bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Evaluation of Novell Wood-PVC Systems
Authors: Kuknyó Tímea , Szabó Tamás József
Published: March 2013

To protect the environment and conserve resources WPC (Wood-Plastic-Composite) materials are gaining foothold. Since in the construction industry both PVC (high weathering resistance, flame retardant, lightweight, long lifetime) and wood (natural, decorative, renewable) are well known and liked materials wood-PVC composites are also sought for. Numerous research and development/improvement efforts are on the way to produce commercially successful systems. The main hindrance is the compatibility issue between the components. This work describes a novel method – a work in progress – applied for a selected wood type, which was processed and validated using physical and mechanical tests. It was found that the prepared composite system is somewhat softer and more flexible than the original matrix PVC composition, but the thermal stability and the application temperature has been improved. It was also found that the PVC encloses the wood particles, shielding them from the environment and the humidity, thus protecting it from mold and microorganisms eve in humid conditions. A further step in the work is performing the tests focusing on the processing behavior of the material.
Effect of Crystallinity on PLA’s Microbiological Behaviour
Authors: Kun Eva , Kálmán Marossy
Published: March 2013

Recent work describes changes in polylactic acid samples with different crystallinity during microbiological degradation. We treated PLA at 93°C for different periods of time, which yielded samples with particular crystallinity. The fraction of crystalline phase was determined by differential scanning calorimetry, and the visual effect of crystallinity was measured by colorimetric method with black and white backgrounds. The medium for biological degradation process was living sludge under room temperature and normal atmospheric pressure. Furthermore, the change in mass was also measured. The results show that increased crystallinity reduces the rate of mass lost. The volumetric proportion of crystallinity is in direct correlation with opacity, so checking transparency is also a suitable possibility for estimating crystallinity. DSC, colorimetric method and visual observation experiments confirm that crystallinity has increased proportionally by the time of heat treatment and caused opacity. The experiments show that water uptake happened faster and in much higher volume in polymers having dominantly amorphous structure than in the case of samples with higher crystallinity. In the case of materials with only 2.43% crystallinity, weight lost began later because they had a greater water uptake during the first 7-12 days, while this period took only 7 days with a very low water uptake for samples containing approximately 35% crystalline phase. After swelling, weight loss of the crystalline samples was much slower than that of samples containing more amorphous parts, because crystalline phases inhibit the diffusion of small water molecules and the microbes with it.
Modelling of Ion Distribution in Single, Binary and Ternary Ion Exchanged Zeolite Used for Biomedical Applications
Authors: Kaali Peter , Czél György
Published: March 2013

Based on the previously published sodium and Ag, Cu, Zn ion-exchange and re-excange experiments we took an attempt to modeling its structure. We also took in account the ion release experimental results and the rigorous survey of the literature data when we positioned the ions in zeolite crystal structure. Therefore the current study aimed to modeling the ion distribution of single, binary and ternary ion-exchanged zeolite systems used for antimicrobial purposes, where the variation of silver, copper and zinc is incorporated into the zeolite structure. The tool of modelling was “CrystalMaker6” developed by CrystalMaker Software Ltd.
Laboratory Preparation and Characterization of Electroless Nickel Coated Powders of Industrially Produced Aluminium and Iron(III) Oxides
Authors: Török Tamas I. , Pázmán Judit , Szabó Máté , Janó Viktoria
Published: March 2013

Small batches of two oxide powders falling in the particle size range of about 30-230 μm were received from industrial sources and were electroless nickel (EN) coated in order to prepare properly modified reinforcing particles for further laboratory experiments with the Laser Melt Injection (LMI) technique to produce particle reinforced steel composite surface layers. The partially calcined alumina (Al2O3) as well as the hydrothermally recycled crystalline iron(III) oxide precipitate were characterized first to check their exact size ranges, specific surface areas and major chemical contaminants so that the best possible EN plating technique would be selected and applied. It was revealed soon that the sensitization and activation pre-treatment steps could not be omitted and after their proper adjustment, also the composition and pH of a relatively commonly used hypophosphite reducing type bath had to be modified to the given purpose. Eventually a slightly alkaline EN bath was successfully prepared with which both industrial oxide powders surface could be nickel coated soundly, which final result was demonstrated also by several metallographic testing techniques showing the microstructure of the quite evenly and fully coated oxide particles.
Investigation of the Kinetic of a Bainitic Reaction upon Heating in a CuAlNiMn and a CuAlNiMnFe Shape Memory Alloy
Authors: Benke Marton , Mertinger Valéria , Barkoczy Peter
Published: March 2013

The examination of solid state processes leading to the degradation of the shape memory behaviour is essential with respect to the suitability of shape memory alloys. Besides degradation processes occurring during relatively long periods of time called ageing, bainitic reactions that suddenly degrade the shape memory behaviour were also observed in many Cu-based shape memory alloys. The mechanisms and effects of the bainitic reactions on the shape memory characteristics were investigated in many Cu-based systems, but the kinetic of the reaction was not examined so far. In the present paper, an examination was carried out on a CuAlNiMn and a CuAlNiMnFe shape memory alloy to reveal what kinetic model describes the bainitic reaction occurring and thus completely destroying the shape memory effect during one stage of heating.
Scanning Transmission Electron Microscopy Analysis of Diesel Soot Particles for Source Attribution
Authors: Palotás Árpád Bence
Published: March 2013

Scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) has been used to characterize the elemental composition of diesel soot samples. The STEM employed in this investigation is the Vacuum Generators Microscope HB603, with a microanalytical resolution approaching 1 nm, allowing the analysis of individual soot particles and aggregates. Quantification of the EDX spectra is accomplished after background and absorption corrections. This information can then be used to pinpoint the fuels and combustion process from which the soot originated. Six diesel soots were analyzed in this study including three from a U.S. Bureau of Mines diesel test engine, two from a West Virginia University diesel test engine, and one from an Orion diesel bus engine. This research showed that soot impurities were found throughout the aggregates, and that only one or two soot particles were necessary to obtain a chemical fingerprint. Some of these elements may be traced to the fuel and lubricant. Other elements were components of the engine itself that combined with the soot particulates during the combustion process. The concept of using a ‘Truth Table’ for the purpose of source attribution is also introduced.
Analysis of Lead in SnAg Based Solders Using X-Ray Fluorescence
Authors: Koncz-Horváth Dániel , Gácsi Zoltána
Published: March 2013

This paper reports the results of ED-XRF method for the determination of low-level contaminated solders. The method was calibrated for the analysis of part-per-million (ppm) levels of Pb and major levels of other elements. In this work, two types of Sn-Ag based solder alloys are used; the ternary Sn-3.0wt%Ag-0.5wt%Cu (SAC305) and the 6-part Sn-3.5wt%Ag-3.2wt%Bi-1.6wt%Sb-0.5wt%Cu-0.15wt%Ni were examined. Empirical calibration and fundamental parameter calibration were used to analyze samples. The results of this study demonstrate the differences between the applied calibration methods for detection of Pb. Screening analysis of bulk samples from variant production lines were also discussed.
Effect of High Rotating Magnetic Field on the Solidified Structure of Al–7wt.%Si–1wt.%Fe Alloy
Authors: Roósz András , Kovács Jenő , Rónaföldi Arnold , Kovács Árpád
Published: March 2013

Al–7wt.-% Si–1wt.-% Fe alloy was solidified unidirectionally in the Crystallizer with High Rotating Magnetic Field (CHRMF). The diameter of sample was 8 mm and its length was 120 mm. The parameters of solidification were as follows: solid/liquid interface velocity ~0.082 mm/s, temperature gradient 7+/-1 K/mm, magnetic induction 0 and 150 mT, frequency of magnetic field 0 and 50 Hz. The structure solidified without rotating magnetic field (RMF) showed a homogeneous, columnar dendritic one. The structure solidified by using magnetic stirring showed a dual periodicity. On the one hand, the branches of the “Christmas tree”-like structure known from the earlier experiments contained Al+Si binary eutectic. On the other hand, bands with higher Fe- and Si-content formed in the sample, which were at a larger distance from each other than the branches of the “Christmas tree” structure. The developed microstructure was analyzed by SEM with EDS. The average Si- and Fe-concentrations were measured on the longitudinal section at given places along the length of sample. Furthermore the Si- and the Fe-concentrations close to the bands and among the bands as well as the composition of the compound phases were determined.
Simulation of Grains Growing as Influenced by Triple Line Dragging
Authors: Ito Kunio
Published: March 2013

A grain whose orientation and size were specified was embedded in a matrix grain structure. The matrix contained texture components in certain special orientations and those in general orientations, and the embedded grain had a certain special three-orientations-relation with grains in the former components. The dependence of growing behavior of an embedded grain on its number of faces of a grain has been examined by a modified Potts MC type 3D simulation and found to depend on the triple line dragging, suggesting that three-orientations-relation dependent triple line dragging can change the crystallographic texture through grain coarsening.
A New Approach to Solute Effect on Grain Boundary Migration
Authors: Yan Huang
Published: March 2013

Solute drag theory is critically revisited and an alternative approach is presented to account for the effect of solute elements on grain boundary migration during annealing. A fundamental new concept is introduced in the model that, in the linear range of irreversible thermodynamics, solute atoms segregated in a grain boundary will not lag behind when the boundary migrates. While lagging behind is the very essential assumption for the solute drag theory. Instead of blaming the lagging behind, the mobility drop due to solute addition is attributed to the decrease in boundary energy as a result of boundary segregation. According to this model, grain boundary mobility is dependent on solute concentration rather than migration rate. The predictions of the model are compared with experimental results, with a good agreement.
On the Generalisation of JMAK's Theory
Authors: Rios Paulo R. , Villa Elena
Published: March 2013

In their pioneer work Johnson-Mehl, Avrami and Kolmogorov (JMAK) developed well-known analytical expressions to describe the transformation kinetics of nucleation and growth transformations. Their work and its subsequent development has been extensively applied by Vandermeer and coworkers to recrystallisation studies. With the help of methods from Stochastic Geometry it has been possible to generalise JMAK's equations to situations well beyond their original assumptions. Although the motivation for this paper was recrystallisation the expressions derived here may be applied to nucleation and growth reactions in general.
Modelling Time-Dependent Nucleation of Recrystallization in Aluminium Alloys
Authors: Marthinsen Knut , Friis Jesper , Engler Olaf
Published: March 2013

The basic equations and mathematical framework of a mean-field model for recovery and recrystallization, the latter based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) approach, capable of handling time-dependent nucleation of recrystallization, is presented. Different approaches to account for time-dependent nucleation are discussed. A physically-based nucleation model where “nucleation” of recrystallization is brought about by “abnormal” subgrain growth seems most appealing, in terms of realism and mathematical convenience. Its implementation and effects on the recrystallization behavior are demonstrated through an example of back-annealing after cold deformation of a generic aluminium alloy case
Ferrite Recrystallization in Cold-Rolled Dual Phase Steel
Authors: Costa Fernando S. , Barbosa Ronaldo , Melo Túlio M.F. , Murari Fabio D.
Published: March 2013

The ferrite recrystallization of a cold rolled dual phase steel with 0.09%C-2.06%Mn was investigated by means of isothermal treatments at the temperatures of 600, 650, 680 and 710°C as well as during continuous heating. From the isothermal treatments the softening kinetics was mathematically adjusted to the AJMK model and the activation energy associated with the ferrite recrystallization process was estimated as 310 ± 22 kJ/mol. Vickers hardness measurements in the ferrite were carried out on samples subjected to heating at a constant rate from room temperature and quenched at temperatures up to 760°C. The results allowed to observe three main stages of the ferrite softening: (1) from room temperature to about 500°C the ferrite hardness remains constant; (2) between 550°C and 640°C, the hardness systematically increases with temperature. This effect was interpreted as being caused by the increase of carbon dissolved in the ferrite, coming from the dissolution of the adjacent pearlite colonies; (3) above 660°C the ferrite hardness decreased rapidly with temperature due to the recrystallization process. Analysis by means of SEM and EBSD indicated that the recrystallization process started mostly in regions severely deformed, which were predominantly orientated along the γ fiber ( parallel to the sheet normal direction).
Martensite Formation and Recrystallization Behavior in 17Mn0.06C2Si3Al1Ni TRIP/TWIP Steel after Hot and Cold Rolling
Authors: de Dafé Sara Silva Ferreira , Moreira Débora Rezende , Matoso Mariana de Souza , Gonzalez Berenice Mendonça , Santos Dagoberto Brandão
Published: March 2013

This work evaluates the evolution of the microstructure and its influence on the mechanical behavior of steel containing 17% Mn, 0.06% C, 2% Si, 3% Al, and 1% Ni after hot rolling at 1070°C, cold rolling with 44% reduction, and annealing at 700°C for different time periods. The resultant athermal, strain-induced martensite and austenite grains were analyzed by optical and scanning electron microscopy (SEM). The volume fractions of the g, e, and α’ phases of martensite were confirmed by X-ray diffraction, dilatometry, and SEM-electron backscatter diffraction (EBSD) techniques. It was found that cold reduction results in the formation of more a’ martensite. The Vickers microhardness values were higher for the cold-rolled condition and lower for recrystallized samples, as expected. However, this reduction is counterbalanced by the formation of athermal e and a’ martensite during the cooling process. The sizes of the recrystallized grains change exponentially during their growth and remain within 1–3 mm. The yield and tensile strength of the hot-rolled steel reach values close to 250 and 800 MPa, respectively, with a total elongation of 40%, which demonstrates the high work-hardening rate of the steel.
Recrystallization and Grain Growth Behavior of few Low Carbon Steels after Severe Cold Rolling and Annealing
Authors: Ray Ranjit K. , Saha Rajib
Published: March 2013

Less attention has been paid to study the recrystallization and grain growth behavior of severe plastically deformed (SPD) metals specially steels that are deformed to very high strain by conventional rolling method. Present work has been focused on systematic investigation of recrystallization and grain growth behavior of a Aluminium Killed (AK), an Interstitial Free (IF) and an Interstitial Free High Strength (IFHS) steels that were subjected to very high levels of strain (ԑeqv= 4.51) by cold rolling. The cold rolled steels show fine lamellar structure with very strong texture consists of both γ and α fibre. All the steels show formation of ultrafine grains and dramatic rise in the intensity of α fibre component in the early stages of annealing. However, progress of annealing for longer time leads to an increase in the mean grain size as well as γ fibre intensity. The results also indicate that the heavily cold rolled material exhibit selective growth of specific texture components.It appears that microstructure and texture is closely related to the observed phenomenon.
Measurement of Strain and Lattice Rotation in the Particle Deformation Zone
Authors: Ko Lawrence C.L. , da Fonseca Joao Quinta
Published: March 2013

It is known that there is lattice rotation around the particles after deformation, in a so-called Particle Deformation Zone (PDZ), which is thought to be important in randomizing the texture after recrystallization though Particle Stimulated Nucleation (PSN). However, the role of the local distribution of stored energy and its link to local lattice rotation is not well understood, making it impossible to successfully predict PSN efficiency. Here, we present a new method for studying the deformation around particles with the use of Digital Image Correlation (DIC) of High-Resolution Scanning Electron Microscopy (HRSEM) image and Electron BackScatter Diffraction (EBSD) map. Combining these two techniques makes it possible, for the first time, to relate the local deformation fields to remnant changes in local lattice orientation. Initial measurements are made on a model Al-Si alloy deformed in plane-strain condition by channel die compression up to 30%. Our analysis shows that the material deforms heterogeneously with high levels of deformation localized along slip bands. EBSD analysis shows that the lattice distortion in these bands is minimal. The HRDIC analysis clearly shows particles interrupt the slip banding. Local lattice rotation measured by EBSD is considerably less than expected from the measured deformation.
Texture Evolution of a Cold-Rolled Fe-28Mn-0.28C TWIP Steel during Recrystallization
Authors: Haase Christian , Barrales-Mora Luis Antonio , Molodov Dmitri A. , Gottstein Günter
Published: March 2013

Texture evolution during static primary recrystallization of an austenitic Fe-28Mn-0.28C TWIP steel was analyzed. The cold-rolled material, which showed a Brass-type texture at medium (30% and 50%), and additionally a γ-fiber at high (80%) deformation degrees, was subjected to isothermal annealing at 700°C. The influence of rolling degree/starting texture on the development of particular texture components was studied. After recrystallization a weakened, retained rolling texture was observed for the examined reduction levels. In addition to the deformation components, Brass and Goss, further α-fiber components were formed mainly by annealing twinning leading to the development of this fiber.
Formation of a Random Recrystallization Texture in Heavily Cold Rolled and Annealed Al-1%Si Alloy
Authors: Chen Yan Li , Huang Tian Lin , Gong Xu , Wu Gui Lin , Liu Qing , Huang Xiao Xu
Published: March 2013

An Al-1%Si alloy cold rolled to a von Misses stain of 4.5 was isothermally annealed at 210°C. A random recrystallization texture was obtained, which was attributed to the effects of particles of different sizes on the nucleation and growth of grains during recrystallization.
Coupling of Local Texture and Microstructure Evolution during Restoration Processes in Aluminum Deformed to Large Strains
Authors: Hansen Niels , Yu Tian Bo , Mishin Oleg , Huang Xiao Xu
Published: March 2013

The coupling between local texture and microstructure is analyzed during restoration processes in aluminum cold-rolled to high and ultrahigh strains. The deformed microstructure is composed of lamellae with orientations of rolling texture components that occupy different volume fractions and vary in the spatial distribution. The individual lamellae are separated by low and high angle boundaries and significant local differences are produced in the deformed microstructure both in terms of the stored energy and boundary mobility. These differences influence recovery and recrystallization processes, resulting in significant local variations in mechanisms and kinetics of these processes. The observations suggest that the characterization of the local texture and microstructure both in the deformed state and after annealing is important in order to underpin the analysis of recovery and recrystallization on the sample scale.
Effects of Driving Force and Boundary Migration Velocity on Formation of Recrystallization Texture in Cold Rolled Pure Aluminum Sheets
Authors: Mao Wei Min , Yang Ping
Published: March 2013

The effects of net driving force for migration of high angle grain boundaries were emphasized beside many other factors which could influence the process of texture formation during recrystallization annealing of 95% cold rolled pure aluminum sheets. The net driving force consists basically of stored energy. However, it could be reduced by recovery, boundary drag, solute drag and Zener drag in different extents, in which only boundary drag is mis-orientation dependent. It was indicated that both oriented nucleation and oriented growth have obvious influence on recrystallization texture, and how far they influence the texture depends also on the level of net driving force when the grain growth starts during annealing. Oriented growth, which is induced by the differences in boundary drag of differently oriented grains, and the corresponding texture formation, could be observed easily when the recrystallization proceeds under relative higher solute drag and Zener drag in commercial purity aluminum. The oriented nucleation process prevails during recrystallization of sufficiently recovered high purity aluminum with very low solute drag and Zener drag, after which strong cube texture forms. In this case the oriented growth indicates limited effect. Both the oriented growth and oriented nucleation will fail if high purity deformation matrix without clear solute drag and Zener drag has not experienced an obvious recovery before recrystallization grain growth, since extremely high net driving force leads to very small critical nucleus size and multiplicity of growing grains, which results in randomization of recrystallization texture.
Microstructural Evolution of AA6082 with Small Aluminides under Hot Torsion and Friction Stir Processing
Authors: Poletti Cecilia , Krumphals Friedrich , Mitsche Stefan , Gao Zeng
Published: March 2013

The hot rolled AA6082 aluminium alloy with aluminide dispersoids is deformed up to large strains to obtain a fine grained microstructure. Friction stir spot welding (FSSW) is carried out on rolled plates by means of a device provided by MTS System Corporation. FEM simulations determine that the material can flow up to local strains between 10 and 50 when the material reaches temperatures between 300-500°C. With this information, hot torsion tests at constant temperatures are carried out in a Gleeble ® 3800 machine for different strain rates. In both cases, in situ water quenching is applied to freeze the microstructure and avoid any static recrystallization effect after hot deformation. Light optical microscopy is used to identify the evolution of the grains as a function of the local deformation parameters determined by FEM simulations. The microstructure development by FSSW as well as by torsion is then further characterized by means of EBSD. At small strains the material deforms mainly by dynamic recovery with small low angle grain boundary formation and boundary dragging by fine aluminides and Mg2Si. At large strains grain refinement by continuous dynamic recrystallization takes place heterogeneously as a function of the original crystallographic orientation and precipitation state of each grain.
Recrystallization of Cold-Rolled Zr Single Crystals
Authors: Isaenkova Margarita , Perlovich Yuriy , Krapivka Nikolay , Fesenko Vladimir , Krymskaya Olga , Sudakova Alina
Published: March 2013

Recrystallization of rolled Zr single crystals is considered in comparison with analogous recrystallization processes in rolled coarse-grained iodide Zr and polycrystalline plates of commercially pure Zr. Diffractometric X-ray methods were used by texture and X-ray line profile measurements. The treatment of obtained data included construction of correlation diagrams, connecting as-rolled and recrystallized conditions of samples. A number of recrystallization mechanisms, operating in rolled α-Zr under annealing, were revealed on the basis of found regularities of texture changes.
Effects of Widening during Rolling on the Subsequent Recrystallization Kinetics of Copper
Authors: Lin Feng Xiang , Leffers Torben , Pantleon Wolfgang , Jensen Dorte Juul
Published: March 2013

Recrystallization kinetics in copper cold-rolled to 90% reduction with and without significant widening was investigated by electron backscatter diffraction. It was found that the recrystallization process was slightly retarded and the development of cube recrystallization texture was largely inhibited in the widening sample. Cube grains were observed to have a growth advantage by a factor of 2 in the non-widening sample, while this growth advantage was not observed in the widening sample. The recrystallization kinetics and the development of cube texture in the two samples are discussed.
Recrystallization Texture of Heavily Cold Rolled Polycrystalline Nickel Sheets with and without Strong Starting Cube Texture
Authors: Bhattacharjee Pinaki Prasad , Takatsuji Yoshihiro , Miyajima Yoji , Terada Daisuke , Tsuji Nobuhiro
Published: March 2013

The evolution of texture is studied in high purity (~99.7%) nickel sheets with widely different starting cube texture ({001}) intensities following heavy cold rolling and annealing. For this purpose two nickel sheets with strong and weak starting recrystallization cube texture (SSCT and WSCT, respectively) prepared by Accumulative Roll Bonding and conventional rolling, respectively, followed by annealing are used as the starting materials for subsequent processing. These sheets are cold rolled to 90% reduction in thickness and annealed at different temperatures. Profuse cube oriented bands could be identified in the SSCT nickel sheet after 90% cold rolling as opposed to rather insignificant presence of cube regions in the WSCT nickel sheet. However, the WSCT nickel sheets consistently show stronger cube texture after annealing treatments as compared to the SSCT material. The failure to observe recrystallization cube texture in SSCT is attributed to the inhibited nucleation of cube grains owing to the unfavorable misorientation environment surrounding cube regions in the deformed matrix.
The Industrial Application of Microstructure Modelling: A View out of the Process Window
Authors: Hinton John , Lee Joseph , Löffler Hans Ulrich
Published: March 2013

Integrated model based control systems are an essential part of modern plant operations. The production requirements have evolved from achieving geometric tolerances to becoming a large, flexible, but accurate metallurgical instrument. Within the steel industry, on-line process and microstructure monitoring systems have been realised for many years on hot strip mills. At recent conferences (including ReX&GG IV), Siemens has described the successful implementation of these models in steel plate production; in applications where there is increased complexity in through thickness microstructure and the final products have safety critical applications. Even with advanced on-line systems and tailored production routes there is a relatively comfortable process window in modern steel manufacture. For the plant builder, light structural metals titanium and magnesium, and harder nickel based high temperature alloys represent another level of complexity and process control requirements. This paper examines the potential of microstructure modelling with respect to the process design for manufacturing wrought products in alternative alloy systems. Metallurgical aspects will be considered and their practical implications discussed. The continued expansion of these materials into markets where high strength/weight ratios, corrosion resistance or high temperature properties are desirable (e.g. automotive, offshore, chemical, aerospace) make this worthwhile from an industrial perspective.
Modeling of Dual-Phase Grain Structure in Ti-6Al-4V during Isothermal and Non-Isothermal Heat Treatment by Using Cellular Automata
Authors: Krumphals Alfred , Poletti Cecilia , Warchomicka Fernando , Stockinger Martin , Sommitsch Christof
Published: March 2013

In the titanium alloy Ti-6Al-4V the dual-phase grain structure, which forms during thermo-mechanical processing, is of high importance due to its effect on the mechanical properties. In general the most significant microstructural parameters are the amount of alpha and beta phase as well as their grain size. For this reason a new cellular automata method (CA) was developed to predict the evolving grain structure during isothermal and non-isothermal heat treatment. The probabilistic CA model is based on the diffusion controlled movement of grain and phase boundaries. During temperature changes an algorithm is adjusting alpha and beta phase fraction to maintain equilibrium phase values. Hence, the CA is capable to calculate grain coarsening as well as grain growth and shrinking in the two-phase area while heating and isothermal holding at forging temperature. The initial microstructure can be imported form virtual created microstructures, real micrographs and EBSD-images. The results are mean grain diameters, grain size distributions and virtually simulated microstructures which can be easily compared with real micrographs. The predicted microstructures are showing a good correlation to data in literature and experimental results.
Boundary Structure-Dependent Grain Growth Behavior in Polycrystals: Model and Principle
Authors: Kang Suk Joong L.
Published: March 2013

This paper reviews our recent investigations on grain growth in ceramics. Grain growth behavior has been found to be governed by the grain boundary structure: normal growth with a stationary relative grain size distribution for rough boundaries and non-normal (nonstationary) growth for faceted boundaries. Based on the concept of nonlinear migration of faceted boundaries, the mixed control model of grain growth is introduced and the principle of microstructural evolution is deduced. This principle states that various types of grain growth behavior are predicted as a result of the coupling effect between the maximum driving force for growth and the critical driving force for appreciable migration of the boundary. A wealth of experimental results supports the theoretical predictions of grain growth behavior, showing the generality of the suggested principle of microstructural evolution. Application of this principle is also demonstrated for the fabrication of single crystals as well as polycrystals with desired microstructures.
Recrystallization and Grain Coarsening Control in Processing High Niobium Microalloyed Line Pipe Steels
Authors: Subramanian Sundaresa V. , Rehman M. Kashif , Zurob Hatem , Shang Cheng Jia
Published: March 2013

The effect of solute niobium in retarding coarsening kinetics of austenite in upstream thermo mechanical processing of high niobium (0.1wt%Nb) low interstitial steel is analyzed. Solute drag effect of niobium in retarding boundary mobility in static recrystallization is examined in thermo-mechanical rolling of high Nb microalloyed steel. The importance of austenite grain refinement prior to pancaking in compact strip rolling of high Nb microallyed steel as a means to increase surface area to volume ratio of pancaked austenite grain is emphasized. This is to promote adequate nucleation sites for phase transformation even under conditions low total rolling reduction below temperature of no recrystallization.
Microstructure Evolution in an Austenitic Stainless Steel during Wire Rolling
Authors: Yvell Karin , Engberg Göran
Published: March 2013

A wire rod block at Fagersta Stainless AB, Sweden, consists of eight pairs of rolls with consecutive round-oval-round grooves. Test bars of an austenitic stainless steel of type AISI 304L that had been preheated to 930±70°C were manually fed into the wire block. By entering a guide after one of the roll pair, the bar was led out from the block into a water-filled tube for rapid quenching. The guide was moved successively from the first to the last pair of rolls and test bars were collected after each roll pair. In order to characterize the original structure one bar was preheated and directly water quenched without rolling. The aim of this study was to characterize the microstructure evolution during the wire rod rolling using electron backscatter diffraction. The size evolution for all grains, the recrystallized grains and for the subgrains in the deformed grains has been estimated and the fraction of recrystallized grains has been determined. During the first 3 passes almost no recrystallization is observed and strain accumulates. Partial recrystallization then occurs and for the last 3 passes the recrystallization is almost complete and the texture is nearly random.
Tailoring Dynamic Recrystallization in Ni- and Fe-Base High Temperature Alloys
Authors: Rivera-Diaz-del-Castillo Pedro , Galindo Nava Enrique
Published: March 2013

Theory for describing the conditions leading to dynamic recrystallization in FCC metals is introduced. The approach also describes stress-strain curves when this process occurs, and is unique in incorporating the effects of strain rate and temperature employing only physical parameters as input. The novelty of the approach stems from incorporating an incubation period in the equations describing the progress of dislocation density with strain; beyond such incubation dislocation free grains form. The energy barrier to ignite grain growth is expressed as a function of the strain energy stored in the material and a statistical entropy contribution due to the degrees of freedom available to a dislocation for annihilation. The incubation strain is obtained by performing an energy balance between the stored energy on the subgrain boundaries, the slip energy for boundary migration and the interfacial energy required for grain nucleation. The application of this work to Fe and Ni multicomponent alloys has lead to transition maps in temperature-strain rate space indicating the conditions for dynamic recrystallization occurrence.
Effect of Austenitising and Deformation Temperatures on Dynamic Recrystallisation in Nb-Ti Microalloyed Steel
Authors: Kostryzhev Andrii G. , Al Shahrani Abdullah , Zhu Chen , Ringer Simon P. , Pereloma Elena V.
Published: March 2013

An investigation into the influence of the reheat temperature and the austenite deformation temperature on Nb precipitation and recrystallisation kinetics was carried out for a steel containing 0.081C–0.021Ti–0.064Nb (wt. %). Thermo-mechanical processing was carried out using a Gleeble 3500 simulator. The austenite grain structure was correlated to the dispersive properties of Nb atom clustering and precipitation. Irrespective of the reheat temperature, deformation to 0.75 strain at 1075 °C produced a fully recrystallised austenitic microstructure. After deformation at 975 °C, only partial recrystallisation was observed in the samples reheated to the higher temperature, whereas samples reheated to the lower temperature were fully recrystallised. The influence of solute drag and particle pinning effects on the recrystallisation rate is discussed.
Influence of (Al, Nb, V) Precipitates on the Recrystallization Inhibition in Microalloyed Steels
Authors: Gómez Manuel , Quispe Alberto , Medina Sebastián F.
Published: March 2013

Under certain conditions of temperature, time and deformation, static recrystallization of austenite in microalloyed steels can be temporarily inhibited by means of the strain-induced precipitation of nanoparticles that cause a pinning effect on austenite grain boundaries in motion. This inhibition can be seen by the formation of a “plateau” in the curves of static recrystallization of austenite obtained from double-deformation tests carried out under isothermal conditions. In this work, several microalloyed steels with different compositions are studied by hot torsion tests in order to characterize the kinetics of recrystallization and its inhibition. The precipitation state in austenite is studied in several samples by means of transmission electron microscopy. The influence of the type of microalloying element (Al, Nb, V) and the mean size of the precipitates on the duration time of the plateau is studied and relationships between these variables can be obtained. Particularly, it is seen that Al-alloyed steels present a much coarser particle size and a considerably shorter plateau compared to Nb and V-microalloyed steels.
Influence of Finishing Rolling Variables on the Austenite Recrystallization and Grain Growth
Authors: Carretero Olalla Victor , Mouriño Nuria Sánchez , Thibaux Philippe , Kestens Leo A.I. , Petrov Roumen H.
Published: March 2013

The austenite recrystallization and grain growth during thermo-mechanical control processing (TMCP) of a pipeline steel grade is described and analysed in terms of precipitation state progress. The influences of finish rolling temperature and cooling rate on the link between microstructure-precipitation evolution and their consequent effect on the mechanical properties were examined. Two stage controlled rolling (roughing and finishing) was carried out on a laboratory rolling mill for a set of completed and interrupted schedules. Subsequent to rolling, two different cooling routes were used (air-cooling and accelerated water cooling (ACC) together with coiling simulation). From the combination of transmission electron microscopy (TEM) observations, detailed texture analysis and inductively coupled plasma-mass spectroscopy (ICPMS) precipitates quantification, consistent correlations between precipitation state and microstructure at every stage of TMCP can be recognized. The role of grain size and precipitation on final mechanical properties was discussed based on different strengthening mechanisms.
Study of Recrystallization in High Manganese Steels by Means of the EBSD Technique
Authors: Llanos Laura , Pereda Beatriz , Jorge Badiola Denis , Rodriguez-Ibabe J.M. , López Beatriz
Published: March 2013

The softening processes that take place after hot deformation in two high Mn steels, one of them microalloyed with 0.1%Nb, have been investigated. Double hit torsion tests were carried out in order to determine the mechanical softening at temperatures ranging from 900 to 1100°C. In addition, the applicability of different parameters obtained by means of the Electron Back Scattering Diffraction (EBSD) technique to estimate the recrystallized fraction was investigated. It has been found that the Grain Orientation Spread (GOS) is the parameter that best allows quantifying the recrystallized fraction under the conditions investigated. The correlation between the mechanical softening and the recrystallized fraction measured by EBSD depends on the material and deformation conditions. A good correlation between both values is observed for the base steel at all the temperatures. However, for the Nb microalloyed steel, although at high temperatures a good correlation is also observed, at low temperatures the mechanical softening fraction tends to be larger than the recrystallized fraction denoting that recovery has an important contribution.
Effect of Reheating on Grain Size Evolution in High Strength Linepipe Steel
Authors: Chastukhin Andrey V. , Ringinen Dmitry A. , Khadeev Grigory E. , Efron Leonid I.
Published: March 2013

The effects of slab reheat temperature and soaking time are studied to characterize austenite grain growth, microstructure homogeneity and dissolution of precipitates in linepipe X80 grade steel. It is shown that the uniformity of austenite microstructure strongly depends on the slab reheat temperature and soaking time. With increasing reheat temperature an abnormal growth of individual grains is observed that stems from gradual dissolution of microalloy carbonitrides. As the result, individual grain boundaries become unpinned and mobile thus "nucleating" secondary recrystallization. The highest reheat temperature at which the dissolution kinetics of precipitates is still slow enough to prevent the onset of secondary recrystallization within long soaking times is 1160°C. The as reheated austenite microstructure and the character of austenite grain size distribution are inherited throughout the entire roughing rolling sequence and even further downstream to the finishing rolling entry.
Microstructure through an Ice Sheet
Authors: Binder Tobias , Weikusat Ilka , Freitag Johannes , Garbe Christoph S. , Wagenbach Dietmar , Kipfstuhl Sepp
Published: March 2013

Ice cores through an ice sheet can be regarded as a sample of a unique natural deformation experiment lasting up to a million years. Compared to other geological materials forming the earth‘s crust, the microstructure is directly accessible over the full depth. Controlled sublimation etching of polished ice sections reveals pores, air bubbles, grain boundaries and sub-grain boundaries at the surface. The microstructural features emanating at the surface are scanned. A dedicated method of digital image processing has been developed to extract and characterize the grain boundary networks. First preliminary results obtained from an ice core drilled through the Greenland ice sheet are presented. We discuss the role of small grains in grain size analysis and derive from the shape of grain boundaries the acting driving forces for grain boundary migration.
Triple Junction Motion – A New Recovery Mechanism in Metals Deformed to Large Strains
Authors: Yu Tian Bo , Hansen Niels , Huang Xiao Xu
Published: March 2013

A phenomenologically new recovery mechanism – triple junction motion is presented. This recovery mechanism is found to be the dominant one at low and medium temperatures in highly strained aluminum, which has a very fine microstructure, composed of lamellae with the thickness of a few hundred nanometers. Triple junction motion leads to removal of thin lamellae and to a consequent increase of the thickness of neighboring lamellae. This recovery mechanism therefore increases the average lamellar boundary spacing and causes a gradual transition from a lamellar structure to a more equiaxed structure preceding recrystallization.
Texture Formation in AZ91 Magnesium Alloy during High-Temperature Uniaxial Compression
Authors: Kim Jinuk , Okayasu Kazuto , Fukutomi Hiroshi
Published: March 2013

Texture development in Magnesium alloy AZ91 having a weak (0001) texture before deformation is studied by uniaxial compression tests at 673K and 723K, strain rates ranging from 5.0×10-4s-1 to 5.0×10-2s-1 up to a strain of -1.0. The fiber texture is formed in all of the deformation conditions. The main component of the texture varies depending on deformation conditions. The position of maximum axis density varies depending on final stress. It is concluded that the (0001) fiber texture develops by continuous dynamic recrystallization.
Ferrite Grain Coarsening from Hot Rolled Austenite in ODS Steels
Authors: Wu Xiao Chao , Ukai Shigeharu , Miyata Ryota , Sugino Yoshito , Oono Naoko , Hayashi Shigenari , Ohtsuka Satoshi , Kaito Takeji
Published: March 2013

The hot rolling at temperature range of 1100 °C to 862 °C and subsequent air-cooling induce a formation of the coarse ferrite grains in the 9CrODS steels. This coarse ferrite is produced by transformation from the severely hot rolled γ-grains to ferrite. Formation process and mechanism of the transformed coarse ferrite are interpreted in terms of a nucleation, growth and coalescence of the same variant ferrite grains under a variant restriction rule.
Development of Very Tough Ferritic Stainless Steels by Optimizing the Recrystallized Microstructure
Authors: Gao Fei , Liu Zhen Yu
Published: March 2013

In this work, the conventional rolling (CR) and warm rolling (WR) have been carried out with an ultra purified ferritic stainless steel. After different rolling processes and subsequent recrystallization annealing, different recrystallized microstructure characteristics had been obtained. It was observed that as compared to the conventional process, the warm rolling and subsequent recrystallization annealing could obviously refine the recrystallized microstructure of the hot band. The ductile-to-brittle transition for the ultra purified ferritic stainless steel can be closely related to the occurrence of deformation twinning. The refined microstructure can decrease the temperature at which twinning occurs and, consequently, the ductile-brittle transition temperature for the ultra purified ferritic stainless steel was lowered to be below -40°C, and its notch toughness was significantly improved when the fine grain route can be applied.
Anisotropy of Mechanical Properties of API-X70 Spiral Welded Pipe Steels
Authors: Al Jabr Haytham M. , Speer John G. , Matlock David K. , Zhang Peng , Cho Sang Hyun
Published: March 2013

The effects of microstructure and texture on the toughness anisotropy of two API-X70 pipeline steels were investigated. One steel contained no nickel (0Ni) and the other contained 0.3 wt pct nickel (0.3Ni). Charpy V-notch impact testing was conducted on plate samples for both steels in three directions: longitudinal (L), transverse (T), and diagonal (D) with respect to the rolling direction. The microstructures of both steels were mixed and consisted of acicular ferrite, granular bainite, and small amounts of polygonal ferrite, with martensite-austenite and retained austenite islands as secondary phases. The ductile to brittle transition temperatures (DBTT) for the Charpy impact test were higher in the D direction for both plates, with a pronounced increase in the 0Ni steel. The anisotropy in toughness was mainly attributed to the crystallographic texture.
Study of Recovery and Recrystallisation in a Folded Al Alloy
Authors: Ubhi Harvinder Singh , Brough Ian , Larsen Kim
Published: March 2013

Changes in the microstructure and crystallographic orientations during in-situ heating of folded Al 0.1%Mg have been followed by SEM and EBSD. The folding process results in both strain and texture gradients across the folded region which in turn can influence the recovery and recrystallisation processes as well as crystallographic texture. This work is an extension of ex-situ heating experiments on folded nickel 200, titanium and ferritic steel [1,2]. The present findings illustrates that during isothermal in-situ heating at 295oC nucleation and growth starts close to the surface where the deformation is highest, new grains form and grow in a region about quarter depth of the sheet thickness. After this grain growth occurs resulting in large grains that meet up at the centre line. These results are consistent with those found in ex-situ heated Ni200 alloy [2], where fine grains were found in the compressed and tensile regions with large grains in the middle of the sheet.