bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Nb Carbo-Nitride Precipitation Conditions on Abnormal Grain Growth in Nb Added Steels
Authors: Murakami Toshio , Hatano Hitoshi , Shindo Yosuke , Nagahama Mutsuhiro , Yaguchi Hiroshi
Published: March 2009

In order to investigate the effects of Nb carbo-nitride precipitation conditions on
abnormal grain growth behavior during high temperature carburizing, size of Nb carbo-nitride
precipitates was controlled by precipitation treatment at 1173-1273K for 0.6-54ks, and the
specimens were quasi-carburized at 1323K. Abnormal grain growth was enhanced when the size of
Nb precipitates was fine or coarse, so there is a suitable size range in Nb precipitates to suppress
abnormal grain growth. The reason why abnormal grain growth was enhanced is the lack of pinning
force as the conventional theory proposed by Hillert or Gladman; however, it cannot be explained
by this theory that small precipitates promote abnormal grain growth. It is considered that Ostwald
ripening rate of precipitates is also an important factor in controlling abnormal grain growth in
addition to the amount and size of precipitates and austenite grain size, which were parameters in
the Gladman‘s theory on abnormal grain growth behavior.
Effect of Niobium on Zn-Coated Dual Phase Steel Sheet
Authors: Hashimoto Shunichi
Published: March 2009

Dual Phase (DP) steel sheets, mainly 590 MPa TS grade steel, have been applied to
structural parts of automobile because of their good formability, large bake hardenability and high
crash worthiness. Although the concept of DP steel was established as early as the mid-1970th, the
literature contains little discussion of Zn-coated DP steel, which has been the main application in
recent years. In manufacturing Zn-coated DP steel, chemical composition which secures adequate
Zn coatability and appropriate heat cycles, including galvannealing, must be considered.
In this paper, the effect of Nb on the tensile properties, stretch flange formability and bake
hardenability of 590 MPa TS grade DP steel is discussed. The base chemical composition was
0.05%C-2%Mn-0.5%Cr steel. The effect of Nb on the above-mentioned properties was studied
using 0.05%Nb added steel and found that the addition of 0.05%Nb results in improved elongation,
stretch flangeability and bake hardenability with higher tensile strength under both simulated GA
and GI heat cycles. These improved properties by the addition of Nb are brought about by the grain
refinement of ferrite matrix and finer dispersion of martensite.
Diffusion-Controlled Phase Transformation under High Magnetic Field in Medium and High Carbon Steels
Authors: Zhang Yu Dong , Esling Claude , Zhao Xiang , Zuo Liang
Published: March 2009

The new phase equilibrium of Fe-C diagram under magnetic field has been theoretically
calculated. Results show that the magnetic field mainly shifts the γ⁄α+γ equilibrium line and the
eutectoid point to the high carbon and high temperature sides. Based on this result, an experimental
setup has been launched to investigate the effect of magnetic field on austenite decomposition in
medium carbon and high carbon steels. The thermodynamic and kinetic effects of the high magnetic
field on proeutectoid transformation at different cooling rates have been studied. It was found that
for medium carbon steels, the magnetic field increases the amount of proeutectoid ferrite and
accelerates the diffusional decomposition of austenite at medium and relatively fast cooling rates
(10°C/min and 46°C/min). But there is no special grain growth along the field direction. The results
led to a proposal of a new rapid annealing under a high magnetic field. However, when cooling is
slow (2°C/min), the magnetic field shows a strong tendency to promote the proeutectoid ferrite
grains to grow along the field direction through the magnetic dipolar interaction, which leads to the
formation of an elongated grain structure. Moreover, the magnetic field also exhibits influence on
the austenite decomposition in hypereutectoid steel by changing the amount of secondary cementite
and lamellar spacing of pearlite.
Nano-Carbides and the Strength of Steels as Assessed by Electrical Resistivity Studies
Authors: Lesuer D.R. , Frommeyer Georg , Sherby Oleg D. , Syn C.K.
Published: March 2009

The work of Frommeyer on electrical conductivity measurements in pearlitic steels is
reviewed to provide insight into microstructures developed during wire drawing. Electrical
conductivity measurements were made as a function of drawing strain (up to ε = 6.0) for wires with
strength exceeding 3500MPa. The results show that electrical conductivity increases during wiredrawing
to a maximum value, then decreases with further deformation finally reaching a steady
state value that is equal to the original conductivity. The initial increase is the result of pearlite plate
orientation in the direction of wire-drawing, which makes the path of conduction through the ferrite
plates more accessible. At a critical strain the cementite plates begin to fragment and the electrical
conductivity decreases to a steady state value that is the same as that observed prior to wire
drawing. With increasing strain, the cementite particles are refined and the strength increases due to
the reduction in inter-particle spacing. It is concluded that the electrical conductivity of the wires is
solely dependent on the amount of iron carbides provided they are randomly distributed as plates or
as particles. An estimate was made that indicates the carbide particle size is approximately 3 - 5 nm
in the steady state range of electrical conductivity.
N--H Interaction in Nitrided Fe--Nb Alloys
Authors: Sakamoto Masatoshi
Published: March 2009

Internal friction of nitrogen in α iron has known as Snoek peak of N atom resolv
ed in the octahedral interstitial site of bcc. When M atom ( Mn, Mo, Si, et.al)
which has the affinity bigger than Fe were added ,another peaks due to the jump
of N from Fe-Fe site to Fe-M site appear in the upper temperature side and
complicate the Snoek peak curve of N.
In this paper, the Snoek peak curve was studied in Fe-0.4wt%Nb-0.02wt%N alloys.
This alloy showed no other peaks in the upper side to 373K and had only the
single peak of N in Fe-Fe site. Internal friction measured by torsion pendulum
method at about 1 Hz. After that this alloy was cooled from 373K to room
temperature and reheated to 373K, but Snoek peak of N which showed on the first
measurement just after nitriding disappeared completely and internal friction was
only background. One of the reasons of it is the precipitation of Fe16N2 under
heating and resolved N atoms disappeared. So these specimens were reheated to
873K and quenched, but Snoek peak of N was not measured. This shows the
disappearance of N atom from Fe-Fe site.
The mixture gas of a few % NH3 and H2 was used in this study. Therefore after
nitriding much of H atoms were resolved in α iron alloys. Because the diffusion
rate of H atom in α iron is bigger than N atom , it expected that H atoms can
combine with Nb atoms before coming N atoms. And the appearance of Snoek
peak of N in these alloys is considered. After that, in the heating to 373K H atom
leave Nb and go away from the surface, and N atoms combine with Nb in place
of H atoms. Nb has the very strong affinity with N, so these alloys have no peaks.
When they reheated to the nitriding temperature N atoms can not diffuse from
Fe-Nb site to Fe-Fe site. Then Snoek peak of N can not appears again in these
alloys. Therefore, when Fe-Nb alloys were nitrided in NH3 and H2 mixture gas H
atom plays very important part and it needs that the interaction of N-H atoms will
be considered in these nitrided Fe-Nb alloys.
Diffusion Properties of Internal Interfaces in Bulk Nanocrystalline Materials: Radiotracer Investigation
Authors: Divinski Sergiy V. , Lee Jai Sung , Herzig Christian
Published: March 2009

The radiotracer technique was applied to measure self- (Fe, Ni) and solute- (Ag) grain
boundary diffusion in nanocrystalline Fe-40wt.%Ni alloy. The nanocrystalline material was
prepared by pressureless sintering of the nanoalloy powders. The nano-sized crystallites were
found to be clustered in micrometer-large agglomerates. Two types of internal interfaces with
fundamentally different properties exist in the nanomaterial: the grain boundaries between the
nanocrystallites and the interfaces between the agglomerates. A complete and consistent model of
the diffusion processes in such material is elaborated. Whereas the nanocrystalline boundaries
reveal diffusivities, which are similar to those in coarse-grained material, diffusion along interagglomerate
interfaces occurs faster by orders of magnitude. This behavior is explained by a nonrelaxed
structure of the inter-agglomerate interfaces.
New Materials and Construction Methods for Multi-Material-Design, Lightweight Construction and Modularity in Future Vehicle Concepts
Authors: Friedrich Horst E. , Kopp Gundolf
Published: March 2009

Besides reducing fuel consumption, the chief motivating factor behind the development of
new vehicle structures is the desire to decrease climate-affecting emissions. One approach to addressing
this involves reducing the vehicle mass and, as such, the various strategies relating to
lightweight construction. Various methods of lightweight construction are used as a basis for deriving
the technically relevant criteria for designs and material concepts. The work conducted in this field
today centres around the synthesis of construction method and material development with the objective
of devising a multi-material-design [1, 2].
Modularisation is an economic approach aimed at shaping the diversification of the vehicle concepts
and implementing this effectively [3]. As a result of hybrid and later fuel cell drives, the requirements
on the vehicle concepts will continue to grow in future. Modularisation also sometimes
opposes the striving for a high level of integration.
The modular lightweight concept of the DLR aims at designing powertrain evolutions in a scalable
and cost-efficient manner and in a way that retains the concept flexibility or, in some cases, even
increases this.
These approaches lead to the strategy known as “hybrid3”. This strategy not only involves
matching different materials and various construction methods with each other, but also taking account
of the integration of functional effects. This entails, for example, optimising the design of
thin-walled structural components in terms of their vibratory or acoustic properties with structure-
integrated, active materials. Further examples of the approach with “hybrid3” effects could be
selectable surfaces or integrated energy conversion.
The various development directions are depicted in the form of a roadmap and discussed on the
basis of forward-looking examples from the field of vehicle construction.
Mechanical Properties and Microstructures of Beta-Type Titanium Alloy for Biomedical Applications
Authors: Akahori Toshikazu , Niinomi Mitsuo , Fukui Hisao , Ogawa Michiharu
Published: March 2009

Plain and notch fatigue properties of a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ),
which was subjected to various thermomechanical treatments, were investigated in order to judge its
potential for biomedical applications.
Microstructures of TNTZ aged at 723 K for 259.2 ks after cold rolling and those aged at 723 K for
259.2 ks after solution treatment are composed of a precipitated α phase in the β phase. However,
microstructures of TNTZ aged at 598 and 673 K for 259.2 ks after cold rolling and aged at 598 K and
673 K for 259.2 ks after solution treatment are composed of a precipitated ω phase, and precipitated α
and ω phases in the β phase, respectively. Futher, plain fatigue strengths of TNTZ aged after solution
treatment and those of TNTZ aged after cold rolling increase with the aging temperature. In particular,
TNTZ aged at 723 K after cold rolling exhibits the highest fatigue strength in both the low- and
high-cycle fatigue life regions. Futher, the run-out, which is about 770 MPa, is nearly equal to that of
hot-rolled Ti-6Al-4V ELI conducted with aging, which is one of the representative α+β-type titanium
alloys for biomedical applications. The notch fatigue strengths of TNTZ aged at stress concentration
factors of 2 and 6 decrease by 30% – 40% and 50% – 60%, respectively, as compared with the plain
fatigue strengths in the low-cycle fatigue life region. Futher, the notch run-out range from 450 to 490
MPa and from 220 to 300 MPa, respecitvely; an exception to this is TNTZ aged at 598 K after cold
rolling, which has a high volume fraction of the ω phase. Single- and multi- fatigue cracks initiate at
the bottom of the notch at stress concentration factors of 2 and 6, respectively.
Effect of Calcium Phosphate Glass on Proliferation and Differentiation of MG-63 Cells in HA Scaffolds
Authors: Kim Yeon Ung , LeGeros Racquel Z. , Kim Kyoung Nam , Kim Kwang Mahn , Lee Yong Keun
Published: March 2009

This study examined the possibility of synthesis of biphasic calcium phosphate by
sintering a mixture of hydroxyapatite and calcium phosphate glass. The effect of the
concentration of calcium phosphate glass in a mixture on the proliferation and differentiation
of MG-63 preosteoblast-like cells in a hydtoxyapatite scaffold was investigated. The addition
of 5 wt% of calcium phosphate glass significantly improved the level of attachment,
proliferation and differentiation of MG-63 cells onto the hydroxyapatite scaffolds, particularly
when the surface was modified with 2% bovine serum albumin (p<0.05). Under these
conditions, type I collagen was expressed and the extracellular matrix was formed by 1 week,
and the ALP gene was expressed at 4 weeks.
Phase Transformation and its Effect on Dry Sliding Wear of Electro-Pressure Sintered Cobalt and Cobalt-Base Composites
Authors: Kim Yong Suk , Kang Suk Ha , Kim Tai Woong
Published: March 2009

Room-temperature dry sliding wear behavior of hot-pressure sintered monolithic Co, Co-
20 wt.% CuSn and Co-20 wt.% WC composites were investigated. Wear tests of the materials were
carried out using a pin-on-disk wear tester at various loads of 10N-100N under a constant sliding
speed condition of 0.38m/s against glass (83% SiO2) beads. Sliding distances were varied with a
range of 100m-600m. A scanning electron microscopy was used to examine worn surfaces, cross
sections, and wear debris. X-ray diffraction (XRD) was utilized to identify phases of the specimen
and wear debris. All specimens exhibited low friction coefficients ranging from 0.12 to 0.4. The
sintered Co exhibited distinctive wear that was characterized by shallow dug canals on worn surface,
a very thin detaching surface layer, and fine debris. Thermal transformation of the Co specimen
from ε (hcp) phase to α (fcc) phase occurred during the wear of the Co, which was inferred from
XRD analysis of the wear debris. The transformation was suggested to cause the thin detaching
surface layer and the fine wear debris of the sintered Co. The wear of the Co-CuSn composite
proceeded by shear deformation of the CuSn particles, while WC particles of the Co-WC composite
sustained most of the applied load, which resulted in the low wear rate with fine wear debris of the
Co-WC composite.
Bend and Shear Tests: Suitable Methods for Mechanical Characterization of Laminated Composite Materials
Authors: Carreño Fernando , Pozuelo M. , Jiménez José A. , Ruano Oscar
Published: March 2009

Bend and shear tests were used to characterize the improvement in impact behavior of
various ultrahigh carbon steel laminated composites. These tests turned out to deliver much more
useful information about the mechanical properties of the laminates than the Charpy impact tests
and were especially interesting for characterization of laminates of very high toughness values.
The toughness of the various laminates was controlled by the rolling conditions that determined
the quality of the bond and the appearance of delamination by the interfaces. The bend test allows
determination of yield and maximum stresses, absorbed energy and permits graphical visualization
of layer fracture and delaminations as testing proceeds. The shear test allows mechanical
characterization of the bond quality between layers, permitting prediction of possible
delaminations, and therefore, the mechanical properties of the layered material.
Application of Inclined Cooling Plate to Fabrication of Semi-Solid Cast Iron
Authors: Shim Sung Yong , Seong Hwan Goo , Jeong Jin Ho , Lim Su Gun
Published: March 2009

The influence of angles of inclined cooling plate on cast structure and mechanical
properties of cast iron was investigated experimentally in 3.1 wt.% C containing hypoeutectic semisolid
cast irons fabricated by flowing the molten melt over the inclined cooling plate and pouring
into a preheated permanent mold. The variables used in this study were angles of the cooling plate
(5 ~ 15 deg) and the mold temperatures (500~700 deg). The microstructure of resultant specimens
were characterized by measuring grain sizes of primary austenite and its solid fraction, using an
optical microscope equipped with a digital image analyzer. It was shown that the spherical-like
austenite (1.4 aspect ratio) was formed at the cast iron specimens prepared in employing a 10 deg
angle of the inclined cooling plate. This was ascribed to the relative extent of duration time of the
flowing melt which determine the solidification rate of the melt. The peak hardness and impact
values were achieved in the semi-solid cast iron specimen with relatively more spherical austenite.
The measured values were approximately 44HRC and 1.71 J/cm2.
Recycling of 6061 Aluminum Alloy Cutting Chips Using Hot Extrusion and Hot Rolling
Authors: Suzuki Kazutaka , Huang Xin Sheng , Watazu Akira , Shigematsu Ichinori , Saito Naobumi
Published: March 2009

Possibilities of the consolidation process using hot extrusion and subsequent hot rolling
were investigated in order to recycle the cutting chips of the aluminum alloy efficiently. For the
rolling process, differential speed rolling (DSR) was also applied in addition to normal rolling.
Several kinds of cutting chips with different size and cleanliness were collected through turning 6061
aluminum alloy round bars. From these cutting chips, recycled material sheets were produced under
various processing conditions via hot extrusion and subsequent hot rolling. Non-recycled material
sheets were also prepared for comparison. All samples were characterized by optical microscopy,
SEM(EBSP), X-ray texture analysis, tensile test and corrosion test. As a result, it was found that the
recycled material sheets produced under optimum processing conditions had smaller grain sizes than
those of the non-recycled ones, therefore the mechanical properties and the corrosion resistance of the
recycled material sheets were almost comparable to those of the non-recycled ones. Moreover,
concerning the DSR processed sheets, the traces of the chip interface, which were clearly observed in
the normally rolled ones, almost disappeared, and the appearances were remarkably improved. Then
the DSR processed sheets significantly surpassed the non-recycled ones in the tensile properties and
the corrosion resistance.
Densification and Dielectric Properties of Glass/Ceramic Composites Sintered with Various Borosilicate Glass
Authors: Yoon Sang Ok , Kim Kwan Soo , Kim Shin , Shim Sang Heung , Park Jong Guk
Published: March 2009

Al2O3 and TiO2 were sintered with three types (lead, zinc, bismuth) of borosilicate glass.
Their microwave dielectric properties and sintering behavior were investigated as functions of glass
type, glass addition (10~50 vol%) and sintering temperature (600~950°C for 2 hrs). Sintering
characteristics were well described in terms of softening temperature, second phase, and excessive
liquid. In particular, Bi2O3 addition to the glass enhanced reaction with Al2O3 and TiO2 to form liquid
phase and second phase. In terms of dielectric properties glass/Al2O3 composites for application to
substrates while glass/TiO2 composites for filters were shown to be appropriate.
Theoretical Prediction of Ternary Site Occupancies in ZrCr2 and NbCr2 Laves Phases
Authors: Yao Q. , Xing H. , Liu S. , Sun Jian
Published: March 2009

Site occupancies of ternary additions (Ti, V, and W) in the C15 ZrCr2 and NbCr2 Laves
phases were predicted theoretically by first-principles calculations based on density functional theory.
The results suggest that Ti preferentially occupies the Zr and Nb sites in ZrCr2 and NbCr2,
respectively. V and W substitute the Cr sites in both ZrCr2 and NbCr2. The calculations of heats of
formation also show that the occupancy of W on the Cr sites and of Ti on the Zr sites stabilize ZrCr2.
For NbCr2, the occupancy of V on the Cr sites and of Ti on the Nb sites increases the phase stability.
Global and Local Structural Evolution during Deformation and Annealing of FCC Metals
Authors: Hansen Niels
Published: March 2009

Deformation of metals from medium to high strain significantly affect the deformation structure as well as the recovery and recrystallization behaviour when deformed samples are annealed. This behaviour is illustrated for FCC metals of medium to high stacking fault energy, with emphasis on the behaviour of aluminium and aluminium alloys deformed by cold rolling to large strain. The analysis encompasses hardness testing, EBSD and TEM. The deformation microstructure is a lamellar structure of dislocation boundaries and high angle boundaries where the percentages of the latter increases to about 60-80% at large strain. The macrotexture is a typical rolling texture, which is composed of individual texture components present as micrometre and submicrometre size volumes. In the lamellar structure correlations have been established between microstructural parameters and local orientations showing for example variations in stored energy between the texture components and large variations in the spatial distributions of the high angle lamellar boundaries. Such local variations can affect the structural coarsening during recovery at low temperature leading to significant structural difference on a local scale. The local variations in the deformed structure can also significantly affect the structural changes taking place locally during high temperature annealing thereby affecting the evolution of the structure and texture on a macroscopic scale.
Observations of Strain Induced Precipitation during the Thermomechanical Processing of AA6111 Alloy
Authors: Song Y. , Cross M.D.J. , Rainforth Mark W. , Wynne Bradley P.
Published: March 2009

The effect of interpass time during thermomechanical processing of AA61111 on flow behaviour and microstructure evolution has been investigated. This was achieved using plane strain compression testing undertaken on the Sheffield thermomechanical compression (TMC) facility, using the hit-hold-hit-quench approach. Following solution treatment at 560°C for 1200s, samples were water mist quenched to 320°C and deformed at a constant strain rate of 85s-1 to an initial strain of 0.5, unloaded and held for delay times of 0.019, 6, 60, 600 and 6000s and then given a second deformation for a further strain of 0.5, followed by a water quench to room temperature. Hardening of the alloy was observed, the extent of which was dependent on the hold time. The microstructure of the samples was quantified by TEM in order to determine the extent of strain induced precipitation. TEM identified precipitation, predominantly β and Q phases, on dislocation lines, the size and volume fraction of which were a function of the hold time. The coarsening rate during the hold period of the precipitates was considerably faster than for coarsening following a conventional precipitation treatment. The size of the microband structure at the end of the double deformation was a function of the hold time, suggesting that coarsening of the precipitates during the hold had altered the Zener pinning potential. The implication of these observations on the thermomechanical processing of 6xxx alloys is discussed.
Effect of Changing Strain Rate during Warm Deformation on Static Recrystallisation of IF Steel
Authors: Prentice C. , Sellars C.M.
Published: March 2009

Plane strain compression tests have been carried out on Ti stabilised interstitial free steel
at 700oC with constant and changing strain rates. Specimens were annealed in a salt bath at 750oC
to determine the effects of changing strain rate on the kinetics of static recrystallisation and on the
recrystallised grain size. After relatively slow changes in rate, the recrystallisation behaviour at the
end of the change was the same as for tests at constant strain rate with the final value. For faster
changes in rate, there were transients in recrystallisation rate and recrystallised grain size at the end
of the change in strain rate at a strain of 1.0. These were removed by a further increment of 0.1
strain at constant rate. In all cases the recrystallised grain size correlated with the subgrain size
present at the end of deformation.
The Effect of Strain and Strain Path during Deformation on the Recrystallisation of a Particle Containing Aluminum-Manganese Alloy
Authors: Higginson R.L.
Published: March 2009

The effect of strain path on an aluminium-manganese alloy has been studied using single
pass rolling and simple compression tests. Strain paths of 0, 90 and180° have been studied in terms
of texture development and recrystallisation behaviour and compared with equivalent positions in
the rolled slab. The effects of the individual deformations on the dislocation sub-structure have
been studied using transmission electron microscopy. The study has shown that although samples
can be deformed to the same strain via nominally the same stain path change the deformation mode
can fundamentally influence the sub-structure developed during each deformation stage.
Microstructure and Texture of Dynamically Recrystallized Copper and Copper – Tin Alloys
Authors: McDonald D.T. , Humphreys John F. , Bate Pete S.
Published: March 2009

The microstructure and texture in dynamically recrystallized copper and two copper – tin alloys (2wt% and 4.5wt% tin) has been investigated. Specimens were deformed in channel-die plane strain compression to true strains from 0.1 to 1.22 within the temperature range 200°C to 700°C, and the resulting microstructures were investigated with the use of high resolution electron backscatter diffraction (EBSD). Dynamic recrystallization was initiated by the bulging of preexisting high angle grain boundaries (HAGB), and occurred primarily by strain induced boundary migration (SIBM) and twinning. The addition of tin led to an increase in the temperature at which dynamic recrystallization initiated, and furthermore to a smaller dynamically recrystallized grain size. This was attributed to the effects of solute drag causing lower HAGB mobility. Dynamic recrystallization was observed to weaken the deformation texture components of brass and Goss, as well as introduce a cube texture component which generally tended to strengthen with temperature but weaken with increasing tin additions.
Structural Dependence of Grain Boundary Energy in Fe-Based Polycrystals Identified by OIM Measurements
Authors: Gobernado Patricia , Kestens Leo
Published: March 2009

The (relative) grain boundary energy of random high angle boundaries has been measured
in several Fe-based polycrystals. Crystallographic data obtained by orientation contrast microscopy
(OIM) are combined with the geometrical configuration of grain boundaries at triple junctions. A
two-parameter representation of the relative grain boundary energy in terms of misorientation angle
and misorientation axis is presented. In the applied procedure a variation of the energy values
assigned to one boundary was observed depending on the triangulation path chosen by the operator
to connect the arbitrary initial boundary with the boundary under consideration. Results show no
evidence of correspondence between the observed energy cusps and the presence of CSL
boundaries.
Effect of Initial Austenite Microstructure on the Softening – Precipitation Interaction in a Low Nb Microalloyed Steel
Authors: Iparraguirre C. , Fernández-Calvo Ana Isabel , López Beatriz
Published: March 2009

The influence of initial grain size on the softening-precipitation interaction in a low niobium microalloyed steel has been investigated. The study has revealed that for the largest initial grain size (1000 μm), the recrystallised fraction remains lower than the softening fraction until relatively long times are reached. In contrast, for the smallest initial grain size (166 μm) both magnitudes are similar. As a result, precipitation interacts with recrystallisation in the case of the finest austenite grain size, whereas for the coarsest one, since recrystallisation is significantly retarded, interaction with recovery process is observed. Apparently, the initial austenite grain size does not affect precipitation kinetics.
Surface Texture Evolution during α-γ-α Transformation in Mn and Al Alloyed Ultra-Low Carbon Steel
Authors: Gautam Jai , Petrov Roumen H. , Kestens Leo
Published: March 2009

This paper investigates the surface texture evolution during α−γ−α phase transformation.
After austenite annealing of the cold rolled sheets a weak texture was formed at the surface of ultra
low carbon steel alloyed with Mn and Al. This texture consists of <100>//ND and <110>//ND fiber
orientations with an intensity of approximately 2 X random. This surface texture is confined to a
mono-layer of surface grains which are in direct contact with the metal/vapour interface. In order to
interpret this surface effect, two alternative mechanisms were considered: (i) one assumption
attributes the occurrence of the specific surface texture to the minimization of the outer surface
energy and (ii) according to an alternative hypothesis the release of elastic work parallel to ND in
the surface area is responsible for the observed surface fibers. After analyzing the experimental data
it is concluded that the evidence in support of hypothesis (i) is the more convincing in this
experiment.
Mechanism of Texture Evolution during Primary Recrystallisation and Grain Growth in a Zr-2Hf Alloy
Authors: Zhu K. , Bacroix Brigitte , Chauveau Thierry , Chaubet D. , Castelnau Olivier
Published: March 2009

The evolution of crystallographic texture in a Zr-2Hf alloy has been investigated during deformation, primary recrystallisation and normal grain growth. The as-deformed states (50-90% deformation) are characterized by a major tilted {0001}<1010> texture component and this component is reinforced with increasing deformation. A decrease in the intensity of the tilted {0001}<10 10> component and a continuous increase in the intensity of the tilted {0001}<1120 > component take place during primary recrystallisation. Normal grain growth is associated with the coarsening of grains with the {0001}<1120 > orientation. This texture evolution is interpreted on the basis of the evaluation of the stored energy and the consideration of specific grain boundaries with low energy and/or high mobility.
A Fundamental Model of Aluminum Single Crystal Behavior with Physical Description of Kinematic Work Hardening
Authors: Saai Afaf , Tabourot Laurent , Déprés Christophe , Louche Herve
Published: March 2009

In this paper, we present a fundamental model of FCC single crystal behaviour at room
temperature: this model includes kinematic work hardening derived from the elementary description
of the collective dislocations density evolution during cyclic loading. This kinematic work
hardening is then coupled with the isotropic work hardening mechanism. Using this original model,
a simulation of a tensile test on a single crystal sample is carried out in the case of an initial crystal
orientation that promotes single glide even at rather large strains. The evolution of resolved shear
stresses on the primary and secondary slip systems are interpreted by means of the interaction
between the evolution of isotropic and kinematic work hardening variables. The evolution of the
model state-variables including applied resolved shear strain, dislocation densities, and critical
shear stresses are represented as functions of the evolution of crystalline orientation during plastic
deformation.
Modelling the Influence of Cementite on Static Recrystallisation in Cold-Rolled Low-Carbon Steels
Authors: Capdevila Carlos , De Cock Tommy , Caballero Francisca García , García de Andrés Carlos
Published: March 2009

In this work the prominent influence of Particle Stimulated Nucleation (PSN) on the overall process of nucleation and subsequent grain growth is discussed and a global recrystallisation kinetics model is proposed. This model accounts for the effect of the most relevant industrial parameters, such as cold reduction and annealing temperature. Moreover, not only the role of the cementite content, which is function of the nominal carbon content, is included in the model, but also the morphology of the second phase particles. Experimental evidence is given to ascertain the accuracy of the theoretical predictions.
The Effective Conductivity of 2D Porous Materials with Temperature Dependent Material Properties
Authors: Pesetskaya Ekaterina , Öchsner Andreas , Rogosin Sergei
Published: March 2009

The effective conductivity of 2D doubly periodic porous materials with temperature
dependent material properties is investigated. An arbitrary number of disjoint parallel cylindri-
cal pores in a representative cell is considered. A multiply connected unbounded domain in the
complex plane can serve as a geometrical description of such kind of materials. The problem
of determination of the effective conductivity can be reduced to a boundary value problem for
the Laplace equation on the multiply connected domain. This problem is analytically solved by
the method of functional equations. An explicit formula for the effective conductivity is found.
It contains the basic models’ parameters and elliptic Eisenstein functions.
Thermal Post-Impact Behavior of Closed-Cell Cellular Structures with Fillers – Part I
Authors: Vesenjak Matej , Öchsner Andreas , Ren Zoran
Published: March 2009

The study describes the behavior of regular closed-cell cellular structure with gaseous fillers under impact conditions and consequent post-impact thermal conduction due to the compression of filler gas. Two dependent but different analyses types have been carried out for this purpose: (i) a strongly coupled fluid-structure interaction and (ii) a weakly coupled thermalstructural analysis. This paper describes the structural analyses of the closed-cell cellular structure under impact loading. The explicit code LS-DYNA was used to computationally determine the behavior of cellular structure under compressive dynamic loading, where one unit volume element of the cellular structure has been discretised with finite elements considering a simultaneous strongly coupled interaction with the gaseous pore filler. Closed-cell cellular structures with different relative densities and initial pore pressures have been considered. Computational simulations have shown that the gaseous filler influences the mechanical behavior of cellular structure regarding the loading type, relative density and type of the base material. It was determined that the filler’s temperature significantly increases due to the compressive impact loading, which might influence the macroscopic behavior of the cellular structure.
Thermal Post-Impact Behavior of Closed-Cell Cellular Structures with Fillers – Part II
Authors: Vesenjak Matej , Žunič Zoran , Öchsner Andreas , Ren Zoran
Published: March 2009

The paper describes the post-impact thermal conduction of regular closed-cell cellular structure with gaseous fillers due to the dynamic compression. Two different but subsequent computational analyses have been carried out for this purpose. To define the behavior of the cellular structure under compressive dynamic loading, a unit volume element of the cellular structure has been analyzed with the explicit finite element code LS-DYNA by considering a strongly coupled interaction of the cellular structure base material with the gaseous pore filler. The resulting deformed cellular structure has then been imported in the finite volume code ANSYS CFX 10.0 for further weakly coupled thermal-structural analyses of post-impact heat conduction through the base material and filler gas. The increased temperature and pressure of the filler gas after compressive impact loading from the initial analyses have been used as initial conditions for the thermal analyses, where only the heat conduction due to the gas compression has been taken into account. This paper considers only the closed-cell cellular structure with two different relative densities and air inside the pores. Computational simulations have shown a low overall temperature increase of the cellular structure due to filler gas compression. The temperature increase of the base material is expected to be higher at lower relative densities. The presented procedure illustrates a convenient approach to solving strongly coupled fluid-structure interaction problems by considering also a weakly coupled thermal-structural solution, which can be used for a wide range of engineering applications.
A Model for Rapid Solidification for Plasma Spraying
Authors: Ben Naoua Salwa , El Ganaoui Mohammed , Sammouda Habib , Fauchais Pierre
Published: March 2009

A two-dimensional heat transfer model, extended phase change, is developed with an
enthalpy formulation in order to predict the splat/substrate thermal story and its effects on plasma
surface interaction. The model validated with respect to experimental results is used to estimate the
early solidification of yttria stabilized zirconia splat deposited on a cooled substrate. Simulations
quantify transfers in terms of some working parameters such that the splat thickness, the
splat/substrate contact quality, the latent heat of solidification and the initial temperatures.
An Experimental Study on Synthesis and Characterization of Silica Nanoparticles Prepared by Sol-Gel Method
Authors: Shokuhfar Ali , Shokuhfar Tolou , Ghazinejad M. , Babazade R. , Tabatabae S.
Published: March 2009

Monodispersed nanometer-sized particles proved to be very important and advantageous
in many industrial applications. One of the notable groups of these particles is silica (SiO2)
nanoparticles which are widely utilized in developing numerous products such as electrical and
thermal insulators, humidity sensors, varnish, etc. Since the quality of some of these products
depends highly on the purity and size distribution of the silica particles, it is necessary to produce
silica nanoparticles of narrow size distribution and very high purity. In this research silica
nanoparticles, with a relatively narrow size distribution, have been synthesized via the hydrolysis
reaction of tetraethoxisilane (TEOS) in the solution of deionized water and ethanol (C2H5OH), and
in the presence of ammonia (NH3) as a catalyst. The nature, morphology and the size of the silica
particles has been studied using Scanning Electron Microscopy (SEM), Transmission Electron
Microscopy (TEM) and X-ray diffraction. Results indicate that the morphology, structure and the
diameter of silica particles depend strongly on the molar ratios of the reactants.
Carbothermal Reduction and Nitridation of Çanakkale Origin Kaolin for SiAlON Powder Production
Authors: Tatli Zafer , Demir Adem , Caliskan F.
Published: March 2009

SiAlON ceramics were successfully produced in the form of powders from high purity
kaolin, a hydrated aluminium silicate, Al2Si2O5(OH)4 type of clay mineral (comprises 83.85%
kaolinite, 13.59% quartz, 0.88% feldspar, 1.37% others) of Canakkale-Can origin. Factors affecting
SiAlON powder production were temperature, holding time, gas-flow rate and preparation methods.
System optimisation was achieved following the results succeeded from numerous testing and
characterisation (with XRD, SEM, EDS, BET, etc.) of each test. Changing in gas flow rate,
temperature and holding time at plateau temperature had influences on the final powder yield, their
morphologies and phase formation. The best conversion of kaolin clay mineral to SiAlON ceramic
powder was the test run at 1475oC for 4 hour under 1 lt/min N2-flow. Product after the process was
mainly of β'- Si3Al3O3N5 (z=3) powder along with small amounts of Al2O3, mullite and AlN phases.
Some powder product exhibits furry type of wiskers morphology, which may be useful for using as
a reinforcing material in particulate composite bodies.
An Introduction to the Glass Formation and Properties of Ca-Si-Al-O-N-F Glasses
Authors: Hanifi Amir R. , Genson Annaik , Pomeroy Michael J. , Hampshire Stuart
Published: March 2009

Ca-Sialon glasses have been known for some time [1] and they are effectively calciumalumino- silicate glasses containing nitrogen which improves their mechanical properties. Calciumalumino- silicate glasses containing fluorine are known to have useful characteristics as potential bioactive materials [2]. Therefore, the combination of both nitrogen and fluorine additions to these glasses may give useful bioglasses with enhanced mechanical stability.Addition of fluorine to oxynitride glasses was not reported previously and this paper gives the first report of the glass forming regions (and evaluation of some properties) in the Ca-Si-Al-O-N-F system. Within the previously defined [1] glass forming region in the Ca-Si-Al-O-N system, homogeneous, dense glasses are formed. Addition of fluorine extends the glass forming region but also increases the reactivity of the glass melts. One major problem is fluorine loss as SiF4, but also loss of nitrogen, which affects the final composition and results in porous samples. To suppress the fluorine loss and CaF2 precipitation, consideration of the ratio of cations to fluorine and the coordination number of Al atoms is important. Discussion of the role of cations in these oxyfluoronitride glasses is presented.
An Investigation of the Mechanical Properties and Fracture Characteristic of Hot-Pressed Boron Nitride Ceramics
Authors: Ertug B. , Boyraz T. , Addemir O.
Published: March 2009

The overall mechanical characterization of hot-pressed hexagonal boron nitride (h-BN)
based ceramics was performed. Hardness, flexure strength and fracture toughness (KIC)
measurements were carried out using Vickers indentations, 3-point bending tests and SEVNB
method, respectively. The fracture characteristics of hot-pressed h-BN ceramics were investigated
by analyzing fracture surfaces using scanning electron microscope (SEM). The hardness, ranged
from HV = 0.20GPa to HV = 0.25GPa, which was higher in the surfaces parallel to the hot-press
direction due to the perpendicular alignment of the basal planes of the h-BN platelets to the hotpress
direction. The fracture toughness and flexure strength values were determined to be 2.6
MPa.m1/2 and 0.14 GPa, respectively. A single KIC value was obtained since a slight variation of the
fracture toughness was observed with the orientation of h-BN. The microstructural observations of
h-BN grains indicated completely brittle fracture with intergranular voids and microcracks revealing
a mixed mode of fracture.
Pressureless Sintering of Hexagonal Boron Nitride Powders
Authors: Ay Nuran , Tore I.
Published: March 2009

Pressureless sintering of hexagonal boron nitride (BN) with and without additives was performed using a powder which was previously nitrided at 900oC and then heat treated at 1400oC. Sintering additives were B2O3 (2, 4, 6 wt %) and Y2O3 (2, 4, 6 wt %) and sintering temperatures was 1900oC. Sintered samples were characterized by XRD, SEM, micro hardness, density and mercury porosimeter measurements. Maximum density values of samples were 1.56 g/cm3 without additives and 1.63 g/cm3 with additives. Hardness values of samples were found to improve with the presence of additives.
Relevance of Polaron/Soliton-Like Transport Mechanisms in Cascade Resonant Isomeric Transitions of Q1D-Molecular Chains
Authors: Keković G. , Raković D. , Davidović David
Published: March 2009

Our recently proposed quantum approach to biomolecular isomeric-conformational
changes and recognition processes, additionally supported by biomolecular resonant recognition
model and by quantum-chemical theory of biomolecular non-radiative resonant transitions, is
hereby extended to cascade resonant transitions via close intermediate participating isomeric states -
which might be related to polaron/soliton-like energy and charge transport mechanisms in Q1Dmolecular
chains, whose relevance is explored in this paper.
Conduction Mechanism Based Model of Organic Field Effect Transistor Structure
Authors: Šašić Rajko M. , Lukić P.M.
Published: March 2009

Carriers mobility model of olygomer and polymer semiconductor based OFET (Organic
Field Effect Transistor) structures is presented in this paper. Starting from the conduction
mechanism in the mentioned organic materials, a carrier mobility dependence on temperature,
electric field and trap density μ(T,E,NT) was investigated, inspiring directly the current-voltage I(V)
model of OFET structures. Subsequent simulations were also performed and the obtained results
compared with the data available in the literature.
Characterization of Target Material for X-Ray Generator by Monte Carlo Method
Authors: Stanković Srboljub J. , Ilić R.D. , Ciraj-Bjelac O. , Kovačević M. , Davidović David
Published: March 2009

The adequate choice of different target materials for X-ray generators is a very important
subject of engineers’ practice and research. In the present work we analyze theoretically the
transport of electrons through the anode material and the production of the corresponding
bremsstrahlung radiation. In our analysis we simulate the particle transport with the help of the
FOTELP code, which is based on the Monte Carlo simulation. Our main aim is to develop an
efficient and handy method, which could be helpful in improving the design of the X-ray tube
components and in reducing of the patient dose, while keeping the image quality. The obtained
results are encouraging.
Barium Hexaferrite Prepared by Hydrothermal Synthesis
Authors: Drofenik Miha , Kristl M. , Žnidaršić Andrej , Lisjak Darja
Published: March 2009

Nanoparticles of barium hexaferrite were prepared by controlled hydrothermal synthesis
at 280oC. During the synthesis, the composition of the precursor and the suspension concentration
were controlled. The as-synthesized crystalline barium hexaferrite platelets of about 50 nm in length
and 5 nm in thickness exhibited a saturation magnetization of 40 emu/g.
Adsorption of some Weak Organic Electrolytes from Aqueous Solutions on Silica
Authors: Milonjić S.K. , Zhigunova L.K. , Pavasović V.Lj.
Published: March 2009

The adsorption of organic electrolytes from aqueous solutions on various adsorbents has
been frequently investigated because of its importance in water purification. Phenol and substituted
phenols are very common contaminants of water. In this paper, the adsorption results of some weak
organic electrolytes (hydrochinon, phloroglucin and acidum gallicum) from aqueous solutions on
silica are presented. The adsorption of the organics was investigated by the batch method. Effects of
solution pHs (in the 2-10 range) and concentrations of these compounds on the adsorption were
investigated. In the case of acidum gallicum, adsorption isotherms (in the 2-6 pH range) were
determined. The obtained results indicate that the amount of adsorbed acidum gallicum increases
with its increasing concentration. The maximum adsorption was recorded at pH=2-3 (pH equal to
pHpzc of SiO2) with acidum gallicum molecule being undissociated (pKa= 4.41). The experimental
data were fitted with different adsorption isotherms models. The maximum amount of acidum
gallicum adsorbed as well as the Freundlich constants of adsorption were calculated. The adsorption
of hydrochinon and phloroglucin from aqueous solutions (in the investigated pH range) on silica
was negligible.