bluuebunny/crossref_metadata_2025 huggingface dataset:
Grades 92 and 23: Weldability Assessment and Long-Term Performances for Power Generation Applications
Authors: Bauné Emmanuel , Galand E. , Leduey B. , Liberati G. , Cumino G. , Caminada S. , Di Gianfrancesco A. , Cipolla L.
Published: March 2009

Increased efficiency and emission reduction in modern power plants lead to the use
of new advanced materials with enhanced creep strength, with the objective to increase the steam
parameters of power plants. With over ten years on market and wide experience related to its use,
ASTM Grade 92 is becoming one of the most required materials when high service temperatures
are reached (max. 610°C). Its composition, with 9%Cr and 1.5%W, gives rise to martensitic
microstructures which offer very high creep strength and long term stability. The improved
weldability and creep-strength between 500 and 580°C of the low alloy ASTM Grade 23, as well as
a cost advantage over higher Cr materials in this temperature range, make it one of the possible
candidates to meet the stringent requirements of modern power plants.
Air Liquide Welding (ALW) has optimized and distributes a complete product family for the
welding of Grades 23 and 92. TenarisDalmine (TD) focused on the development of Grade 23 tubes
and pipes and is working on the development of Grade 92. A deep characterization work of the
microstructural evolution and long term creep performances of these high temperature resistant
materials was thus undertaken by ALW and TD, in collaboration with the Centro Sviluppo
Materiali (CSM). The joint characterization program consisted in the assessment of welded joints
creep properties. Welded joints were produced using the gas tungsten (GTAW), shielded metal
(SMAW) and submerged arc welding (SAW) processes. Mechanical and creep properties of
weldments were measured both in the as welded and post weld heat treated conditions and proper
WPS’s were designed in a manner such that industrial production needs were satisfied. Short term
creep resistance of cross weld specimens was measured to be within the base material acceptance
criteria. Long term base material and cross weld creep performance evaluation are now in progress.
Welding Characteristic of Super Alloys for Nd:YAG Laser
Authors: Kim Jeng O , Suh Jeong , Lee Jae Hoon , Ryu Sang Hyun , Noh Ji Whan
Published: March 2009

The optimized condition has been researched, for welding super alloys (Inconel 600,
Inconel 625 and Haynes 230), which are used for liquid thruster of an artificial satellite. In the
experiment of “bead-on-plate”, these materials are welded using continuous Nd:YAG laser and
electron beam. The penetration depth and bead width are measured by optical microscope. The
hardness of 1mm depth from welding surface is measured by micro Vickers hardness tester. The
tension is tested for measuring the strength of welding part. The tension strength of welding
specimen using the Nd:YAG laser is compared with that of the welding specimen using the electron
beam.
A Comparison of Weld Properties with or without Filler Wire on Laser Welding of Magnesium Alloy for Car Industry
Authors: Lee Mok Young , Chang Woong Seong , Kim Sook Hwan
Published: March 2009

Magnesium alloys are becoming important material for light weight car body, due to their
low specific density but high specific strength. However they have a poor weldability, caused by
high oxidization tendency and low vapour temperature. In this study, the welding performance of
magnesium alloy was investigated for automobile application. The material was rolled magnesium
alloy sheet contains 3wt%Al, 1wt%Zn and Mg balance. The effects of filler wire addition was
investigated on 2kW Nd:YAG laser welding. For the results, the mechanical properties of welded
specimen were similar with base metal in laser welding with and without filler wire. The bridging
ability was improved with filler wire without weld properties deterioration on laser welding of
magnesium alloy.
Corrosion Monitoring Characteristics of Plasma RF Sputtered Mg Thin Films under Cyclic Wet-Dry Conditions
Authors: Lee Myeong Hoon , Kim Jong Do , Bae Il Yong
Published: March 2009

In general, magnesium metal is not used as uncoated material on account of its corrosion
characteristic. This work was done by preparing 99.99% pure magnesium coating films by RF
magnetron sputtering onto SPCC substrates [1]. The individual preparation conditions of gas
pressures and bias voltages were 1×10-2 ~ 1×10-3 Torr and 0V ~ -300V, respectively. The analysis
about crystal orientation, morphology and electrochemical characteristic of Mg thin films was
performed by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM),
electrochemical impedance spectroscopy (EIS) etc.. It is as a results of experiment that the
morphology of the sputtered films changed from a columnar structure to a granular structure when
Ar gas pressure increased or bias voltage decreased. Also, the prepared Mg thin film’s morphology
did not have defects and pinholes, and the corrosion resistance was improved by the formation of a
homogeneous passive layer.
Effect of Chemical Composition of Welding Wire and Low Temperature Steel Plate on the Weld Properties Made by SAW
Authors: Sung Hee Joon , Goo Yeon Baeg , Kim Kyeong Ju , Choi Kee Young
Published: March 2009

Chemical composition effect on the weld properties for low temperature steel was
evaluated. The alloy elements of interest at the weld metal were Cr and Mo, which come from the
steel plate and welding wire, respectively. Both side one run SAW process was carried out in a Ygroove
butt joint. Microstructure of the weld metal is strongly dependent on the chemical
composition of the steel plate and the welding wire, due to high dilution. The microstructure of the
weld metal became fine acicular ferrite by increasing Cr and Mo content because of high
hardenability effect. The weld metal having Cr and Mo possessed the highest impact toughness at
low temperatures among the weld metals studied. Cr seems to have more effect than Mo on the
toughness of the weld metal.
Geometrical and Welding Conditions on Through-Thickness Residual Stress in Primary Piping of Girth Welded Joints
Authors: Katsuyama Jinya , Mochizuki Masahito , Mori Hiroaki , Asano W. , An Gyu Baek , Toyoda Masao
Published: March 2009

Recently, stress corrosion cracking (SCC) of primary piping of stainless steel has been
observed. SCC is considered to initiate and progress at near the welding zone in butt-welded pipes,
because of the tensile residual stress introduced by welding. In present work, three-dimensional and
axisymmetric thermo-elastic-plastic finite element analyses have been carried out, in order to clarify
the effect of geometrical and welding conditions on through-thickness residual stress. In particular,
butt-welding joints of SUS316L pipes have been examined. The residual stress was simulated by
three-dimensional and axisymmetric models and the results were compared and discussed in detail.
Measurement of Through-Thickness Residual Stress in Primary Piping of Girth Welded Joint
Authors: Mochizuki Masahito , Okano Shigetaka , An Gyu Baek , Toyoda Masao
Published: March 2009

The welding residual stress of a butt-welded pipe joint is evaluated, using inherent strain
analysis. The residual stress distribution is obtained in detail along the thickness direction. The
residual stresses are similar to values obtained by direct measurement on the specimen surface; as if
though direct measurement is not used for the inherent strain analysis. These results indicate that
inherent strain analysis is effective in evaluating through-thickness residual stress in primary piping
of girth welded joint.
Angular Distortion Reduction by In-Process Control Welding Using Back Heating Source
Authors: Okano Shigetaka , Mochizuki Masahito , Toyoda Masao
Published: March 2009

In order to reduce the number of fabricating processes, it is preferable to control welding
distortion during welding; instead of using restraints before the process, or correcting the distortion
after the process. The benefits of eliminating extra processes include the reduction of the time and
manufacturing cost. This paper presents a method of back heating and welding in tandem, with the
back heating occurring at a constant distance from the welding torch during welding. Traditionally,
the back heating method has reduced angular distortion in two different ways; One is to bend the
welded material in the opposite direction, and the other is homogenization of temperature
distribution along the thickness. But, it has recently become known that the angular distortion
produced by multiple heat sources, in tandem placement, is not always predicted by the total heat
input to the welded joint; and it is possible for the distortion to differ greatly due to factors such as
the distance between two heat sources, heat input parameters, and the heat input ratio. Based on
these findings, angular distortion is expected to be reduced more effectively by choosing the proper
condition for the heat source arrangement in back heating. In this paper, reduction of angular
distortion by in-process control welding, using a back heating source, is numerically analyzed by
the three-dimensional thermal elastic-plastic analysis, considering moving heat source with weld
metal deposition. It was confirmed that the back heating method is effective in reducing angular
distortion without restraint or correction. Proper condition concerning the heat source arrangement
can be chosen and angular distortion can be perfectly controlled by back heating with ten percent of
the welding heat input.
A Study for the Fatigue Failure Mode Assessment of Fillet Weldments
Authors: Kim Myung Hyun , Kang Sung Won , Kim Jeong Hwan , Lee Jae Myung , Kim Hyoung Rae
Published: March 2009

In this study, a methodology for the assessment of fatigue failure modes of weldments due
to partial penetration weld has been carried out by using structural stress method. Structural stress
calculation procedure, using shell element based on equilibrium consideration using nodal forces and
moments, is employed. It is important to note that the structural stress calculation procedures for
partial penetration welds can be used to determine a minimum weld leg length, beyond which, weld
root failure modes can be effectively suppressed. An example study, with respect to a fillet weld leg
length design, is compared with a design criterion, and they are found to be in agreement.
Optional Correlation Function Method in Kriging for Stochastic Optimal Design
Authors: Im Jong Bin , Ro Young Hee , Lee Soo Yong , Park Jung Sun
Published: March 2009

This paper is focused on the three strategies to improve efficiency and accuracy of
approximate optimization models using Kriging. The strategies are performed by the stochastic
process which is called stochastic-localization method as the criterion to move the local domains
and the design of experiments, the classical design and space-filling design. We also propose the
methodology conducted by the max-min reused sampling and a sequential adaptation algorithm of
correlation functions. The proposed strategies are applied to the known analytical function such as
Sandgren’s pressure vessel and three-bar truss for practical examples.
A Study on the Development of Mach Peening for Prolonging Fatigue Life of Machine Structural Alloy Steel
Authors: Lim Bok Kyu
Published: March 2009

The light weight components, crucial in automobiles and machinery, is require hight
strength. Mach peening process is one of many of techniques utilized for improving fatigue
properties. From the results of rotary bending fatigue tests, the fatigue strength increases up to
129% in mach peening specimen compared with un-peening. A layer of highly compressed residual
stress is obtained by mach peening. The compressive residual stress, induced by mach peening,
seems to be an important factor for increasing the fatigue strength.
Analysis of Welding Residual Stress of Steel Pipes
Authors: Choi Kwang
Published: March 2009

This study was aimed at evaluation of residual stress of steel pipe structures. The production
process of pipes was complex (at first bending was done by roll forming or press forming and
welding was final process of making of steel pipes). So there could be expected high residual
stresses in steel pipes. In order to evaluate the changes of residual stress measurements of residual
stress were done for the circular pipe (thickness 16 mm). For the evaluation of residual stress, holedrilling
method (ASTM E837) was applied. The results showed that along the weld line high tensile
stress were measured as expected, and high tensile stresses were measured where large plastic
deformation developed.
And in order to assist the experimental results, numerical method (finite element method) was
applied. In finite element analysis, non-linear analysis of processes was considered. In welding
(final case of pipe making), thermal-elastic-plastic analysis was done considering material
properties according to temperature. The calculations showed there were good agreements with
experimental results. And from results, experimental results could be more effectively assisted
through numerical method in welded pipes production.
The Variations of Quality Characteristics According to Environmental Factors of High Tension Bolt, Nut and Washer Set
Authors: Suk H.G. , Kim D.S. , Kim Song Hee , Cho I.S.
Published: March 2009

Because the fastener tension of high strength bolt, nut, and washer set is subject to the
environmental factors such as temperature, humidity and storage period, extreme care should be taken
during the joining and storage of such products. In case quality change is anticipated, the parts shall
certainly be inspected.
Shape Memory Alloys: Material Modeling and Device Finite Element Simulations
Authors: Auricchio Ferdinando , Reali Alessandro
Published: March 2009

The use of shape memory alloys (SMA) in an increasing number of applications
in many ¯elds of engineering, such as biomedical engineering, is leading to a growing interest
toward an exhaustive modeling of their macroscopic behavior in order to construct reliable
simulation tools for SMA devices.
In this paper we review a robust three-dimensional model able to reproduce both pseudo-elastic
and shape-memory behaviors and we report numerical studies where it is used for the simulation
of SMA-based biomedical devices.
3D Reconstruction of Ni4Ti3 Precipitates in a Ni51Ti49 Alloy in a FIB/SEM Dual-Beam System
Authors: Cao Shan Shan , Tirry Wim , Van den Broek Wouter , Schryvers D.
Published: March 2009

Ni4Ti3 precipitates play an important role in the shape memory and superelastic behaviour
of thermo-mechanically treated Ni-Ti material. The 3D morphology and distribution of such
precipitates with lenticular shape and rhombohedral atomic structure in the austenitic B2 matrix of a
binary Ni-rich Ni-Ti alloy has been elucidated via a slice & view procedure in a Dual-Beam
FIB/SEM system. With the sequence of cross-section SE images obtained from the SEM, a 3D
reconstruction has been achieved after proper alignment and image processing, from which both
qualitative and quantitative analysis can be performed. Careful imaging is needed to ensure that all
variants of the precipitates are observed with equal probability, regardless sample orientation.
Moreover, due to the weak contrast of the precipitates, proper imaging conditions need to be selected
to allow for semi-automated image treatment. Finally, a volume ratio of 10.2% for the Ni4Ti3
precipitates could be calculated, summed over all variants, which yields a net composition of
Ni50.36Ti49.64 for the matrix, leading to an increase of 113 degrees for the martensitic start temperature
Ms. Also, the expected relative orientation of the different variants of the precipitates could be
confirmed. In the near future, other quantitative measures on the distribution of the precipitates can be
expected.
Strain Glass: Glassy Martensite
Authors: Wang Yu , Ren Xiao Bing , Otsuka Kazuhiro
Published: March 2009

“Glass”, a frozen disordered-state, has been found in areas as diverse as amorphous
solids, magnetic alloys, ferroelectrics, superconductors, and even in models of biological evolutions.
In the present review we introduce a new class of glass–the “strain-glass”, which was discovered very
recently. Strain glass is derived from a martensitic system, where the local-strain is frozen in
disordered configuration. The first example of strain glass was found in the well-studied Ni-rich
Ti50-xNi50+x martensitic system in its “non-transforming” composition regime (x>1.5). Contrasting to
the familiar martensitic transition, the strain glass transition is not accompanied by a change in the
average structure, or a thermal peak in the DSC measurement. It involves a dynamic freezing process
with broken ergodicity, during which nano-sized martensite domains are frozen. More interestingly,
the seemingly “non-martensitic” strain glass exhibits unexpected properties: shape memory effect and
superelasticity, like a normal martensitic alloy. Strain glass bears a striking similarity with other two
classes of glasses: cluster-spin glass and ferroelectric relaxor. These ferroic-transition-derived glasses
can be considered as a more general class of glass: ferroic glass. The finding of strain glass may
provide new opportunities for martensite research from both fundamental side and application side.
A Triple-Scale Crystal Plasticity Simulation on Yield Behavior of Annealed FCC Fine-Grained Metals
Authors: Kurosawa Eisuke , Aoyagi Yoshiteru , Tadano Yuichi , Shizawa Kazuyuki
Published: March 2009

In this study, the conventional Bailey-Hirsch’s relationship is extended in order to express
the increase of critical resolved shear stress due to the lack of dislocation lines in a grain. This model
is introduced into a triple-scale crystal plasticity model based on geometrically necessary crystal
defects and the homogenization method. A FE simulation is carried out based on the proposed model
for FCC polycrystals with different grain sizes. It is numerically predicted that yield behavior of
fine-grained metals depends on the initial dislocation density and the initial grain size. Furthermore,
yield point drop that is observed in annealed FCC fine-grained metal can be reproduced.
The New Approach to Produce Al Sheets with UFG Structure Using SPD Processing
Authors: Yunusova N.F. , Islamgaliev Rinat K. , Safiullin I.F. , Valiev Ruslan
Published: March 2009

Microstructure and mechanical properties of the ultrafine-grained (UFG) 1421 aluminum
alloy processed by equal channel angular pressing (ECAP) have been studied. This UFG material
was successfully rolled under the conditions of superplasticity. It was established that the rolled
material exhibited not only the enhanced superplasticity, but also high strength retaining initial
ductility at room temperature after additional short-term annealing and low-temperature aging.
Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT
Authors: Kurmanaeva Lilia , Ivanisenko Yulia , Markmann J. , Valiev Ruslan , Fecht Hans Jorg
Published: March 2009

Investigations of mechanical properties of nanocrystalline (nc) materials are still in
interest of materials science, because they offer wide application as structural materials thanks to
their outstanding mechanical properties. NC materials demonstrate superior hardness and strength
as compared with their coarse grained counterparts, but very often they possess a limited ductility or
show low uniform elongation due to poor strain hardening ability. Here, we present the results of
investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60)
alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion,
which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents
led to the decrease of the resulted grain size and change in deformation behavior, because of
decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the
higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had
also increased with increase of strength.
Enhanced Strength and Ductility in Hypo-Eutectoid Cu-Al Alloys through ECAP and Annealing
Authors: Xia Shao Hua , Vychigzhanina L.V. , Wang Jing Tao , Alexandrov Igor V.
Published: March 2009

In the present investigation, a bimodal structured alloy with ultrafine-grained
(UFG) eutectoid matrix embedded with micrometer-grained pre-eutectoid phase was
introduced into the hypo-eutectoid Cu-10.8wt.%Al and Cu-11.3wt.%Al alloys by
means of pre-pressing heat-treatment, equal-channel-angular pressing (ECAP) and
subsequent annealing. Different size of micrometer grained pre-eutectoid phase was
obtained by controlling the cooling rate during pre-pressing heat-treatment of the
hypo-eutectoid alloy. The tensile deformation behavior of the developed
microstructures is characterized by a maximum tensile yield strength up to 800MPa,
which is three times higher than that of the un-treated alloy. It is found that the size of
the micrometer grained pre-eutectoid phase is critical to the improvement of the
bimodal structured alloy. With larger micrometer grained pre-eutectoid phase, no
obvious improvement in plastic elongation was observed with the increase of volume
fraction of the pre-eutectoid phase from 20% to 40%, but a decrease in the yield
tensile strength was observed. An optimal combination of strength and ductility was
obtained particularly in those samples embedded with small-sized micrometer-grained
pre-eutectoid phase, which provide extra strain gradient hardening effect.
Study of Texture Evolution of Pure Magnesium during ECAE Using EBSD
Authors: Biswas Somjeet , Dhinwal Satyaveer Singh , Bhowmik Ayan , Suwas Satyam
Published: March 2009

Commercially Pure Magnesium initially hot rolled and having a basal texture was
deformed by Equal Channel Angular Extrusion (ECAE). ECAE was carried out upto 8 passes in a
90° die following routes A and Bc through a processing sequence involving two temperatures,
namely 523 and 473 K. Texture and microstructure formed were studied using electron back scatter
diffraction (EBSD) technique. In addition to significant reduction in grain size, strong <0002> fiber
texture inclined at an angle ~ 45o from the extrusion axis formed in the material. Texture was also
analyzed by orientation distribution function (ODF) and compared vis-à-vis shear texture. A
significant amount of dynamic recrystallization occurred during ECAE, which apparently did not
influence texture.
Nanoglasses: A Way to Solid Materials with Tunable Atomic Structures and Properties
Authors: Gleiter Herbert
Published: March 2009

Recently, a new class of materials - called nanoglasses - with a glassy structure was
synthesized. The novel feature of these materials is that the atomic structure in the entire volume of
the material as well as the density of the material can be tuned. Nanoglasses are generated by
introducing interfaces into metallic glasses on a nanometer scale. Interfaces in these nanoglasses
delocalize upon annealing, so that the free volume associated with these interfaces spreads
throughout the volume of the glass. This delocalization changes the atomic structure and the density
of the glass throughout the volume. In fact, by controlling the spacing between the interfaces
introduced into the glass as well as the degree of the delocalization (by modifying the annealing
time and/or annealing temperature), the atomic structures as well as the density (and hence all
structure/density dependent properties) of nanoglasses may be controlled. A comparable tuning of
the atomic structure/density of crystalline materials is not conceivable, because defects in crystals
do not delocalize upon annealing.
Development of Extrusion and Rolling Textures during ECAP of Mg-Alloys
Authors: Brokmeier Heinz Günter , Gan Wei Min , Zheng Ming Yi , Zuberova Zuzana , Estrin Yuri
Published: March 2009

Crystallographic texture includes much information on a material’s behaviour that
depends on the processed material itself, the particular thermomechanical processing it has
undergone, and the quality of the process. ECAP processed pure Mg and Mg alloys were
characterised by their texture and are discussed in terms of texture symmetry. For all types of
deformation, including ECAP, the basal plain orientation has to follow certain general rules.
Particularly for larger number of passes the ECAP texture can be explained in terms of standard
rolling or extrusion textures.
Structure and Fatigue Properties of the Mg Alloy AM60 Processed by ECAP
Authors: Islamgaliev Rinat K. , Kulyasova Olya B. , Mingler Bernhard , Zehetbauer Michael J. , Minkow Alexander
Published: March 2009

This paper reports on the microstructures and fatigue properties of ultrafine-grained
(UFG) AM60 magnesium alloy processed by equal channel angular pressing (ECAP) at various
temperatures. After ECAP processing, samples exhibited an increase in fatigue endurance limit,
which correlates well with a decrease in grain size. In case of lowest ECAP temperature, the mean
grain size is as small as 1 2m which leads to an increase in fatigue endurance limit by 70 % in
comparison to coarse-grained alloy. The temperature of ECAP not only governs the grain size and
misorientation angles of grain boundaries but also the volume fraction of precipitates, thus affecting
the probability of twinning and grain growth after fatigue treatment.
Thermal Stability of Ultrafine Grains in Al-Fe-Mn-Si Foils Prepared by ARB and Subsequent Rolling
Authors: Homola Petr , Slámová Margarita , Sláma P. , Cieslar Miroslav
Published: March 2009

Accumulative Roll Bonding (ARB) is a severe plastic deformation process that allows
producing ultrafine-grained materials (UFG). UFG sheets exhibit enhanced strength and very fine
grain structure. Foils used as fins in heat exchangers have to be very thin but must exhibit high
strength combined with relatively high formability. Thus, materials produced using ARB may fulfil
the exacting requirements on foil properties for such applications. The thermal stability of Al-Fe-
Mn-Si foils produced using ARB and subsequent cold rolling was studied and compared with
conventionally cold rolled (CCR) counterparts. The stability was assessed by isothermal annealing
in the temperature range from 200 to 450 °C. Electron back scatter diffraction in a scanning electron
microscope and transmission electron microscopy examinations of foils microstructure in the
deformed and annealed states allowed the monitoring of structural changes. The magnitude of
mechanical properties changes due to annealing was evaluated by microhardness measurements.
Significant hardness increase was observed after annealing at 200 °C only in the ARB samples and
was assigned to an annealing-induced hardening. The CCR foil exhibits higher non-recrystallized
fraction and smaller mean lamellae boundary spacing in the temperature interval of 200-250 °C than
ARB foils. The annealing at 450 °C results in identical hardness values and fully recrystallized
microstructure of all foils, regardless the method used for their manufacturing. However, the ARB
samples show higher stability of the refined substructure than their cold rolled counterparts due to
continuous recrystallization occurring in the ARB foils.
Effect of Cryorolling Strain on Precipitation Kinetics of Al 7075 Alloy
Authors: Jayaganthan R. , Panigrahi Sushanta Kumar
Published: March 2009

The effect of rolling strain on precipitation kinetics of Al 7075 alloy processed at liquid
nitrogen temperature has been investigated in the present work. The Al 7075 alloy plates were
solutionized and cryorolled with thickness reduction of 35% and 90%. The microstructural
characterizations of the bulk and cryorolled Al alloy samples were carried out by electron
backscatter diffraction analysis (EBSD) and transmission electron microscopy (TEM), respectively.
The cryorolled Al alloys upon 90% thickness reduction exhibit ultrafine grained microstructure.
The DSC results of cryorolled Al 7075 alloys obtained at different heating rates are used to
calculate activation energies for the evolution of precipitates. The influence of different reduction
rates on activation energy of precipitate formation in the cryorolled Al 7075 alloys was analyzed.
The present study has shown that an ultrafine-grained Al 7075 alloy exhibits a higher driving force
for the precipitation formation when compared to that of its bulk Al alloys.
Athermal and Thermal Limits of the Grain Refinement by SPD
Authors: Hafok Martin , Pippan Reinhard
Published: March 2009

Severe plastic deformation, SPD, enables the grain refinement of bulk materials.
However, at strains larger than a critical value, no further microstructural refinement can be
observed. This regime is denoted as saturation region of the microstructural size. It will be shown
that this regime can be divided into a thermal and an athermal part. The transition between these
two regimes was examined in an Al-3wt.%Mg alloy. The single phase alloy was deformed by high
pressure torsion (HPT) at various temperatures and different rotational speeds. During the HPTdeformation
the flow stress was measured by a torque cell in a temperature range between -196°C
(evaporation temperature of the liquid nitrogen) and 450°C. The temperature and the strain rate
dependent behavior reveal a shift of the onset of the thermal activated regime towards higher
temperatures by an increase of the strain rate.
Annealing Behavior of ECAP Deformed Aluminum Alloy 3103
Authors: Molodova Xenia , Gottstein Günter
Published: March 2009

In the present study the microstructure evolution of the aluminum alloy 3103 subjected to
ECAP up to eight passes applying route Bc was investigated after deformation and subsequent
isothermal annealing. The deformed and annealed states were analyzed by SEM, EBSD, optical
microscopy and microhardness tests. It will be demonstrated that this ECAP deformed material
shows an increased stability against discontinuous recrystallization with growing number of passes.
Microstructure and Corrosion Properties of Fine-Grained Mg-Based Alloys
Authors: Hadzima Branislav , Janeček Miloš , Suchý Peter , Müller Julia , Wagner Lothar
Published: March 2009

The influence of various processing routes (casting, extrusion, ECAP) on microstructure
evolution and electrochemical properties of the magnesium alloy AZ80 were investigated. Both
extrusion and ECAP were found to result in significant grain refinement (by a factor of 100 in the
ECAP alloy) of the as cast AZ80 alloy. The electrochemical impedance spectroscopy was used to
characterize the electrochemical properties of the surface of different microstructure states of the
alloy. After the exposure to the corrosion environment containig aggressive chloride ions (0.1M
NaCl) a complex polarization layer consisting of two different layers was formed on the specimen
surface. The first compact layer directly adjoined to the specimen surface while the second porous
layer was formed on the first layer. Microstructure changes due to extrusion and equal channel
angular pressing were found to influence the stability of these layers. In the as cast alloy the
compact layer was broken already during the first 24 hours of the exposure, while the compact layer
in the extruded specimen remained unchanged up to 72 hours of the exposure. In the ECAP
specimen both layers remained stable even after 96 hours of the exposure and no degradation
occurred. Enhanced electrochemical properties were therefore found in the ultrafine-grained ECAP
specimen.
Mineralization Layers on Glasses of the Si-Ca-P-Mg System in a Physiologically Buffered Plasmatic Electrolyte
Authors: Cachinho Sandra C.P. , Correia Rui N. , Fernandes Maria Helena F.V.
Published: March 2009

Mineralization experiments on glasses of the Si-Ca-P-Mg system were carried out for 7 days in
carbonated simulated inorganic plasma (CSIP) buffered with CO2/HCO3
-. This method enables
physiological buffering of the solution within the 7.3–7.4 pH interval by maintaining a HCO3
-
concentration between 24 and 27 mmol.L-1, which is the normal concentration range in blood
plasma. XRD, SEM/EDS and FTIR were used to characterise the glass surfaces. All glasses
exhibited an apatite-like deposit whose Ca/P ratio was dependent on glass composition.
Viscous Sintering in a Glass-Alumina System
Authors: Margarida M. , Lima R.A. , Monteiro Regina da Conceição Corredeira
Published: March 2009

The densification during sintering of borosilicate glass matrix composites with 25 vol. %
alumina (Al2O3) particles was investigated. The powder compacts, isostatically pressed at 200 MPa,
were sintered at a temperature within the range 800-1000º C and maintained at this temperature
during various times. The sintering behaviour of the composites was investigated by density
measurement and by axial and radial shrinkage measurements. The crystalline phases present in the
sintered composites were identified by XRD and the microstructure was analyzed by SEM. For
temperatures up to 900 °C, the relative density of the composites increased continuously with
sintering temperature and sintering time, while for higher temperatures, the density increased
rapidly and then slowed down to achieve a nearly constant value after sintering the composites for
30 minutes. The composites exhibited isotropic shrinkage behaviour when sintered at 800 °C and
850 °C, but at higher temperatures slightly higher axial shrinkage than radial shrinkage was
observed. The shrinkage behaviour and microstructural characteristics of the composites indicate
that densification during sintering can be attributed to the viscous flow of the borosilicate glass.
Optimization of Ceramic Shells for Contact with Reactive Alloys
Authors: Duarte Teresa P. , Neto Rui J.L. , Félix Rui , Lino F. Jorge
Published: March 2009

Companies are continuously under pressure to innovate their products and processes. In
Portugal, there are already several examples of enterprises that have chosen research groups,
associated to universities, to straighten collaboration seeking the development of new materials and
advanced technological processes, to produce components with complex shapes, high surface
quality, and others, at low cost, for continuously more demanding applications. Unfortunately, these
cases are still a very small number, and many efforts have to be done to enlarge the collaboration
university-companies. Ti and other reactive alloys are important groups of metals that are under
intense and continuous research and development. For example, the high mechanical properties, low
density, osteointegration behavior, corrosion resistance to fluids and tissues of the human body, the
ability to be sterilized, and the possibility to obtain complex shapes, makes Ti a very attractive
material for medical applications. The investment casting process, using lost wax or lost rapid
prototyping models, allows designers a great amount of freedom and capacity to quickly produce
castings of high dimensional accuracy and excellent surface quality suitable for different
applications. Many of the castings obtained by this process are immediately ready for use, avoiding
costly machining operations and joining processes, making the process very attractive to produce
precision parts in Ti and other reactive alloys. However, the high reactivity of the Ti raises several
compatibility problems with the traditional materials employed on the ceramic shells for casting
steels and non ferrous alloys. The fragile surface layer obtained on the interface Ti-ceramic shell,
result of the Ti reaction with oxygen and nitrogen of the shell, significantly reduces the mechanical
properties of the cast parts, making them useless. The aim of the present work is the study of the
interface properties of the Ti-ceramic shell, in order to be able to manufacture ceramic shells of low
chemical reactivity for the investment casting process of reactive alloys, namely; titanium alloys,
inconel, aluminotitanates, and others. Ceramic shells manufactured with calcium and yttria
stabilized zirconia and other non reactive ceramics were employed and the metallic interface
characterized in terms of microscopic and microhardness properties.
Elastic Properties of Microwave Sintered Hydroxyapatite
Authors: Oliveira Fernando A. Costa , Pascaud Patricia , Domingues Joaquim , Marcelo Teresa , Fernandes Jorge Cruz , Rosa Luis Guerra
Published: March 2009

Hydroxyapatite (HA) is widely used as a bone repair material. The use of microwave
radiation as energy source for powders densification opens new opportunities for sintering HA at
lower temperatures than by conventional sintering (electric furnace). The aim of this work was to
compare the densification behaviour of a commercial hydroxyapatite powder under microwave and
conventional heating conditions through evaluation of the elastic properties of the resulting sintered
materials. The effect of green density, sintering temperature and dwell time on the Young’s
modulus E (measured by the impulse excitation of vibration method) of microwave sintered HA
was evaluated by using the Taguchi method. Under the set of controlled parameters investigated,
green density was the most significant factor affecting E. It was verified that the highest E values
obtained with each sintering process are similar (104 and 105 GPa for microwave and conventional
sintering, respectively). These values were obtained at 1250°C for 2 h in conventional sintering and
at 1200°C for 10 min with microwave sintering. This illustrates the advantage of microwave
processing on energy and time savings over conventional sintering.
Consolidation of Copper-Copper Nitride Nanocomposite Powders via Warm Extrusion
Authors: Livramento Vanessa , Correia Jose Brito , Neves Filipe , Calinas Rosa , Vieira Maria-Teresa Freire
Published: March 2009

Copper nitride films prepared by sputtering have applications such as optical data storage
material, insulation barriers in micro electronic devices and coatings for mechanical applications.
The present study examines nanocomposites prepared by mechanical alloying of copper with
copper nitride under nitrogen atmosphere, at room temperature, in order to establish a comparison
with properties of Cu-N sputtered films. The powders were consolidated into bulk samples via
warm extrusion at temperatures ranging from 300 to 500°C (0.42-0.64 Tf) after encapsulation
without degassing. The as-milled powders and the extruded materials were studied using X-ray
diffraction, optical microscopy, scanning and transmission electron microscopy and microhardness
measurements. Also, the TEM observation of the extruded sample indicates a mean grain size of
about 50 nm. This evidences a higher thermal stability of the as-milled powders and the advantage
of using a fast consolidation process, at a relatively low temperature. Therefore, the consolidated
material did not show the dramatic softening associated with recrystallization. The consolidation of
nanostructured copper-copper nitride composite powders via warm extrusion, without major grain
coarsening, was demonstrated.
Structure and Properties of Hybrid Polyurethane Composites with Carboxyalumoxanes
Authors: Jurczyk-Kowalska Magdalena , Ryszkowska Joanna
Published: March 2009

Carboxyalumoxanes have been incorporated into a polyurethane matrix by in situ
polymerization. The filler was dispersed in the polyurethane matrix by either both ultrasonic and
mechanical mixing or by mechanical mixing alone. The physico-mechanical properties of the
composites have been characterized using scanning electron microscopy (SEM), atomic force
microscopy (AFM), differential scanning calorimetry (DSC) and thermogravimetric analysis
(TGA). Using ultrasound improves the degree of dispersion of the fillers in the matrix, but it also
causes changes in the structure of the polyurethane matrix.
A PZT Based Material for Bimorph Type Transducers and a New Optical Method to Evaluate the Bimorph Performance
Authors: Miclea Cornel , Tanasoiu Constantin , Miclea Corneliu Florin , Spanulescu I. , Plavitu C.N. , Cioangher M. , Trupina L. , Miclea C.T. , Susu M.
Published: March 2009

The displacement devices using piezoceramic sensors play an important role in many
fields. Soft type piezoelectric materials used for such sensors are more appealing because of their
lower coercive field, relatively low modulus of elasticity, high electromechanical coupling factors
and piezoelectric strain coefficients. We designed a PZT type material doped with niobium and
nickel to increase the strain coefficient and still retaining a high coupling coefficient. The chemical
formula was Pb0.97Ba0.08Nb0.03Ni0.06Zr0.46Ti0.40O3. The main piezoelectric parameters were: d33=680
pm/V, d31=-235 pm/V, kp=0.64 and k31=0.42. A unimorph transducer was made from a thin sheet of
such a piezoceramic material, tightly bonded on a thin optically polished glass plate and mounted as
a cantilever. The performance of this transducer was evaluated by means of a new optical method
which makes use of the Moiré deflectometry and provides high precision. The method is rather
simply and consists mainly in the following: the Moiré fringes rotate when the bimorph bends under
the influence of the electric field and by measuring the rotating angle of the fringes one can easily
determine the bimorph curvature and the free end displacement.
New Oligothienyl-Imidazo-Phenanthroline Chromophores for NLO Applications
Authors: Batista Rosa M.F. , Costa Susana P.G. , Lodeiro Carlos , Belsley Michael , de Matos Gomes E. , Raposo M. Manuela M.
Published: March 2009

A new series of oligothienyl-imidazo-phenanthrolines 3 were synthesised in good to
excellent yields by condensation of 5,6-phenantroline-dione 2 with formyl-thiophene derivatives 1
in the presence of ammonium acetate in glacial acetic acid. Furthermore, their solvatochromism and
molecular optical nonlinearities were determined and comparatively studied. The experimental
results indicate that phenanthrolines 3, due to their moderate solvatochromic properties and good
optical nonlinearities, could be used as suitable probes for the determination of solvent polarity and
as nonlinear optical materials.
5-Arylazo-2,2´-Bithiophenes: A Novel Promising Series of NLO Chromophores
Authors: Raposo M. Manuela M. , Ferreira Ana M. , Belsley Michael , de Matos Gomes E. , Moura J.C.V.P.
Published: March 2009

The synthesis of 5-arylazo- substituted bithiophenes and their UV-visible,
solvatochromic and nonlinear optical properties (NLO) are described. In agreement with the
solvatochromic data and also with the second-order molecular NLO characterization, the new
donor-acceptor systems could find application as suitable solvatochromic probes and also as new
NLO materials.
Synthesis of Y3Fe5O12 via Thermal Decomposition of Polynuclear Coordination Compounds
Authors: Patron L. , Carp O. , Mindru I. , Marinescu Gabriela , Diamandescu L. , Reller Armin
Published: March 2009

The possibility of obtaining yttrium iron garnet (Y3Fe5O12, YIG) through thermal
decomposition of two coordination compounds with malate and gluconate anions as ligands,
(NH4)6[Y3Fe5(C4O5H4)6(C4O5H3)6]·12H2O and (NH4)6[Y3Fe5(C6O7H10)6(C6O7H9)6]·8H2O. A
mixture of simple oxides, namely Y2O3 and α-Fe2O3, orthorhombic ferrite YFeO3 and small
amounts Y3Fe5O12, is generated from the thermolysis of malate compound, while a clean Y3Fe5O12
is obtained from gluconate compound.
Study of SiGe Alloys with Different Germanium Concentrations Implanted with Mn and As Ions
Authors: Magalhães S. , Sobolev Nikolai A. , Abrosimov Nikolay V. , Alves Eduardo
Published: March 2009

In this work we studied the structural properties of SiGe alloys with different Ge molar
compositions co-implanted with manganese and arsenic ions. The ions were implanted at room
temperature to fluences of 1×1015, 5×1015 and 1×1016 cm–2 and energies of 170 keV (Mn) and 200
keV (As) in order to achieve the overlap of the implanted profiles. The alloys were studied with
Rutherford Backscattering/Channeling spectrometry (RBS/C) and X-ray Diffraction (XRD)
techniques. After implantation the implanted region (150 nm) turns into amorphous according with
RBS/C. The evolution of the lattice parameter was studied using XRD. The annealing at 550°C
induces the recrystallization of the amorphous layer for the sample implanted with the lower fluence
and the full recovery is complete after annealing at 700°C. The samples implanted with higher
fluences did not reveal any noticeable recovery. The Mn and As profiles do not exhibit significant
changes during the annealing at 550oC.
Optical and Microstructural Investigations of Porous Silicon Coated with a-Si:H Using PECVD Technique
Authors: Prabakaran R. , Aguas Hugo , Pereira Luís , Elangovan E. , Fortunato Elvira , Martins Rodrigo , Ferreira Isabel
Published: March 2009

In the present work, the spectroscopic ellipsometry (1.5 - 5.5 eV) was used to investigate
the effects of current density induced microstructural variations and their influence on the electronic
states of as-prepared and a-Si:H coated porous silicon (PS). The pseudodielectric responses of the
low and high current densities (5 and 40 mA/cm2) were analyzed using a multilayer model within
the effective medium approximation. The FTIR investigation reveals the enhancement of surface
oxide (Si-Ox) layer with current density and the improvement of the Si-Hx band after a-Si:H
coating.
Spin Disorder Resistivity and Electronic Specific Heat of Gd4(Co1-xCux)3 Compounds
Authors: Seixas T.M. , Salgueiro da Silva M.A. , de Lima O.F. , Lopez J. , Braun Hans F. , Eska G.
Published: March 2009

In this work, we present a study of the spin disorder resistivity ( ρm∞) and the electronic
specific heat coefficient ( γ) in Gd4(Co1-xCux)3 compounds, with x = 0, 0.05, 0.10, 0.20, 0.30. The
experimental results show a strongly non-linear dependence of ρm∞ on the de Gennes factor which,
in similar intermetallic compounds, is usually attributed to the existence of spin fluctuations on the
Co 3d bands and its amplification by the thermal disorder of the Gd magnetic moments through the
Gd-Co exchange coupling. Using a novel combined analysis of ρm∞ and γ, we show, however, that
only electron band structure changes are involved in the anomalous behaviour of ρm∞ and that a
linear dependence of ρm∞ on the de Gennes factor is obtained when the variation of the effective
mass is properly taken into account.
Phase Separation of La0.70-xErxSr0.30MnO3 and its Effect on Magnetic and Magnetocaloric Properties
Authors: Amaral João S. , Reis Mário S. , Araújo João P. , Mendonça Tânia M. , Tavares Pedro B. , Amaral Vitor S. , Vieira Joaquim M.
Published: March 2009

Manganites of general formula ABMnO3 (where A is a trivalent rare-earth ion and B is a
divalent dopant) have interesting properties, namely colossal magnetoresistance and their
applicability as materials for active magnetic regenerators. La0.70Sr0.30MnO3 (LSMO) is a
ferromagnet presenting considerable magnetocaloric effect, with operating temperature TC ~ 370 K
and magnetic entropy variation comparable to pure Gadolinium. The high value of TC makes LSMO
unsuitable for room-temperature magnetic refrigeration applications, but by substituting La with the
high-magnetic moment ion Er, TC is lowered and total magnetic entropy increases. We have found a
limit of solid solubility of Er ions in LSMO, in samples prepared by either solid state or sol-gel
techniques in previous works [1], in accordance with other authors [2]. We now present a more
detailed study of this limit of solubility, with more samples prepared with Er substitution close to
the solubility limit and SEM microscopy clearly showing the changes in microstructure caused by
the formation of a secondary ErMnO3 phase, in accordance with x-ray diffraction data and TC
variation along the series. The magnetocaloric properties of the series are also presented, showing
the increase of Relative Cooling Power along the series, in applied magnetic fields up to 1 T.