bluuebunny/crossref_metadata_2025 huggingface dataset:
Room-Temperature Short-Range Ordering in Fe-Si Alloys Observed by Internal Friction
Authors: González Fernando , Ruiz Daniel , Houbaert Yvan
Published: March 2009

Research performed at Ghent University, regarding new production methods for
electrical steel, has shown that high silicon steel suffers an ageing phenomenon at room
temperature. Recent studies carried out by the same group using different analysis techniques
(Mossbauer spectroscopy, neutron diffraction, etc) brought to light a probable process of ordering
towards the D03-structure, which is responsible for the observed low ductility during cold rolling
and makes the processing of steel extremely difficult. In addition, the Si-steels become more brittle
as the delay time between hot and cold rolling is increased.
Frequency dependent internal friction (FDIF) studies were performed on different Fe - Si alloys
with a Si content varying from 3.73 at. % to 8.7 at. % immediately after several thermal treatments
and compared with ultra-low carbon steel. The evolution of relaxation peaks during the IF
measurements, performed at constant room temperature, helps to understand the ageing
mechanisms. Three processes have been observed: firstly, as expected, addition of Si reduces the
carbon Snoek peak. Secondly, a peak associated to C - Si is formed. Thirdly, a low frequency peak
associated with Zener relaxation (Si atom pairs) appears for a content of approximately 3.77 wt. %
Si. The two latter peaks decrease with ageing time and in the case of the Zener peak there is a
notable displacement to higher frequencies with a small increase of the Si content. The reduction of
the peaks during the ageing after annealing is more noticeable in quenched specimens than in air
cooled ones, and in furnace cooled specimens the reduction is even smaller, indicating that the
process is really an ageing phenomenon.
Room temperature short-range ordering might explain both the lowering of the Zener peak and
the observed macroscopic embrittlement.
Solid State Transformations in Cu/In-48Sn/Cu Diffusion Soldered Interconnections
Authors: Wojewoda Joanna
Published: March 2009

Paper describes solid state phenomena occurring during the formation of interconnections
intended to the electronic industry. Diffusion soldering technology is an undemanding and
functional tool to use when the growth of intermetallic phase(s) is desired and controlled in order to
obtain the joint consisted solely of an intermetallic phase. Scanning and transmission electron
microscopy investigations of the microstructure and sequence of appearance of the intermetallics
within the joined area are discussed. The diffusion path describing the chemical composition
changes across the interconnection was found to correlate with microstructure transformations. The
growth kinetics of the δ′[Cu41(Sn,In)11] phase was determined in the temperature range of 300 –
350 °C.
Solid Phase’s Transformations in Boron Carbide Based Composites during Heat Treatment
Authors: Kommel Lembit A. , Kimmari Eduard
Published: March 2009

Lightweight B4C/Al composites were produced from powders of boron carbide and
aluminum by self-propagating high-temperature synthesis (SHS). The effects of postdensification
heat treatment at different temperatures and environmental conditions on phase transformations and
properties evolution were studied. Heat treatment processing that followed the synthesis was applied
using low heating rate in temperature range from 400°C up to 1500°C. An interconnected
multiphase (B4C, Al3BC, and c-BN) microstructure was produced in composite as a result of heat
treatment at temperatures below 1080°C. The formation of hard and brittle reaction products (AlN,
AlB2, Al4C3, and Al8B4C7) at temperatures above 1150°C causes decrease in bending strength and
increase in resistance to unlubricated sliding wear.
Assessment of Heterogeneity of Welded Joint of Two Different Metals by Modeling of Diffusion of Substitution Elements
Authors: Řeháčková Lenka , Kalousek Jaroslav , Dobrovská Jana , Dostál Zdenek , Stránský Karel
Published: March 2009

The paper presents original methodology for assessment of heterogeneity of welded joint by measurement of concentration profiles of substitution elements in three straight lines in a plane perpendicular to the weld interface. The weld joint is formed by low-alloyed CrNiMoV steel and low-alloy silicon steel. Three concentration profiles are evaluated by modeling of diffusion based on solution of the 2nd Fick’s law. Primary goal of evaluation consists in assessment of chemical heterogeneity in the narrow area on both sides of the weld joint on the basis of their mutual position. Experimental data are optimized by original adaptation of the Levenberg–Marquardt’s algorithm of non-linear regression. Modeling comprises also determination of diffusivities and graphical representation of their temperature dependencies. The paper deals with diffusion of silicon as an example of many other investigated elements.
A Semi-Empirical Parameterization of Interatomic Interactions Based on the Statistical-Thermodynamic Analysis of the Data on Radiation Dif-fraction and Phase Equilibria in F.C.C.-Ni–Fe Alloys
Authors: Bokoch S.M. , Tatarenko Valentin A.
Published: March 2009

Using both the statistical-thermodynamics methods within the scope of the selfconsistent field approximation and the diffraction data on coherent (or diffuse) scattering of X-rays (or thermal neutrons) from (dis)ordered f.c.c.-Ni–Fe alloys of various compositions, the estimation of interatomic interactions (including their magnetic contribution) and their temperature– concentration dependences were obtained. Based on the static concentration-wave representation, the expressions for configuration free energies of L12-Ni3Fe-type permalloy, L10-NiFe-type elinvar and L12-Fe3Ni-type invar were analyzed, considering explicit expressions for configuration entropies of atomic and magnetic subsystems with their configuration internal energies. Phase diagram of a system at issue was plotted within the field of the presence of f.c.c.-Ni–Fe alloys; their phase boundaries, equilibrium (static) properties near critical points (order parameter, etc.), and possible microstructures developed by composition-controlled magnetic transitions and/or order–disorder constant-composition solid–solid phase transformations were discussed. The obtained results were compared with available experimental data.
A Short Review of Shape Memory Alloys Thermomechanical Models
Authors: Lexcellent Christian , Gibeau Elie
Published: March 2009

At first, some comments are made concerning the capacity of prediction of the microstructure for shape memory alloys by the Crystallographical Theory of Martensite. Secondly, the basic foundations of the phenomenological modeling of shape memory alloys behavior at the macroscopic scale are given. A special attention is devoted to the yield surface of phase transformation initiation in the stress space and its convex dual: the set of effective transformation strains in the strain space.
Stress Impact on Reactive Diffusion in Nano-Structures of Spherical Symmetry
Authors: Ene C.B. , Nowak C. , Schmitz Guido
Published: March 2009

To investigate the influence of stress on reactive diffusion, a remarkably clear experiment has been designed. Thin film Al/Cu/Al and Cu/Al/Cu triple layers are deposited on curved substrates of 25 nm radius and investigated by atom probe tomography. Due to the specific geometry, the excess volume of the reaction product induces compressive and dilatational stress on opposite sides of the product layer, even in the case of semi-coherent or incoherent interphase boundaries. The resulting stress gradient leads to additional driving force, which accelerates or decelerates the reaction rate in dependence on the stacking sequence of the layer material. By quantitative analysis, the induced level of stress can be quantified from the modified growth rate of the product.
Effects of Temperature and Strain Rate on the Evolution of Thickness of Transformed Adiabatic Shear Band
Authors: Wang X.B.
Published: March 2009

The coexistent phenomenon of deformed and transformed adiabatic shear bands (ASBs) is analyzed using Johnson-Cook model and gradient-dependent plasticity for heterogeneous ductile metal material. The size of deformed ASB is described by the internal length reflecting the heterogeneity of material. Microstructural effect leads to a nonuniform distribution of temperature rise in deformed ASB. When the peak temperature in deformed ASB exceeds the transformation temperature, a transformed ASB appears at the center of deformed ASB. With a decrease of flow shear stress, the width of transformed ASB increases until its upper bound, i.e., the size of deformed ASB, is reached. The effects of initial temperature and strain rate on the occurrence of transformation, evolution of the thickness of transformed ASB, distributions of local temperature and plastic shear deformation in ASB are investigated. Lower initial temperature results in higher peak shear stress, later occurrence of shear strain localization, lower shear stress when transformation occurs, later occurrence of transformation, thinner transformed ASB, lower peak temperature in ASB, and lower value of local plastic shear deformation in the boundaries of transformed ASB. At higher strain rates, the transformed ASB is wider; the peak temperature in ASB is higher; the value of local plastic shear deformation in the boundaries of transformed ASB is higher; the flow shear stress that corresponds to transformation is higher; earlier occurrence of transformation and higher peak shear stress will be expected.
Hydrogen-Induced Phase Transformations in Mg-Ni Alloys
Authors: Novák Pavel , Vojtěch Dalibor , Knotek Vítězslav , Šerák Jan , Fabián Thomáš
Published: March 2009

Hydrogen is suggested as a promising fuel of the near future for the utilization in automotive and mobile applications. Therefore, safe and effective hydrogen storage systems need to be developed. One of the possibilities, suitable especially for mobile applications, is the storage of hydrogen in the form of light-metal hydrides. In this work we studied microstructure and hydrogen absorption and desorption kinetics in selected Mg-Ni alloys. Hydrogen saturation was carried out by the cathodic polarization in alkaline water-based solution. It was confirmed that hydrogen could be stored in the Mg2Ni intermetallic phase forming Mg2NiH0.3 phase using this technology. MgH2 hydride is also formed when the temperature of 90 °C is applied. The total content of hydrogen in the material after saturation is approx. 0.7 wt. % according to the thermogravimetry analysis. This low value is caused probably by the surface oxidation, blocking further hydrogen diffusion. Thermal hydrogen desorption tests showed that the Mg2NiH0.3 phase is able to release hydrogen even at temperatures lower than 100 °C.
Kinetics of Phase Transformations in Mg2Ni-H System
Authors: Čermák Jiří , Král Lubomir , David B. , Stloukal Ivo
Published: March 2009

Kinetics of hydrogen desorption from Mg2NiH4 was studied. Experimental material was prepared by two techniques – by melting and casting and by ball-milling and compacting into pellets. Experimental materials were hydrogen charged at elevated temperature and pressure. The pellets were charged in two different regimes resulting in structures with high fraction of twinned low-temperature phase LT2 and with low fraction of LT2. It was made an attempt to measure diffusion coefficients of hydrogen and its temperature dependence both in high-temperature (HT) and in low-temperature (LT) phases of Mg2NiH4. The measurement was carried out in temperature interval from 449 K to 576 K by the volumetric method. It was found that the LT2 slows-down the desorption rate considerably.
Atomistic Simulations of the Aluminum-Silicon Interfaces under Shear Loading
Authors: Noreyan Alice , Stoilov Vesselin
Published: March 2009

In the present study molecular dynamics simulations were carried out to investigate the
deformation of pure FCC aluminum and diamond cubic silicon interfaces under shear stress. A
second nearest-neighbor modified embedded atom method was used to describe the interactions
between Al-Al, Si-Si and Al-Si atoms. The critical shear stress (CSS) was determined for various
Al/Si and Al/Al interfaces with different alignments and orientations. Structural analyses show that
the deformation is localized at approximately 10 Å thickness of the interface in Al. The critical
shear stress of Al/Si interface was found to be significantly lower than the critical tensile stress due
to the partial stick-slip in sliding. In addition, it has been proven that there is no explicit relationship
between shear and tensile critical stresses, which is fundamentally different from isotropic
materials, where the shear stress is about half of the tensile stress. The misorientation has a dramatic
effect in reducing shear stress at Al/Al interfaces, but has no effect on CSS in Al/Si. As a result, it
was shown that introducing Si improves the strength of the interface (and the composite material in
general) for different grain orientations.
Ab-Initio Calculation for the Study of Nano Scale Silicon Based Device Structure
Authors: Chakraborty Sudip , Sashidhar G. , Ghaisas S.V. , Sundararajan V.
Published: March 2009

Motivated by the possibility of scaling down of various electronic devices at the nanolevel,
we have chosen a simple p-n junction like device in silicon structure. An aggregation of
seventy-eight silicon atoms, passivated by oxygen is considered. We compute the electronic
structure of such a cluster and then the density of states and the optical spectra for this aggregate are
compared with a modified one. The modification is introduced by substituting phosphorus and
boron atom within this cluster of silicon atoms in both sides in order to make a p-n junction like
situation. A variant of this p-n junction like structure is introduced by adding a layer of oxygen
between the phosphorus and boron regions. Comparison of the electronic structures of all these
systems reveals several interesting properties.
Molecular Dynamics Simulation of Nanocrystalline Tantalum under Uniaxial Tension
Authors: Pan Zhi Liang , Li Yu Long , Wei Qiu Ming
Published: March 2009

Using molecular dynamics (MD) simulation, we have investigated the mechanical
properties and the microstructural evolution of nanocrystalline tantalum (NC-Ta, grain size from 3.25
nm to ~13.0 nm) under uniaxial tension. The results show the flow stress at a given offset strain
decreases as the grain size is decreased within the grain size regime studied, implying an inverse
Hall-Petch effect. A strain rate sensitivity of ~0.14, more than triple that of coarse-grain Ta, is derived
from the simulation results. Twinning is regarded to be a secondary deformation mechanism based on
the simulations. Similar to nanocrystalline iron, stress-induced phase transitions from body-centered
cubic (BCC) to face-centered cubic (FCC) and hexagonal close-packed (HCP) structures take place
locally during the deformation process, The maximum fraction of FCC atoms varies linearly with the
tensile strength. We can thus conclude that a critical stress exists for the phase transition to occur. It is
also observed that the higher the imposed strain rate, the further delayed is the phase transition. Such
phase transitions are found to occur only at relatively low simulation temperatures, and are reversible
with respect to stress.
Electrospray Nanocoating of Microfibres
Authors: Jaworek A. , Krupa A. , Sobczyk A.T. , Lackowski M. , Czech T. , Ramakrishna Seeram , Sundarrajan S. , Pliszka Damian
Published: March 2009

The paper presents experimental results of electrospray deposition of nanopowder onto
microfibers. The process is designed to form fibrous filters with an enhanced collection efficiency
in the submicron range by covering the fabric with a catalytic material. Polyamide fibres were
coated with Al2O3, ZnO, MgO, or TiO2 nanoparticles. The structures obtained were porous at the
nanometer scale which increased the total surface area of the catalyst.
The Effect of Grain Size Distribution on the Mechanical Properties of Nanometals
Authors: Tengen T.B. , Wejrzanowski Tomasz , Iwankiewicz R. , Kurzydlowski Krzysztof Jan
Published: March 2009

Predicting the properties of a material from knowledge of the internal microstructures is
attracting significant interest in the fields of materials design and engineering. The most commonly
used expression, known as Hall-Petch Relationship (HPR), reports on the relationship between the
flow stress and the average grain size. However, there is much evidence that other statistical
information that the grain size distribution in materials may have significant impact on the
mechanical properties. These could even be more pronounced in the case of grains of the
nanometer size, where the HPR is no longer valid and the Reverse-HPR is more applicable. This
paper proposes a statistical model for the relationship between flow stress and grain size
distribution. The model considered different deformation mechanisms and was used to predict
mechanical properties of aluminium and copper. The results obtained with the model shows that
the dispersion of grain size distribution plays an important role in the design of desirable
mechanical properties. In particular, it was found that that the dependence of a material’s
mechanical properties on grain size dispersion also follows the HPR to Inverse-HPR type of
behaviour. The results also show that copper is more sensitive to changes in grain size distribution
than aluminium.
The Influence of the Initial State on Microstructure and Mechanical Properties of Hydrostatically Extruded Titanium
Authors: Topolski Krzysztof , Garbacz Halina , Pachla Wacław , Kurzydlowski Krzysztof Jan
Published: March 2009

Titanium was subjected to hydrostatic extrusion, a method of producing Severe
Plastic Deformation (SPD). The experiments were aimed at refining the microstructure of
the titanium in order to improve some of its mechanical properties. The effect of the initial
state of titanium on the process of extrusion process and the final product was
investigated. The results of these investigations are used to establish the optimum
conditions for the hydrostatic extrusion process and more easily selecting the initial
condition of the material according to the intended application of the extruded product.
Structural, Magnetic and Electronic Properties of Surface Oxidised Fe Nanoparticles
Authors: Przewoźnik Janusz , Tyliszczak T. , Rybicki D. , Żukrowski Jan , Szczerba W. , Sikora M. , Kapusta Czesław , Stepankova H. , Pacheco R.F. , Serrate David , Ibarra M.R.
Published: March 2009

A combined XRD, Mössbauer, SEM, STXM and NMR study of naturally oxidised, ball
milled iron powders is presented. The XRD patterns show the peaks of the bcc-Fe phase with the
line widths increasing with the milling time. This corresponds to a flattening of the crystallites, as
confirmed by SEM, and increased strain due to the accumulation of defects. The effect is consistent
with the variation of the Mössbauer line-widths with the milling time. Scanning Transmission Xray
Microscopy (STXM) measurements provided oxygen maps of the particles and revealed that the
dominant oxide in the nanometric oxide layer is magnetite. The 57Fe spin echo NMR study reveals a
dominant signal corresponding to a bcc-Fe core and a much weaker resonance corresponding to a
magnetite amount of less than 1%.
First Principle Investigation of Structural Properties of Potassium Doped Fullerene Clusters – Kn(C60)2
Authors: Sokół M. , Gburski Z.
Published: March 2009

First principle simulations for the nanosystems Kn(C60)2, (n = 1, 2) composed of two
fullerene (C60) molecules and one or two potassium (K) atoms have been undertaken. A very
effective delocalization of the 4s1 valence electron of potassium was observed, the potassium atom
in practice becomes an ion. The adsorption binding energy of potassium atom(s) is Ea = -
1.923 ± 0.04 eV, - 3.819 ± 0.04 eV for K(C60)2 and K2(C60)2, respectively. The reported large
values of adsorption energy should cause a significant change in electronic properties of alkali
doped fullerene clusters.
Preparation and Characterization of Polymer/Multi-Walled Carbon Nanotube Nanocomposites
Authors: Mohlala M. Sarah , Ray Suprakas Sinha
Published: March 2009

This paper describes the preparation, characterization and properties of nanostructured
composite materials based on poly(butylene adipate-co-polycaprolactam) (PBA-co-PCL)/multiwalled
carbon nanotubes (MWCNTs) and polycaprolactone (PCL)/MWCNTs. The
polymer/MWCNTs nanocomposites were prepared by mixing the polymers with various amounts
of MWCNTs using both solution and melt blending processes. The dispersion of MWCNTs into the
polymer matrix was analyzed by transmission electron microscopy (TEM) and the thermal stability
of the nanocomposites was studied by thermal gravimetric analysis (TGA). Differential scanning
calorimetry (DSC) was used to study the crystallization and melting behaviour of the polymer
matrices containing the MWCNTs.
Strategies for Re-Heating Steel Billets for Thixoforming
Authors: Behrens Bernd-Arno , Fischer Dirk , Rassili Ahmed
Published: March 2009

Inductive re-heating of billets is the state-of-the-art method to enable the desired liquid
fraction for thixoforming. In laboratory experiments the temperature might be directly controlled
since it is usually possible to apply thermocouples for temperature measurements. Due to technical
restrictions temperature measurements especially in the interior of a billet are difficult in industrial
heating processes. For this reason, thixoforming billets are heated without temperature monitoring
by using proven heating functions. Such functions are usually obtained by trial-and-error or on the
basis of FEA simulations. In both cases exhaustive experimental work is usually necessary. Moreover,
FEA simulations require thermo-physical material data that is difficult to obtain for industrial
relevant heating processes.
In this paper an alternative method of experimentally obtaining optimized heating functions by using
a fuzzy logic controller is introduced. Under steady-state environmental conditions this method
allows a quick and reproducible re-heating. The main advantages of the fuzzy logic based approach
are that no specific material data is required, system specific properties such as the efficiency have
not be explicitly determined and that the practical implementation could be realized with a minimum
of experimental work.
Compocasting of an Al-Si-SiCp Composite Using Powder Injection Method
Authors: Ghahremainian M. , NIROUMAND BEHZAD
Published: March 2009

In this work Al-7wt%Si-10wt%SiCp composites were produced by injection of the
reinforcement in the form of SiCp particles or a specially made particulate composite powder of
aluminum and SiCp into the melt of proper composition at a temperature corresponding to 10%
solid fraction. This paper presents the results of the investigation on the effects of reinforcement
addition form, reinforcement addition temperature, stirring speed and magnesium addition on the
incorporation and distribution of the reinforcement particles. The results showed that incorporation
of SiCp particles was considerably improved by their injection in the form of milled Al/SiCp
composite powder. Better particle wetting, improved particle dispersion and reduced particles size
were achieved by injection of milled Al/SiCp composite powder instead of SiCp powder.
Magnesium addition and high temperature injection were necessary for achieving good
incorporation. Reinforcement incorporation was improved by increasing the stirring speed up to 500
rpm, after which the incorporation decreased slowly.
Twin Roll Casting and Melt Conditioned Twin-Roll Casting of Magnesium
Authors: Bian Zan , Bayandorian I. , Zhang H.W. , Fan Z.
Published: March 2009

Recently, BCAST at Brunel University has developed a MCAST (melt conditioning by
advanced shear technology) process for conditioning liquid metal at temperature either above or
bellow the alloy liquidus using a high shear twin-screw mechanism. The MCAST process has now
been combined with the twin roll casting (TRC) process to form an innovative technology, namely,
the melt conditioned twin roll casting (MC-TRC) process for casting Al-alloy and Mg-alloy strips.
During the MC-TRC process, liquid alloy with a specified temperature is continuously fed into the
MCAST machine. By intensive shearing under the high shear rate and high intensity of turbulence,
the liquid is transformed into conditioned melt with uniform temperature and composition
throughout the whole volume. The conditioned melt is then fed continuously into the twin-roll
caster for strip production. The experimental results show that the AZ91D MC-TRC strips with
different thicknesses have fine and uniform microstructure. The strip consists of equiaxed grains
with a mean size of 60-70μm. The strip displays extremely uniform grain size and composition
throughout the whole cross-section. Investigation also shows that both TRC and MC-TRC processes
with reduced deformation are effective to reduce the formation of defects, particularly the formation
of the central line segregations.
Effects of T5 and T6 Heat Treatments Applied to Rheocast A356 Parts for Automotive Applications
Authors: Rosso Mario , Peter Ildiko , Villa R.
Published: March 2009

The correlation between the evaluation of the mechanical and of the fatigue behaviour of
the rheocast, T5 and T6 heat treated SSM A356 aluminium alloy with respect to the microstructures
of the component has been investigated. The study has been carried out on a suspension arm
injected in a rheocasting 800 tons plant in Stampal S.p.A. The new rheocasting is a process that
allows obtaining the alloys in a semisolid state directly from the liquid state, by controlled cooling
of the molten alloys. The resulting microstructures are very fine, free from defects and
homogeneous: these characteristics improve the mechanical properties of the alloys and specially
the response to cyclic stress, an important issue for a suspension component. After a preliminary
tensile test analysis, axial high frequency fatigue tests have been carried out at room temperature on
specimen cut out from the suspension arm to determine the Wöhler curve and the number of cycles
to failure. The results of this work allow a comparison of the effects of heat treatment process, T5 or
T6, on Semi-Solid components for industrial applications in the automotive field.
On the basis of these analysis the correlation between microstructure and mechanical performances
can be established.
Semi-Solid Extrusion of Complex-Shaped Steel Rods Using Ceramic Dies
Authors: Muenstermann Simon , Telle Rainer , Knauf Frederik , Hirt Gerhard
Published: March 2009

Isothermal semi-solid extrusion experiments using steel grade X210CrW12 as work material
were performed on an industrial forging machine. An improved and up-scaled tool design was
applied, based on the concept of self-heating ceramic dies tested in previous laboratory-scale studies
and allowing for die preheating temperatures of up to 1400°C.
Steel rods of complex cross sectional geometry were formed at low extrusion forces. Shape accuracy
of as-formed rods is accurate and metallurgical examination yields no evidence of liquid phase
separation. With a view on the intended industrial implementation construction of ceramic tools has
to be improved in order to avoid rupture of ceramic parts due to thermo-mechanically induced stresses
and to benefit from the advantages inherent to ceramics in metal forming.
Deposition of Oxides as Tool Protection for Large Thixoforming Dies by Using the Pulsed MSIP-PVD Process
Authors: Bobzin Kirsten , Bagcivan Nazlim , Immich Philipp
Published: March 2009

Oxide coatings offer great potential for their use in forming operations in the semi-solid
state. Advantages of these types of coatings are high resistance against abrasive wear, high hot
hardness and low thermal conductivity. Nevertheless deposition by pulsed Magnetron Sputter Ion
Plating-PVD for oxide coatings is quite challenging: deposition rates are low and insulating layers
on the target surface can cause arcing. On laboratory scale it was possible to deposit γ-Alumina
using PVD in a temperature range, where hot working steel can be utilized. The next important step
in the development towards an industrial application for larger forming tools is the upscaling
process to larger coating units. In this work the process development of oxide coatings on an
industrial coating unit for large tools was described. To increase adhesion of oxide top-layer
additional bond coats were applied. Different process parameters like oxygen content, total pressure
and substrate bias were varied, to improve the performance. The relationship between coating
properties and process parameters of the deposited films were characterized by X-Ray-diffraction,
Nanoindentation and Scanning Electron Microscopy (SEM). By using reactive pulsed PVD-process
it was possible to deposit γ-Al2O3 on large steel tools for semi-solid melt protection. The developed
coatings showed for thixoforging processes of X210CrW12 an extraordinary stability in field tests.
The lifetime of the permanent moulds was increased by using PVD thin film coatings as a tool
protection.
Thixoforming of Steel: A State of the Art from an Industrial Point of View
Authors: Cezard Pierre , Sourmail T.
Published: March 2009

Since the first research works in the end of 1980s on the semi-solid forming of steel, this
process has presented a great interest and a real industrial potential. Several research teams, all over
the world, have shown the feasibility of such a process. Working on the parameters which have an
influence on the process, they pointed out the "technical locks" which must be overcome to allow
industrialization of the process. A first and perhaps most important difficulty is the reliability of the
forming tools in an industrial production context. Much work has therefore been devoted to identify
ways to increase tools life. A second important point is the possibility to obtain sound
microstructure and satisfactory mechanical properties. This paper is a state of the art review on the
subject of the thixoforming of steel, restricted to forming of semi-solid reheated steel. Semi-solid
forming process carried out after partial solidification are therefore not covered. The reader
interested in such processes may refer to the review recently published by Hirt et al. [1].
The present review considers, in turn, the different steps of an hypothetical production line and their
particular challenges, from the raw material to the final product.
A Comparison of Measuring Devices Used to Prevent Wall Slip in Viscosity Measurements of Metallic Suspensions
Authors: Modigell Michael , Pape Lars
Published: March 2009

When analysing semi-solid metal alloys or any other suspension in rheometers a major
problem is related to wall slip effects which lead to an underestimation of the suspensions viscosity.
Using smooth rotating rods in rotational rheometry for analysing suspensions a thin particle free
layer of liquid is formed at the surface of the rod due to near-wall segregation. Thus, mainly the
viscosity of this layer is measured which is much lower than the one of the bulk phase. Kiljanski [1]
proposed a method for rotational rheometers to recalculate such measurements to get viscosity
values without slip effects. A device-related change to minimize wall slip is the use of rotating rods
with grooved surfaces. Therewith near-wall mixing is produced to destroy the particle free layer.
Alternatively, the use of multiple blade vanes is proposed in the literature to avoid wall slip. The
differences of the two measuring devices (grooved, vane) are discussed at the example of
measurements for a low melting tin-lead alloy in the semi-solid state. It is figured out whether a
vane geometry is also suitable to be applied for rheological measurements on metallic suspensions.
Reynolds’ Dilatancy and Shear Bands in Semi-Solid Alloys
Authors: Gourlay Christopher M. , Otarawanna Somboon , Meylan B. , Dahle Arne K.
Published: March 2009

This paper studies the conditions under which strain localisation occurs in partially solid
alloys and compares localisation in rheology experiments with features in the industrial processes of
Thixomolding® and high pressure die casting (HPDC). To study the fundamentals of localisation,
vane rheometry, modified to measure volumetric changes, is used to shear magnesium alloy AZ91
during solidification. Deformation is found to readily localise when the initial microstructure consists
of an assembly of crystals in contact. It is shown that such microstructures expand as they are sheared
due to Reynolds’ dilatancy, and that localisation takes the form of dilatant shear bands. A study of
microstructural features in industrial castings demonstrates that similar dilatant shear bands can form
during Thixomoulding® and HPDC.
Melt Conditioned Direct Chill Casting (MC-DC) of Wrought Al-Alloys
Authors: Haghayeghi Reza , Liu Yuan , Fan Zhong Yun
Published: March 2009

Melt Conditioned Direct Chill (MC-DC) casting is a new development for producing
high-quality billets and slabs. In the MC-DC process, liquid metal is continuously fed into a
MCAST (melt conditioning by advanced shear technology) machine, where the liquid metal is
subjected to high shear rate and high degree of turbulence provided by a twin screw mechanism at
temperatures either above or below the alloy liquidus, and the conditioned liquid metal is then fed
continuously into a Direct Chill (DC) caster to produce billets or slabs. The MC-DC process is
applicable to both Al- and Mg-alloys. In this paper we present our experimental investigations of the
effects of processing parameters on the microstructural and compositional uniformity of 5xxx and
7xxx series Al-alloys. It has been confirmed by our experiments that the MC-DC process can
produce billets and slabs with fine and uniform microstructure, uniform chemical compositions and
much reduced cast defects, such as porosity and cracks.
Microstructural Evolution of AZ91 Alloy Containing 3%Ca Prepared by Cooling Slope
Authors: Khosravani Ali , Aashuri Hossein , Davami P. , Narimannezhad A. , Foroughi A. , Kiani M.
Published: March 2009

Globulization of the grain refined AZ91 magnesium alloy with Ca on a cooling slope was
investigated. Dendritic morphology of the grains was transferred into round and well distributed
small particles as a result of grain-refinement effect of Ca in the alloy. Semi-solid holding of the
alloy was carried out at different temperatures to improve the spherecity of the globules. Results
show that, remelting at 540 °C for 30 min provides the best shape factor for the alloy. The study of
coarsening kinetic in this alloy showed lower growth rate alternative other research which used
same condition for produce semi-solid billet just in using Ca.
Evaluation of Surface Chemical Segregation of Semi-Solid Cast Aluminium Alloy A356
Authors: Govender Gonasagren , Möller Heinrich
Published: March 2009

In order for SSM forming to produce homogeneous properties in a casting, it is important
that there is a uniform distribution of the primary grains. Besides producing a sound casting free of
porosity, the amount of liquid segregation must be minimized. The surface liquid segregation
phenomenon was investigated on high pressure die cast (HPDC) A356 alloy. SSM slurries were
prepared using the CSIR Rheocasting System and plates of 4mm × 80mm × 100mm were HPDC.
The chemical composition depth profile from the surface was determined using optical emission
spectroscopy (OES) and glow discharge optical emission spectroscopy (GDOES). It was found that
a 0.5-1.0 mm eutectic rich layer existed on the surface of the alloy. The thickness of the segregation
layer depended on the location on the casting. It was found that this layer was insignificant close to
the gate of the casting but was relatively consistent over most of the plate. Although this
segregation layer did not impact on the bulk mechanical properties, hardness tests did reveal that
this region had significantly higher hardness values which may have a considerable impact on the
fatigue properties.
Development of Non-Dendritic Microstructure of Aluminum Alloy in Semi-Solid State under Ultrasonic Vibration
Authors: Wu Shu Sen , Zhao Jun Wen , Zhang Li Ping , An Ping , Mao You Wu
Published: March 2009

The effect of processing parameters on the semi-solid microstructure has been
investigated in the course of semi-solid slurry preparation of A356 Al alloy by ultrasonic vibration
method. The A356 melt in temperature of 630660°C was poured into a special metal cup, and
exposed to ultrasonic vibration at 20 kHz or isothermal holding for a certain time after vibration.
The results show that the semi-solid slurry with primary α-Al crystals smaller than 90 μm and an
average shape coefficient F S (SF was defined as SF4 A/L2P) above 0.5 could be prepared by
ultrasonic vibration for a time less than 144 s. In the isothermal holding period after a short time of
ultrasonic vibration, the average particle diameter increased with the increase of holding time, but
F S decreased at first, and then increased a little. It was discovered that ultrasonic vibration is a good
method to prepare semi-solid slurry with fine and relatively round primary crystals due to cavitation
and acoustic streaming effects.
Effect of Ultrasounds Treatment on Alloys for Semisolid Application
Authors: Pola Annalisa , Arrighini Alberto , Roberti Roberto
Published: March 2009

Semisolid metallic alloys are commercially produced by means of mechanical or
electromagnetic stirring. Among the mechanical devices, the rotating pin immersed in a solidifying
alloy seems to be easier to manage in industrial practice although it can induce some porosity,
depending on the shape of the pin.
As known, ultrasounds are mechanical waves which, when applied to liquid metals, increase the
number of solidification nuclei, so that the cast products show superior mechanical performances, as a
consequence of the finer grain structure.
In this paper the use of ultrasound waves applied to different alloys during solidification was studied
in order to obtain feedstock for semisolid die-casting application.
A dedicated ultrasound power unit, together with a proper sonicator pin, was designed and
manufactured by the authors and, subsequently, the effect of the ultrasonic treatment on the
microstructure of A356 aluminum alloy and ZA27 zinc alloy was investigated.
All the produced samples were characterized by metallographic analyses to measure the globule size
and shape factor, which are main criteria for thixo-microstructure assessment.
The results were compared to those obtained with traditional mechanical stirring, showing the higher
capability of ultrasound treatment in producing better semisolid microstructure.
An optimized combination of process parameters seems to be necessary to get a reasonable
thixotropic structure in treating ZA27 alloy.
Less severe production conditions are needed in the case of aluminum alloy, revealing the potentiality
of ultrasounds as an alternative treatment to traditional mechanical stirring, with the further advantage
of alloy degassing and grain refinement, without the use of expensive addictions (TiB2).
Trials were finally performed on a continuous casting pilot plant in combination with electromagnetic
stirring to produce semisolid billets.
Alloy Characterization to Adapt Steels to Thixoforming: Study of a High Chromium High Carbon Steel
Authors: Fraipont Celine , Lecomte-Beckers Jacqueline
Published: March 2009

This paper deals with the examination of the influence of alloying elements on the
thixoformability of a Cr steel. It focuses on the liquid fraction curves of different Cr steels with
modifications of composition. The effect of composition modifications was observed. The solid
fraction versus temperature has been obtained by a thermodynamics software (MTData) and by
Differential Scanning Calorimetry (DSC), limited to low heating rates. MTData permits to obtain
information on the influence of alloying elements, with the advantage of the possibility to change
the chemical composition very easily. The DSC tests determine the influence of the heating rate on
these curves.
FSI-Analysis of the MMC-Thixoforging Process Regarding the Rheology of the Aluminiumcast-Alloy AlSi7Mg0,3
Authors: Unseld Peter , Liewald Mathias
Published: March 2009

This paper illustrates investigations regarding the infiltration process of the thixotropic
cast-alloy AlSi7Mg0,3 into laminated fibre woven fabrics by Fluid-Structure Interaction Analysis
(FSI). As results of such FSI-Analysis on the one hand the kinematical behaviour of the
reinforcement due to the infiltration process on the macroscopic and microscopic level on the other
hand fluiddynamical effects of the regarded alloy are achieved. Thus in the run-up to timeconsuming
and cost-intensive experiments, informative bases like fluidic optimizing of the cavity or
the configuration and insertion of the reinforcement component can be numerically developed.
Furthermore a reliable prediction of transient permeability of the fibre fabric is possible, which
effects the infiltration process significantly.
Numerical input data such as rheological parameters characterizing the behaviour of partial
solidified alloys have been conducted. Therefor basic rheological tests of the aluminium cast-alloy
AlSi7Mg0,3, like `HYSTERESIS TESTS´, `SHEAR RATE JUMP TESTS´ and detection of `STATIC´ and
`DYNAMIC YIELD POINTS´ and the `DIFFERENTIAL STRUCTURAL PARAMETER´ have been conducted.
Furthermore `EVOLUTION OF VISCOSITY´ has been correlated with thermodynamical calculations
using ThermoCalc®. Finally the infiltration of a textile semi-finished part (carbon fibre fabric /
canvas bonding) by A356 is discussed as an example to demonstrate the feasibility of FSI-Analysis,
taking into account a two-way coupling between the interacting CSM- and CFD-Codes.
A One Phase Thermomechanical Model for Semi-Solid Thixoforming
Authors: Koeune R. , Ponthot Jean Philippe
Published: March 2009

In order to model thixoforming processes, previous papers presented a thermomechanical
one-phase modelling. This first version of constitutive model revealed several
limitations: the model could not degenerate properly to pure solid or liquid behaviour neither to free
solid suspensions. The aim of this paper was to propose solutions to overcome these limitations.
The Natural and Artificial Aging Response of Semi-Solid Metal Processed Alloy A356
Authors: Möller Heinrich , Govender Gonasagren , Stumpf Waldo
Published: March 2009

The heat treatment cycles that are currently applied to semi-solid processed components are mostly
those that are in use for dendritic casting alloys. These heat treatments are not necessarily the
optimum treatments for non-dendritic microstructures. For rheocast alloy A356, it is shown that
natural aging prior to artificial aging causes the time-to-peak-hardness to be longer compared to the
time when only artificial aging is used. Furthermore, a hardness plateau is maintained during
artificial aging at 180oC between 1 and 5 hours without any prior natural aging. A natural aging
period as short as 1 hour results in a hardness peak (rather than a plateau) to be reached during
artificial aging after 4 hours at 180oC.
Feasibility of Recycling Aluminum Alloy Scrap by Semisolid Extrusion
Authors: Sugiyama Sumio , Yanagimoto Jun
Published: March 2009

The feasibility of recycling machining grindings of aluminum alloys by semisolid process
has been investigated. Machining grindings of A2011 aluminum alloy produced experimentally by
lathe machining were used. The material is put into a metal mold and compressed up to 90 % of the
true density at room temperature. The metal mold with the compressed machining grindings is
heated up to a specified temperature. Afterwards, the metal mold is set into the extrusion container,
and extrusion in hot and semisolid range was carried out. In this experimental study, extrusion load,
internal structure of the product and mechanical properties (tensile strength, elongation, hardness) of
the product are assessed. It was proven that semisolid extrusion is about 40% less extrusion load
compared with that of hot extrusion, the shape of the machining grindings remained in the hot
extrusion and the semisolid extrusion products extrusion ratios higher than 10 have excellent
elongation property, which is comparable to the commercialized product.
Development of the Gas Induced Semi-Solid Metal Process for Aluminum Die Casting Applications
Authors: Wannasin J. , Junudom S. , Rattanochaikul T. , Flemings Merton C.
Published: March 2009

A simple and efficient rheocasting process that has recently been invented is being
developed for aluminum die casting applications. The process called Gas Induced Semi-Solid (GISS)
utilizes the combination of local rapid heat extraction and agitation achieved by the injection of fine
gas bubbles through a graphite diffuser to create semi-solid slurry. In the GISS process, the die casting
machine and the process cycle remain little changed from those of conventional die casting. The GISS
unit creates a low solid fraction of semi-solid slurry in the ladle during the ladle transfer to the shot
sleeve. The semi-solid slurry is then poured directly into the shot sleeve. This paper presents the
detailed description of the process. The results of the semi-solid die casting experiments with ADC10
alloy using the GISS process are also reported and discussed.
Constitutive Models of Vascular Tissue
Authors: Mirota Kryspin
Published: March 2009

Knowledge of mechanical properties of vascular tissue - especially arterial tissue - is
fundamental to understanding of vascular hemodynamic function. This work takes into
consideration problems connected with description of mechanical behavior of main constitutes of
the tissue and overall wall material in relation with local flow state and geometry factor.
Wavelet Analysis of Barkhausen Noise in Reconstructing Distributions of Residual Stress
Authors: Kownacki Cezary
Published: March 2009

The paper presents an application of non-destructive estimate of approximate
distributions of residual stresses as the function of surface layer depth. The application uses an
innovative technique of wavelet analysis of Barkhausen noise, which is able to estimate layout of
surface layer properties as the function of measurement depth in the range greater than that offered
by other methods of non-destructive testing. The estimate of stress distribution as the function of
depth is compared with the result obtained from X-ray stress test using electrolytic etching. The
comparison presents very similar curves of stress distribution, so the wavelet analysis of
Barkhausen noise can be considered as a reliable method of non-destructive testing of an
engineering object.
Method of Dynamic Parameters Measurement of High-Speed DAC's
Authors: Kvedaras Vygaudas , Kvedaras Rokas , Ustinavičius Tomas
Published: March 2009

Developed sampling device and algorithm of digital signal processing for automated
measurement of settling times of fast DACs is represented. The new sampling device with
numerically controlled oscillators allows realizing of the different types of the time scale
transformation. Using of sigma-delta ADC and FIFO memory allows significant simplification of
the device. The equations of time scale transformation ratio and sampling step are presented.
Results of the research of developed digital signal processing algorithm are submitted.
Pendulum-Generator as New Energy Source
Authors: Korouji G. , Hanitsch Rolf , Hübner B.
Published: March 2009

For a number of applications in the logistics sector, an energy supply is needed in order
to supply sensors. The use of batteries only is cumbersome because of the recharge problems.
A novel generator is described which utilises the stochastic vibrations related to transportation of
containers. The principle is outlined and details of the prototype are given.