bluuebunny/crossref_metadata_2025 huggingface dataset:
An EBSD Study of Austenite Formation and Stability in Low-Alloy TRIP Steels
Authors: Ryde Lena , Hagström Joacim , Hutchinson W. Bevis
Published: March 2009

Work has been carried out at KIMAB to determine the best, industrially feasible, conditions for producing TRIP steel sheet with the aim of obtaining a tensile strength of 600 MPa and a ductility of 30% through a hot-dip galvanising process schedule. Two of the most promising steels were selected to study the microstructures and to follow the transformation from ferrite to austenite in more detail, as well as to examine the stability of the austenite during deformation. This investigation has been performed mainly with the aid of the EBSD technique.
A Criterion for Conventional Dynamic Recrystallization: Application to Magnesium Alloys
Authors: Barnett Matthew R. , Beer Aiden G.
Published: March 2009

An analytical approximation for the steady state dynamic recrystallized grain size is combined with a simple nucleation criterion to assess the propensity for dynamic recrystallization. In line with observation, the criterion predicts dynamic recrystallization in 99.9995% pure Al but not in material 99.5% pure. It also agrees with the observation that zone refined ferrite can display dynamic recrystallization at high temperatures and low strain rates but not at lower hot working temperatures. The criterion is applied here to common wrought magnesium alloys to argue that conventional dynamic recrystallization is expected under "normal" hot working conditions.
Role of Recovery in the Recrystallization Simulation Application to a Cold Rolled IF-Ti Steel and a Cold Drawn Copper Wire
Authors: Volovitch Polina , Baudin Thierry , Penelle Richard , Caleyo F. , Barrallier Laurent
Published: March 2009

A simple model including the recovery and nucleation kinetics is proposed to simulate recrystallization using a Monte Carlo technique. Nucleation is simulated on the basis of equations describing stored energy evolution and subgrain growth kinetics. The parameters describing the stored energy evolution during recovery are shown to influence not only the relative number, orientation and local distribution of nuclei, but also the recrystallization kinetics and the final texture. The estimated kinetics of nucleation, the mean stored energy evolution as well as the preferential texture of first nuclei are in agreement with experimental observations for annealing 40% cold-rolled IF-Ti steel and cold drawn copper wires.
A Model for Multi Peak Dynamic Recrystallization in Copper
Authors: García V.G. , Cabrera Jose María , Prado Jose Manuel
Published: March 2009

Modelling hot flow stress during grain refinement operations of fcc metals has largely included the use of an Avrami type equation to describe the decrease in stress due to Dynamic Recrystallization (DRX). However when refining large-grained copper, the processing temperatures and strain rates often produce a multi peak behaviour, which is not predictable by an Avrami equation alone. If an initial grain size, D0, is greater than the stable dynamically recrystallized grain size, Drex, which is a function of the Zener-Hollomon Parameter, Z, then the material will tend to refine. However if the current the Zener-Hollomon value, given by current temperature and strain rate conditions, is lower than a critical value, Zc, which depends on D0, then a multi peak stress behaviour is expected while refining. The latter Relative-Grain-Size model (i.e. the D0-Zc and Drex-Z relationships plotted on the same log-log graph) is a practical model that allows determination of whether a material will grain coarsen or refine and whether the dynamic recrystallization behaviour will be monotonic or with multi peaks. The present authors devised a dynamic recrystallization algorithm to measure the stress due to the diminishing initial grain volume and to measure the correction stress due to recrystallizing grains. Analysis on the hot (600°C-950°C) compression data of a 99.9% pure copper inductively lead to the use of an Avrami type equation to describe the stress contribution produced by the deformation of the remaining initial grain volume and a damped cosine equation to describe the stress contribution of the synchronized volume of new grains. This work discusses the experimental evidence and analytical findings that inductively support the mathematical description of the stress-strain curve given by a Damped Cosine Avrami Model for discontinuous DRX.
Modelling Deformation Structures in Metals Based on an Entropic Analysis
Authors: Huang Ming Xin , Rivera-Díaz-del-Castillo Pedro E.J. , van der Zwaag Sybrand
Published: March 2009

Non-equilibrium thermodynamics theory is applied to the description of plastic
deformation in pure FCC metals at the steady state. The saturation flow stress is predicted
as a function of temperature and strain rate for Al, Cu, Ni and Ag. The implications on the
cell/subgrain size and dislocation density are explored.
Properties and Dynamics of Bulk Subgrains Probed In-Situ Using a Novel X-Ray Diffraction Method
Authors: Jakobsen Bo , Lienert Ulrich , Almer Jonathan , Pantleon Wolfgang , Poulsen Henning Friis
Published: March 2009

The synchrotron based X-ray diffraction method “High angular resolution 3DXRD” is briefly introduced. The technique enables the investigation of individual dislocation free regions in a dislocation structure, in-situ within the bulk. Results on the strain distribution within a single grain in a copper sample deformed in tension to 2%, and kept under load, are presented. It is found that the dislocation free regions of the dislocation structure on average are subjected to compressive strain with respect to the mean (tensile) strain in the grain. Results on the dynamics of individual dislocation free regions during straining are further reviewed, with special focus on the observation of intermittent behaviour.
Subgrain Rotation Recrystallization in Minerals
Authors: Drury M.R. , Pennock G.M.
Published: March 2009

Subgrain rotation is a common mechanism of continuous dynamic recrystallization in minerals and some metals. The mechanism involves new grain boundary formation by progressive rotation of subgrains or subgrain boundary migration in regions with an orientation gradient. This paper reviews the status of our current knowledge of rotation recrystallization in minerals. In minerals a misorientation angle (θ) of 10˚ is often taken as the transition from subgrain boundary to grain boundary but recent studies on olivine indicate a much higher transition angle between 15-25˚. In contrast to a high transition angle, the onset of subgrain boundary mobility may occur at much lower angles between 3-10˚. In consequence, rotation recrystallization in minerals often involves an initial stage of subgrain rotation followed by subgrain growth once medium angle boundaries have formed. Current models assume that all subgrain boundaries increase in misorientation with strain. However, recent studies show that many different types of subgrain boundary develop in minerals. The formation of new high angle grain boundaries is only likely along some types of geometrically necessary boundary (GNB). The mineral halite (NaCl) is often quoted as the classic example of rotation recrystallization yet recent electron backscattered diffraction (EBSD) studies show that only limited grain sub-division occurs in NaCl polycrystals. This grain sub-division occurs on the scale of large subgrains that divide the old grain into a few domains and not by the rotation of the smaller equiaxed subgrains, as envisaged in current models. The small scale, equiaxed, mainly low angle network of subgrain boundaries that develop in many minerals may be incidental boundaries, as found in metals, or could be smaller length-scale GNBs. As minerals have high plastic anisotropy and a limited number of slip systems GNBs may dominate over incidental subgrain boundaries formed by trapping of statistically stored dislocations. New and extended models for rotation recrystallization are needed that consider i) incidental subgrain boundaries as well as different types of GNB, ii) the potential high mobility of medium angle (3-15˚) subgrain boundaries and iii) a link between the development of subgrain misorientation and texture development.
Overview of Quick Plastic Forming Technology
Authors: Krajewski Paul E. , Schroth James G.
Published: March 2009

General Motors has developed Quick Plastic Forming (QPF) as a hot blow forming process
capable of producing aluminum closure panels at high volumes. This technology has been
successfully implemented for automotive liftgates and decklids with complex shapes. This talk will
review key elements of the QPF process, describe some of the technical achievements realized in this
process, and identify areas for future research in process, material, and lubricant development.
Flux Evaluation in Anisotropic Heat Conduction Using the Modified Local Green’s Function Method (MLGFM): Comparative Studies
Authors: Muñoz-Rojas Pablo A. , Vaz M.
Published: March 2009

The Modified Local Green’s Function Method (MLGFM) is an integral method which
uses appropriately chosen Green’s function projections obtained numerically with the aid of
auxiliary finite element problems. Its applicability includes those cases for which a fundamental
solution does not exist or is very cumbersome. The MLGFM was studied intensely in the 90´s with
promising results, especially for tractions and heat fluxes at the boundaries. The present contribution
compares this method for heat flux evaluation in anisotropic media with finite volumes and finite
elements. The latter approximates heat fluxes using a superconvergent patch recovery scheme,
whereas the former computes flux quantities directly at nodes. The numerical example uses linear
elements and includes non-homogeneous temperature and flux boundary conditions.
Self-Affine Patterns of Boride Layers
Authors: Campos-Silva Ivan , Ramírez G. , Balankin Alexander S. , Torres R.
Published: March 2009

In this study, the evaluation of interfaces on iron boride Fe2B growth obtained by paste
boriding process was carried out. Fractal geometry is used like a powerful tool for the roughness
analysis present during iron boride growth. Experiments were performed in AISI 1045 steel at
temperatures of 1193K for exposure times of 2, 4 and 6 h, and 1223K for treatment times of 2, 4, 5
and 6 h, varying the boron paste thicknesses in the range of 1 – 5 mm for each temperature and
time. The fronts of the interfaces in iron boride coatings were characterized and digitized with mean
of an optic microscope and Scion Image software. Self-affine methods were applied to the interface
growths for validate the fractality of the system. It was established that the interface width, ω ,
scales to ω (L) ∼ L H , where H represents the roughness exponent of the boride layers.
Calculation of the Effective Thermal Conductivity in Composites Using Finite Element and Monte Carlo Methods
Authors: Fiedler Thomas , Öchsner Andreas , Muthubandara Nilindu , Belova Irina V. , Murch Graeme E.
Published: March 2009

In this paper, the Finite Element and lattice Monte Carlo methods are used to calculate
the effective thermal conductivity of two models of a composite: circular and square inclusions
arranged in a square planar arrangement. A new lattice Monte Carlo method based around Fick’s
First Law is also presented. Excellent agreement is found between these quite different methods. It
is also shown that the results are in excellent agreement with the century-old Maxwell Equation.
Influence of Type of Cations on Intergranular Phase Crystallisation of SiAlON Ceramics
Authors: Acikbas N.C. , Kara Alpagut , Turan Servet , Kara Ferhat , Mandal Hasan , Bitterlich Bernd
Published: March 2009

25α:75β SiAlON composition was designed with different cations and at different
molar ratios. Effect of the type of cations both on the composition and the type of intergranular
phase investigated after gas pressure sintering and further post sintering heat treatment.
ZrO2-TiN Composites
Authors: Salehi Sedigheh , Biest Omer Vander , Vleugels Jef
Published: March 2009

1.75 mol % Y2O3-stabilized ZrO2-based composites with 35-95 vol % TiN were fully
densified by hot pressing for 1 hour at 1550°C under a load of 28 MPa. The TiN grain size was
found to increase with increasing TiN content, resulting in a decreasing hardness and strength. The
best mechanical properties, i.e., an indentation toughness of 5.9 MPa.m1/2 in combination with a
Vickers hardness of 14.7 GPa and an excellent bending strength of 1674 MPa were obtained for the
composites with 40 vol % TiN. The active toughening mechanisms were identified and their
contribution to the overall composite toughness is discussed. Transformation toughening was found
to be the primary toughening mechanism in all investigated composites.
The Growth and the Reaction Mechanism of Si3N4 Powder from Silica
Authors: Atasoy Ahmet
Published: March 2009

The behaviour of silica during the carbothermal reduction nitriding process at
temperatures between 1300-1500°C was studied by means of X-ray diffraction and scanning
electron microscope analysis. The experimental runs were allowed to proceed up to 1 h in presence
of nitrogen flow. The following mechanism of reduction nitriding of silica which was based on the
experimental observation was proposed. Initially the impurity of the starting material is reduced
before 1300°C. SiO2 was reduced into SiO gas phase by active carbon and it was vaporised out of
the mixture. The nucleation of α-Si3N4 was formed vapour-gas reaction took place and deposited on
the surface of the mixture as well as around the reaction crucible. In the third stage, α-Si3N4
transforms to one dimensional direction which was β-Si3N4 particle. This was followed by the
formation of SiC at temperature above 1450°C.
Liquid Phase Sintering of Aluminum Nitride
Authors: Komeya Katsutoshi , Tatami Junichi
Published: March 2009

Liquid-phase sintering of aluminum nitride (AlN) with additives was reviewed. The most important innovation was the discovery of critical sintering aids for AlN densification, specifically rare-earth compounds and alkali-earth compounds. These additives are extremely valuable for increasing thermal conductivity by trapping and removing oxygen in the AlN lattice during firing. Consequently, thermal conductivities in AlN ceramics of 100 to 260W/mK were developed. We also studied the effects of parameters such as raw powder, additives, composition, and firing condition in liquid-phase sintering with AlN-sintering aids, focusing on oxygen impurities in the system. The sintering behavior of powder compacts was investigated by evaluating the densification, the lattice constant c for AlN, and the dihedral angle of the interface between the AlN grains and the grain boundary liquid-phase. In our results, the change in densification was closely related to changes in the lattice constant c and the dihedral angle. That is, the sintered density increased with an increase in the oxygen dissolved in the AlN grains and with the improvement in wettability between the solid and liquid phase.
Mechanochemical Nitride Synthesis
Authors: Thompson Derek P.
Published: March 2009

A frequent criticism of nitride materials during the last 30 years, and especially those
designed for structural applications has been that the cost is too high by a factor of (say) 10. In the
competition with cheaper materials (albeit with poorer properties and shorter lifetimes), users have
generally preferred to go for the cheaper option, rather than the more expensive nitrides. Despite
many attempts to address this issue, the cost of nitride processing has remained high – due to the
high price of starting materials, the high temperatures needed for firing, and also the finishing costs
(often involving diamond machining), and this has been a major factor limiting the market share
enjoyed by these materials.
A number of studies have been reported recently using the technique of mechanochemical
synthesis, in which nitrogen is incorporated (usually via ammonia) into the starting powders during
a high-energy milling process (at room temperature). In the subsequent firing, considerably lower
temperatures are needed to produce the resulting final nitride product(s). In this presentation, the
technique of mechanochemical synthesis is discussed, the range of materials that have been
produced are reviewed, and the potential of this technique for reducing the cost of bulk nitride
production is reviewed.
Densification of Sr-Mg Doped SiAlONs with GPS and SPS
Authors: Kurama S. , Herrmann Mathias
Published: March 2009

At temperature above 1200°C, the thermal stability of α-SiAlON phases has been
debated since 1992; however, it has been discussed if any α-SiAlON phase can be formed in Ce,
La, Eu and Sr-doped SiAlON systems. In our previous studies it was shown that the use of Mg-Ce
and Mg-Sr elements as dopants SiAlON compositions, in which all elements just have very low or
no stability in the α-SiAlON structure, would promote the stability of Mg-Ce elements in the α-
SiAlON phase [1, 2]. However, in Mg-Sr systems, it was obtained that Mg2+ is predominantly
incorporated in α-SiAlON structure whereas Sr2+ mainly remains in the grain boundaries [2]. In this
study, by applying spark plasma sintering (SPS) (at 1400-1700°C) and post-sintering thermal heat
treatment (at 1500°C for 5 hrs and 1700°C for 2hrs) Mg or Mg-Sr doped SiAlON (50:50 mole
ratios) ceramics were prepared. The results were compared with GPS sintered samples data. The
effect of sintering temperature on densification process, phase transformation, microstructure and
mechanical properties of samples were investigated. The results showed that by using SPS, Sr-Mg
doped samples can be sintered at lower temperature (at 1600°C) than at GPS (at 1800°C) and it has
no Sr-doped grain boundary phases.
Analysis of SiC CVD Growth in a Horizontal Hot-Wall Reactor by Experiment and 3D Modelling
Authors: Shishkin Y. , Myers-Ward Rachael L. , Saddow Stephen E. , Galyukov Alexander , Vorob'ev A.N. , Brovin D. , Bazarevskiy D. , Talalaev R.A. , Makarov Yuri
Published: March 2009

A fully-comprehensive three-dimensional simulation of a CVD epitaxial growth process
has been undertaken and is reported here. Based on a previously developed simulation platform,
which connects fluid dynamics and thermal temperature profiling with chemical species kinetics, a
complete model of the reaction process in a low pressure hot-wall CVD reactor has been developed.
Close agreement between the growth rate observed experimentally and simulated theoretically has
been achieved. Such an approach should provide the researcher with sufficient insight into the
expected growth rate in the reactor as well as any variations in growth across the hot zone.
A Texture Component Model for Predicting Recrystallization Textures
Authors: Winning Myrjam , Raabe Dierk , Brahme Abhijit P.
Published: March 2009

The study presents an analytical model for predicting crystallographic textures and the final grain size during primary static recrystallization of metals using texture components. The kinetics is formulated as a tensorial variant of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The tensor form is required since the kinetic and crystallographic evolution of the microstructure is described in terms of a limited set of growing (recrystallizing) and swept (deformed) texture components. The number of components required defines the order of the tensor since the kinetic coupling occurs between all recrystallizing and all deformed components. The new method is particularly developed for the fast and physically-based process simulation of recrystallization textures with respect to processing. The present paper introduces the method and applies it to the primary recrystallization of low carbon steels.
Prediction of the Microstructural Evolution during Hot Strip Rolling of Nb Microalloyed Steels
Authors: Lissel Linda , Engberg Göran
Published: March 2009

A physically based model is used to describe the microstructural evolution of Nb microalloyed steels during hot rolling. The model is based on a physical description of dislocation density evolution, where the generation and recovery of dislocations determines the flow stress and also the driving force for recrystallization. In the model, abnormally growing subgrains are assumed to be the nuclei of recrystallized grains and recrystallization starts when the subgrains reach a critical size and configuration. The model is used to predict the flow stress during rolling in SSAB Tunnplåt’s hot strip mill. The predicted flow stress in each stand was compared to the stresses calculated by a friction-hill roll-force model. Good fit is obtained between the predicted values by the microstructure model and the measured mill data, with an agreement generally within the interval ±15%.
Preliminary Simulation for Competing Behaviors between Recrystallization and Transformation in Dual Phase Steels
Authors: Okuda Kaneharu , Yoshida Hiromi , Nagataki Yasunobu , Tanaka Yasushi , Rollett Anthony D.
Published: March 2009

The competitive behaviors between recrystallization and transformation during annealing
in dual phase high-strength steels are studied both by experiments and by computer simulations. The
Monte Carlo code was applied to simulate such competing behavior, explained the experimental
results, as follows. (1) The progress of the transformation is affected by the starting point of the
transformation in the course of recrystallization. Namely, if the transformation starts at the later stage
of recrystallization, the n-value in JMAK equation is relatively high. (2) If the stored energy (driving
force) of the transformation is above 5 times larger than that of the recrystallization, the effect of the
stored energy is quite small. (3) If the number of nuclei were increased, the transformation proceeds a
little faster, and then the transformed microstructures are significantly refined. When the
transformation initiates at the early stage of the recrystallization, the number of nuclei can be
increased by nucleation from the deformed matrix compared with the one from fully recrystallized
matrix.
Topology Based Growth Law and New Analytical Grain Size Distribution Function of 3D Grain Growth
Authors: Streitenberger Peter , Zöllner Dana
Published: March 2009

Based on topological considerations and results of Monte Carlo Potts model simulations of three-dimensional normal grain growth it is shown that, contrary to Hillert’s assumption, the average self-similar volume change rate is a non-linear function of the relative grain size, which in the range of observed grain sizes can be approximated by a quadratic polynomial. In particular, based on an adequate modification of the effective growth law, a new analytical grain size distribution function is derived, which yields an excellent representation of the simulated grain size distribution.
Recrystallization Behaviour of Cold Rolled Aluminum Alloy AA 3103 in a Magnetic Field
Authors: Bhaumik Sheila , Molodova Xenia , Molodov Dmitri A. , Gottstein Günter
Published: March 2009

The recrystallization behavior of 71% cold rolled aluminum alloy 3103 was investigated by measuring the crystallographic texture and the grain microstructure during heat treatment at 288°C, 310°C and 330°C in a magnetic field of 17 T. The results revealed that the application of a magnetic field substantially enhances recrystallization kinetics.
Microstructures of Microwave Heated Soda-Lime Glass - Fe Composite and Ni-Zr-Nb-Ti-Pt Metallic Glass
Authors: Yoshikawa Noboru , Louzguine-Luzgin Dmitri V. , Maishiko Kenichi , Wang Hai Chuan , Xie Guo Qiang , Sato Motoyasu , Taniguchi Shoji , Inoue Akihisa
Published: March 2009

In this study, microwave (MW) heating of Fe powder in the separated electric (E-) and magnetic
(H-) fields was performed first, and the heating behaviors on the field dependence were investigated.
It was shown that they are heated better in H- field than in E- field. The MW heating mechanism of
metals were briefly discussed.
MW heating of soda-lime glass alone was not easy, however addition of iron powder enhanced the
heating, depending on the volume fraction of the powder. Occurrence of deformation and melting of
the glass spheres was observed. This technique is applicable to fabrication of glass-metal
composites and vitrification of waste matters.
MW heating of Ni-based metal glass was attempted with no external pressure and in an inert
atmosphere, it was also shown that heating was better accomplished in H- field. Weakly sintered
body was possibly obtained with retention of the amorphous phase.
Nucleation Mechanism of 40˚<111> Rotated Grains during Recrystallization in Heavily Cold-Rolled Ni3Al Single Crystals
Authors: Demura Masahiko , Xu Ya , Kishida Kyosuke , Hirano Toshiyuki
Published: March 2009

Primary recrystallization textures were examined in the 84% and 95% cold-rolled boron-free Ni3Al single crystals with a Goss texture using the electron backscatter diffraction method. It was found that the main components of the textures in the specimens heat-treated at 873K/0.5h had a 40° rotation relationship about <111> to the original, Goss texture. All the eight variants of 40°<111> rotated grains existed. However, the number density is not even but dependent on whether the rotation axis is identical to the normal of slip planes activated during the prior cold rolling. The ratio of the number density among the variants was same in both the 84% and 95% cold-rolled foils. Based on these results, the formation of these 40°<111> rotated grains was explained assuming the modified multiple twinning mechanism where the annealing twinning occurred at the activated slip planes, followed by the subsequent twinning.
Recrystallisation at Intercritical Annealing in Low Carbon Steels
Authors: Maruyama Naoki , Ogawa T. , Takahashi M.
Published: March 2009

Subgrain growth in deformed ferrite and incomplete recrystallisation during intercritical
annealing in low carbon (LC) steels was investigated by EBSD and FEGTEM/EDS. It was
confirmed that fine dual phase (α+γ) microstructures could be obtained even without the addition of
microalloying elements such as Nb and Ti, if the steels were heated above Ac1 temperature before
the completion of primary recrystallisation and then intercritically annealed. The fine microstructure
was found to be mainly due to the inhibition of primary recrystallisation, and also due to the
inhibition of subgrain growth in deformed matrix by finely dispersed γ phase formed during
heating. Mn segregation at α/γ interfaces seems to indicate that the kinetics of boundary migration
in the existence of γ is controlled by the volume diffusion of substitutional alloying elements across
the α/γ interfaces.
Influence of Nb Stabilization on the Recovery and Recrystallization Kinetics of a Ferritic Stainless Steel: Consequences on Magnetic Losses
Authors: Meyer Nicolas , Bréchet Yves , Véron Muriel , Mantel Marc , Dubois Pierre Emmanuel , Geoffroy Oliver
Published: March 2009

Softening kinetics of two 17% chromium (Cr) stainless steel grades that differ in niobium (Nb) content are compared. In the experiments, we observed that a low Nb stabilization makes recrystallization nucleation much faster and prevents incomplete recrystallization. A qualitative interpretation, based on interaction with precipitates, is proposed and explains the main features of the softening kinetics as well as the microstructures obtained. For the Nb stabilized grade, magnetic losses were measured in the deformed state and after recrystallization. Above a specific magnetizing frequency, the deformed state led to smaller losses than the recrystallized state. These results are believed to be attributed to a grain size effect.
Recent Advances in the Simulation of Recrystallization and Grain Growth
Authors: Gottstein Günter , Shvindlerman Lasar S. , Crumbach Mischa , Barrales-Mora L.A.
Published: March 2009

Modeling and simulation of recrystallization, grain growth, and related phenomena are important tools for the fundamental understanding of microstructural evolution and prediction of engineering properties. In particular for ultra fine grained and nanocrystalline materials proper account of microstructural evolution is essential for the optimal processing of these materials. It is shown that for modeling of softening phenomena it is important to discriminate between discontinuous primary recrystallization and discontinuous grain growth owing to their quite different underlying physics. Recent developments in recrystallization modeling and simulation of grain growth are addressed, in particular nucleation of recrystallization and junction effects in grain growth. Major progress is also expected from atomistic modeling and quantum-mechanical computations for making available specific material properties.
3D Spatial Distribution of Nuclei in 90% Cold Rolled Aluminium
Authors: Sükösd Zsuzsanna , Hannesson Kristofer , Wu Gui Lin , Juul Jensen Dorte
Published: March 2009

The distribution of nucleation sites in 90% cold rolled aluminium (AA1050) annealed for 1h at
280°C has been determined by serial sectioning the sample and characterizing each section using
the electron back scattering pattern (EBSP) method in the SEM. In total 1844 nuclei are identified.
It was found that the nuclei are not randomly distributed but clustered preferentially along TD-RD
planes in the sample. The results are presented and implications of clustered nucleation on
recrystallization kinetics are discussed.
Low Temperature Recrystallization of High Purity Iron Severely Deformed by ARB Process
Authors: Terada Daisuke , Li Bo Long , Sugiyama Masaaki , Tsuji Nobuhiro
Published: March 2009

Recrystallization behavior of SPD processed high purity iron was studied. The 99.95%
iron sheet was deformed by the accumulative roll-bonding (ARB) process up to 8 cycles (equivalent
strain of 6.4) at ambient temperature. Subsequently, the ARB-processed specimens were annealed for
1.8ks at various temperatures from 300°C to 500°C. The microstructures of these specimens were
characterized by TEM and SEM/EBSP. The microstructure of the as-ARB-processed specimens
showed the lamellar boundary structure elongated along RD, which was the typical microstructure of
the ARB-processed materials. The mean interval of the lamellar boundaries was about 100 nm. After
annealing at 400°C, the ARB specimen showed a partially recrystallized microstructure composed of
equiaxed grains with grain size larger than 10 5m and the recovered lamellar boundary structure.
After annealing above 500°C, the microstructures were filled with equiaxed recrystallized grains.
These results suggest that conventional discontinuous recrystallization characterized by nucleation
and growth occurs during annealing at annealing temperature above 400 °C. In previous work
reported about the annealing behavior of the low carbon IF steel ARB processed, the continuous
recrystallization occurred during annealing at annealing temperature above 600 °C. The
recrystallization temperature of the pure iron was much lower than the IF steel and the
recrystallization process were significantly different. This difference was suggested to be caused by
inhomogeneous microstructure in the pure iron ARB-processed.
Nucleation of Dynamic Recrystallization at the Grain Boundaries of Copper Bicrystals
Authors: Miura Hiromi , Sakai Taku , Mogawa R. , Jonas John J.
Published: March 2009

Orientation-controlled copper bicrystals containing symmetrical 70o [0 0 1] tilt boundaries were
deformed in tension at 923 K and at three initial strain rates from 4.2 x 10-5s-1 to 4.2 x 10-3s-1. The load was
applied parallel to the grain boundary so as to eliminate grain boundary sliding. The nucleation of dynamic
recrystallization (DRX) was investigated using optical microscopy and orientation imaging microscopy
methods. After grain-boundary migration (GBM) and bulging, nuclei appeared behind the most deeply bulged
grain boundary regions. The critical strain for nucleation was less than one-half of the peak strain and largely
independent of the strain rate. At a fixed strain, nucleation is more frequent and the grain size finer as the strain
rate is increased. All the nuclei were twin-related (Σ3) to the matrices. Furthermore, most of the twinning plane
traces were parallel to the inactive slip traces of the bicrystals. This indicates that twin variant selection is
essentially unaffected by dislocation motion. The observed mechanism of nucleation of DRX is discussed in
relation to the occurrence of GBM and twinning.
Formation of Ultrafine Ferrite Grains during Interrupted Multi-Pass Deformation under Hot Torsion
Authors: Barbosa Ronaldo , Santos Dagoberto Brandão , Lino Roney Eduardo
Published: March 2009

Strain induced transformation (SIT) of austenite into ferrite has been frequently used as a
powerful ferrite grain refinement mechanism. Ordinarily ferrite grain sizes of the order of 1-3μm
are achieved via mechanical testing such as compression and torsion. Nonetheless, most of the work
done so far employed continuous deformation in the range of 0.8 for compression experiments and
in excess of this for torsion. SIT is a promising technique which may be used during actual hot
rolling processing. However, in this case, not only deformations are applied with time interrupts
between them but also the amount of total deformation allowable is relatively low, in order to attend
to flatness and final gauges requirements. This work explores the consequences on SIT
microstructure of deformation given in multiple passes as opposite to the usual continuous
deformation presented in the literature. Multiple pass deformation at high temperature led to partial
dynamic recrystallization and to a mixture of coarse and fine ferrite grains. Multiple pass
deformation at the vicinity of Ar3 produced, on the hand, finer ferrite grains indicating that SIT took
place. In this case, ferrite grains in the range of 1-3μm were produced and a much more
homogeneous distribution of these grains was present.
Relationship between Grain Boundary Diffusion and Ferrite Grain Size Formed through Dynamic Recrystallization during Large Strain Deformation
Authors: Torizuka Shiro , Murty S.V.S. Narayana
Published: March 2009

During large strain deformation of materials, the high angle grain boundary spacing
approaches the order of mean thermal diffusion distances for given deformation conditions. Based on
the results of microstructural and grain size analysis in low carbon steel subjected to large strain-high Z
deformation, the evolved ferrite grain size was found to be controlled by the Zener-Hollomon parameter and
grain boundary diffusion was found to be the controlling mechanism.
Relation between Ridging and Texture Components in Al-Mg-Si Alloy
Authors: Ikeda Kenichi , Yoshihara Takahiro , Takata Naoki , Nakashima Hideharu
Published: March 2009

Al-Mg-Si alloy is the suitable material for the automotive body application. However, it is found that a rope-like profile (ridging) develops when the Al-Mg-Si alloy sheet is stretched along the transverse direction. In this study, in order to clarify the formation process of ridging developed in Al-Mg-Si alloy, the relation between ridging and texture components of the sheet was investigated by 3D profile microscope and SEM/EBSD method. It was found that the ridging developed remarkably in the hot-rolled (at higher temperature) and annealed sheets. In ridging sample, there was the band of cube oriented grains (cube band). It was also found that the region of cube band corresponded to the ridges and valleys which caused a rope-like profile in the sheets. It could be thought that the difference of plastic deformability between cube-oriented grains and other oriented grains led to the development of ridging. This assumption is supported by the lower Taylor factor of cube oriented grains than other oriented grains. From these results, it was concluded that the development of ridging was strongly affected by the distribution of cube oriented grains.
The Effect of Copper Content on the Dynamic Grain Growth in AL-Cu-Zr Systems
Authors: Sotoudeh Kasra , Bate Pete S. , Humphreys John F.
Published: March 2009

The effect of copper content on dynamic grain growth in Al-Cu-Zr system was investigated by studying the microstructural development and texture evolution during uniaxial tensile deformation of Al-2wt%Cu-0.3wt.%Zr and Al-4wt%Cu-0.4wt.%Zr alloys at 450°C with a strain rate of 10-3s-1, with a similar initial microstructure in both materials. The initial microstructure consisted of layers of different orientations, the layers being separated by high-angle grain boundaries with low-angle boundaries separating grains within the layers. The initial grain spacing was about 5m and the texture was typical of rolled aluminium alloys. The 4wt.%Cu alloy gave a higher strain rate sensitivity index, m, and a greater ductility compared to the low copper content alloy. An increase in grain size occurred in both materials due to deformation, but this dynamic grain growth (DGG) was much greater in the material with the higher copper content. This was associated with a more rapid conversion of low-angle boundaries to high angle ones in the 4wt%Cu material which is consistent with changes in crystallographic texture occurring during deformation.
Correlation between Boundary Energy and Grain Boundary Character Distribution in Fe-Based Polycrystals
Authors: Gobernado Patricia , Petrov Roumen H. , Kestens Leo
Published: March 2009

The grain boundary energy anisotropy in BCC Fe-based polycrystals is considered. The correlation between the energy in BCC random grain boundaries and the distribution of grain boundary planes in the bulk was examined with a special attention on the presence of low index (low surface energy) planes in the internal surfaces. For a BCC structure, {100} and {110} planes are known to be the lowest energy planes dominating the equilibrium crystal shapes. Experimental evidences demonstrated that these planes were predominant in the texture of surfaces controlled by surface energy [2]. Moreover, the relation between the grain boundary character distribution and the crystallographic dependence on the grain boundary energy in the bulk after annealing treatment was studied. The grain character boundary distribution (GCBD) was calculated using the crystallographic information obtained from OIM-EBSD maps from samples showing columnar grains. Preliminary results showed no particular distribution trend within the standard stereographic triangle (001-101-111).
Dislocation Structure of 10° Low-Angle Tilt Grain Boundary in α-Al2O3
Authors: Tochigi E. , Nakamura A. , Shibata Naoya , Yamamoto Takahisa , Lagerlöf K.P.D. , Ikuhara Yuichi
Published: March 2009

Dislocation structure of 10º low-angle tilt grain boundary in α-Al2O3 has been observed by high-resolution electron microscopy (HRTEM). It was found that perfect <1120> edge dislocations, which are introduced to compensate the misorientation, dissociated into two mixed partial dislocations with {1120} stacking-fault in between. The distances between the two partials were estimated by the force balances between repulsive forces of periodical dislocations and attractive forces from stacking-fault. The stacking-fault energy for 10o low-angle tilt grain boundary was estimated to be much higher than the previously reported value.
Development of Instrumented Composite Cylinders
Authors: Hernández-Moreno H. , Collombet Francis , Douchin Bernard , Davies Peter , González Jorge Luis
Published: March 2009

This paper describes a technique to fabricate instrumented composite cylinders made by the filament winding process and based on the insertion of Bragg grating sensors contained in an optical fiber, so that real time monitoring of the temperature and strain response can be made. The main advantage of this method is that, for the first time, the strain response of the wound layers as a function of time and temperature can be monitored during fabrication without alteration of the composite structure, since the sensor is a filament itself. The sensor data reveals the existence of several phenomena related to the manufacturing process and material response. The results show that during the curing stage of the fabrication of the composite cylinders there is a dimensional contraction without change in temperature which indicates that a material transformation occurs, and also that at the last stage there is a residual compressive strain which may affect the in-service behavior of the composite cylinder.
Composite Coatings Elaborated by Plasma Spraying of Dry Coated Particles
Authors: Cuenca-Alvarez R. , Ageorges H. , Fauchais Pierre
Published: March 2009

The influence of dry particle coating on the properties of coatings produced by d.c. arc
plasma spraying is reported. A mechanofusion process is used to coat coarser metallic particles with
fine ceramic particles without using either binders or solvents. The key parameters affecting the
mechanofusion process and the corresponding plasma spraying method have been varied in order to
increase the hardness of the resulting composite coatings. Efforts have been made to disperse
homogeneously hard particles (α-Al2O3, SiC) into a metallic matrix (316L stainless steel) and check
if it is possible to limit the oxidation of metallic particles during their flight in the plasma jet
flowing in air. The hardness of resulting composite coatings depends on the metallic particle size
even when the hard ceramic particles are homogenously dispersed into the metallic matrix. Spraying
mechanofused powder composed of finer stainless steel particles (64 ,m), results in finer structured
deposits that show a higher oxide content. On the contrary, a low oxidation rate of the metallic
matrix is observed when coarser metallic particles (120 ,m), covered by a binary layer of α-Al2O3
and SiC are sprayed.
Austenite-Ferrite Transformation in Hot Rolled Mn-Cr-Mo Dual Phase Steels
Authors: López-Baltazar Alejandro , Salinas-Rodríguez Armando , Nava-Vázquez Enrique
Published: March 2009

Interrupted cooling in the run-out table after hot rolling is a processing strategy to produce dual phase ferrite-martensite steel strips. The effects of interrupted cooling temperature and time after austenitizing at 1150 °C are investigated. This is done to establish the conditions for austenite to transform into ferrite-martensite microstructures in a Mn-Cr-Mo strip produced from a CSP (Continuous Strip Processing)-type thin slab. The results show that dual phase microstructures can only be obtained when interrupted cooling is performed at 725<T<800 °C. The amount of martensite and the strength level that can be developed increase as the interrupted cooling temperature increases. Formation of pearlite during the isothermal holding causes a rapid decrease in the level of strength that can be developed in this type of structural material.
Influence of Processing Parameters on Interfacial Heat Transfer Coefficient at the Metal-Die Interface of Die Cast AM50 Alloy
Authors: Guo Zhi Peng , Xiong Shou Mei , Cho Sang Hyun , Choi Jeong Kil
Published: March 2009

This paper focuses on the determination of the heat flow density (HFD) and interfacial heat
transfer coefficient (IHTC) during the high pressure die casting (HPDC) process of AM50 alloy. A
specially designed “step shape” casting is used during the die casting experiment. Based on the
temperature measurements inside the die, HFD and IHTC are successfully determined. Calculation
results indicate that HFD and IHTC at the metal-die interface increases sharply right after the fast
injection process until approaching their maximum values, and after that their values decrease to a
much lower level until the dies are opened. Casting thickness has a great influence on both of the HFD
and IHTC. Process parameters, such as the intensification pressure, the piston velocity, have little
influences on HFD while on the other hand the die temperature has a great influence on the HFD. The
IHTC seems to be independent upon all those process parameters so the IHTC peak values maintain at
a particular level when the casting thickness is fixed.
3D Microstructure Development during Unconstrained Solidification of Aluminum Alloys
Authors: Ruvalcaba D. , Eskin Dmitry G. , Katgerman Laurens
Published: March 2009

In the present investigation, serial sectioning and 3D reconstructions are made on samples
quenched at selected temperatures during unconstrained solidification in order to observe the
evolution in morphology of coarse dendrites in 3D. The 3D microstructure reconstruction during the
solidification of an Al−7 wt.% Cu alloy allowed the identification of a complex coarse morphology
of dendrites. High-ordered branches present different morphologies at different temperatures and
locations in the microstructure due to coarsening and coalescence. 3D visualization of complex
dendritic structures is discussed in the present investigation.
Study on Process of Magnesium Alloy Investment Casting
Authors: Yang Guang Yu , Jie Wan Qi , Hao Qi Tang , Li Jie Hua
Published: March 2009

The process of different sorts of magnesium alloys investment casting is studied using a
mold materials composed of zircon and colloided silica binder. The investment shell is flushed out
employing protective gas mixture of 1% HFC134a and inert gas. The castings with perfect appearance
and high metallurgical quality are produced successfully for ZC62 and ME-1magnesium alloy
respectively. The mechanical properties of the castings reached the ASTM standard.
Control of Carbides and Graphite in Ni-Hard Type Cast Iron for Hot Strip Mills
Authors: Villanueva Bravo Sergio , Yamamoto Kaoru , Miyahara Hirofumi , Ogi Keisaku
Published: March 2009

The carbide and graphite formation and redistribution of alloy elements during
solidification were investigated on Ni-hard type cast iron (Fe-C-Si-Ni-Cr-Mo) to develop higher
quality rolls for hot steel strip mills. By the control of Ni and Si contents of iron, eutectic graphite
flakes crystallize even in cast irons containing strong carbide formers such as V, Nb and Cr. The
crystallization of Ni-hard type cast iron with V and Nb proceeds in the order of primary , + MC,
+ M3C and + graphite eutectic. Since the influence of each alloying element on graphite formation
is estimated based on the solubility of C in molten iron, the change in graphite forming tendency of
residual liquid is evaluated by the parameter expressing the solubility limit of C to molten iron. The
amount of graphite increases with the decreasing of solubility parameter. In addition, inoculation with
ferrosilicon effectively increases the graphite flakes.
Liquid Metal Free Surface Motion Submerged in an AC Magnetic Field
Authors: Iwai Kazuhiko , Asai Shigeo
Published: March 2009

Free surface motion of a liquid metal submerged in an alternating magnetic field has been
examined. A copper vessel filled with a liquid gallium is set in a coil for the imposition of the
alternating magnetic field. The alternating magnetic field penetrates into a liquid gallium only from
an upper free surface because thickness of the copper vessel is larger than the electromagnetic skin
layer of copper. Time variation of displacement of the standing wave loop excited on the free
surface is detected by a laser level sensor. The standing wave was suppressed not only by
intensification of the magnetic field magnitude but also increase of the magnetic field frequency.
Large Linear and Volume Magnetostriction in Fe-Ga Alloys
Authors: Jiang Cheng Bao , Liu Jing Hua , Gao Fang , Xu Hui Bin
Published: March 2009

The growth velocity has a significant effect on the preferred orientation of the directionally
solidified Fe81Ga19 magnetostrictive alloy. Strong <100> preferred orientation was obtained for a
velocity range from 10mm/h to 20mm/h. An excellent magnetostriction λ100 of 294×10-6 was
achieved for the <100> oriented crystal at a pre-stress of 74.1MPa. Linear and volume
magnetostrictions were investigated in the as-cast Fe81Ga19 alloys with A2 phase by measuring the
change in length along the three-dimensional directions of the samples. Due to the contribution of the
volume magnetostriction, the longitudinal magnetostriction increased from 27 ppm at 0.3 T to 47 ppm
at 2.0 T. The volume magnetostriction can be drastically enhanced by doping Ga in Fe.