%), one of the common wrought Mg alloys. Since three tensile samples were cut in 0°, 45°, 90° to the extrusion direction, the initial bar texture influences on the mechanical behavior differently. In-situ texture measurements were carried out using hard X-rays under loading condition. According to the initial texture loading results in a variation of the mechanical behavior (yield strength, ultimate tensile strength and strain hardening rate) and in different final textures. The different texture development in each sample relates directly to the activation of different deformation systems, which is strongly influenced by the initial texture
Work Hardening and Textures in hcp Materials
Authors: Sánchez P. , Pochettino A.
Published: March 2009

An analysis of the hardening process in grains and its effect on texture development of hcp materials is performed. It corresponds to the cases of Zr and Zn, which present different c/a relationship and, consequently, their deformation modes and the associated activities are different. The self consistent viscoplastic model is used for the prediction of texture evolution Results show the importance of the self and latent hardening introduced by the prismatic slip in Zr and the latent hardening effects introduced by pyramidal  slip on compressive twinning in Zn.
Modeling of Length Changes and Textures during Free End Torsion of Cylindrical Bars
Authors: Qods Fathallah , Tóth László S. , van Houtte Paul
Published: March 2009

The Swift effect, i.e. the length changes during torsion of solid bars with axial freedom of deformation is analysed theoretically for polycrystalline copper. In the simulations, the bar is divided into 5 tubes and in each tube the texture development is simulated with the help of the Taylor viscoplastic polycrystal model. The distribution of the hydrostatic stress is obtained from the equilibrium equation and the zero axial force requirement is satisfied with the help of an iterative scheme. The simulations reproduce faithfully the observed axial deformation and texture development. A second technique, based on the minimum plastic power is also applied to predict the length changes and textures. This technique leads to results which are nearly equivalent to the results obtained from the technique based on the equilibrium equation.
The Application of ODF Analysis for Drawing Sheet of Weak Textured Materials
Authors: Wu Qiu Lin , Fang Wei , Hu Xiao Jun , Fu Zuming , Li Limin
Published: March 2009

For multi crystal materials, particularly multi-crystal metallic materials, it is unavoidable to make its crystal orientation change during the process. For instance, improving the property of soft magnetic materials should rely on the Cubic texture {100} <001>, but the property of the deep-draw sheet materials is closely related to its texture. Besides the material's composition, the crystal and the microstructure, the texture also takes a very important role in the properties of the materials [1, 2]. The positive pole figure analytic method is comparatively simple and intuitional. This is unquestionable in the texture analysis of cold-rolled samples, as in drawing sheet materials. It shows that the material orientation of isotropy or multiple weak textured materials is coexistent. The ODF analysis can be a good method for resolving this. In the study, the serial ODF analysis is used to analyze the property of nickel based alloys of drawing sheet materials considering different deformation amount, annealing temperature and annealing time in layers. In practice, it can be applied to production techniques.
Complexity of the Anisotropy of Magnetic Susceptibility in Single-Phase Deformed, Low-Grade, Cleaved Mudstone
Authors: Debacker Timothy N. , Sintubin Manuel , Robion Philippe
Published: March 2009

The anisotropy of magnetic susceptibility (AMS) is often interpreted in terms of strain. However, since AMS is controlled by all magnetic (s.l.) carriers present, an AMS interpretation is not straightforward, especially in the presence of composite magnetic fabrics. Considering the large number of factors that may influence rock mineralogy (e.g. sediment source area, metamorphism), it becomes clear that one cannot interpret AMS in terms of strain without applying additional techniques that allow determining the nature and preferred orientation of all magnetic (s.l.) carriers likely influencing the measured AMS. This is discussed using samples from the Brabant Massif (Belgium) and the Moesian Platform (E-Romania).
Friction Effects on Through-Thickness Texture Evolution during Rolling
Authors: Sarkar J. , Cao S. , Saimoto Shigeo
Published: March 2009

Using AA5182 and 5754 aluminum alloys, the role of friction in through-thickness
evolution was demonstrated. Aside from the mechanical parameters such as roll gap geometry and coefficient of friction, the significance of the role of Fe solute in the matrix was revealed.
Characteristics of Hot Compressed Magnesium Alloy AZ31 with Initial Textures Analyzed by Orientation Mapping
Authors: Yang Ping , Meng Li , Mao Wei Min , Chen Leng
Published: March 2009

Orientation mapping based on EBSD technique was applied to reveal the orientations of new grains and their relationships to the surrounding matrices, to analyze Kikuchi band contrast and the influence of strain rates on local orientation evolution. This information is used to understand the dynamic recrystallization mechanism and the relative contribution of plastic slip versus grain boundary glide or grain rotation related with super-plasticity. For this purpose samples with different initial textures were deformed by (quasi-)plain strain compression at two strain rates. It is suggested that the dynamic recrystallization in this alloy proceeds in continuous way by progressive subgrain rotation. No evident non-basal slip of  was observed by referring texture evolution in the sample with initial basal texture. A high strain rate promotes more contribution of plastic slip accompanied by fast orientation changes. The fact that groups of grains with very similar orientations in basal oriented samples is discussed in terms of viscous flow.
Development of Growth Texture in Nanocrystalline Fe-Ni Alloys
Authors: Ha Chang Sik , Park Yong Bum
Published: March 2009

In electroformed pure Ni and Fe-Ni alloys with nanometer-sized crystallites, grain growth that takes place during annealing results in a common texture change. With regard to the macrotextures, the as-deposited textures were of fibre-type characterized by strong <100>//ND and weak <111>//ND components, and the texture development due to grain growth was defined by strong <111>//ND fibre texture with the minor <100>//ND components. It was clarified by means of the microtexture analysis that abnormal growth of the <111>//ND grains occurs in the early stages of grain growth. The possible effects of the abnormal grain growth on the texture evolution have been discussed in terms of the orientation dependence of energy density.
On the Compacting of Powders of the Systems Fe-Cu and Fe-Cu-Diamond
Authors: Silva V.F. da , Sampaio M.V.C. , de Carvalho E.A. , Bobrovinitchii Guerold Sergueevitch , Filgueira Marcello
Published: March 2009

This work aims at the study of the behavior of the powder systems Fe-Cu e Fe- Cu-Diamond under compaction, using the stoichiometries Fe-20Cu (wt%) e Fe-20Cu-4 Diamond (wt%). It was applied pressures at the interval 100 to 600 MPa, and it was used the Balshin and Rong-De’s equations to establish the exact behavior of the systems under pressing: accommodation, plastic deformation and particle’s rearrangement.
Development of a Spray Dryer Device to Produce Ammonium Niobium-Oxalate Precursor
Authors: Oliveira Filho U.C. , Araújo A.C. , Oliveira E.L. , Souza C.P.
Published: March 2009

The main purpose of this paper is to present a spray dryer device developed to synthesize ammonium niobium-oxalate precursor powder with controlled grain size. The dryer device is manufactured using stainless steel 304 and measures 0,48m in outside diameter and 1,9m in height. The spray dryer has a cylindrical shape assembled on a conical base. The central chamber is heated by three 4 KW resistances and is equipped with serpentine coil heaters placed around its main body. This configuration guarantees that the air is at the same temperature of the chamber walls and the adherence of the powder particles on the wall is prevented. The precursor solution is atomized on the air stream downwards from the top to the bottom, at low rates. Powder particles are collected on a 0,4m diameter horizontal plate placed at the bottom portion of the dryer and the wet air is released from the chamber by the opening located under the collecting plate. The synthesis of the niobium oxalate precursor and the results of the decomposition process are described.
Preparation and Characterization of NiAl2O4 Powder by the Pechini and Combustion Methods
Authors: Ribeiro M.A. , de Melo Costa Ana Cristina Figueiredo , Lira Hélio Lucena , de Oliveira J.B.L. , Kiminami Ruth Herta Goldsmith Aliaga , Gama Lucianna
Published: March 2009

Conventional methods to obtain ceramic powders are inadequate for many technological applications because these powders react but slightly to sinterization, displaying weak reproducibility, nonhomogeneity and imprecise stoichiometric control of cations. Better results can be obtained by chemical synthesis because the powder retains its homogeneity on the atomic scale and may be calcined at low temperatures, yielding fine particulate oxides whose chemistry can be precisely controlled. Therefore, the objective of this work was to obtain the NiAl2O4 phase by the Pechini and combustion reaction methods, and comparatively analyze how these two synthesization methods affect the characteristics of the resulting powder, which was characterized by DRX, MEV and BET. The results revealed that both methods yield nanometric and crystalline NiAl2O4 powder having homogenous particle sizes and shapes. The powder obtained by the Pechini method exhibited agglomerate sizes 60% smaller than those obtained by combustion reaction.
Problems Associated with Modeling Interpass Softening during Industrial Hot Strip Rolling
Authors: Poliak Evgueni I. , Jonas John J.
Published: March 2009

The problems associated with the use of conventional rolling mill models are described. These include the unavoidable variations in temperature and strain rate (rolling speed) during rolling. They are exacerbated by the wide variety of mill types and configurations found in industry and their correspondingly broad ranges of interpass time. Finally, a major limitation arises from the approach currently employed to model the “strain accumulation” attributable to incomplete softening between passes, particularly during the processing of microalloyed steels.
A New Frontier in Microalloying: Advanced High Strength, Coated Sheet Steels
Authors: DeArdo Anthony J. , Garcia J.E. , Hua Ming Jian , Garcia C. Isaac
Published: March 2009

TRIP steels containing Mn, Si, Al, Mo, and Nb have been examined using a laboratory simulation of a continuous hot dipped galvanizing line. The evolution of microstructure has been studied as the steel passes through the various stages of CG line processing. Tensile strengths approaching 800 MPa and ductilities approaching 30% have been achieved in the 1.5Mn-0.5Si- 1.0Al-0.015Mo-0.03Nb system.
Contribution to the Understanding of Austenite Stability in a 12Cr-9Ni-4Mo Maraging Steel
Authors: San Martín David , van Dijk Niels H. , Yagodzinskyy Yuriy , Brück Ekkes , van der Zwaag Sybrand
Published: March 2009

Maraging steels show an excellent combination of high strength and ductility, which makes them very attractive in a large variety of potential applications. The present work is concerned with the main factors influencing the stability of metastable austenite in such a steel. At subzero temperatures a large variation in the isothermal transformation behaviour of austenite to martensite has been observed. Factors such as the austenite grain size and the interstitial content in solid solution are known to influence austenite stability and, therefore, the martensitic transformation. In this steel, the addition of titanium results in carbonitride precipitation. These precipitates play an indirect but important role in the stability of austenite by means of removing interstitials from the solid solution and by inhibiting an austenite grain growth. The combination of techniques such as X-ray diffraction, magnetisation measurements, three-dimensional neutron depolarisation, and internal friction measurements enables a complete characterisation of the transformation. A step towards understanding the factors responsible for the variation in the behaviour observed is the main contribution of this work.
Characterisation and Quantification of Complex Bainitic Microstructures in High and Ultra-High Strength Linepipe Steels
Authors: Zajac Stanislaw , Schwinn Volker , Tacke K.H.
Published: March 2009

This paper provides a detailed description of complex bainitic microstructures obtained during the recent development of low carbon linepipe steels with strengths in the range of X100 to X120. New experimental techniques based on a high resolution FEG-SEM and EBSD have been used to characterise and quantify the mixture of ultrafine bainitic ferrite and nanosize second phases in these steels. It was found that the occurrence of incomplete transformation generates new, previously unexplored bainitic microstructures with a wealth of microstructural features that is beyond classification based on conventional concepts. Clear differences in distributions of boundary misorientations and effective grain size were noted between upper, lower and granular bainites. Based on these results a new classification scheme and definition of bainite is proposed.
Characterization of the Residual Stresses in Plastically Deformed Ferrite-Martensite Steels Using Barkhausen Noise Measurements
Authors: Kleber Xavier , Hug-Amalric Aurélie , Merlin Jacques
Published: March 2009

In this work, we show that the measurement of the Barkhausen noise allows the residual stresses in each of the two phases of ferrite-martensite steels to be characterized. We have first studied the effect of a tensile and a compressive stress on the Barkhausen noise signature. We observed that for a ferrite-martensite steel, the application of a tensile stress increases the Barkhausen activity of the martensite and ferrite phases, whereas a compressive one reduces it. In a second time, we induced residual stresses by applying a plastic deformation to ferrite-martensite steels. After a tensile plastic deformation, we observed that (i) compressive residual stresses appear in ferrite, and (ii) tensile residual stresses appear in martensite. An opposite behavior is observed after a compressive plastic deformation. These results show that the Barkhausen noise measurement makes it possible to highlight in a nondestructive way the distribution of the stresses in each of the two phases of a ferrite-martensite steel. This result could be used to characterize industrial Dual- Phases steels that are plastically deformed during mechanical processes.
Amorphous Alumosilicophosphate Coatings for Niobium Alloys
Authors: Sedmale Gaida M. , Kobyakov Vasily P.
Published: March 2009

In the proposed study the less known kinds of thermal barrier coatings used to protect niobium or its alloys against the oxygen corrosion at temperatures above 6000C are discussed. Coatings were obtained from glass in the system BaO(MgO)- Al2O3- SiO2-P2O5 with the softening temperature above 7000C. The development of amorphous coatings from glass includes the preparation of it, deposition on surface of niobium alloy Nb+1% Zr and high-temperature annealing process. The coating can be represented as a multilayer system – top glassy layer (20-25 µm), glasscrystalline (8-10µm) and crystalline interfacial layer (~ 5-8 µm). The interfacial layer forms in the result of diffusion of Nb in a narrow layer close to substrate. Interfacial layer is crystalline and is composed from fine NbP crystals. This layer is the determinative barrier for oxygen diffusion into the substrate at the maximum of operating temperature 950 0C.
Production of Diamond Tools by Brazing
Authors: Tillmann Wolfgang , Osmanda Artur Martin
Published: March 2009

Diamond tools are increasingly gaining importance as cutting materials for various construction materials. The quality of synthetic diamonds, monocrystalline as well as
polycrystalline or CVD-diamonds has been significantly improved over the last years. Integrating these cutting materials requires adequate joining technologies that produce sound joints without exposing the temperature sensitive diamond to too elevated temperatures.

The paper highlights current developments in the joining of synthetic diamonds to steel. Owing to their covalent atomic bonding diamonds cannot easily be wetted and joined by employing conventional brazing alloys. Hence, active agents are needed to foster an interfacial reaction. Different active filler concepts are presented and discussed regarding their joint formation. The brazing temperatures influence not only possible diamond degradation but also the interfacial decomposition of the diamond due to the formation of corresponding reaction layers.
An Investigation of Deformation in Copper Single Crystals Using Equal-Channel Angular Pressing
Authors: Furukawa Minoru , Fukuda Yukihide , Oh-ishi Keiichiro , Horita Z. , Langdon Terence G.
Published: March 2009

This paper describes experiments in which high purity copper single crystals of two different orientations were processed for one pass by equal-channel angular pressing (ECAP) and the deformed structures were examined using optical microscopy (OM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The first single crystal (0° specimen) was oriented within the entrance channel of the die so that the {111} slip plane and the <110> slip direction were parallel to the theoretical shear plane and shear direction, respectively. The second crystal (20° specimen) was oriented with the {111} slip plane and the <110> slip direction rotated by 20° in a clockwise sense from the theoretical shear plane and shear direction, respectively. For the 0° specimen, after passing through the shear plane there were two crystallographic orientations representing the initial orientation and an orientation rotated by 60° in a counter-clockwise sense from the initial orientation. For the 20° specimen, there was an orientation rotated by 20° in a counter-clockwise sense from the initial orientation after passing through the shear plane.
Size Effects in Plasticity: Experiments and Simulations
Authors: Van Swygenhoven Helena
Published: March 2009

Large scale computer simulations suggest that in nanocrystalline metals grain boundaries act as source and sink for dislocations. This suggestion has been the motivation for developing a new in-situ X-ray diffraction technique that allow peak profile analysis of several Bragg diffraction peaks during tensile deformation. Synergies between simulations and experiments are discussed including new applications of the in-situ technique.
Equal Channel Angular Pressing of Metallic Powders for Nanostructured Materials
Authors: Yoon Seung Chae , Kim Hyoung Seop
Published: March 2009

In this study, bottom-up type powder processing and top-down type SPD (severe plastic deformation) approaches were combined in order to achieve both full density and grain refinement of metallic powders with least grain growth, which was considered as a bottle neck of the bottom-up method using the conventional powder metallurgy of compaction and sintering. ECAP (Equal channel angular pressing), one of the most promising method in SPD, was used for the powder consolidation. In the ECAP process of not only solid but also powder metals, knowledge of the density as well as internal stress, strain and strain rate distribution is important for understanding the process. We investigated the consolidation, plastic deformation and microstructure evolution behavior of the metallic powders during ECAP using experimental and theoretical methods. Almost independent behavior of powder densification in the entry channel and shear deformation in the main deformation zone was found by the finite element method in conjunction with a pressure dependent material yield model. It was found that high mechanical strength could be achieved effectively as a result of the well bonded powder contact surface during ECAP process of gas atomized Al-Si powders. The SPD processing of powders is a viable method to achieve both fully density and nanostructured materials.
Microstructure and Mechanical Property of Nano-Duplex Materials Produced by HRS Process
Authors: Hiroshi Fujiwara , Akada Ryota , Yoshita Yuki , Ameyama Kei
Published: March 2009

An SUS316L and a Ti-6Al-4V alloy powders are treated by Mechanical Milling (MM) process, which is one of SPD processes, and then sintered by Hot Roll Sintering (HRS) process. The HRS process consolidates powder by hot rolling of an evacuated metal pipe filled with the powder at elevated temperatures. Those MM powders have a heavy deformed microstructure at the surface region and have a work hardened microstructure in the core region of the powder. In the surface region, a nano grain structure forms after the MM treatment in both materials. In case of the SUS316L powder, such a nano grain structure consists of an equiaxed nano ferrite () grains which has transformed from nano austenite () grains. Volume fraction of the phase decreases with distance from the surface of powder. During HRS the ( + ) nano-duplex structure changes to (sigma () + ) nano-duplex structure by transformation of the to the phase. Thus, the SUS316L HRS material consists of a hybrid structure. That is, a ( + ) nano-duplex structure at the powder shell region, and a work hardened structure in the powder core region. In case of the Ti-6Al-4V MM powder, though no remarkable transformation occurs, a heavy deformed shell and work hardened core hybrid structure is also produced in the powder. By HRS the Ti-6Al-4V MM powder demonstrates a hybrid structure consists of an equiaxed nano grain structure and a coarse martensite structure. These two HRS materials indicate superior mechanical properties. Mechanical properties are improved by the HRS process. The proof stress and tensile strength in the SUS316L HRS material are x3.8 and x2.1 of the SUS316L conventional material, respectively. In the Ti-6Al-4V HRS material, they are x1.7 and x1.5 compared to the Ti-6Al-4V conventional material.
Spatial Uniformity of the Rate of Grain Coarsening in a Submicron Al-Sc Alloy Produced by Severe Plastic Deformation
Authors: Ferry Michael
Published: March 2009

The uniformity of grain coarsening throughout the microstructure of a submicron grained particle-containing aluminium alloy has been investigated using high resolution EBSD. The alloy was processed by equal channel angular pressing (ECAP) and low temperature ageing to generate ~0.8 m diameter grain structure containing a relatively uniform dispersion of nanosized Al3Sc particles. While the initial processing route generated a uniform grain size distribution, the distribution of grain orientations was rather inhomogeneous with certain regions of microstructure containing colonies of grains consisting predominantly of either HAGBs or LAGBs. It was found that, despite the difference in grain boundary character between these regions, the fine particles produced by pre-ageing promote uniform coarsening throughout the microstructure despite the marked differences in boundary character between these regions. An analytical model is outlined which predicts the uniformity of grain coarsening in particle-containing alloys despite the presence of orientation gradients in the microstructure.
Some New Trends in SPD Processing for Fabrication of Bulk Nanostructured Materials
Authors: Valiev Ruslan
Published: March 2009

During the last decade severe plastic deformation (SPD) has become a well established method of materials processing used for fabrication of ultrafine-grained materials with attractive properties. Nowadays SPD processing is rapidly developing and is on the verge of a transition from lab-scale research to commercial production. This paper focuses on several new trends in the development of SPD techniques for effective grain refinement. The paper also presents new SPD processing routes to produce bulk nanocrystalline materials.
Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations
Authors: Mueller Johannes , Durst Karsten , Amberger Dorothea , Göken Matthias
Published: March 2009

The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.
Deformation Behavior of Ultrafine Grained Iron
Authors: Takaki Setsuo , Kawasaki Kenji , Futamura Y. , Tsuchiyama Toshihiro
Published: March 2009

Work hardening behavior and microstructure development during deformation by cold rolling were investigated in iron with different grain size. Grain refinement makes the introduction of dislocation easier. For instance, under the same deformation condition (5% reduction in thickness), dislocation density is the order of 1014m-2 in a coarse grained material (mean grain size; 20μm), while it reaches 7×1015m-2 in an ultrafine grained material (0.25μm). It is well known that the yield stress of metals is enlarged with an increase in dislocation density on the basis of the Bailey-Hirsch relationship. However, it should be noted that the ultrafine grained material never undergoes usual work hardening although the dislocation density is surely enhanced to around the order of 1016m-2: 0.2% proof stress is almost constant at 1.4 ~ 1.5GPa regardless of the amount of deformation. The dislocation density of 1016m-2 is thought to be the limit value which can be achieved by cold working of iron and the yield stress of iron with this dislocation density (ρ) is estimated at 1.1GPa from the Bailey-Hirsch relationship; σd [Pa] = 0.1×109 + 10 ρ1/2. On the other hand, yield stress of iron is enhanced by grain refinement on the basis of the Hall-Petch relationship; σgb [Pa] = 0.1×109 + 0.6×109 d-1/2 as to the grain size d [μm]. This equation indicates that the grain size of 0.35 μm gives the same yield stress as that estimated for the limit of dislocation strengthening (1.1GPa). As a result, it was concluded that work hardening can not take place in ultrafine grained iron with the grain size less than 0.35 μm because dislocation strengthening can not exceed the initial yield stress obtained by grain refinement strengthening.
High Z - Large Strain Deformation Processing and Its Applications
Authors: Torizuka Shiro , Ohmori Akio , Murty S.V.S. Narayana , Nagai Kotobu
Published: March 2009

Ultrafine-grained structures formed dynamically through simple compression at warm deformation temperatures were investigated in a 0.15%C- 0.4%Si-1.5%Mn steel. The effects of strain, strain rate and deformation temperature on the microstructural evolution were examined using an isothermal plane strain compression technique with a pair of anvils. The maximum strain was 4, the deformation temperature was below the AC1 temperature, and the Zener-Hollomon parameter (Z) ranged between 1012 s-1 and 1016 s-1. Ultrafine ferrite grains surrounded by high angle boundaries are generated by simple compression when the strain exceeded a critical value. The number of newly generated ultrafine grains increased with the strain; however, the average sizes were found to be independent of strain. The grain size, `d`, was found to depend on Z parameter. An equation, d (μm) =102.07Z-0.16, was found to satisfy the experimentally obtained data. This study demonstrates the possibility of obtaining ultrafine ferrite through multi-pass caliber rolling as a high Z- large strain deformation technique for producing bulk engineering components. It was also noted that the empirical relation established based on single pass compression tests is valid for multi-pass caliber rolling.