bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the Second Phase on the Microstructure of Magnesium Alloys during Cyclic Extrusion Compression
Authors: Chen Yong Jun , Roven Hans Jørgen , Wang Qu Dong , Liu M. , Lin Jin Bao
Published: March 2009

Cyclic extrusion compression (CEC) is an effective severe plastic deformation (SPD)
process which can be used for fabricating ultrafine grained light materials such as magnesium alloys.
This method introduces three-dimensional compression and shear stresses and the process can be
repeated for a certain number of passes until the desired accumulated strain has been introduced. In
order to reveal the effect of second phases on the microstructure developed in magnesium alloys
during CEC, three different alloys (AZ31, AZ31-1wt.%Si and AZ91) were investigated after CEC 7
passes performed at 225°C. The experimental results show that the CEC process can effectively
refine the microstructures of these alloys and the mean grain size achieved is 1.3µm, 1.5µm and
1.4µm, respectively. It is revealed that the grain size, grain shape and grain boundary structures are
little affected by coarse phase Mg2Si but strongly affected by the fine phase Mg17Al12. The fine
phase Mg17Al12 seems to increase the relative grain misorientations, hence enhancing the formation
of high angle grain boundaries (HAGBs). It is expected that such changes are improving
mechanical properties, subsequent forming behavior and surface quality.
Microstructure and Texture of Mg-Based AZ Alloys after Heavy Deformation under Cyclic Strain Path Change Conditions
Authors: Pospiech Jan , Korbel Andrzej , Bonarski Jan T. , Bochniak Włodzimierz , Tarkowski Leszek
Published: March 2009

The effects associated with the change of the deformation path - such as the replacement
of homogeneous multi-slip by heterogeneous deformation and a decrease of global strain hardening
- have been utilised in the metal forming operation termed KOBO technology. In the case of
extrusion it consists in reversible, cyclic twisting of a billet under the extrusion force. The
technology enables extrusion of metals with very large deformation in one operation at low
temperature. A complex scheme of straining, large cumulated deformation and low temperature of
the process results in a fine grained microstructure of the extruded material (product). The new
technology requires detailed studies of the mechanism of the plastic deformation with the specific
geometry of the zone of metal flow during extrusion. Essential in these studies is the information on
the texture and microstructure in the deformation zone. The aim of this work is therefore to
disclose the deformation mechanisms on the basis of the observations of microstructure and texture
evolution in the zone of plastic flow of the extrudate.
Coarse grained polycrystalline billets of magnesium alloys AZ31 were extruded by KOBO at room
temperature and also by a conventional method at about 400°C. Methods of texture topography as
well as optical observations reveal the specific microstructure and texture in mezzo and micro scale
of heavily deformed material after extrusion. It is worth mentioning that the KOBO process leads to
compact and rather homogeneous extrudates even in the case of AZ alloys. These hexagonal metals
cannot be cold-formed to a high reduction with conventional techniques.
Evolution of Texture in Ultra-Fine Grained Ferrite through Warm-Rolling and Intercritical Annealing
Authors: Chowdhury Sandip Ghosh , Mahato B. , da Silva Hezio Rosa , Lourenço Gustavo Gonçalves , Santos Dagoberto Brandão
Published: March 2009

The ferrite grain size refining is the unique mechanism for increasing both mechanical
strength and formability of steels. Steel with an ultra-fine ferrite grained structure must show a good
relation between mechanical strength, ductility and toughness, while the low carbon content
enhances good welding characteristics. The objective of this work is to investigate the influence of
warm rolling on the evolution of texture in a microalloyed low carbon-manganese (0.11%C,
1.41%Mn, 0.028%Nb and 0.012%Ti) steel with ultra-fine grains produced through out quenching,
warm rolling, followed by sub and intercritical annealing. The evolution of restoration process -
recovery and recrystallization - was followed by optical and scanning microscopy. After subcritical
annealing, the microstructure was formed by spheroidal iron carbides and a ferritic recovered
matrix. Otherwise, after intercritical annealing, the microstructure was composed mainly by ultrafine
grain polygonal ferrite, MA (martensite-austenite) constituent and carbides. The mechanical
behaviour of the steel was evaluated using tensile tests. The mechanical properties have been
correlated with the evolution of texture in the ultra-fine grained ferrites.
Ultrafine Grained Low Carbon Steels Processed by Severe Plastic Deformation
Authors: Dobatkin Sergey V. , Odessky P.D. , Shagalina Svetlana V.
Published: March 2009

The structure, mechanical and functional properties of ultrafine-grained low-carbon steels
have been studied after severe plastic deformation (SPD) by high pressure torsion (HPT) and equalchannel
angular pressing (ECAP). It is revealed that HPT of low carbon steels at a temperature
below 0.3 Tm leads to the formation of nanocrystalline structure with a grain size of <100 nm or a
mixture of oriented substructure and nanograins. ECAP under similar conditions leads to the
formation of submicrocrystalline structure with a grain size of 200-300 nm. The initial martensitic
state compared with the initial ferritic-pearlitic state of the low-carbon steels results in formation of
finer structure after SPD and less intense grain growth upon heating, i.e., results in a higher thermal
stability. Low-carbon low-alloy steels after ECAP are characterized by high strength (UTS > 1000
MPa) and plasticity (EL = 10-15%). The high-strength state after ECAP is retained upon tensile test
testing up to a temperature of 500°C. The submicrocrystalline low-carbon steels after ECAP
processing and subsequent heating is characterized by an increased impact toughness at test
temperatures down to -40°C.
Strain Rate Sensitivity of 31Mn-3Al-3Si TWIP Steel with Partially Recrystallized Fine Grained Structure
Authors: Ueji Rintaro , Harada Kenji , Takemura Akihiko , Kunishige Kazutoshi
Published: March 2009

Strain rate sensitivity of the strength of TWIP (Twinning Induced Plasticity) steel with the
mixture of recrystallized fine grains and rolling-deformation microstructures was studied. The
31mass%Mn-3%Al-3%Si TWIP steel sheet was severely cold-rolled to a reduction of 92% and
subsequently annealed at various temperatures ranging from 600oC to 700oC in order to obtain the
partial recrystallized microstructure with various fraction of recrystallized microstructure. The 600oC
annealed specimen keeps similar morphologies as observed in the as-rolled structure consisting of
both the fine lamellar dislocation cell structure and the twin/matrix lamellar structure; whereas, in the
specimen annealed at 625oC or 675oC , the partially recrystallized fine grains (d~1µm) with a few
dislocations evolve. The volume fraction of recrystallized fine grains increases with increasing of the
annealing temperature while the mean diameter of the recrystallized grains is not changed largely. The
tensile deformation behaviors were measured at various strain rates ranging from 10-3sec-1 to 102sec-1.
The strength and elongation become smaller and larger, respectively, with increasing the fraction of
the recrystallized microstructure. The activation volume of dislocations becomes larger with
increasing the fraction of recrystallized microstructure.
A Comparative Study on Mechanical Properties of Al 7075 Alloy Processed by Rolling at Cryogenic Temperature and Room Temperature
Authors: Panigrahi Sushanta Kumar , Jayaganthan R.
Published: March 2009

The mechanical properties and microstructural characteristics of a precipitation
hardenable Al 7075 alloy subjected to rolling at liquid nitrogen temperature and room temperature
are reported in this present work. The Al 7075 alloy was severely rolled at cryogenic temperature
and room temperature and its mechanical properties were studied by using tensile tests and
hardness. The microstructural characterization of Al 7075 alloy were made using SEM/EBSD, TEM
and DSC. The cryorolled Al 7075 alloys have shown improved mechanical properties as compared
to the room temperature rolled Al alloy. The cryorolled Al alloy after 90% thickness reduction
exhibits ultrafine grain structure as observed from its TEM micrographs. It is observed that the
strength and hardness of the cryorolled materials (CR) at different percentage of thickness
reductions are higher as compared to the room temperature rolled (RTR) materials at the same
strain due to suppression of dynamic recovery and accumulation of higher dislocations density in
the CR materials.
Angular Extrusion of Double-Metal Ingot
Authors: Bonarski Jan T. , Pospiech Jan , Tarkowski Leszek , Kuśnierz Jan
Published: March 2009

Relatively high mechanical strength and simultaneously good plasticity of a crystalline
material are determined by the state of its internal structure, preferably nano- or ultra-fine grained
one. To achieve the above combination of properties, various manners of plastic deformation and
heat treatment are applied in practice. One of the most effective processes in this field is severely
plastic deformation, e.g. by the method of equal angular channel pressing (ECAP). During the
ECAP, favourable effects of grain fragmentation and the formation of specific orientation relations
can be attenuated by the process of structure recovery, especially, when the real temperature of
angular extrusion is elevated for physical or technological reasons.
An attempt to modify the ECAP technology was considered, to avoid the unfavourable temperature
effects and to increase at the same time the efficiency of manufacturing the ultra-fine structure of
material. Extrusion of dual-material (AZ31 + Al) ingot was performed at room temperature. As it
seems, the well known difficulties with plastic deformation of materials with hexagonal lattice
symmetry, like AZ31 alloy, have been decreased.
Both experimental and methodological aspects of the angular extrusion of the dual-material ingot
and chosen microstructure characteristics (texture, stress, morphology) are presented. On the basis
of the suggested modification, the text discusses an explanation of physical origins of the
microstructure evolution in the investigated material revealed by experiments.
Strain Rate Sensitivity of Ultrafine Grained Aluminium Alloy AA6061
Authors: Vevecka-Priftaj Aferdita , Böhner Andreas , May Johannes , Höppel Heinz Werner , Göken Matthias
Published: March 2009

The strain rate sensitivity of the aluminium alloy AA6061 has been investigated in a
conventional grain sized (CG) state and in two different ultrafine grained (UFG) conditions
processed by Equal Channel Angular Pressing (ECAP) for 2 and 6 passes at 100o C. Strain rate
jump tests in compression were performed at different temperatures and the strain-rate sensitivity
exponent m was determined. The tests were accomplished by microstructural investigations before
and after compression testing in CG and UFG conditions. It is shown that all UFG microstructures
exhibit strongly increased strain-rate sensitivity (SRS) compared to the CG state. The SRS increases
with increasing temperature and is more pronounced for the UFG material processed using 6 ECAP
passes. The microstructural investigations show a rather high stability of the grain structure for the
UFG conditions up to 250o C. The results are discussed with respect to the relevant deformation
mechanisms.
Thermal Stability of Severe Plastically Deformed VT-6 (Ti-6Al-4V)
Authors: Rack Henry J. , Qazi Javaid , Allard L. , Valiev Ruslan
Published: March 2009

The thermal stability of equal channel angular extruded VT-6(Ti-6Al-4V) has been
examined using micro-hardness, nano-hardness of the individual αand β phases backscattered
scanning (BSEI) and transmission electron microscopy (TEM). After straining to an equivalent total
equivalent of 6.5 samples were annealed for 1 h at temperatures between 175 and 800 o C followed
by water quenching. Micro and nano-hardness measurements showed an initial hardness increase,
the former rising to a maximum at 175°C, while the latter exhibited a maximum at 500°C. BSEI and
TEM analysis showed that these observations can be understood by considering the microstructure
changes occurring at different length scales. Annealing in the temperature range of 175 to 500°C
did not significantly alter the α and β particle size, while TEM showed that recovery and
continuous recrystallization occurred in the α phase, higher temperatures being required to activate
the recovery and recrystallization processes within the β phase. Finally at temperatures above 600°C
spheroidization and growth of the β phase occurred with the volume fraction of this phase
increasing from 15 pct at lower temperature to 25 pct at 800°C, an equi-axed α+ β microstructure
being observed at this temperature.
Magnetic Parameters of R2Fe14B Compounds with Nanograin Structure
Authors: Tereshina Irina S. , Burkhanov Gennadiy S. , Dobatkin Sergey V. , Chistyakov O.D. , Tereshina Evgeniya A. , Drulis Henry
Published: March 2009

High-purity compounds R2Fe14B (R = Y, Gd, Tb, Dy, Ho and Er) were prepared by arc
melting using rare-earth metals purified by vacuum distillation-sublimation. The compounds
R2Fe14B are single-phase and have well-defined directional structure. Nanocrystalline structure was
formed by severe plastic deformation of the samples by means of torsion for 5 turns on the
Bridgeman anvil under the pressure of 4 GPa at room temperature. The performed investigations of
magnetic properties of these compounds allowed us to obtain reliable quantitative data on the
intrinsic magnetic parameters, such as saturation magnetization, Curie temperature, the remanent
magnetization and coercive force. The enhancement of the remanent magnetization was observed
for R2Fe14B in nanocrystalline states compared with the crystalline samples due to the
intercrystalline exchange interactions.
Corrosion Characteristics of an Ultrafine-Grained Al-Mg-Si Alloy (AA6082)
Authors: Wielage Bernhard , Nickel Daniela , Lampke Thomas , Alisch Gert , Podlesak Harry , Darwich Samer , Hockauf Matthias
Published: March 2009

The corrosion behaviour of the aluminium alloy, AA6082, processed by equal-channel
angular pressing (ECAP) after different passes (route E, room temperature) was studied in
comparison to the coarse-grained counterpart. The results of the electrochemical investigations
(cyclovoltammetry; electrochemical impedance spectroscopy, EIS) are presented in correlation with
the microstructure before and after the corrosion examinations. Both, chemical (precipitations,
phases) and physical (dislocations, high-angle grain boundaries, grain size, low-angle grain
boundaries) inhomogeneities characterize the microstructure of this commercially used Al-Mg-Si
alloy. Results indicate an improved resistance against pitting of the ECAP material expressed by a
reduced pitting density of up to 50 % and lower pit depths. EIS measurements and microstructural
examinations (scanning electron microscopy, transmission electron microscopy, 3D topography
measurement) confirm that ECAP modifies the number, size and distribution of these
inhomogeneities, which leads to a more favourable corrosion behaviour.
The Protective Role of Poly(Borosiloxanes)-Derived Ceramics in Carbon Fiber Composites
Authors: Siqueira Renato Luiz , Pardini Luiz Claudio , Pagotto Yoshida Inez Valéria , Schiavon Marco Antônio
Published: March 2009

This work reports the synthesis and thermal characterization of poly(borosiloxanes)
(PBS) derived from methyltrietoxysilane (MTES) and vinyltriethoxysilane (VTES), aiming to use
these polymers as precursors of ceramic matrices for the protection of carbon fibers in ceramic
matrix composites (CMCs). The resulting materials exhibited better thermal stability than the
carbon fiber, especially the Cfiber/SiBCO composite derived of the methyltriethoxysilane (MTES)
system prepared with a B/Si ratio of 0.5. This study showed that poly(borosiloxanes) are promising
materials for the oxidation protection of carbon fibers, and consequently for thermal protection
systems.
Reactivity of Cork and Lignin for the Production of Activated Carbons
Authors: Carrott Peter J.M. , Ribeiro Carrott Manuela M.L. , Suhas Suhas , Mourão Paulo A.M. , Guerrero C.I. , Delgado L.A.
Published: March 2009

Activated carbons have been prepared by physical activation in CO2 of commercial byproduct
kraft lignin (as received, after de-ashing and after impregnation with NaCl) and natural
cork. The results obtained show that the presence of natural inorganic impurities increases the
reactivity of cork and lignin significantly and also results in limiting values for the micropore
volume and in widening of the micropore size. Pure de-ashed lignin is exceptionally non-reactive
but allows microporous activated carbons to be obtained which have very narrow micropore widths
of ~0.5-0.6nm. When the de-ashed lignin is impregnated with NaCl similar micropore volumes and
widths can be obtained but in a considerably shorter time (~30min instead of ~8h) which would
result in a considerable energy saving and is therefore a promising procedure for the production of
microporous activated carbons from low-cost kraft lignin.
Leaching Behaviour of Industrial Oxidic By-Products: Possibilities to Use as Neutralisation Agent in Bioleaching
Authors: Cunha M.L. , Gahan C.S. , Menad N. , Sandström Åke
Published: March 2009

In this study chemical leaching with sulphuric acid has been performed on 10 selected
oxidic by-products in order to determine their neutralising capacity. The ultimate aim with this work
is to replace the lime or limestone normally used in bioleaching operations to maintain pH at 1.5,
the optimum pH-level for bioleaching microorganisms, with oxidic by-products. The investigated
by-products includes three ashes from combustion for energy production, five slag samples from
ore and scrap based steelmaking, an EAF dust and mesa lime from a paper and pulp industry, slaked
lime (Ca(OH)2) was used as reference material. The neutralising potential of the by-products were
evaluated by leaching them with sulphuric acid and comparing the amount of acid needed to that of
the reference. Most of the by-products examined had good neutralisation potential and some had
even higher capacities than Ca(OH)2. Neutralisation kinetics were lower for some slag products due
to slow dissolution of some of the silicates present, but kinetics are considered good enough since
stirred tank bioleaching is a relatively slow process. Zinc recoveries from the zinc containing
materials were high, which thus is an additional benefit if these materials were to be used for
neutralisation in a bioleaching process for zinc recovery.
Textural Development of Activated Carbon Prepared from Recycled PET with Different Chemical Activation Agents
Authors: Cansado Isabel P.P. , Ribeiro Carrott Manuela M.L. , Carrott Peter J.M. , Mourão Paulo A.M.
Published: March 2009

Activated carbons (AC) were prepared from waste granulated Polyethyleneterephthalate
(PET) by chemical activation with phosphoric acid, sodium hydroxide and potassium hydroxide.
All AC were characterised by N2 adsorption at 77 K, and those prepared with H3PO4 had a narrow
pore size around 0.8 nm, those prepared with NaOH had a larger pore size higher than 1.52 nm and
those prepared with KOH presented a pore size varying between 0.66 and 1.58 nm. The results
suggest that H3PO4 and NaOH are not the most suitable activating agents for preparing AC with a
high pore volume from waste PET. The AC produced with KOH presented a very high porosity,
which passed through a maximum of 0.75 cm3g-1, due to an enlargement of the small micropores
with an increase of the carbonisation temperature.
New Eco-Friendly Gypsum Materials for Civil Construction
Authors: Eires Rute , Camões Aires , Jalali Saíd
Published: March 2009

The sustainable world’s economic growth and people’s life improvement greatly depend
on the use of alternative products in the architecture and construction, such as industrial wastes
conventionally called “green materials”. This paper concerns the main results of an experimental
work carried out with the objective of developing new composite materials based on gypsum and
incorporating waste material as granulated cork, a by-product of cork industry, and cellulose fibres,
a waste of paper industry. Such materials are intended to be used as composite boards for non
structural elements of construction, such as dry walls and ceiling. Cork (bark of the plant Quercus
Suber L), a substance largely produced in Portugal, is a material whose characteristics are of
considerable interest for the construction industry. It is regarded as a strategic material with
enormous potential by its reduced density, elasticity, compressibility, waterproof, vibration
absorption, thermal and acoustic insulation efficiency [1]. During the first stage of this research
work the gypsum binder and its properties were studied. Then, composites with mineral additions
(added to increase the waterproofing and resistance) were also developed and submitted to tests to
determine their physical and mechanical properties. In last stage, reinforced composites using
different industrial by-products have been developed. This paper will present the properties and the
manufacture methods used to produce the above mentioned eco-friendly composites that can ease
ways for using industrial wastes as new construction materials, with excellent inherent thermal and
acoustic properties.
Investigation of Crystallization in an Amorphous Cu-Based Alloy by X-Ray
Authors: Nagy E. , Janovszky Dóra , Svéda Mária , Tomolya Kinga , Varga L.K. , Sólyom Jenő , Roósz András
Published: March 2009

Recently one of the most significant research-field in the development of amorphous
alloys is the research of the Cu-based amorphous alloys. The Zr-based alloys developed earlier can
be replaced by the newly developed Cu-based alloys as the high price of the Zr-based alloys limits
their utilization in spite of their favourable properties. Production of Cu-based alloys having the
same or more favourite properties than Zr-based alloys is cheaper and this fact can promote their
increasing utilization. Cu-Zr-Ti and Cu-Hf-Ti alloy systems – they are Cu-based alloys – have
excellent mechanical properties. In this paper investigations of crystallization of amorphous
Cu44,25Zr36Ag14,75Ti5 powder produced by ball milling (these processes have not been investigated
yet according to the reference data) are described. In the course of investigation of the
crystallization process, samples were heated to a temperature of investigation by means of a DSC
equipment and the developed state was frozen by chilling. The investigation of the developed
structure and to identify the phases formed during heat treatment, X-ray diffraction method was
used.
Control of the Particle Size of Gold on Tin Modified Silica Support
Authors: Somodi Ferenc , Borbáth Irina , Hegedűs Mihály , Sajó István E. , Margitfalvi József L.
Published: March 2009

In this study we describe a two-step synthesis method for the preparation of gold
nanoparticles supported on tin modified silica. The key step of the preparation procedure is the
formation of surface grafted organotin complexes. The reduction of these surface species in a
hydrogen atmosphere resulted in both metallic (Sno) and ionic (Sn2+) forms of tin. These forms of
tin are capable to reduce gold from chloroauric acid solution forming gold nanoparticles with high
dispersion on the surface of silica. It has been found that the particle size of gold strongly depends
on the pH value of the gold solution and the presence or absence of ammonia.
Infrared Examination of Electrically Conductor Si3N4 Nanocomposites
Authors: Fényi Balazs , Platzer A. , Hegman Norbert , Balázsi Csaba
Published: March 2009

The Si3N4 is one of the leader high-tech ceramic nowadays. As a result of numerous
developments excellent mechanical properties of the material are increased by carbon additives. In
our previous investigation the electrical effect of the additives was examined. In our work thermo
radiation measurements were used by infrared camera technique on conductor Si3N4 ceramic
composites in infrared wavelength range. The thermal properties of the developed ceramic
composites were determined. This is not easy with the ordinary methods because of the fashioning
and geometrical parameters of the material. During the experiments the emissivity of our
composites was determined by infrared thermography measurements. Based on a theoretical
thermal conductivity model an evaluation method that allows a derivation of thermal conductivities
of special geometry conductive materials from results of infrared measurements was established.
The Examination of Weld Line Properties in Injection Molded PP Composites
Authors: Solymossy Balázs , Kovács József Gábor
Published: March 2009

This paper focuses on the effect of different fiber content on the mechanical properties of
specimens with and without weld lines. The effect of three different melt temperatures and holding
pressures were also investigated. For the experiments dumbbell shaped standard tensile specimens
with and without weld lines were injection molded from PP (TVK’s H116F homopolymer) and
short glass fiber (0, 10, 20, 30, 40 wt%). The mechanical properties of these composites were
determined by quasi-static (standard tensile testing) and dynamic (Charpy impact test) testing
methods and the corresponding weld line factors were calculated. The fracture surfaces were
analyzed with the help of scanning electron microscopy (SEM). From the results of the tensile and
Charpy-impact tests, it was ascertained that the temperatures and the holding pressures during
injection molding did not affect the tensile and impact properties, but fiber length had a major
impact on the mechanical properties of this specific composite. By increasing the fiber content, the
tensile strength increased until a peak and declined after. Whereas the impact resistance decreased
by the increasing fiber content in the whole examination window. Comparing the weld lined and
weld line free specimens, it was concluded that weld lines did significantly decrease the tensile
strength and impact properties due to the unfavorable fiber orientation beside the weld line which
was visualized by scanning electron microscopy.
Optimization of the Flame-Spraying Process and Improvement of Properties of a NiCrBSi Coating by Heat Treatment
Authors: Grum Janez , Bergant Zoran
Published: March 2009

The paper describes a study of adhesion strength of wear and corrosion resistant NiCrBSi coatings produced under different flame-spraying conditions on mild steel with 0.08 % carbon. Flame-sprayed coatings often show weak bonding strength to the substrate concerned; therefore, usability of a machine component treated in this way is limited only in case of lower mechanical loads on flame-spray coated parts, and at the same time it is subjected to wear and chemical influences. In order to measure adhesive strength of coatings, the standardized tensile adhesive test (TAT) was used. A Taguchi method was used to perform experiments and analyse results to find the most favourable combination of spraying parameters, i.e. surface roughness, preheat temperature, spraying distance, and type of oxy-acetylene flame, to provide a high-quality adhesive strenght with the substrate. Subsequent heat treatment of the NiCrBSi coating showed significant adhesion strength increase and improvement of microstructural properties.
Solid-State Transformation Produced by Laser Treatment and Mechanical Alloying of Fe-Ni-Cu(P) Powders
Authors: Herczeg Szabolcs , Takács János , Csanády Ágnes , Kakuk Gyula , Sólyom Jenő , Tranta Ferenc , Sajó István E. , Papp Katalin , Hargitai Hajnalka
Published: March 2009

The comparison of the phase transformations going on due to high energy ball milling (HEBM) and
produced by pressure-less Direct Metal Laser Sintering (DMLS developed by EOS company) was
carried out, by using an α-Fe, Ni and Cu3P powder mixture. It could be shown by X-ray
diffractograms (XRD) of the two type of products, that by mechanical alloying a similar phase
transformation occurs due to solid state reactions between the metal partners as in the case of laser
sintering, in a given range of laser scanning speed in a laboratory laser equipment. According to the
XRD evaluation the same metastable, γ-steel like phases were formed.
The Effect of Temperature and Composition to the Rheological Properties of Asphalt Pavements
Authors: Gömze László A. , Géber Róbert , Csányi Tamásné Judit
Published: March 2009

Ceramics, concretes and asphalt-mixtures are the most popular building materials in
Hungary, because of the highway programme of the government. In spite of their large popularity,
some of the mechanical properties of ceramics, concretes and asphalts are not investigated enough
till today. Particularly, there is no mechanical model usable to understand and explain the
rheological behaviours of these materials with different compositions of mineral raw materials.
It is well known, that the viscosity of viscous materials, viscoelastic materials, and viscoplastic
materials dynamically decreases, as the temperature increases. The decrease of viscosity by leaps
and bounds could be extremely dangerous in case of asphalt pavements in the range of 55 – 75 °C,
due to the crossing of cars on the low viscosity pavements which suffer inelastic deformation, as a
result.
Using a Rheo-tribometer instrument developed by L. A. Gömze and others, the authors have
investigated and tested asphalt mixtures with different composition of mineral raw materials, and
would like to reveal and review the dependence of the rheological properties of these pavements
against the temperature, and the intensity of the dependence.
Bulk Ultrafine-Grained Nickel Consolidated from Nanopowders
Authors: Gubicza Jenő , Bui Quang Hien , Fellah F. , Szász N. , Dirras Guy
Published: March 2009

Ultrafine-grained samples were consolidated from Ni nanopowders with the nominal
particle size of 50 and 100 nm by Hot Isostatic Pressing (HIP) and Spark Plasma Sintering (SPS).
The higher nickel-oxide content and the smaller grain size of SPS-processed samples result in a
higher yield strength at room temperature compared with HIP-processed specimen. It is found that
during compression the dislocation density increases while the twins decay in both samples,
indicating that the deformation is mediated mainly by dislocations. As a consequence of the higher
oxide content, the flow stress of the SPS-processed samples saturates at small strain values while
the HIP-processed specimen shows strain hardening even at the strain value of 0.35. After saturation
of the flow stress for SPS-processed samples the deformation is most probably mediated rather by
grain rotation or grain boundary-related mechanisms such as sliding and/or decohesion instead of
dislocation motion.
MOS Light Emitting Devices Based on Rare-Earth Ion Implantation
Authors: Rebohle L. , Skorupa Wolfgang
Published: March 2009

In this article we will give an overview of our work devoted to Si-based light emission
which was done in the last years. Si-based light emitters were fabricated by ion implantation of rare
earth elements into the oxide layer of a conventional MOS structure. Efficient electroluminescence
was obtained for the wavelength range from UV to the visible by using a transparent top electrode
made of indium-tin oxide. In the case of Tb-implantation the best devices reach an external
quantum efficiency of 16 % which corresponds to a power efficiency in the order of 0.3 %. The
properties of the microstructure, the IV characteristics and the electroluminescence spectra were
evaluated. The electroluminescence was found to be caused by hot electron impact excitation of
rare earth ions, and the electric phenomena of charge transport, luminescence centre excitation,
quenching and degradation are explained in detail.
Present Status of Deep UV Nitride Light Emitters
Authors: Khan Asif , Balakrishnan Krishnan
Published: March 2009

Ultraviolet light emitting diodes with emission wavelengths less than 400 nm have been developed using the AlInGaN material system. Rapid progress in material growth, device fabrication and packaging enabled demonstration of deep-UV light-emitting devices with emission from 400 to 210 nm with varying efficiencies. For high aluminum alloy compositions needed for the shorter wavelength devices, these materials border between having material properties like conventional semiconductors and insulators, adding a degree of complexity to developing efficient light emitting devices. This chapter provides a review of III-nitride based UV light emitting devices including technical developments that allow for emission in the ultraviolet spectrum, and an overview of their applications in optoelectronic systems.
The Effect of Niobium Content on the Curie Temperature and Microstructure of the Pr14Fe79.9-xCo16B6Nbx Alloys
Authors: Barbosa Luzinete Pereira , Takiishi Hidetoshi , de Faria Jr. Rubens Nunes , Rodrigues Daniel , Janasi S.R. , Stranguetti A.
Published: March 2009

This study reports the results of investigations carried out to determine the Curie
temperature (Tc) of various homogenized praseodymium-based alloys represented by the formula:
Pr14Fe79.9-xCo16B6Nbx (where x = 0, 0.01, 0.05, 0.1, 0.15, 0.50). The influence of niobium content
on the microstructure of these alloys has investigated. The Curie temperature decreased about 3 °C
for x = 0.5 at. %. It has been observed a remarkable grain refinement on the microstructure of the
Pr14Fe79.8Co16B6Nb0.1 alloy when compared to the niobium-free alloy (x = 0 at. %).
Ga-Modified Nanostructured ZnO: Characterization and Application in Dye-Sensitized Solar Cells
Authors: Gonçalves Agnaldo S. , Nogueira Ana Flavia , Davolos Marian R. , Masaki Naruhiko , Yanagida Shozo , Antônio Selma G. , Paiva-Santos Carlos de Oliveira
Published: March 2009

ZnO has received great attention in many applications due to its electronic and
optical properties. We report on the preparation of ZnO and gallium-containing ZnO
(ZnO:Ga) nanoparticles by the precipitation method. The nanoparticles have the wurtzite
structure and a high crystallinity. Gallium ions are present as Ga3+, as evidenced by the
binding energies through XPS. Porosity and surface area of the powder increased under
increasing gallium level, explained by the smaller particle size of ZnO:Ga samples compared
with ZnO. The estimated optical band gap of ZnO was 3.2 eV, comparable to ZnO:Ga.
Structural Evaluation of Mechanically Alloyed Ti-Nb Powders
Authors: Giffoni Y.A. , Ramos Erika Coaglia Trindade , Sandim Hugo Ricardo Zschommler , Pacheco M.T.T. , Silva Gilbert , Ramos Alfeu Saraiva
Published: March 2009

This work discusses on the structural evaluation of mechanically alloyed Ti-Nb powders.
The Nb amount was varied between 20 and 50 wt-%. The milling process was carried out in a
planetary Fritsch P-5 ball mill under Ar atmosphere. The structural evaluation was conducted by
scanning electron microscopy, X-ray diffraction, and energy dispersive spectrometry. During ball
milling it was noted an excessive agglomeration of ductile Ti-Nb powders on the balls and vial
surfaces, and the final amount of remaining powders was then drastically reduced into the vials.
This fact was more pronounced with the increased Nb amount in starting powders. Typical lamella
structures were formed during ball milling, which were refined for the longest milling times, and
fine and homogeneous structures were formed in Ti-Nb (Nb=20-50wt-%) powders. XRD results
indicated that the full width at half maximum values of Ti peaks were continuously increased while
that the crystallite sizes were reduced for longer milling times due to the severe plastic deformation
provided during ball milling of Ti-Nb powders. However, the EDS analysis revealed the presence of
Nb-rich regions in Ti-Nb powders after ball milling. The critical ball milling behavior of ductile Ti-
Nb powders contributed for reducing the yield powder and increasing the structural heterogeneity.
Structural Evaluation of Ti-22.2Si-11.1B Powders Milled with PCA Addition
Authors: Silva Gilbert , Ramos Erika Coaglia Trindade , da Silva N.S. , Ramos Alfeu Saraiva
Published: March 2009

A large amount of the Ti6Si2B compound can be formed by mechanical alloying and
subsequent heat treatment from the elemental Ti-22.2at%Si-11.1at%B powder mixture, but the
yield powder after ball milling is reduced due to an excessive agglomeration of ductile particles on
the balls and vial surfaces. This work reports on the structural evaluation of Ti-22.2at%Si-11.1at%B
powders milled with PCA addition, varying its amount between 1 and 2 wt-%. The milling process
was carried out in a planetary ball mill under argon atmosphere, and the milled powders were then
heated at 1200oC for 1h under Ar atmosphere in order to obtain equilibrium structures. Samples
were characterized by X-ray diffraction, scanning electron microscopy, and thermal analysis.
Results revealed that the PCA addition reduced the excessive agglomeration during the ball milling
of Ti-22.2at-%Si-11.1at-%B powders. After heating at 1200oC for 1h, the Ti5Si3, Ti3O and/or Ti2C
phases were preferentially formed in Ti-22.2at%Si-11.1at%B powders milled with PCA addition,
and the Ti6Si2B formation was inhibited.
Viscosity Measuring Methods for Feedstocks Directly on Injection Molding Machines
Authors: Gornik Christian
Published: March 2009

There are various methods for testing the viscosity of MIM feedstocks and described in
the literature, e.g. melt-indexer, capillary viscosimeter, etc. Typical factors taken into consideration
for choosing a proper method for feedstock characterization are the costs and the time needed for
measuring. The paper presents three methods which have been developed to check the feedstock
consistency directly on the injection molding machine. The first method is based on a slit-die
rheometer. The second method considers the energy which is needed for conveying the melt inside
of the plastification unit. And the third method is similar to a melt indexer but also in this case the
measurement is done directly on the injection molding machine. These novel methods are suitable
to detect inconsistencies in feedstock preparation.
Ti-13Nb-13Zr Foams for Surgical Implants
Authors: Henriques Vinicius André Rodrigues , Galvani Eduardo T. , Cairo Carlos Alberto Alves , Taddei Elisa B.
Published: March 2009

The use of titanium and its alloy as biomaterial is increasing due to their low
modulus, superior biocompatibility and enhanced corrosion resistance when compared to
more conventional stainless steel and cobalt-based alloys. Ti-13Nb-13Zr is a titanium alloy
specifically developed for surgical implants. In this work, highly porous titanium foams, with
porosities above from 50%, are reached using an efficient powder metallurgical process,
which includes the introduction of a selected spacer into the starting powders. Samples were
produced by mixing of initial metallic powders followed by uniaxial and cold isostatic
pressing with subsequent densification by sintering. The samples presented a Widmanstättenlike
microstructure in an open cellular morphology with pore size between 200-500 μm.
Mechanical Properties of Two MIM Processed Nickel-Based Superalloys
Authors: Nobrega Bernardo N. , Eberle Tiago , Ristow Waldyr
Published: March 2009

A PADS (Plasma Assisted Debinding and Sintering) reactor developed by Lupatech S.A.
has been employed to MIM process two Ni-based superalloys under Argon, at temperatures in the
1280 -1310 °C range, and for 2 to 3 hours. Both materials have chemical compositions similar to that
of standard Nimonic® 90 but differ considerably in their powder characteristics. One type of powder
was gas-atomized whereas the other was water-atomized. Samples of both materials in as-sintered
states as well as subject to different HIP and heat treating conditions have been characterized
mechanically in tensile tests and by HV measurements. The best overall results are attained by the
water-atomized material sintered at lower temperatures. The PADS processing of these superalloys
shows marked advantages over more conventional PM processing technologies. These results are
particularly relevant to the development of turbine components for the automotive and aerospace
industries.
Pressure Aided Sintering of Ultrafine Powders of WC with Addition of Co
Authors: Borges L.H.F. , Oliveira H.C.P. , Guimarães R.S. , Kobayashi T. , Filgueira Marcello
Published: March 2009

Hardmetal alloys are processed by liquid phase sintering, which consist of one refractory
carbide, embebided in to a tough matrix of Co. These alloys extensively are used in applications
that demand abrasion resistance and high hardness. The present work has as objective to analyze the
sintering of ultrafine powders of tungsten carbide (WC) with the addition of 10%wtCo. The alloys
had been prepared by using high pressure and high temperature technique. The sintering of the
WC/10%pCo alloy was processed at the 3, 4 and 5 GPa, in temperatures of 1300,1400 and 1500°C,
during 2 and 4 minutes. The analysis was made by microstructure, densification, structure, Vickers
hardness and fracture toughness. The best results was density = 98.9%, hardness HV30 =10,77GPa
and fracture toughness KIC = 15,57 MPa.m1/2.
Processing and Microstructural Characterization of Porous Alumina-Zirconia Ceramic Using CMC and PVC
Authors: Hirschmann Ana Coh O. , Nono Maria do Carmo de Andrade , Riehl R.R. , Silva C.R.M.
Published: March 2009

Porous materials are of significant interest due to their wide application in catalysis,
separation, lightweight structural materials, biomaterials and other areas. Porous ceramics are
produced within a wide range of porosities and pore sizes depending on the application intended.
Porosity and pore size distribution can be carefully controlled by the choice of organic composite
and the amount added. The material may have two types of pores: open and closed pores. The open
pores, also called interconnected pores, are those which are in contact with the external surface of
the material, being very useful for the manufacture of ceramic filters. A high number of closed pores
are important for the manufacturing of materials used in thermal applications. There are many
methods for obtaining porous ceramics, in general consisting in adding to the ceramic matrix
organic particles, which volatilize during the first heat-up. The objective of this study was to
produce ceramic composite nanostructure of alumina and yttria stabilized zirconia (Y-TZP) with
micrometric pore sizes. The effects of ZrO2 additions in the mechanical properties of Al2O3 have
been intensively investigated, due to the possible increase of the mechanical strength of this
material. The organic particles used to create the pores were CMC and PVC. The microstructure of
the porous ceramic samples obtained was evaluated considering the degree of sinterization of the
nanoparticles, pores formation, porosity, specific surface of the pores and the distribution of the
interconnecting pores.
Comparative Study on Turning CI and CGI Using Silicon Nitride Cutting Tools
Authors: Souza José Vitor C. , Nono Maria do Carmo de Andrade , Silva Olivério Moreira Macedo , Ribeiro M.V.
Published: March 2009

There has been a great interest for improving the machining of cast iron materials in the
automotive and other industries. Comparative studies for tool used to machine grey cast iron (CI)
and compacted graphite iron (CGI) on dry machining were also performed in order to find out why
in this case the tool lifetime is not significantly higher. However the machining these materials
while considering turning with the traditional high-speed steel and carbide cutting tools present any
disadvantages. One of these disadvantages is that all the traditional machining processes involve the
cooling fluid to remove the heat generated on workpiece due to friction during cutting. This paper
present a new generation of ceramic cutting tool exhibiting improved properties and important
advances in machining CI and CGI. The tool performance was analyzed in function of flank wear,
temperature and roughness, while can be observed that main effects were found for tool wear, were
abrasion to CI and inter-diffusion of constituting elements between tool and CGI, causing crater.
However the difference in tool lifetime can be explained by the formation of a MnS layer on the
tool surface in the case of grey CI. This layer is missing in the case of CGI.
Combustion Synthesis of NiO/YSZ Composite
Authors: Yoshito Walter Kenji , Scapin Marcos A. , Ussui Valter , Lazar Dolores Ribeiro Ricci , Paschoal José Octavio Armani
Published: March 2009

Nickel oxide-yttria stabilized zirconia (NiO-YSZ) anode materials were synthesized by
combustion process involving metal nitrate-urea decomposition. The precursor was heated to
evaporate water undergoing dehydration, and then the mixtures froth and swell. Further heating
produces large amounts of gases that ignite at ambient atmosphere. Different nitrate/urea initial
molar ratios were employed in order to investigate the influence of the reaction temperature in the
physical characteristics of the powder composite. The flame temperature was measured by infrared
optical pyrometer. The combustion was rapid and self-sustaining, with flame temperatures ranging
from 870 to 1330°C. The as-synthesized powders were uniaxially pressed and sintered in air.
Powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy
(SEM), helium picnometry for density measurements and gas adsorption technique (BET). The
ceramic samples were evaluated by SEM and Archimedes density measurements.
The Hydration of Magnesium Phosphate Cements: Effect of Powder Characteristics on the Reaction Kinetics
Authors: Arlete Carvalho M. , Segadães Ana M.
Published: March 2009

The setting reaction of magnesium phosphate cements starts with water addition to a
mixture of ammonium phosphate and magnesium oxide, is very fast and takes place at room
temperature (cold setting). Literature shows that controversy is still going on about the reaction
mechanism, hence, about the effect on the setting time of factors such as the water/cement ratio or
the magnesia specific surface area. This work is focused on the magnesia powder characteristics,
which were varied by calcining MgO at temperatures ranging from 900 to 1050°C, for periods of 30
to 60 min. Cement pastes were obtained by mixing MgO and diammonium phosphate with water
and setting aids. The pastes were left to set in air and were characterized in terms of mineralogical
composition (XRD) and microstructure (SEM). The results obtained show how the combined effect
of the magnesia characteristics can be used to control the workability and adjust the setting time.
Bactericide Effect of Powder Glasses Submitted to Na+/Ag+ Ionic Exchange in Ionic Media Containing Different Concentration of AgNO3
Authors: Fiori M.A. , Paula M.M.S. , Angioletto Elidio , Fiori J. , Santos M.F. , Riella Humberto Gracher
Published: March 2009

This work presents preliminary results of powder glasses with bactericide effect obtained by ionic
exchange between sodium ions, present in glass composition, and silver ions, present in the ionic exchange
medium. The powder glass was submitted to ionic exchange in ionic medium containing different
concentration of silver species. The results showed a bactericide effect dependence on AgNO3 concentration
in the ionic medium. Agar Diffusion Test on Escherichia coli bacteria, EDS analyses was applied to the
samples; the results showed there is a critical concentration of silver ions incorporated in the powder glass
and a limit to bactericide effect. The tests and analyses reveled that 6 wt% of AgNO3 in ionic medium was
the critical concentration.