bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Developments within Semi-Solid Forming at the Institute for Metal Forming Technology
Authors: Liewald Mathias , Unseld Peter
Published: March 2009

This paper illustrates several research activities being carried out within the Center of Competence
for Casting and Thixoforging Stuttgart (CCT `NOVUS´).
A new method for manufacturing Metal Matrix Composites out of the semi-solid state has been
developed at the Institute for Metal Forming Technology, Universitaet Stuttgart, and applied for
patent pending. Within this new manufacturing method for the production of fibre and particle
reinforced composites now disadvantages of liquid-phase-techniques can be reduced in combination
with decreased manufacturing costs compared to conventional MMC-production technologies due
to short cycle times and the ability of near-net-shape forming.
It is obvious that manufacturing process in the fabrication of metal matrix composite materials will
influence in some extent the performance of these materials. A current research project at the
Institute for Metal Forming Technology (IFU), contributes implementing specific boundary
condition of the manufacturing process to numerical analysis. Such boundary conditions exert direct
influence on product quality. For manufacturing of metal matrix composites limiting factors are e.g.
temperature, pressure, deformation, etc. Detecting input-parameter for numerical analysis basic
rheological parameters, such as static and dynamic yield points, hysteresis and shear rate jump tests,
detection of the differential structural parameter, evolution of apparent viscosity of different castalloys
are topics of current research project at the Institue for Metal Forming Technology.
For reheating-process of semi-solid alloys new technologies have been developed and applied for
patent pending by the Institute for Control Engineering of Machine Tools and Manufacturing Units
(ISW). The two main advantages of this technique as compared with other induction heating
techniques are the direct online determination of liquid-, solid fraction and heating-homogeneity as
well as robustness against variations of prematerial (chemical composition, billet-diameter, etc.).
Thixo-Extrusion of 5182 Aluminium Alloy
Authors: Kapranos Plato , Nakamura Ryoji , Bertoli Ermanno , Pola Annalisa , Azpilgain Zigor , Hurtado Inaki
Published: March 2009

Extrusion is a well established technology for the production of complex sections of aluminium
alloys. Thixo-extrusion in comparison to traditional hot-extrusion offers several advantages such as
lower extrusion and friction forces, higher material fluidity, longer tool life etc. Aluminium alloy
5182 is an important commercial alloy characterized by high strength and ductility, high corrosion
resistance and good formability; it is commonly used for the production of wrought automotive
components and it is also suitable for semi-solid applications thanks to its wide solidification range.
The aim of this paper is to attempt the shaping of 5182 Al-Mg alloy through the thixo-extrusion
process using a ceramic tool and evaluating the effect of different routes of making the feedstock on
the semisolid microstructure. Particularly, two different methods were investigated: Near-solidus
casting and Roll-casting using a cooling slope.
All the samples produced were characterized by metallographic analysis in order to measure globule
size and shape factor, as the main criteria used for assessing thixo-formability.
Numerical Simulation of Induction Heating of Aluminum Alloy Billets
Authors: Barman N. , Mukherjee J. , Dutta Pradip
Published: March 2009

In this work, a numerical model for induction heating is proposed. The heating process
considers only interaction of electromagnetic effects and heat transfer, and is represented by an
unsteady heat diffusion equation. The numerical simulation of the process is performed using a
finite volume method in which the induction heating is represented by a volumetric heat source
term. The heat source term is evaluated analytically using principles based on Faraday’s and Biot-
Savart laws. The technique is applied to the case of induction heating of a cylindrical A356
aluminum alloy billet. The model predicts magnetic flux density and temperature distribution during
the heating process. The effects of process parameters, such as frequency and current density, on the
temperature distribution are also studied. The results show that nearly uniform distribution of
temperature can be achieved when the billet is heated slowly with low frequency and low supply
current density.
The Microstructure Evolvement and Simulation Analysis during Semi-Solid Processing of Aluminum Alloy
Authors: Yang Yi Tao , Wang Jian Fu , Zhang Heng Hua , Shao Guang Jie
Published: March 2009

To enhance the comprehension on the internal rule of microstructure evolvement and
quality-controlled relativity, the microstructure during the induction reheating of billets and die
casting of parts was systematically investigated. According to general structure observation and aided
analysis of some computer simulations, the quantitative relationships between microscopic
morphology (including solid fraction and grain shape) and formation state was minutely discussed.
The experimental results showed that liquid and solid phase in semi-solid slurry had different filling
tendency, fluid velocity of liquid phase in the area of high filling speed was relative quick and easy to
flow into far area and corner. Solid particles far from gate possessed fine and round grain. Moreover,
the structure configuration of original billets markedly affected forming process; billets with fine and
round grain were required for the die-castings of complex shape and thin thickness. In the case of the
big change in shape and thickness of die-castings, the design of gating system and the control of
plunger speed should be so properly carried out as to avoid unequal distribution of solid and liquid
phase in die-casting part as soon as possible.
Study on Microstructure-Processing Relationship of a Semisolid Rheocasting A357 Aluminum Alloy
Authors: Kang Yong Lin , Yang Liu Qing , Song Ren Bo , Zhang Fan , Tao Tao
Published: March 2009

An improved and self-developed semisolid preparing and rheomoulding device —
rotating barrel rheomoulding machine (RBRM) for light alloys in laboratory is introduced in this
paper. It mainly consists of a melting furnace, a shearing system with two relative-rotating conical
barrels, a central temperature control unit, gas protection system and a die-casting system.
Microstructure-processing relationship of A357 aluminum alloy obtained by the RBRM process is
investigated by different intensity of turbulence and different shear rate. The experimental results
show that the improved RBRM is capable of eliminating coarse dendrites, and producing small and
spherical solid particles uniformly distributed in a eutectic matrix. In addition, the process can
eliminate entrapped gas and reduce fine shrinkage pores in the specimens as well. Compared with
the original self-developed device in our laboratory, the improved equipment has the following
advantages: accurate control of stirring temperature; small volume and convenient manipulation;
fine and spherical solid particles, chemical and microstructural uniformity throughout the specimens
and so on.
Microstructure Evolution and Mechanical Properties of Rheoformed YL112 Aluminum Alloy
Authors: Yang Xiang Jie , Guo Hong Min
Published: March 2009

Rheo-die casting (RDC) based on LSPSF (low superheat pouring with a shear field)
rheocasting process has been exploited. In case of secondary die casting aluminum alloy YL112,
LSPSF allowed for preparation of sound semi-solid slurry in 15-20s that fully meet the production
rate of HPDC, the primary α-Al exhibiting a mean equivalent diameter of 70 μm and shape factor of
0.93, without any entrapped eutectic. Compared to conventional HPDC, RDC improves
microstructures in castings. Secondary solidification of semi-solid slurry takes place uniformly
throughout the entire cavity, producing an extremely fine and uniform microstructure. The
experimental results show the RDC 380 alloy has much improved integrity and mechanical
properties, particularly elongation, and heat treatment can be used to enhance the mechanical
properties.
The Influence of Heat Treatments for Laser Welded Semi Solid Metal Cast A356 Alloy on the Fracture Mode of Tensile Specimens
Authors: Kunene G. , Govender Gonasagren , Ivanchev L. , Knutsen R.D. , Burger H.P.
Published: March 2009

The CSIR rheo-process was used to prepare the aluminium A356 SSM slurries and
thereafter plates (4x80x100 mm3) were cast using a 50 Ton Edgewick HPDC machine. Plates in the
as cast, T4 and T6 heat treatment conditions which had passed radiography were then butt laser
welded. It was found that the pre-weld as cast, T4 and post-weld T4 heat treated specimens
fractured in the base metal. However, the pre-weld T6 heat treated specimens were found to have
fractured in the heat affected zone (HAZ).
On the Modeling of Semisolid Suspensions
Authors: Alexandrou Andreas N.
Published: March 2009

Due to the distinct rheology of semisolid slurries the process has well established
advantages over competing near-net-shape manufacturing technologies. Despite the obvious
advantages of the process its adoption by the casting industry, however, has been slow. This is
primarily due to lack of confidence of how these slurries flow in die cavities. The added cost
associated with the specially prepared slurry has also affected the process commercial success.
Nevertheless despite these problems attention to the semi-solid metal process has indeed increased
over the years. The main focus of this review is the modeling of semisolid slurries. The objective
here is to present an overview of relevant aspects of modeling by focusing on the physics of the
slurry and by stressing consistent mathematical and analysis methods to determine the material
constants.
Development of In-Mold Rheocasting Process
Authors: Kim Shae K. , Lee Young Chul
Published: March 2009

Novel In-mold rheocasting, which can satisfy all the development direction of rheocasting,
has been successfully developed. In-mold rheocasting requires no additional processing equipment
except diecasting machine, no grain refinement procedure and no additional cycling time to produce
slurry-on-demand. Process concept of In-mold rheocasting is simply based on the paradigm shift from
HOW to WHERE for producing slurry-on-demand and the shift from obtaining PERFECT solid
globules to casting OPTIMUM products. Optimum external field can be generated in mold, that is, in
die cavity exactly around biscuit. This paper will demonstrate the possibility to achieve
slurry-on-demand by In-mold rheocasting and some commercial products.
Thixoforming of Hypereutectic Al/Si Automotive Pistons
Authors: Atkinson H.V. , Ward P.J.
Published: March 2009

For hypereutectic Al/Si alloys, one of the advantages of thixoforming in comparison with casting
routes is the relatively short processing times at high temperatures and hence limited coarsening of
the Si phase. Coarse silicon particles give poor mechanical properties. Here two hypereutectic Al/Si
alloys (magneto-hydro-dynamically (MHD) stirred A390 from Pechiney and an extruded A390 alloy
from Showa in Japan) have been thixoformed to form pistons. Opening up the die entrance to the
full width of the crown made the flow into the die more uniform and helped to reduce the tendency
for large pores to form due to swirling of the slurry. Die heating reduced cold shuts in the skirt (thin
section) of the piston. Placing inserts into the die to make holes for the piston pins (i.e. having an
obstacle in the thicker regions) evened up the flow between the thick and the thin regions in the die.
Massive pores experienced in earlier shots were then eliminated. Placing ceramic material in the die
entrance considerably reduced the shrinkage porosity in the crown. The use of the Showa alloy,
where the globular semisolid microstructure is achieved by a solid state deformation route rather
than MHD, gave reduced shrinkage porosity and eliminated macrosegregation of the eutectic and
the silicon. Computer modeling has aided optimization of the die.
Thixoforming of Steel: Parameters and Means for Industrialization
Authors: Rassili Ahmed , Robelet Marc , Bigot Régis
Published: March 2009

The deformation process of steel in the semi-solid state, or thixoforming is an alternative
solution to the classical industrial processes that are the casting or the hot forging.
Thixoformed steel parts are of better quality and may substitute advantageously parts realized in
cast iron leading to an improvement of the rigidity, for example, but also parts in aluminium alloys
obtained by the main deformation processes: for lower volume, thixoformed steel parts, keeping the
same functionality, present superior mechanical properties than the parts realized in aluminium
alloys. The industrial development of the steel thixoforming must be accompanied by the
knowledge and the various parameters control of the process: steel grades definition and
elaboration, the homogeneous high-temperature heating of the slug before deformation, conception
or re-conception of the part to adapt it to the process and the practice properties, the equipment
definitions which are used for the deformation operation at the semi-solid state. The handling
system is also important in the thixoforming process; it is going to allow the slug transfer, at the
semi-solid state, between the heating zone and the tooling or to evacuate the thixoformed part
towards the mean assuring the quality heat treatment of the part. The means choice which are
industrially going to ensure the process have a big importance to obtain successful production line
and so, a cost reduction by “finished” part competitive with regard to processes used classically
today. After the description of the applicable key points to the main parameters and the solutions
used to obtain a successful product: high mechanical characteristics, near net shape or net shape
geometry, no flash and limited machining operation, ... are described , The investigations finished
with an approach comparing the part cost realised by thixoforming process with regard to classical
processes.
Sub Liquidus Casting Technology for the Production of High Integrity Component
Authors: Forn Antonio , Menargues Sergi , Martín Enric , Picas Josep A.
Published: March 2009

This work is a contribution to improve the knowledge of components behavior produced
by semi-solid processes particularly the Sub-Liquidus-Casting process. Die design was supported by
using the Procast simulation program. The effect of the different variables of the process in
structural integrity of the product has been described and analyzed. The components were produced
using A356 alloy formed on a pilot plant with a 400 Ton THT press. The components study was
made by RX, metallographic analysis and mechanical tests. The effects of T5 and T6 heat
treatments were also studied.
Laser Surface Modification of Tool Steel for Semi-Solid Steel Forming
Authors: Brabazon Dermot , Naher Sumsun , Biggs Patrick
Published: March 2009

This paper presents an analysis of the effect of CO2 laser processing parameters on the
surface modification and heat treatment of steels. The CO2 laser and sample movement process
parameters are presented. The controlled operation of these in conjunction with each other is
required to obtain better surface hardness and structure. H13 tool steel samples were rotated at high
speeds to keep exposure times below 0.3s. Laser processed samples were analysed using EDX
spectroscopy, optical microscopy, Vickers and Martens micro-hardness testing, and X-ray
diffraction (XRD). Results show how the hardness profile through the surface is related to the laser
treatment and resultant microstructures. Increased surface hardness was noted due to a complete
microstructural transformation to an amorphous state in the glazed samples. The usefulness of such
coatings on tool steels, in conjunction with other thermal barriers, for the forming of semi-solid
steel alloys is presented.
Servomechanical Press: A New Press Concept for Semisolid Forging
Authors: Azpilgain Zigor , Ortubay R. , Blanco A. , Hurtado Inaki
Published: March 2009

Semisolid forging process requires special movement of the ram, until now only
achievable with hydraulic presses. The upper die, placed on the press ram, must move fast during
forming of the component in order to reduce segregation phenomena, and, once the part is shaped,
the die must squeeze the material so that the contraction of the material is overcome and no
shrinkage defects are formed. Traditional mechanical presses are not able to reproduce this kind of
cycles, only possible with hydraulic presses. The introduction of servo motors in mechanical presses
makes possible the achievement of those requirements, and, therefore, the use of these presses for
the semisolid forging processes. The main characteristic of this type of machines is the elimination
of the flywheel and the clutch; in the solution proposed by the press builder Fagor, the AC servo
motor drives the ram of the press by using a transmission based on gears and a crank. This paper
presents some of the results achieved during the semisolid forging of A356 aluminium alloy using a
400 tons Fagor servo motor driven mechanical press installed at the University of Mondragon.
EN AC-46500 Injected by Semi-Solid Rheocasting
Authors: Campillo Manel , Baile Maite T. , Menargues Sergi , Forn Antonio
Published: March 2009

EN AC-46500 aluminium components are formed by Semi-Solid Rheocasting (SSR) in
an industrial plant using a 700 tons high pressure machine. The dies wear was designed by the
PLCO model of the ProCast simulation software. The components have had a good structural
integrity and the mechanical properties after T6 treatment have been equivalent to that obtained by
the same alloy by die cast.
The present work describes the SSR forming process, the resulting microstructure as well as the
optimization of the ageing heat treatment by hardness evolution. The results of the tensile tests
make these clear.
The Use of CrNiCo-Based Superalloy as Die Material in Semi-Solid Processing of Steels
Authors: Birol Yücel
Published: March 2009

Semi-solid processing of aluminium and magnesium alloys has matured to become a well
established manufacturing route for the production of intricate, thin-walled parts with mechanical
properties as good as forged grades. This innovative forming technology, however, still remains as a
major challenge in the case of steels. One major limitation in the thixoforming of steels has been
the lack of suitable tool materials which could withstand the complex load profile and significantly
increased forming temperatures which promote chemical interaction between forming dies and
liquid steel. For industrial application to be attractive, the lifetime of the thixoforming tools has to
be sufficient to ensure the cost effectiveness of this technology. Forming experiments using
conventional hot working tool steel as die material have shown massive wear and plastic
deformation. Several alternatives including copper alloys, titanium-zirconium-molybdenum based
high temperature application alloy TZM, graphite and ceramics with and without suitable ceramic
coatings have been tested with limited success. An attempt was made in the present work to
investigate the applicability of CrNiCo-based superalloy dies in small scale forming tests in an
effort to contribute to the development of semi-solid processing of steels.
Thixotropic Strength and Thixotropic Criteria in Semi-Solid Processing
Authors: Keung W.C. , Lee Y.F. , Shan Wei Wei , Luo Shou Jing
Published: March 2009

Thixotropy is essential to semi-solid processing, and because of it the semi-solid material is
characterized by ‘shear shinning’. Here, thixotropic strength and thixotropic criteria in semi-solid
processing are put forward based on related theories and experiments, and thixotropic mechanism and
its influencing factors are also investigated. The results are as follows: 1) the term of thixotropic
strength means that with constant shear rate at semi-solid temperature, the semi-solid body begins to
flow when the shear stress reach a certain value. This value of shear stress is defined as the thixotropic
strength; 2) Thixotropic behavior happens with ‘shear thinning’ because of the deagglomeration of
solid particles, while ‘shear thickening’ happens because of the agglomeration at the same time. With
increasing shear time, the shear stress increases first and then decreases rapidly to reach a stable value.
3) There are three important factors that influence ‘thixotropic strength’: temperature (hence solid
content), initial microstructure (including size, shape factor and uniformity of solid particles) and
shear rate.
Analysis of Rheological Properties of Steel near Solidus Point Using Gleeble® Simulator
Authors: Sołek Krzysztof P. , Mitura Zbigniew , Karbowniczek Mirosław , Kapranos Plato , Kuziak Roman , Dutkiewicz Jan
Published: March 2009

The main goal of this work is the analysis of rheological properties of steel alloy at high
temperatures, just below the solidus point, and in the semi-solid state with low liquid phase content.
Data obtained from the analysis can form the basis of numerical simulation for designing and
optimizing the thixoforming processes. The rheological properties should be known over a wide
temperature range so that the simulations could also predict defects such as incomplete die filling.
The analysis concerned M2 tool steel alloy. The paper also discusses development of globular
microstructure in partially melted steel.
The Determination of Semi-Solid Processing Ability Using a Novel Rheo-Characterizer Apparatus
Authors: da Silva Manel , Lemieux Alain , Blanchette Hugues , Chen X.-G.
Published: March 2009

The “Rheo-Characterizer” is an apparatus designed to assess the quality control of the
semi-solid material. The working principle is based on the recording and subsequent analysis of the
force required to transversally cut the semi-solid slurry at constant speed. Semi-solid slurries
produced under different conditions while using the SEED process were analyzed with the “Rheo-
Characterizer”. The TiB2 grain refiner was also added to evaluate the impact on the microstructure
and the cutting force. The microstructural features were measured and the grain size was analyzed
for the different processing conditions. The effect of the cutting temperature on the resulting curve
was also investigated. The results show that the “Rheo-Characterizer” is capable of differentiating
between the varied microstructural morphologies and the solid fraction of the billet.
Controlling the Semisolid Grain Size during Solidification
Authors: StJohn David H. , Easton Mark , Qian Ma
Published: March 2009

This paper will use a new method for predicting grain size and then apply it to various
solidification environments to reveal which factors are dominant in determining the final grain size.
This study will only focus on methods where the grain size is set during a solidification process.
These processes include grain refinement by inoculation of the melt with grain refining particles,
increasing the cooling rate, low superheat casting, ultrasonic treatment and the use of chill moulds.
Each of these methods can control the grain size to some extent but in order to predict the outcome
it needs to be understood how the alloy constitution, inoculant particle characteristics and the
casting conditions affect the prime nucleation event for the formation of new grains. These
methodologies are currently being used, or have potential to be used, for the production of fine
spherical grained semi-solid slurries.
Study of Microstructural Evolution and Phase’s Morphology after Partial Remelting in A356 Alloy
Authors: Mahdavi A. , Bigdeli M. , Hajian Heidary M. , Khomamizadeh F.
Published: March 2009

In this work, effective parameters of SIMA process to obtain non dendritic
microstructure in A356 alloy were investigated. In addition, the effect of SIMA process on the
evolution of morphology of silicon and intermetallic phases in this alloy was studied.
Microstructure images obtained from optical microscopy and SEM observation showed that
increase in plastic work up to 40% and then holding of samples in the semi solid state at
temperature of 580oC, causes that primary dendritic structure changes to non dendritic, fine and
globular structure, but optimum reheating time completely depended on initial thickness of samples.
If all parameters of SIMA process are the same, the grain boundaries of thinner samples begin to
wet and following globalization will be completed in shorter reheating time rather than thicker ones.
Moreover, it was found that the intermetallic phases lost their angular or needle morphology and
gradually changed to rounded morphology and even to globular form. Also the optimum reheating
time thoroughly depends on primary casting microstructure as the finer casting microstructure begin
to globalize faster than thicker one under more little stains.
Investigations on Thermal Influences for Thixoforging and Thixojoining of Steel Components
Authors: Baadjou René , Knauf Frederik , Hirt Gerhard
Published: March 2009

At the Institute of Metal Forming (IBF) current investigations within the framework of
the Collaborative Research Centre 289 are mainly concentrated on forming of semi-solid precursor
material of the steel grades X210CrW12 and 100Cr6. One important task is the precise temperature
for the composition of solid and liquid phase fraction in the preheated billet. Experimental
measurements and numerical simulations show significant heat losses during transport of the billet
and after its insertion into the die. These developing temperature gradients influence strongly the
resulting temperature field in the formed component. In case of the forming tools the critical
increase of the temperature depending on the tool material is shown. As fundamental research in the
field of thixojoining the temperature development of the inserts is analysed and demonstrates the
feasibility of joining higher and lower melting materials into the semi-solid matrix.
Fabrication of Metal Matrix Composites under Intensive Shearing
Authors: Hari Babu N. , Tzamtzis S. , Barekar N. , Patel J.B. , Fan Z.
Published: March 2009

Current processing methods for metal matrix composites (MMC) often produces
agglomerated reinforced particles in the ductile matrix and also form unwanted brittle secondary
phases due to chemical reaction between matrix and the reinforcement. As a result they exhibit
extremely low ductility. In addition to the low ductility, the current processing methods are not
economical for producing engineering components. In this paper we demonstrate that these
problems can be solved to a certain extent by a novel rheo-process. The key step in this process is
application of sufficient shear stress on particulate clusters embedded in liquid metal to overcome
the average cohesive force of the clusters. Very high shear stress can be achieved by using the
specially designed twin-screw machine, developed at Brunel University, in which the liquid
undergoes high shear stress and high intensity of turbulence. Experiments with Al alloys and SiC
reinforcement reveal that, under high shear stress and turbulence conditions Al liquid penetrates
into the clusters and disperse the individual particle within the cluster, thus leading to a uniform
microstructure.
Heat Treatment Processes of A2024 Rheoforging Alloy and Morphology Investigation by Nanoindentation and Atomic Force Microscopy
Authors: Kim D.S. , Kang C.G. , Lee S.M.
Published: March 2009

This study demonstrated nanoindentation techniques of investigating the effects of size
and feature in a microstructure on the mechanical properties of rheology-forged aluminum alloy.
Mechanical properties and tribological characteristics of rheology-forged Al2024 wrought
aluminum alloy in terms of T6 heat treatment were investigated by varying the aging time by
nanoindentation and nanoscratch techniques. By nanoindentation/nanoscratch tests and atomic force
microscopy, it was demonstrated that the 4 hour aged material exhibites the highest hardness
because of the intermediate precipitate phase θ″, which was precipitated by T6 heat treatment at
495°C. Moreover, the friction coefficients in the precipitates in the eutectic phase region were lower
than those in the primary α phase region.
Comparison of Microstructural Changes in a SIMA Processed A356 Aluminum Alloy after Unidirectional Compression and Rolling: Effect of Pressure Depth
Authors: Hajian Heidary M. , Bigdeli M. , Mahdavi A. , Khomamizadeh F.
Published: March 2009

In this study, in order to compare effect of unidirectional compression and rolling on
final microstructure of strain induced melt activated (SIMA) A356 aluminum alloy, rectangular
samples with dimensions of 3cm×5cm in area and 1cm in thickness and cylindrical specimens with
2.5cm in diameter and 1cm in length, have been prepared for rolling and compressing processes,
respectively. Then, these samples were plastically deformed at a same strain in ambient
temperature. Afterward, the strained samples were cut into equal quarters. In the next stage, to
produce globular microstructure, these specimens were partially remelted in 580°C for different
times. Results obtained from light microscopy showed that specimen's thickness and so, its strain
affected zones influence on the globulization of dendrites. In addition, it was seen that at a given
strain and constant diameter, increase of H/D ratio led to increase of needed time for reaching a
certain sphericity in cylindrical samples. Also, it was showed that microstructural evolutions during
SIMA processing of both rolled and unidirectional compressed samples were relatively identical.
However, at a same condition, ultimate size of globulized dendrites in the rolled samples was
smaller than those of compressed ones.
Study of ECAP Processing Routes on Semi-Solid Microstructure Evolution of A356 Alloy
Authors: Moradi M. , Nili-Ahmadabadi Mahmoud , Heidarian B. , Parsa M.H.
Published: March 2009

Semi- solid (SS) processing technologies provide the production of metal parts with
homogeneous, fine and globular – grained microstructure. This is one of the most successful and
reliable methods to produce near net shape products exhibiting good mechanical properties.
Production of feed stock with non-dendritic and spherical structure is the critical factors in semisolid
forming. Among several processes to obtain a globular microstructure, the SIMA (strain
induced melt activated) process is simple and advantageous with respect to equipment and
eliminating the melting stage before reheating. In this research, Al (A356) has been used and in
order to induce strain, ECAP (equal channel angular pressing) method has been applied. ECAP is a
method in which a great strain is induced and severe plastic deformation without any changes in
cross section area occurs. To induce larger strain, ECAP process was carried out on annealed
specimens up to several passes in route A (no rotation of samples around linear axis between each
pass) and Bc (90◦ rotation of samples around linear axis between each pass), in ambient temperature.
The reheating condition was optimized and the comparison between different routes and number of
passes was investigated. The microstructure evolution of deformed and reheated Al (A356) was
characterized by SEM (Scanning electron microscopy) and optical microscopy. In addition, the
relation between the induced strain with size and shape of particles has been studied.
Rheological Behavior of Semi-Solid Slurry of A356 Alloy at High Shear and Cooling Rates
Authors: Barman N. , Dutta Pradip
Published: March 2009

The rheological behavior of semisolid aluminium alloy (A356) slurry is investigated by
using a concentric cylinder viscometer under high cooling rate (30 to 50°C/min) and high shear rate
(650 to 1500s-1) conditions. Two different series of experiments are carried out. In all of these
experiments, the pellets of A356 alloy are poured into the outer cylinder where they melt completely
by resistance heating. When the inner cylinder is placed concentrically, the molten metal resides in
the annular space between the cylinders. As the inner cylinder rotates, the alloy is sheared
continuously during cooling from a temperature of 630°C, and a slurry forms. In the first series of
experiments, for different cooling rates, shearing continues under a constant shear rate until rotation
of the inner cylinder stops. During experiments, the temperature of the slurry is measured
continuously using a K-type thermocouple, from which the solid fraction is calculated. In the second
series of experiments, the molten alloy is cooled and sheared continuously at different shear rates
for a given cooling rate. The apparent viscosity of the slurry is calculated by measuring the torque
applied to the inner cylinder and its rotational speed. The results show that the slurry viscosity
increases with increasing fraction of solid and increasing cooling rate, and it decreases with
increasing shear rate. At high values of shear and cooling rates, the viscosity varies gradually up to a
solid fraction of about 0.5.
The MSMT Process for Semi-Solid Slurry Production
Authors: Zeng Yi Dan , Zhang Zhi Feng , Xu Jun , Shi Li Kai
Published: March 2009

A new slurry making method for rheocasting termed “Melt Spreading and Mixing
Technique” (MSMT), based on forced uniform solidification theory, has been proposed, by which
the bulk metal is dispersed into thin liquid film that is cooled rapidly and uniformly to allow
copious nucleation. With a model alloy Al-wt%6.5Si to conduct a series of experiments, feasibility
of this method and influence of process parameters upon slurry microstructure were studied. The
results show that semisolid slurry for mass production with uniformly fine nondendritic
microstructures can be obtained consistently and continuously by optimizing process parameters.
Influence of Processing Route on the Properties of Magnesium Alloys
Authors: Hagen Frank , Hort Norbert , Dieringa Hajo , Kainer Karl Ulrich
Published: March 2009

Magnesium alloys had gained an increasing interest in recent years due to their promising
property profile for light weight constructions. They offer drastic advantages in weight reductions in
automotive industries compared to steel or even aluminium. Therefore they can be used to decrease
the emission of green house gases as requested by the EU directive for the reduction of CO2 emissions
and moreover due to their recyclability they also help to fulfill the requirements from the EU directive
regarding the end of life of vehicles. But still there are some limitations with regard to strength,
mostly at elevated temperatures above 130 °C. To overcome these limitations alloy development as
well as process optimization has to be done for further enhancement of the range of magnesium
applications. This paper will show and discuss the property profiles of the standard magnesium alloy
AZ91D compared to the recently developed, heat resistant magnesium alloy MRI153. The alloys
have been processed using normal high pressure die casting (HPDC), New Rheocasting (NRC) and
Thixomolding® (TM). As methods of investigation tensile and creep tests have been applied. The
creep properties have been determined in the temperature range of 135-150 °C and loads of
50-85 MPa. All these trials have been accompanied by metallographic observations (light optical
metallography, SEM) and density measurements to investigate the influence of the processing routes
on microstructure and the porosity of the materials. It will be shown that the differences in the
property profile of the chosen alloys are dependent on their different chemical compositions as well
as on different microstructures that are obtained by the different processing routes. While in the case
of AZ91D, TM is showing advantages compared to HPDC for room temperature applications, the
NRC in combination with the heat resistant alloy leads to an improvement of creep rates by two
orders of magnitudes.
Mechanical Analysis of Semi-Solid Metals Shear Deformation during Compression
Authors: Luo Shou Jing , Chen Qiang , Gao Xiao Rong
Published: March 2009

Rheological behavior of semi-solid metals during isothermal compression is the most basic
forming way for semi-solid die forging. In this paper, based on the metal plastic deformation and high
pressure solidification theory, the shear deformation mechanisms of semi-solid metals were analyzed
during isothermal compression. Experimental observations and theoretical analyses for AZ91D and
composite Al/Al2O3 in the semi-solid state were performed with thermal simulation tests. The results
for theoretical analyses and experimental observations show that the shear deformation of semi-solid
metals has been realized by metal inhomogeneous flowing from macroscopic view and by grain
boundary inhomogeneous migrating from microscopic view respectively during compression.
A Novel Process for Fabrication of Globular Structure by Equal Channel Angular Pressing and Isothermal Treatment of Semisolid Metal
Authors: Meidani H. , Hossein Nedjad S. , Nili-Ahmadabadi Mahmoud
Published: March 2009

A new process for fabrication of semisolid billets is introduced, which involves equal
channel angular pressing and isothermal heating in the semisolid state. The process leads to a
relatively fine globular microstructure. The microstructure evolution during isothermal treatment is
studied and it is shown that dendrites breaking up has happened during equal channel angular
pressing in semisolid state. The microstructural evolution during isothermal heating and the
mechanism for the formation of the globular structure is tried to be understood and also modeled.
Quick Semi-Solid Slurry Making Method Using Metallic Cup
Authors: Pahlevani Farshid , Anzai Koichi , Niyama E.
Published: March 2009

The needs for high-strength and light weight structural materials have increased in
automotive and aerospace structure applications. The semi-solid processed light alloys inherently
offer the opportunity to produce high integrity components for these requirements. Various
processing methods exist for applying agitation to a molten metal during solidification to obtain
metal slurries suitable for semi-solid metal processing. In this paper, a new technique (Cup-Cast
method) to achieve semi-solid metal structure using agitation and direct spherical growth during
solidification is reported. Cup-Cast method is the most quick and simple semi-solid processing
route which semi-solid slurry would be prepared just by pouring molten metal into a metallic cup. In
this study Cup-Cast method was introduced and effect of process parameters on micro-structural
characterization of slurry prepared by this method was investigated.
Study on Semi-Solid Continuous Roll-Casting Strips of AZ91D Magnesium Alloy
Authors: Xie Shui Sheng , He You Feng , Huang Guo Jie , Geng Mao Peng , Zhang Ying
Published: March 2009

Semi-solid Continuous roll-casting process applied to produce the AZ91D magnesium
strips and its microstructure was studied in this paper. In order to examine further process ability
and forming property of the roll-casting strips, hot and cold rolling and punching experiments were
investigated. It was clarified that it is significant to combine the semi-solid process techniques with
roll-casting techniques, through which we can get high quality magnesium alloy strips with nondendritic
structure and improve the overall properties of the products. The largest deformation by
cold rolling and hot rolling can reach 18% and 21% respectively with one-pass roller.
X-Ray Microtomography Investigation of the Effect of Ba Additions on the Microstructure of Partially Remelted Al-4%Cu Alloys
Authors: Terzi Sofiane , Limodin Nathalie , Boller Elodie , Salvo Luc , Suéry Michel
Published: March 2009

The aim of this work is to study by X-Ray microtomography carried out at ESRF
Grenoble the microstructure of an Al-4wt%Cu alloy which was previously cold rolled to obtain
globules of the solid phase upon heating in the semi-solid range. Since this process produced
entrapped liquid in the globules, 3D quantification of this liquid was performed. Moreover, the
influence of the addition to the alloy of a small amount of Ba, which has been shown to decrease the
contiguity between the solid globules as a consequence of the decrease of the solid-liquid interfacial
energy σsl, was investigated. It is in particular shown that the amount of entrapped liquid is much
larger in the Ba-containing alloy in agreement with the reduction of σsl, whereas the size of the
liquid pockets is similar. In addition characterization of the interglobular liquid shows that the
interface area between this liquid and the solid per unit volume is larger for the alloys containing Ba
in agreement with previous observations carried out on 2D sections. The influence of strain during
cold rolling is also reported but it is shown to have a quite limited influence on the previous
parameters.
A Comparison of Deep Drawing and Ironing of Metal Alloy Strip Produced Conventionally and Non-Conventionally via Semi Solid Material Processing
Authors: de Pádua Lima Filho Antonio , Yamasaki Márcio Iuji , Ono Leandro Akita , Nampo Lourenço , Padilha Alcides
Published: March 2009

A semi solid thin strip continuous casting process was used to obtain 50%wt
Pb/50%wtSn strip by single and twin roll processing at speed of 15 m/min. A 50%wt Pb/50%wtSn
plate ingot was also cast for rolling conventionally into strips of 1.4 mm thickness and 45 mm width
for comparison with those achieved non-conventionally. This hypoeutectic alloy has a solidification
interval and fusion temperature of approximately 31°C and 215°C respectively. The casting alloy
temperature was around 280°C as measured by a type K immersion thermocouple prior to pouring
into a tundish designed to maintain a constant melt flow on the cooling slope during semi solid
material production. A nozzle with a weir ensures that the semi solid material is dragged smoothly
by the lower roll, producing strip with minimum contamination of slag/oxide. The temperatures of
the cooling slope and the lower roll were also monitored using K type thermocouples. The coiled
semi solid strip, which has a thickness of 1.5 mm and 45 mm width, was rolled conventionally in
order to obtain 1.2 mm thick strip. The coiled thixorolled strip had a thickness of 1.2 mm and
achieved practically the same width as the conventional strips. Blanks of 40 mm diameter were cut
from the strips in a mechanical press, ready for deep drawing and ironing for mechanical
characterization. All the strips achieved from non-conventional processing had the same mechanical
performance as those achieved conventionally. The limiting drawing ratio (LDR) achieved was
approximately 2.0 for all strips. Microscopy examination was made in order to observe phase
segregation during processing.
Morphological Features of Silicon Rich Phase in Powder Thixoformed Spray Atomized Hyper-Eutectic Al-Si Alloy
Authors: Kiani M. , Aashuri Hossein , Nategh S. , Foroughi A. , Narimannezhad A. , Khosravani Ali
Published: March 2009

Microstructural evolution of the spray atomized and powder thixoformed hyper-eutectic
A390 aluminum alloy was investigated. The spray atomized powder revealed homogeneous and
very fine silicon particles distribution, due to the rapid solidification of the alloy. The semi-solid
powders were extruded into a closed die cavity through a hole for the plastic deformation of the
powder particles. A drop forge of 45kg weight at different heights was used in this investigation.
Remarkable rearrangement and growth of the silicon rich phase was revealed in the final stage.
Numerical Simulation of Semi-Solid AZ91D Magnesium Alloy in Thixoforming Process
Authors: Ji Ze Sheng , Yan Hong Hua , Hu Mao Liang , Zheng Xiao Ping
Published: March 2009

In the process of metal plastic forming severe plastic deformations occur to the workpiece.
As a result the constitutive relations between material and geometry are nonlinear. One of the most
common tools to solve such problems is the finite element method. In thixoforming processes of
semi-solid metal many factors affect thixoforming fluidity. Therefore it is important to simplify the
problem and predict the metal flow properties. For that reason the thixoforming process of semi-solid
AZ91D magnesium alloy was modeled with the theory of rigid viscoplastic finite element method
using the commercial finite element software DEFORM-3DTM. The fluid and effective stress-strain
fields in the thixoforming process were obtained and the relationships among stress, strain rate and
temperature were analyzed.
Processing of Al-45Sn-10Cu Based Immiscible Alloy by a Rheomixing Process
Authors: Kotadia H.R. , Patel J.B. , Fan Zhong Yun , Doernberg Evelyn , Schmid-Fetzer Rainer
Published: March 2009

The growing importance of Al-Sn based alloys for producing self lubricating bearing
materials in automotive industries necessitates the development of new alloys for improved
performance. The recent thermodynamic work by Schmid-Fetzer at Clausthal University of
Technology predicted that the addition of Cu to the binary Al-Sn system makes the miscibility gap
stable. With the guidance of the calculated phase diagram, experimental investigations were
conducted on the ternary Al-Sn-Cu system to understand the solidification behaviour of this
immiscible system under intensive forced convection. The experimental focus was to investigate the
effects of shear rate, shearing temperature and cooling rate on the solidified microstructure.
Influence of Processing Parameters on Microstructure of Casting Rolling Semi-Solid AZ91D Magnesium Alloy
Authors: Zhang Ying , Geng Mao Peng , Cheng Lei , Wang Yan Chun
Published: March 2009

Semi-solid AZ91D magnesium slurry was prepared by mechanical stirring method and
the evolution of microstructure under different technological parameters such as casting
temperature, standing time, stirring time and stirring speed et al were studied. The results show that
the technological parameters have great influence on the microstructure of the semi-solid
magnesium slurry. Neither too high nor too low stirring speed is a benefit to form the semi-solid
state; stirring time is also not too long; higher casting temperature is unfavorable; with the
increasing of standing time, the steady-state apparent viscosity of the slurry increases rapidly, the
number of nucleation increases and the crystalline structure becomes finer.
Microstructure and Thermal Plasticity of Semi-Solid M2 Steel Casting Ingots Using Inclined Slope Pre-Crystallization Method
Authors: He You Feng , Xing Shu Ming , Xie Shui Sheng , Huang Guo Jie , Gou Jun Nian
Published: March 2009

Semi-solid M2 steel casting ingots were prepared using inclined slope pre-crystallization
method, and the microstructure at different slope length and thermal plasticity of ingots were
investigated in this paper. It was clarified that semi-solid processing technology can solve the
serious problem of eutectic carbides segregation in casting microstructure. The dendritic primary
austenite grains are changed into non-dentritic or equiaxed grains, and the eutectic ledeburite
carbide networks are fine. So, it improves the thermal plasticity of casting ingots, and the carbide
distribution of the semi-solid casting ingots is better than conventional casting after being forged.
Microstructural Evolution of SiCp/AZ61 Composites during Partial Remelting
Authors: Yan Hong , Zhang Fa Yun , Pan Wei
Published: March 2009

The microstructural evolution of SiCp/AZ61 composites during partial remelting was
investigated. The results indicated that the suitable technological parameters of SiCp/AZ61
composites were the reheating temperature of 595°C ~ 600°C and isothermal holding time of
30min ~ 60min. The separation of microstructure of AZ61 matrix was faster than that of SiCp/AZ61
composites during the initial stage. In the meantime, SiCp/AZ61composites hold high stability
during remelting process and a fine semi-solid thixoforming microstructure can be obtained with
increases in temperature and holding time. In addition, the samples of SiCp/AZ61composites were
susceptible to serious deformation and running out above 610°C.