bluuebunny/crossref_metadata_2025 huggingface dataset:
New Perspective in Recent Solid Acid Catalyst
Authors: Yarmo Mohd Ambar , Shariff Raja Saadiah Raja , Omar Siti Rohaya , Ching Juan Joon , Haron Roziana
Published: March 2009

This paper will review on the latest development on solid acid catalysts used in
industries as well in research activities. Application of heterogeneous acid catalysis becomes
current trend for many industries due to world wide environmental concern. Conventional synthetic
or natural zeolites widely used for petrochemical processing, has some limitation because its pore
size is normally smaller than reactant molecules. To overcome this challenge new delaminated
zeolite process was introduced. In this process specific synthetic zeolite (i.e. ferrierite) was swelled
up using specific surfactant followed by sonification to produce the delaminated zeolite. Further
modification of this material such as sulfonification reaction to its surface has been found to
improve the catalytic activity and selectivity for esterification reaction. Other acid catalyst systems
based on mesoporous molecular sieves and Keggin heteropolyacids (HPA) are also discussed in
this paper.
Application of Optical Fiber Bragg Grating Sensor for Structure Monitoring
Authors: Abd-Rahman M. Kamil , Taib M. Nasir , Azmi Ibrahim
Published: March 2009

Fiber Bragg gratings (FBG) are extensively used in optical add-drop multiplexers/demultiplexers, optical cross-connect switches, optical sensors and many others in optical fiber telecommunication networks. In this study, FBG was employed as an optical sensor for pile monitoring on steel and concrete structures particularly in bridges and buildings. The measurement was conducted in accordance to PWD (Public Works Department) requirements and the test showed compatible results to the vibrating wire strain gauge (VWSG) used in pile monitoring by PWD. The FBG sensors mounted onto the mild steel rod as a device-under-test have provided high sensitivity, good accuracy and linearity.
Ionic Hopping Transport in Chitosan-Based Polymer Electrolytes
Authors: Khiar A.S.A. , Majid S.R. , Idris N.H. , Hassan M.F. , Puteh R. , Arof A.K.
Published: March 2009

Measurement of the ionic conductivity for the CA-NH4CF3SO3-DMC system was carried
out at frequencies of 50 Hz to1 MHz and also at temperatures of 298 K to 313 K. The plot of log σ
versus 1000/T shows a linear behavior suggesting that the samples obey the Arrhenius relationship.
The electrical relaxation of the system was analyzed using the complex electric modulus M* of the
sample with the highest ionic conductivity at various temperatures. The analysis of electrical
modulus and dissipation factor (tan δ) shows that charge transport occurs through a hopping
mechanism.
Effects of Indium Depositions on Porous Silicon Nanostructure (PSN)
Authors: Abdullah Shahrum , Muhamad Muhamad Rasat , Sekak K.A.
Published: March 2009

The effects of Indium doped on Porous Silicon Nanostructure (PSN) have been studied. The Electroluminescence studies on Indium-doped porous silicon nanostructure (In:PSN) are presented. The main objective of this paper is study the EL effects of Indium doping on PSN. Porous silicon nanostructure layers have been formed by anodically etching unpolished p-type Si [100] wafer with surface resistivity of 1-10 ohm cm-1 in Hydroflouric (HF) solution at 1:1 ratio of Ethanol. Indium (In) was doped on PSN using cathodic electrodeposition composed of InCl3 and ethanol electrolythe. A diode structure has been fabricated comprising semi-transparent Au/In:PSN/p-Si substrate/Al ohmic contact electrode to observe the EL spectra. The In:PSN device shows increasing on EL and PL Intensity as well as blue-shift EL and PL spectrum is observed. Possible reasons for the enhancement will be discussed. Technological application of PSN as a light emitter would have significant impact on numerous technologies such as display panels or integrated circuits with optoelectronic devices (IO) on board and sensors.
The Effects of Deposition Pressure on the Optical and Structural Properties of d.c. PECVD Hydrogenated Amorphous Carbon Films
Authors: Awang Rozidawati , Tong Goh Boon , Ab. Gani Siti Meriam , Ritikos Richard , Rahman Saadah Abdul
Published: March 2009

A direct-current plasma enhanced chemical vapour deposition (PECVD) system was
designed and built in-house for the deposition of hydrogenated amorphous carbon(a-C:H) thin films.
In this work, a-C:H thin films prepared using this system at different deposition pressures were
studied. The influence of deposition pressure on the deposition rate, energy gap, bonded hydrogen
content and structure of the film has been investigated. The characterization techniques were
determined from optical transmission spectroscopy, Fourier transform infrared spectroscopy and Xray
diffraction measurements. The results demonstrated that the deposition pressure had strong
influence on the deposition rate, optical energy gap and the bonded H content in the film. Evidence
of crystallinity was observed in films prepared at low deposition pressure.
Effect of Ethylene Sulphite on the Conductivity and Morphology of PEO-KOH Films
Authors: Hassan M.F. , Idris N.H. , Majid S.R. , Winie Tan , Khiar A.S.A. , Arof A.K.
Published: March 2009

The plasticized PEO-KOH films have been investigated using the electrochemical
impedance spectroscopy (EIS), X-ray diffraction (XRD) and scanning electron microscopy (SEM).
The conductivity of films increased by about 2 orders of magnitude from 10-5 to 10-3 S cm-1 at r.t.
on addition of 0.5 wt.% of ethylene sulphite (ES). The degree of crystallinity was calculated from
the XRD patterns. SEM micrographs show that the plasticized films were porous. The highest
conductivity of plasticized films at r.t. was (1.3 ± 0.2) x 10-3 S cm-1 for the film with 0.5 wt.% of
ES content. The number density of mobile ions was shown to increase indicating that ES has
dissociated more salts into ions and thereby increasing the conductivity.
Mechanochemical Synthesis of Bi4Ti3O12
Authors: Lazarević Z.Ž. , Stojanović B.D. , Varela José Arana
Published: March 2009

Our efforts were directed to the preparation of bismuth titanate – Bi4Ti3O12 (BIT) by mechanically assisted synthesis. The mechanical activation was applied to prepare bismuth titanate, Bi4Ti3O12, from bismuth oxide, Bi2O3, and titanium oxide, TiO2 (in an anatase crystal form). Mechanochemical synthesis was performed in a planetary ball mill in air atmosphere. Bismuth titanate ceramics was obtained by sintering at 1000 oC. The formation of Bi4Ti3O12 in the sintered samples was confirmed by X-ray diffraction analysis. Scanning electron microscopy, SEM, was used to study the particle size and powder morphology. The obtained results indicate that Bi4Ti3O12 from the powder synthesized by high-energy ball milling exhibits good sinterability, showing advantage of the mechanochemical process over conventional solid-state reaction.
The Influence of Tribophysical Activation on Zn2TiO4 Synthesis
Authors: Obradović N. , Labus Nebojsa , Srećković Tatjana , Ristić Momcilo M.
Published: March 2009

The influence of tribophysical activation on Zn2TiO4 synthesis along with the changes in
powders during tribophysical treatment was observed. Mixtures of ZnO and TiO2 powders were
mechanically activated using a high-energy ball mill at different time intervals from 0 to 300
minutes. XRD was performed in order to obtain information about phase composition variations.
Microstructure parameters were revealed from an approximation method. Particle size distribution
along with scanning electron microscopy gave very useful information about powder morphology.
Surface Characteristics and Modification of Different Carbon Materials
Authors: Baćić-Vukčević M. , Udovičić A. , Laušević Z. , Perić-Grujić A. , Laušević M.
Published: March 2009

In this work, surface characteristics of different carbon materials were investigated. The
materials under consideration were: activated carbon, carbon monolith, carbon felt and glassy
carbon (powder, plate and broken plate). The surface functional groups of the studied carbon
materials were determined by Boehm’s method and point of zero charge by mass titration. The
specific surface area was studied by BET method with N2 adsorption. As a specific test for surface
activity, cementation of silver from aqueous solution of silver salts was used. The rate of silver
deposition on the carbon materials was studied as a function of immersion time (AgNO3
concentration 75 mg/dm3), as well as a function of concentration of AgNO3 solution (25, 50, 75,
100, 125 mg/dm3) by atomic absorption spectrometry (AAS) to determine the concentration of Ag
in the solution. The morphology of silver coatings was characterized by scanning electron
microscopy (SEM) and structural characteristics by X-ray diffraction. The results obtained show
that metallic silver deposits were formed at the surface of all examined samples. Oxygen complexes
at the surface of glassy carbon samples were analysed by temperature programmed desorption
(TPD) before and after silver deposition in order to establish the mechanism of silver deposition.
Structural and Dielectric Properties of BaTi1-xSnxO3 Ceramics
Authors: Marković S. , Mitrić M. , Cvjetićanin N. , Uskokovic Dragan P.
Published: March 2009

BaTi1-xSnxO3 (BTS) powders, with x ranging from 0 to 1, were synthesized by solid-state
reaction technique. The powders were pressed into pellets and sintered at 1370 and 1420 oC. The
structural characterization of sintered BTS samples was made at room temperature using X-ray
diffraction and Raman spectroscopy measurements. The BTS samples were found to be singlephase
solid solutions. Dielectric properties of sintered BTS samples were studied as a function of
sintering temperatures and tin contents, too. For samples with x ranging from 0 up to 0.15, it has been
found that the Curie temperature decreases while the maximum of the dielectric constant increases
with increasing tin content. These samples have relatively high dielectric constants, contrary to x >
0.2 samples with very low dielectric constants. It is noticed that BTS ceramics sintered at 1420 oC
exhibit better dielectric properties than those sintered at 1370 oC.
Segmented Thermistors Printed by NTC Nanometric Paste and Applied in Volume Air-Flow Sensors
Authors: Aleksić Obrad S. , Savić S.M. , Luković Mica D. , Radulović K.T. , Lukić L.S.
Published: March 2009

An investigation path starting from (Mn,Ni,Co,Fe)3O4 nanometric powder preparation,
NTC thick-film characterization, realization and optimization of new planar thermistor geometries
to custom design thermistors and their application for temperature and volume airflow sensors was
recently determined. The aim was to make custom designed segmented NTC thermistors printed
and sintered on alumina. Two types of volume airflow sensors were formed: indirectly heated and
self-heated. A pair of segmented thermistors was placed in an air guide and connected to differential
branches of the Wheatstone bridge. A heater was placed in the middle between the thermistors for
the indirectly heated type, while for the self-heated type the same thermistors were self-heated by a
constant current source. First the thermistor responses vs. the airflow (calibration curves) were
measured, and then thermistor responses in time (inertia) to fast airflow changes from the minimum
to the maxi
Oscillatory Phenomena during Anodic Copper Electrodissolution in Trifluoroacetic Acid Solution
Authors: Potkonjak N. , Kolar-Anić Lj. , Potkonjak T. , Blagojević S. Nikola , Anić S.
Published: March 2009

This work presents the current oscillation phenomena observed in an electrochemical Cu/0.5 M CF3COOH system. The dynamical response of this new oscillator was followed by both current density-potential (j-E) and current density-time (j-t) curves. The current oscillation phenomena of the investigated system were monitored over various potential scan rates and constant applied potentials as control parameters. The increase of potential scan rate significantly decreases both the potential range of current oscillations and the frequency of oscillations. At the j-t curves both the simple and the complex (period adding) oscillations were found. Moreover, with the increase of applied potential, the increase of period of oscillations and current oscillation amplitudes were observed. It appears that the period of current oscillations exponentially grows with applied potential.
Morphology and Phase Composition of Ni-Co Alloy Powders Electrodeposited from Ammonium Sulfate-Boric Acid Electrolyte
Authors: Jović Vlada D. , Maksimović V. , Pavlović M.G. , Jović B.M.
Published: March 2009

In this paper the morphology of Ni-Co powders electrodeposited from ammonium sulfate-boric acid containing electrolyte is investigated as a function of alloy powder composition. Composition of the electrolyte, i.e. the ratio of Ni2+/Co2+ concentration is found to influence both, the alloy phase composition and the morphology of Ni-Co alloy powders. At the highest ratio of Ni2+/Co2+ ions concentration, typical 2D fern-like dendritic particles were obtained. With decrease of Ni2+/Co2+ ions ratio among 2D fern-like dendrites, 3D dendrites and different agglomerates of a size of about 100 μm, being either compact (typical for pure Co powder) or composed of a large number of small 3D dendrites on their surface were obtained. According to the X-ray analysis, with decreasing Ni2+/Co2+ concentration ratio the amount of f.c.c. β-Ni phase was found to decrease, while the amount of h.c.p. α-Co phase was found to increase being accompanied by the appearance of the f.c.c. Co phase at Ni2+/Co2+ = 0.33.
Radiological Characterization of Semiconductor Materials in Field Effect Transistor Dosimeter by Monte Carlo Method
Authors: Stanković Srboljub J. , Ilić R.D. , Petrović M. , Lončar B. , Vasić A.
Published: March 2009

The use of semiconductor materials in radiation processing, radiation therapy and
diagnostics, and detection of cosmic radiation motivated development of numerical methods for its
radiological characterization. This paper presents the application of the Monte Carlo method using
the FOTELP-2K4 code for radiological characterization of Metal Oxide Semiconductor Field Effect
Transistor (MOSFET) dosimeter. The advantages of MOSFET dosimeters include small size,
immediate readout, and ease of use for a wide photon energy range. In order to determine the
dosimeter response accurately, distribution of the absorbed dose in the MOSFET structure has been
investigated. Our results show that the absorbed dose distribution calculated by the presented
simulation model compares well with the published data.
Optical Properties of Simple Bilayer Polymer Light Emitting Diode
Authors: Arsoski V. , Ramović R.M. , Srećković Milesa
Published: March 2009

Optical properties of bilayer organic light-emitting diodes (OLEDs) based on MEH-PPV (2-methoxy, 5-(2′-ethyl-hexoxy)-1,4-phenylene vinylene) and Alq3 (tris(8-hydroxy-quinolinato) aluminum) are investigated in this paper. Numerical method solving 1D model based on driftdiffusion, continuity and Poisson`s equations extended by boundary conditions in treatment of internal organic interface is applied. The obtained space charge densities were employed in the emissive singlet exciton continuity equation resulting in the singlet exciton distribution and the emission zone profile. Dipole methods were utilized for the simulation of light emission in a layered medium. The electroluminescence (EL) spectra of OLED are considered by taking into account dominant interference effects. The exciton quenching near electrodes, allowing for a dominant nonradiative decay, is treated through effective emission zone narrowing.
The Properties of Dangling Chain-Networks Prepared by Cyclotrimerisation of Telechelic Diisocyanates
Authors: Budinski-Simendić J. , Špírková M. , Dušek K. , Dikić T. , Radičević R. , Prendzov S. , Krakovsky Ivan , Ilavsky M.
Published: March 2009

Here, as part of our experimental investigations dealing with poly(urethane-isocyanurate) networks, we investigate model irregular networks with increasing amount of dangling chains. In our study such an irregular network topology was obtained by partial substitution of a diol for a monohydroxy component during the preparation of isocyanate terminated precursors. Telechelic diisocyanates were synthesized from aromatic diisocyanate (2,4-TDI), α,ω-dihidroxypoly (oxypropylene) (PPG 2000), and diethyleneglycolmonomethylether (an aliphatic low-molecularweight monool component). The networks in undiluted state were prepared by cyclotrimerisation, in the presence of a catalyst. The network properties were estimated by multiple extraction in solvent, differential scanning calorimetry and photoelastical measurements. Independently of mechanical testing, the fraction and concentration of dangling and elastically active network chains were evaluated by the theory of branching processes (cascade theory). The influence of dangling chains on the mechanical properties was analyzed.
Biological Material and Information
Authors: Jovanić B.R. , Sarvan M.Ž.
Published: March 2009

Information sent by biological materials (plant leaves) into environment is determined by the morphology and by the physiological activity of an assembly. This information can be related to the luminescence spectra emitted by the leaf, being specific for the corresponding photosystem pigments. Such an analysis can provide an increase in our understanding of particular changes in this biological material.
Repairing of Damaged Pressure Pipes with a Composite Sleeve
Authors: Jodin P.
Published: March 2009

Pressure pipes may be externally damaged in different ways: corrosion or notch due to
diving machines. These defects may initiate a fatigue crack, which will be first part-through, then
through the thickness. This results in a weakened region of the tube, then in leak of the pressure
fluid contained in the pipe. There are several ways to repair the tube: changing the portion of tube,
welding of extra metal in the defect, putting a welded metal sleeve or gluing a composite sleeve.
This last solution seems to be the easiest and the cheapest. The advantage is that the repairing sleeve
is made on site and can be put with a given pre-tension. The work presented here is the numerical
study of the fracture mechanics parameters of a part-through crack in a tube submitted to internal
pressure and repaired with a composite sleeve. As there is a transfer of loading from the cracked
tube to the repairing sleeve, the fracture mechanics parameters of the crack such as J-integral or
opening of the crack lips will be modified. The study can be used as a design procedure for such
repairing sleeves.
Toughness after Interrupted Quench
Authors: Shuey R.T. , Tiryakioğlu Murat , Bray Gary H. , Staley James T.
Published: March 2009

We discuss data from a range of heat-treatable aluminum alloys, showing both yield strength and fracture toughness vs time at temperature of interrupted quench. Drop in toughness occurs at much shorter hold time than drop in strength. Concurrently the fracture becomes more intergranular. When later the yield strength falls, fracture becomes more transgranular, and toughness may rise. We attribute this pattern to two mechanisms: 1) Early quench precipitates nucleated on grain and/or subgrain boundaries grow to size sufficient to initiate fracture under tension, long before they withdraw significant solute from subsequent age-hardening. 2) Later quench precipitates nucleated on dispersoids and/or dislocations withdraw solute relatively uniformly, reducing matrix yield strength while increasing matrix ductility. We propose that quantitative modeling of change in strength and toughness with change in quench, requires multiple C-curves for multiple types of quench precipitates, and nonlinear relation of toughness to amount of boundary quench precipitate.
Investigation of Global Buckling Distortion in Welding of a Thin Wall Aluminium T Joint
Authors: Zaeem Mohsen Asle , Nami M.R. , Rajabi I. , Kadivar M.H.
Published: March 2009

In this paper global welding buckling distortion of a thin wall aluminum T joint is
investigated. A thermo-elastoplastic model is employed to determine longitudinal residual stresses;
analysis of thermal model and elastic-viscoplastic (Anand) model are decoupled. Molten puddle
motion (speed of welding) is modeled by using birth and death element method and time dependent
model. Three dimensional nonlinear-transient heat flow analysis has been used to obtain
temperature distribution, and then by applying thermal results and using three dimensional Anand
elastic-viscoplastic model, stress and deformation distributions are obtained. By applying residual
stresses on a structural model and using eigenvalue methods, global buckling instability of the
welded structure is determined. Some experiments are done for validating the numerical results.
Observation of Precipitates in Aluminium Alloys by Sub-Micrometer Resolution Tomography Using Fresnel Zone Plate
Authors: Toda Hiroyuki , Minami Keisuke , Kobayashi Masakazu , Uesugi Kentaro , Takeuchi Akihisa , Kobayashi Toshiro
Published: March 2009

An X-ray microtomography combined with hard X-ray imaging microscopy, that
potentially has a spatial resolution of the order of 10 to 100 nm, has been applied to the
three-dimensional observation of internal microstructural features in overaged Al-Ag alloys. A
Fresnel zone plate is used as an objective with a magnification of 49.3 times. Imaging of resolution
test patterns has indicated spatial resolutions of around 180 and 200 nm in the vertical and horizontal
directions, respectively. This paper reports the first impression of the microstructural imaging by
means of such a high-resolution imaging microtomography. Precipitate microstructures are readily
observed and quantified in terms of volume fraction and orientation. Conventional microtomography
with a simple projection geometry is also applied for comparison purpose at the highest resolution
level currently available at a third generation synchrotron facility. It would appear that the present
technique provides a unique potential to observe the 3-D geometry and spatial distribution of
nanoscopic features inside samples that are several orders of magnitude thicker than thin-foil
specimens for TEM observation.
Control of Earing in Deep Drawing of Roll-Cast AA3003 Aluminium Sheets
Authors: Mahmudi R. , Alaiha M.M.
Published: March 2009

The effect of different parameters during thermo-mechanical processing on the earing
behavior of AA3003 aluminum sheets has been investigated. These were homogenization of the cast
strip, cold rolling, intermediate and final annealing of the sheets at different gauges. The amount of
0/90° earing formed on annealing decreased with cold rolling prior to annealing. Nevertheless, annealing
after partial deformation gave rise to large amounts of 0 to 90° ears to balance subsequent ±45° earing.
Homogenization prior to cold rolling resulted in a fine dispersoid distribution which, in turn, increased
the tendency for 0/90° earing. All of these observations were consistent with textural studies in which
cube and rolling textures were competing to produce positive and negative earing, respectively. It is
concluded that the "non-earing" quality in the present material could be obtained by proper combination
of processing variables such as; homogenization, cold reduction, and annealing cycles.
Improved VDC Casting of Aluminium Alloys through an Understanding of the Surface Properties of the Molten Metal
Authors: Taylor John A. , Bainbridge Ian F.
Published: March 2009

Vertical direct chill (VDC) casting of aluminium alloys is a mature process that has
evolved over many decades through gradual change to both equipment design and casting practice.
Today, air-pressurised, continuous lubrication, hot top mould systems with advanced station
automation are selected as the process of choice for producing extrusion billet. Specific sets of
operating parameters are employed on these stations for each alloy and size combination to produce
optimal billet quality. The designs and parameters are largely derived from past experience and
accumulated know-how. Recent experimental work at the University of Queensland has
concentrated on understanding the way in which the surface properties of liquid aluminium alloys,
e.g., surface tension, wetting angle and oxide skin strength, influence the size and shape of the
naturally-stable meniscus for a given alloy, temperature and atmosphere. The wide range of alloyand
condition-dependent values measured has led to the consideration of how these properties
impact the stability of the enforced molten metal meniscus within the hot top mould cavity. The
actual shape and position of the enforced meniscus is controlled by parameters such as the upstream
conduction distance (UCD) from sub-mould cooling and the molten metal head. The degree of
deviation of this actual meniscus from the predicted stable meniscus is considered to be a key driver
in surface defect formation. This paper reports on liquid alloy property results and proposes how
this knowledge might be used to better design VDC mould systems and casting practices.
Influence of Cooling Rate on Morphology and Distribution of Fe-Containing Intermetallic Compounds in Strip Cast AA1100 Type Alloys
Authors: Ashtari Peyman , Gatenby Kevin , Gallerneault Mark
Published: March 2009

The influence of different cooling regimes on the surface microstructure of strip cast
AA1XXX alloys was investigated. The cooling rate was varied over a wide range using a bench
scale simulation apparatus. It was found that the type and morphology of the intermetallics varied
over a wide range both at the cast surface and in the near surface regions. These observations were
compared to the compounds formed in the bulk of the slab.
It was found that, a surface layer containing a high concentration of alloying elements, an inverse
segregation layer, forms under some conditions and can result in a high density of intermetallics.
By varying casting conditions, the mechanism of formation for these structures was studied. The
surface microstructure of the slabs was characterized as a function of the different local cooling
regimes.
The Effect of Composition and Temperature on the Ageing Response of some Dilute 6xxx Series Alloys
Authors: Jaafar C.N. Aiza , Lorimer Gordon W. , Parson N.C.
Published: March 2009

The effects of composition and temperature on the ageing response and the microstructural
development during ageing treatment of a series of dilute 6xxx series alloys have been investigated. The
alloys contained between 0.22 and 0.79 wt% Si and 0.20 and 0.51 wt% Mg. Some of the alloys were
copper-free, 0.001-0.002 wt% Cu, while others contained additions of 0.1 wt% Cu. Some of the alloys
were ‘balanced’ while others contained excess Si (ExSi). The effects of solution treatment temperature
and artificial ageing (T6) on the precipitation process were investigated using various techniques,
including differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and
analytical transmission electron microscopy (ATEM). MT DATA has been used to predict the phase
relationships as a function of temperature and the MT DATA predictions have been compared with the
phases observed by DSC and ATEM. The morphology and crystal structures of the precipitates formed
were monitored by TEM. The results showed a correlation between the composition and the ageing
response of the alloys.
Secondary Precipitation in Aluminium Alloys & Its Role in Modern Heat Treatment
Authors: Lumley Roger N. , Buha J. , Polmear Ian J. , Morton A.J. , Crosky A.
Published: March 2009

This paper reviews some of the practical outcomes of exploiting secondary precipitation during the heat treatment of aluminium alloys and discusses current understanding of this phenomenon. Recent studies have utilised the techniques of positron annihilation spectroscopy (PAS), 3D atom probe (3DAP) as well as the more traditional transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) to investigate early precipitation events that occur during secondary ageing at low temperatures (~20-65°C). This work has confirmed that clustering and GP zone formation can modify the nature and distribution of precipitates that form when ageing is subsequently resumed at more elevated temperatures. Prospects for achieving further improvements in heat treatment schedules and alloy compositions to take greater advantage of secondary precipitation are also considered.
Thermal Stability of Rapidly Solidified Alloys of Aluminium with Transition Metals
Authors: Vojtěch Dalibor , Verner Jan , Bártová Barbora , Saksl Karel
Published: March 2009

Rapidly solidified (RS) Al-TM (TM = transition metal) alloys are perspective
materials from scientific, as well as technological point of view. Generally, they are produced
by the melt atomization or by the melt spinning. Subsequent compaction is commonly
performed by the hot extrusion. Since transition metals, such as Cr, Fe, Ni, Zr, Ti, Mn and
others, have low diffusion coefficients in solid aluminium (lower by several orders of
magnitude than those of common alloying elements like Cu, Si, Mg, Zn etc.) the RS Al-TM
alloys are characterized by a high thermal stability. In this paper, several RS Al-TM
(TM = Cr, Fe, Ti, Mn, Ni) alloys prepared by the melt spinning and melt atomization are
compared to commercially available 2xxx, 6xxx and 7xxx wrought alloys. The main
structural features of both RS and wrought alloys are described. The RS alloys are
characterized by the presence of micro and nano-scale crystalline and/or quasi-crystalline
phases and supersaturated solid solutions. The elevated-temperature behaviour is compared
for both groups of materials. The thermal stability of the investigated materials is determined
by room temperature hardness measurements after various annealing regimes and a high
thermal stability of the RS alloys is demonstrated. The microstructural changes and phase
transformations occurring in the investigated materials upon heating are described. In the
Al-TM alloys, very slow decomposition of the supersaturated solid solutions, precipitation
and decomposition of the metastable quasi-crystalline phases occur.
3DAP Analysis and Computer Simulation of Nanocluster Formation in the Initial Aging Stage of Al-Zn Alloys
Authors: Komiya Yoshiki , Hirosawa Shoichi , Sato Tatsuo
Published: March 2009

The formation of nanoclusters in the early aging stage is not fully clarified due to their
extremely small sizes. To clarify the atomic-scale clustering of solute atoms, a three-dimensional
atom probe (3DAP) analysis and a Monte Carlo computer simulation have been conducted together
for Al-Zn alloys. The nanoclusters in the alloy aged at room temperature were successfully detected
in the obtained 3DAP maps. From these maps the growth behavior of nanoclusters during aging was
experimentally examined. In the Monte Carlo simulation, on the other hand, many-body nearest
neighbor interactions between atoms and between atoms and a vacancy were taken into account.
The Zn concentration of the clusters calculated in the 4-body interaction model best agreed with
that obtained experimentally, suggesting the importance of many-body interactions. Therefore, it
was confirmed that the combined analysis of 3DAP and the well-constructed Monte Carlo
simulation is useful to make clear the nanocluster formation in alloys.
Recrystallisation Resistance of Extruded and Cold Rolled Aluminium Alloys with Additions of Hf, Sc and Zr
Authors: Hallem Håkon , Rittel W.J. , Forbord Børge , Marthinsen Knut
Published: March 2009

A high recrystallisation resistance is required in aluminium alloys intended for
processing or use at temperatures between 450°C-600°C. Additions of Hf, Sc and Zr significantly
improve the resistance to recrystallisation through the formation of Al3X-dispersoids (X=Hf,Sc,Zr),
and in this work different concentrations and combinations of these elements were added to five
aluminium alloys. The alloys were extruded, subjected to various degrees of cold rolling (0%-80%)
and finally annealed at high temperatures in order to study the structural stability. All variants
displayed a high resistance towards recrystallisation, but the best results were obtained in the alloy
containing only Sc and Zr. In this alloy no signs of recrystallisation were observed even after 1
hour annealing of extruded and 80% cold rolled profiles at 600°C.
The Work Hardening of some Commercial Al Alloys
Authors: Lloyd David J.
Published: March 2009

The work hardening of Al alloys is very important in regards to their formability and
their deformation behavior in service. The majority of the work in the literature has considered
relatively pure materials, and has tended to concentrate on room temperature and elevated
temperature behavior. In Al alloys there is interest in work hardening at lower temperatures
since they are quite restricted in terms of the elevated temperatures at which they can be used. In
this paper the work hardening of commercial 1000, 3000 and 5000 alloys have been investigated
from room temperature down to 85°K. The work hardening has been analyzed using the Voce
approach, and it is shown that this enables the work hardening of the different alloys to be related
to their basic physical metallurgy.
Exfoliation Corrosion Mechanism: Interplay between Intergranular Corrosion and Stress Corrosion Cracking during Exfoliation Corrosion of AA7449
Authors: Hénon C. , Pouget G. , Warner Timothy
Published: March 2009

It is generally considered that exfoliation corrosion is due to the build-up of corrosion products that create a wedging stress that lifts up the surface grains. However, the exfoliation mechanism is still under discussion: possible operating mechanisms include intergranular corrosion of in plane grain boundaries accelerated by the wedging effect, or crack propagation by a “purely” stress corrosion mechanism. The sensitivity to exfoliation corrosion of AA7449 in relation to the intergranular and stress corrosion cracking sensitivity has been addressed in a program of controlled quenches followed by thermal treatments. Our observations demonstrate that the quench rate has a strong effect on intergranular corrosion and exfoliation corrosion sensitivity and in a lesser extent on stress corrosion cracking. In the first moments of the EXCO test, the initiation of corrosion follows the same trends as those revealed by the ASTM G110 test. We observe intergranular initiation for the slow quench rate (~5°C/s) and pitting initiation for samples quenched between 50 to 500°C/s. On the contrary, the final EXCO corrosion quotations do not seem to correlate with the intergranular resistance but rather with SCC resistance.
Temperature-Dependent Shear Strain Localization of Aluminium-Lithium Alloy in Uniaxial Compression Using Zerilli-Armstrong and Gradient Plasticity Models
Authors: Wang X.B.
Published: March 2009

Gradient-dependent plasticity where a characteristic length is involved to consider the
microstructural effect (interactions and interplaying among microstructures due to the heterogeneous
texture) is introduced into Zerilli-Armstrong model based on the framework of thermally activated
dislocation motion. Effect of initial temperature on the distributions of plastic shear strain and
deformation in adiabatic shear band (ASB), the axial compressive stress-axial compressive strain
curve, the shear stress-average plastic shear strain in ASB curve and the plastic shear strain
corresponding to the occurrence of shear strain localization is investigated. The axial deformation
within aluminum-lithium alloy specimen in uniaxial compression in strain-hardening stage is
considered to be uniform. Beyond the peak compressive stress, a single ASB with a certain thickness
determined by internal length is formed and intersects the specimen. The axial plastic deformation is
decomposed into uniform deformation and localized deformation due to the shear slip along ASB.
Lower temperature leads to earlier occurrence of shear strain localization, i.e., lower critical plastic
compressive strain, steeper post-peak shear stress-average plastic shear strain in ASB curve, higher
peak shear stress and more apparent shear strain localization. The calculated distributions of plastic
shear strain and deformation in ASB are highly nonuniform due to the microstructural effect, as
cannot be predicted by classical elastoplastic theory applicable to completely homogenous material.
The predicted average plastic shear strains in ASB for different widths of ASB agree with the
measured values for under-aged Al-Li alloy at 298K and at strain rate of approximately 103s-1.
Large Strain Deformation and Annealing of Aluminium
Authors: Huang X. , Xing Q. , Juul Jensen Dorte , Hansen Niels
Published: March 2009

TEM, Kikuchi diffraction analyses, EBSD, neutron diffraction and hardness measurements have been applied in a study of commercial purity aluminum (AA1200) cold rolled to strains 2 and 4 and afterwards recovered by a heat treatment for 2h at temperatures up to 220 °C. The deformation microstructure is a lamellar structure delineated by dislocation boundaries and high angle boundaries ( ) parallel to the rolling plane. The macrotexture is a typical rolling texture which is composed of individual texture components present as micrometer- and submicrometre-sized volumes. In the lamellar structure, correlations have been established between microstructural parameters and the local texture, showing for example that the density of high angle boundaries and the stored energy vary locally. The local variations affect the annealing behaviors in a way that some regions coarsen faster than others, leading to a recovered structure which is heterogeneous.
Study of Microstructure and Texture Evolution Using In-Situ EBSD Investigations and SE Imaging in SEM
Authors: Bjerkaas Hans , Fjeldbo Snorre Kjørstad , Roven Hans Jørgen , Hjelen Jarle , Chiron Rémi , Furu Trond
Published: March 2009

The crystallographic slip activity in several grains deformed by simple tension is
determined by use of in-situ deformation in combination with Electron Back Scattering Diffraction
(EBSD)-investigations and Secondary Electron (SE) imaging. This technique is also used to
determine grain lattice rotation paths of grains with different initial orientation, providing
information on basic deformation mechanisms of grains present in texture gradients. Both slip
activity and grain lattice rotation paths depend on the initial orientation and are influenced by the
neighbouring grain orientations. This indicates that predictions of the forming behaviour of
extruded profiles with a strong through thickness texture gradient relate to a very complex nature.
Damage Investigation in Aluminium Alloys by X Ray Tomography
Authors: Maire Éric , Grenier J.C. , Babout L.
Published: March 2009

X-ray tomography allows the microstruture of aluminum alloys to be imaged non destructively in
three dimensions (3D). This paper shows different examples of the use of this technique for the
quantification of damage in model and industrial Al based materials. The model materials are used
to setup the technique. The spherical shape of their inclusions makes it easy to compare the
measurements with the prediction of standard model for damage. The industrial materials are
characterized during in situ tensile but also ex situ bulging and plane strain tension tests. The
respective contribution of initiation and growth of damage is measured separately and discussed.
The 3D data are also used to quantify the anisotropy of the effect of damage.
Correlation of Strength with Hardness and Electrical Conductivity for Aluminium Alloy 7010
Authors: Salazar-Guapuriche Manuel A. , Zhao Y.Y. , Pitman Adam , Greene Andrew
Published: March 2009

The tensile strength, proof strength, hardness and electrical conductivity of Al alloy 7010
under different temper and ageing conditions were investigated with the aim to correlate strength
with hardness and electrical conductivity so that the strength of the alloy can be determined nondestructively.
Following the solutionising treatment, continuous age hardening was performed on a
series of test coupons, taken from a large plate, to produce a wide range of precipitation hardening
conditions, which gave rise to progressive variations of strength, hardness and conductivity. The
relationship between strength and hardness was found to be reasonably linear, whereas the
relationship between hardness and strength with electrical conductivity was non-linear. The ageing
conditions and therefore the mechanical properties of the components can be predicted more
accurately by the simultaneous combination of hardness and conductivity values.
An Analysis of Microband Orientation in Hot Deformed Aluminium Alloy AA5052 Using Forward and Reverse Torsion
Authors: Lopez-Pedrosa M. , Wynne Bradley P. , Rainforth Mark W. , Cizek P.
Published: March 2009

The effects of strain path reversal on the macroscopic orientation of microbands in
AA5052 have been studied using high resolution electron backscatter diffraction. Deformation was
carried using two equal steps of forward/forward or forward/reverse torsion at a temperature of
300°C and strain rate of 1s-1 to a total equivalent tensile strain of 0.5. In both cases microbands
were found in the majority of grains examined with many having more than one set. The
microbands appear to cluster at specific angles to the macroscopic deformation. For the
forward/forward condition microbands clustered around -20° and +45° to the maximum principle
stress direction and at ± 30-35° to the principal strain direction. For the forward/reverse condition
significantly more spread in microband angle was observed though peaks were visible at ±35° with
respect to principal stress direction and at -40° and +30° with respect to the principal strain
direction of the reverse torsion. This suggests the microbands formed in the forward deformation
have or are dissolving and any new microbands formed are related to the deformation conditions of
the final strain path.
The Effect of Oxide Scale on the Mechanical Behavior of Low Alloyed Steel at High Temperature
Authors: Favergeon Jérôme , Moulin Gérard , Makni Amine , Lahoche Laurent
Published: March 2009

The mechanical behavior of oxidized low alloyed steel has been studied at
temperatures between 700°C and 900°C. Such a work is carried out to obtain information
about the damages which occur in the oxide scales developed on steels during hot rolling
process. Actually the mechanical behavior is tested with a four point bending apparatus at
high temperature under controlled atmosphere. Some information about mechanical damages
have been collected during the mechanical loading thanks to recording of the sample acoustic
emission. During this study, two procedures have been used which differ in the thermal
scheme used to build the oxide scales. The results obviously show that the procedure has a
great influence on the mechanical behavior of the oxidized low alloyed steel. For instance a
marked decrease of the stress is observed at constant displacement between the 900°C and
800°C tests of one procedure, as the opposite behavior is observed with the other procedure.
Different points are considered to explain such results, as the thermal strains which are only
present in one of the two procedures, the phase transformations in the metal and in the oxide.
Influence of Additional Elements on the Oxidation Behaviour of Nb-Al-Cr Base Alloys
Authors: Taniguchi Shigeji , Tanaka Hideaki , Maeda Tooru
Published: March 2009

Coupon specimens of 30Nb-40Al-(30-x)Cr-xMo (mol %), with x being 0, 7.5, 15,
22.5 or 30, and of 30Nb-40Al-(22.5-y)Cr-7.5Mo-ySi, with y being 5 or 10, were oxidised in
air in a temperature range 1473 to 1773 K for 72 ks. The influence of additions of 0.05 and
0.1% Hf to 30Nb-40Al-22.5Cr-7.5Mo was also examined. Conventional metallographic
examinations were performed for the specimens before and after the oxidation. The major
phase of the specimens is AlNbCr, and their minor phases are Cr2Al and NbAl3, except for
high Mo-content specimens which form AlNbMo, Nb2Al, Mo3Al and MoAl3. The additions of
Si lead to additional formation of Nb5Si3. Virtually Al2O3 scales (a dense and continuous
Al2O3 layer with a thin layer consisting of AlNbO4, CrNbO4 and/or SiO2 on it) are formed at
temperatures up to 1673 K, except for the high Mo-content specimens which form poorly
protective scales. The additions of Hf increase the mass gain to some degree. 5Si forms
protective scales at temperatures up to 1723 K, and 30Cr and 10Si up to 1773 K.
High Temperature Oxidation of TiAl-1.5wt.%Mn-(0, 5, 10)wt.%Y2O3 Alloys
Authors: Lee Dong Bok
Published: March 2009

TiAl-Mn-(0,5,10) wt.%Y2O3 alloys were prepared by the MA-SPS process, and their oxidation behavior was studied between 800 and 1000oC in 1 atm of air. The added Y2O3 particles were segregated along the matrix grain boundaries. The addition of (5~10) wt.%Y2O3, viz. (0.9~1.8) mol%Y2O3 increased the tendency to form the rutile phase along the grain boundaries, resulting in the increment of the oxidation rate and decrement of scale adherence. Mn was oxidized to Mn2O3. The primary mode of scale growth was the outward diffusion of Ti and Mn cations for the outer TiO2 scale, and the inward transport of oxygen anions for the inner (TiO2+Al2O3) mixed scale.
Effect of Coatings on the Creep and Oxidation Behavior of TiAl Alloys at 1173K in Air
Authors: Nishimoto Takumi , Hayashi Shigenari , Narita Toshio
Published: March 2009

The effects of coatings on the creep and oxidation behavior of Ti-50Al alloy were investigated at
1173K in air at a constant loading of 30MPa. The coating was formed by a two-step Cr/Al diffusion
treatment and consisted of an outermost TiAl2 layer, an outer Al-rich γ layer, an intermediate γ,
Laves and β mixture layer, and a Cr diffusion zone. Creep tests were also carried out with sole Cr or
Al coated TiAl and also of uncoated TiAl. The oxide scales formed on the uncoated TiAl and the
sole Cr coated specimens were a mixture of TiO2 and Al2O3, which displayed several exfoliations.
Both the two-step Cr/Al coated TiAl and the sole Al coated specimens formed a protective Al2O3
layer and little oxide exfoliation was observed here. Significant cracks were observed in the sole Al
coated TiAl, while no cracks were observed in the sole Cr coated TiAl; the two-step Cr/Al coated
TiAl showed a number of cracks in the coatings. Low creep rates in the two-step Cr/Al coated TiAl
could be due to the Laves phase with a hexagonal C14 structure in the intermediate, γ, β and Laves
phase mixture, and the high creep rates of the sole Cr coated TiAl may originate in the major β
phase component with a B2 structure in the γ, β, and Laves phase mixture.
New Type of Diffraction Elastic Constants for Stress Determination
Authors: Baczmanski Andrzej , Tidu Albert , Lipiński Paul , Humbert Michel , Wierzbanowski Krzysztof
Published: March 2009

A new method for calculation of the diffraction elastic constants, based on the selfconsistent
model, is proposed and tested. This method is especially useful in the interpretation of
the results of X-ray measurements since the ellipsoidal inclusion near the sample surface is
considered. In X-ray diffraction the information volume of the sample is defined by absorption,
causing unequal contribution of different crystallites to the intensity of the measured peak.
Consequently, the surface grains participate more effectively in diffraction than the grains which are
deeper in the sample.
Evaluation of Uncertainties of Measurement for Residual Stresses in Coatings Determined by the Dilatometric Method
Authors: Ryabchikov Alexander , Lille Harri , Laaneots R.
Published: March 2009

In this study uncertainties of measurement are evaluated for residual stresses in coatings
determined by the method of measurement of the longitudinal deformation of a tubular substrate, a
wire substrate and a strip substrate. Higher uncertainty was observed in the case of applying a thin
coating on a strip substrate. The precision of the equipment depends on the elastic element used for
measurement of the longitudinal deformation of the substrate. Residual stresses were determined in
the galvanic nickel coating deposited on a tubular substrate, a wire substrate and a strip substrate
from the Watts bath. Copper and brass was used as the material of the substrate. The investigated
experimental system is presented.