bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Production of New Aluminum Thixotropic Alloys for the Manufacture of Structural Components by Semisolid Die Casting
Authors: Pola Annalisa , Roberti Roberto , Bertoli Ermanno , Furloni Disman
Published: March 2009

Semi-solid processing is nowadays a powerful technology for the realization of structural
components; in addition to the increase in their mechanical properties, due to the globular structure
instead of the dendritic one, further developments are most likely to be expected from alloy chemical
composition adjustments in order to achieve higher performances compared with the industrially used
A356 and A357.
Aim of this research is to try to set up new aluminium alloys for semisolid foundry applications,
starting from the standard Al-Si system, at the base of all known casting processes. Different chemical
compositions, based on either foundry or wrought Al alloys, have been investigated by means of
computational thermodynamics (Pandat®), producing quantitative data about solidus-liquidus
interval, solid fraction as a function of temperature, phase diagrams i.e. potential for age hardening,
etc..
Some selected alloys, fitting the needs of good castability, proper concentration of hardening
elements in the alpha phase and, obviously, easy production of feedstock material have been
mechanically stirred by means of an experimental apparatus designed and self-constructed in the
foundry laboratory of the university; the effect of different stirring tool configurations on the
semi-solid state obtainment has also been assessed. Subsequently, the manufactured alloys have been
reheated and cast into a simple die, properly designed, for the production of small samples.
Microstructural investigations have been done on the stirred alloy (before and after re-heating), on the
as cast and the heat treated samples to evaluate the efficiency of the designed system and of the
defined alloys. Experimental tests on the processed alloys have been carried out by means of an
instrumented crucible in order to verify the predicted thermodynamic properties supplied by
simulation study (i.e. fs-temperature curve).
Numerical Simulation of Semi-Solid Magnesium Alloy in Continuous Roll-Casting Process
Authors: Xie Shui Sheng , Yang Hao Qiang , Li Lei , Huang Guo Jie
Published: March 2009

It is significative to link the semi-solid process and continuous roll-casting process (CRP),
through which we can get high quality magnesium alloy strips with non-dendritic structure and
improve the overall properties of the products. Furthermore, because CRP of semi-solid metal
combines casting and forming, it shortens the period of technological process. In general, several
technical parameters such as the inlet temperature of semi-solid slurry, the heat transfer between
roll and molten alloy, the roll-casting speed, the position of solidification final point influence on
the strip quality in continuous roll-casting process. Therefore, the effects of the parameter to
continuous roll-casting process should be investigated. In this paper, the finite volume method is
used in the analysis of the CRP, a two-dimensional incompressible non-Newtonian flow with heat
transfer is considered. Based on the simulated results, the optimizational technical parameters are
obtained and the experiment of CRP was carried out. An ideal AZ91D strip with non-dendritic
structure has been obtained and also has been tested by cold rolling and hot rolling. The results
show that microstructure and mechanical properties of the strip are fine.
Dynamic and Static Yield Stress of Metallic Suspensions
Authors: Modigell Michael , Hufschmidt M.
Published: March 2009

Oscillation experiments, creep tests and shear stress ramps have been performed to analyze
the yield stress and its time dependency. It has to be distinguished between iso-structural, dynamic
and static yield stress. The iso-structural yield stress occurs immediately after shearing. Since the
slurry structure remains unchanged, it is equivalent to the structure during shearing. At rest an internal
structure builds up, this leads to an increase of the yield stress, which is referred to as the dynamic
yield stress. It increases until its maximum value, the static yield stress, is reached.
Comparison of Rheological Measurement Techniques for Semi-Solid Aluminium Alloys
Authors: Bührig-Polaczek Andreas , Afrath C. , Modigell Michael , Pape Lars
Published: March 2009

Alloys of a specific microstructure exhibit a shear-rate history-dependent flow behaviour in the
semi-solid state. Rheological studies have been carried out using various experimental techniques
such as concentric cylinder rheometers of Couette or Searle type as well as capillary rheometers and
parallel plate compression tests. With the Searle type rheometer and the capillary rheometer two
different approaches of rheological measurement techniques are discussed and compared regarding
advantages, potentials and its distinct characteristics.
Experiments using the Searle type rheometer have been conducted under steady-state or oscillating
conditions and have been used to verify time-dependency of step responses due to discontinuous or
linear variances of the shear rate. These experiments provide all types of flow curve parameters as
implemented in the numerical simulation. However the variances of the commonly used Couette and
Searle type rheometers are limited to shear-rates which are significantly lower than that appearing in
the technical thixo- or rheocasting processes. For that reason an additional experimental set-up with a
horizontal slot capillary integrated in a shot-controlled high-pressure die-casting machine is used in
order to examine flow properties at shear rate conditions similar to those in real thixocasting
processes.
After an initial examination of low temperature model alloys, such as PbSn15, the experimental
set-up is then adjusted in order to obtain rheological data for light metal alloys such as Aluminium
AlSi7Mg0.3. The Aluminium alloy is processed within each rheometer either as partially solidified or
partially remelted in order to represent conditions of both, the conventional thixocasting and the lately
introduced rheocasting process. Finally the appearance of physical phenomena which affects the
accuracy of rheological experiments such as wall slip is considered for both types of rheometers.
Simulation of Thixoforming: Comparison of Different Constitutive Equations
Authors: Pierret Jean Christophe , Rassili Ahmed , Cezard Pierre
Published: March 2009

The behaviour of the semi-solid material is complex to simulate and many approaches
are proposed in the literature to represent it. In this work, different constitutive equations are
studied: the classical Northon-Hoff law, Joly and Merhabian’s one [1] and an innovative
micromechanical model using homogenisation technique [2]. These constitutive equations have
been implemented in the FE code Forge2® to simulate simple forming tests, such as compression
and direct extrusion. The load-displacement curves using the three constitutive equations are
compared in order to estimate their capabilities.
Microstructures and Mechanical Properties of Melt Extruded Al-Cu Alloys
Authors: Lee Byoung Soo , Joo Dae Heon , Kim Myung Ho
Published: March 2009

Melt extrusion is a new fabrication process with the characteristics of both casting and
extrusion. In this process, a metallic melt which is poured and solidified up to semisolid state in the
container can be directly extruded through the die exit to form a product of bar shape without other
intermediate processes. The effects of various process parameters, such as melt temperature and
extrusion ratio, on the extrusion behavior of Al-Cu alloys in the semisolid state were investigated.
Mechanical properties of the melt extruded Al-Cu alloy were measured and its characteristics are
compared with the microstructure and copper contents in the alloy. Al-Cu alloys were successfully
extruded after squeezing out of liquid during the melt extrusion with smaller force (60 Mpa)
compared to the solid extrusion. Al-Cu alloys bar with the mean grain size of 200 μm was fabricated
by melt extrusion; however, the mechanical properties have nothing to do with the extrusion ratio.
The squeezing out of liquid was get lead to the segregation of the alloys and was affect on the
mechanical properties.
Constitutive Model of Thixotropic Plastic Forming for Semi-Solid AZ61 Magnesium Alloy
Authors: Yan Hong , Zhou Bing Feng
Published: March 2009

Uniaxial compression tests on semi-solid AZ61 alloy fabricated by stain-induced
activation (SIMA) process and the conventional casts were carried out using the Gleedle-1500
dynamic material testing machine. The relationships between stress and stain were analyzed. The
numerical relationships among processing parameters (strain rate z ε& strain z ε temperature T
liquid volume fraction L f ) and stress were studied. The proposed constitutive equation was
established for semi-solid AZ61 magnesium alloy using the multiple nonlinear regression method. A
scientific basic provided for both numerical simulation of processing process of semi- solid AZ61
alloy and rational choice and control of processing parameters.
Application of the Continuous Rheoconversion Process (CRPTM) to Low Temperature HPDC-Part II: Alloy Development & Validation
Authors: Wiesner Stuart , Pan Qin Yue , Apelian Diran
Published: March 2009

The continuous rheoconversion process (CRPTM) is a novel slurry-on-demand process
that was developed at MPI/WPI in 2002. The process is based on a passive liquid mixing technique
in which the nucleation and growth of the primary phase are controlled using a specially designed
“reactor”. The reactor provides heat extraction, copious nucleation, and forced convection during
the initial stage of solidification, thus leading to the formation of globular structures. This paper
presents our recent work on the scale-up of the CRPTM for industrial applications. In Part II of this
paper, we present salient results on alloy optimization via thermodynamic simulations, as well as
validation results obtained from industrial Beta trials.
Microstructure and Stress Variation of Semi-Solid Magnesium Alloy during Isothermal Compression and Its Relationship to Thixotropy
Authors: Shan Wei Wei , Jiang Ju Fu , Luo Shou Jing
Published: March 2009

Thixotropy is the most important characteristic of semi-solid materials, and it is decided
by the variation of microstructure during action of handling. In this paper, for the sake of the
industrial thixoforming and numerical simulation, microstructure and stress variation of semisolid
magnesium alloys during isothermal compression is researched. Here, samples are heated to the
desired temperature in the empty space with various holding times and compressed horizontally.
Stress–strain curves during compression can be given directly by the experimental computer, and
each of curves show a peak stress in a small strain and then decrease rapidly, which originally
because of the thixotropy of semisolid materials. Moreover, thixotropy of semisolid magnesium
alloys is clearer with the evolution of microstructures including agglomeration and deagglomeration
of solid particles and the moving way of liquid at different places and strain under different
conditions. Microstructures during isothermal compression show that the deagglomeration of solid
particles increase with increasing the strain rate, therefore, the thixotropy of semisolid magnesium
alloys increases. However, when solid volume fractions are lower, the agglomeration of solid
particles doesn’t change obviously with increase or decrease factors, meaning that the thixotropy is
smaller. Relationships between thixotropy and microstructure at other different conditions are also
given according to the experiments and analysis.
Rheological Properties of Molten Al-Cu Alloys for Manufacturing Metallic Foam
Authors: Park Soo Han , Um Yong Su , Hur Bo Young
Published: March 2009

The surface tension and the viscosity characteristics of molten metal are the most important
factors in casting process and metallic foam manufacturing especially. The surface tension (by the
modified ring method) and the viscosity (by the rotational method) of molten Al-Cu alloys have been
measured under high purity Ar gas atmosphere. The surface tension and the viscosity of Al-Cu alloys
were investigated in the temperature range of 660-800oC, and the effects of the additional elements
were investigated at the 660~680. The result show that the surface tension and viscosity of these
alloys decrease with increasing temperature together. The viscosity of Al-Cu alloys near the melting
point is about 4.7 to 5.7 [mPa.s]. The effect of additional thickening elements has the tendency that is
the surface tension decreased and the viscosity increased. This anomalous behavior has the relation of
the preferential adsorption of high activity elements on the surface.
Development of Computer Assisted Tool Design for Material Forming Processes
Authors: Kim Man Sig , Lee Eui Yeol
Published: March 2009

Current practice in designing tooling components for semisolid processing requires extensive
commitments of human resources. Even when utilizing currently available Computer Aided Design
(CAD) systems, tool design remains a complex task requiring large amount of design knowledge.
Considerations such as part material, tool material, characteristics of die filling, flow behavior of
semisolid slurries must be carefully thought by the tool designer to reach an acceptable tooling
solution. This paper proposes the framework for computer assisted tool design by integrating tool
design domain knowledge into CAD system to help tool designers.
Numerical Analysis of Two-Phase Thermal Flow for Rheology Forging Process
Authors: Seol D.E. , Kang C.G.
Published: March 2009

The algorithm two-phase flow model, developed in this study, gives die filling patterns,
velocity, temperature and solid fraction of rheology material during rheology forging process. To
calculate the velocity and temperature fields, the respective governing equations corresponding to
the liquid and solid region were adapted. Therefore, respective numerical models considering the
solid and liquid phase co-existent within the rheology material have been developed to predict the
defects of part manufactured by the rheology forging process. This study has focused on the
simulation of the rheology forging process and calculation of the velocity profiles and temperature
distribution. And, to predict the liquid segregation in the part, the deviation of velocity between
liquid and solid region in the two-phase flow model was analysed.
Viscosity–Shear Rate Relationship during the Thixoforming of HP9/4/30 Steel
Authors: Omar M.Z , Atkinson H.V. , Palmiere Eric J. , Howe A.A. , Kapranos Plato
Published: March 2009

Thixoforming involves shaping metal components in the semi-solid state. Work on the
thixoforming of high temperature materials, such as steel, is still at its initial stage; this is mainly
due to the high processing temperatures involved and the potential for oxidation. For thixoforming
to be possible, it is preferable for an alloy to have an appreciable melting range and before forming
the microstructure must ideally consist of solid metal spheroids in a liquid matrix. This paper
discusses the thixoforming load versus displacement curves of HP9/4/30 steel semi-solid slugs
under compression. The data from the corresponding load-displacement curves is converted into
viscosity against shear rate adopting Stefan’s equation for flow between two parallel planes. The
viscosity at processing conditions, i.e. at processing temperatures in the range of 1470 to 1480°C
and zero to two minutes soak times, showed a rapid decrease initially, which corresponds to a rapid
breakdown in the structure, followed by a steady decrease to a near constant value with increasing
rate. The work shows pseudoplasticity (or shear-thinning) behaviour of the HP9/4/30 semi-solid
slurries. This data would be required for modeling the die fill with these slurries.
Development of Heat Resistant Mg-Al-Ca Based Alloys for Casting and Semi-Solid Forming
Authors: Kim Jeong Min , Lee Gun Ha , Jun Joong Hwan , Kim Ki Tae , Jung Woon Jae
Published: March 2009

Mg-8%Al-1%Ca was selected as a base alloy composition and small amounts of minor
alloying elements, RE or Sr, were added. Microstructure of as-cast Mg-8%Al-1%Ca base alloys
consists of dendritic primary Mg, Mg-Al-Ca and Mg17Al12 phases. Mg-Al-RE-(Ca) phase in the
RE-added alloys and Mg-Al-Sr-(Ca) phase in the Sr-added alloys were additionally found. The
creep resistance of Mg-8%Al based alloy was significantly improved by the minor alloying
elements additions with 1%Ca. Comparatively globular primary phase could be obtained after just
30min. through an isothermal heating of as-cast Mg-Al-Ca alloys.
Microstructural Evolution and Deformation Behavior of Stainless Steel in Semi-Solid State
Authors: Li Jing Yuan , Sugiyama Sumio , Yanagimoto Jun
Published: March 2009

Thixoforming or Semi-Solid Metal Forming offers many advantages in comparison with
casting and conventional forging. The purpose of the present study is to provide the basic
microstructure and deformation data for austenitic and ferritic stainless steel under mushy state. As
well known, the stainless steels solidify in different modes according to the different chemical
compositions. In this paper, microstructural evolution of austenitic stainless steel type 304 which
solidifies in FA mode ( L → L +δ → L +δ +γ →δ +γ →γ ),austenitic stainless steel type 310S
which solidifies in A mode ( L → L +γ →γ ), and ferritic stainless steel type 430 which solidifies in
F mode ( L → L +δ →δ )are investigated during partial remelting by way of SIMA (Strain Induced
Melted Activation). The results show that A and F mode of stainless steels melt directly at the grain
boundary without phase transformation during reheating. A banded structure, originating from the
primary dendritic segregation of the original ingots, is observed in type 310S steel during further
heating. On the other hand, a perfect globular and insegregative two-phase semi-solid structure L +δ
can be obtained while heated beyond the banded three-phase L +δ +γ semi-solid state in FA mode
austenitic stainless steel type 304. This spheroidization can be attributed to the peritectic reaction
occurred in the L +δ +γ semi-solid state. In addition, simple compression tests of these alloys in
semi-solid state for varied combination of deformation rate and deformation temperature are
conducted to examine the deformation behavior of stainless steel. Flow stress curves exhibit abrupt
change in various alloys, even though in the same alloy such as type 304, various flow stresses are
observed according to the difference in inner microstructure or morphology. Stress of type 310S steel
shows the most reduction as the deformation temperature increasing at the same strain rate condition.
The Liquid is centralized to periphery by the compression force in all deformed test pieces. Fracture,
observed in all alloys except type 304 steel in globular L +δ semi-solid state, should be resulted
from the lack of liquid in L +δ +γ state of type 304 steel and solidification crack in type 310S and
type 430 steel. Deformation of solid particles occurs only in L +δ +γ state of type 304 steel. Last in
this paper, various deformation mechanisms are proposed for various microstructures.
Development of a Self-Heating Ceramic Tool for the Thixoextrusion of High Melting Point Alloys
Authors: Muenstermann Simon , Uibel Krishna , Tonnesen Thorsten , Telle Rainer
Published: March 2009

A novel ceramic tool concept allows near-isothermal steel thixoextrusion experiments. Thermal
shock impacts are successfully eliminated from the load profile of conventional semi-solid processing
technologies of high melting point alloys. Thus, the application of thermal shock sensitive oxide
ceramics exhibiting excellent corrosion resistance as forming dies is feasible. Extruded steel parts
show high shape accuracy at very low extrusion forces.
In Situ Environmental Scanning Electron Microscopy (ESEM) of Semi-Solid Samples
Authors: Smith A.J. , Atkinson H.V. , Hainsworth S.V. , Dong H.B. , Haghayeghi R.
Published: March 2009

The ESEM (Environmental Scanning Electron Microscope) is an instrument that
circumvents a limitation of conventional SEM, in that samples can be examined in a gaseous
atmosphere rather than a vacuum. With a heating stage, dynamic processes can be observed in situ
at high temperature. In this study, A201 aluminium alloy samples with globular structures have
been examined in the semisolid region. In addition, a manipulator has been installed onto the
heating stage to allow the probing of semi-solid surfaces. The paper shows the potential for
manipulating semi-solid materials in order to better understand thixotropic phenomena.
Thixoforming and Industrial Application of the Semi-Solid Alloy Al-6Si-2Mg
Authors: Xie Li Jun , Xu Jun , Yang Bi Cheng , Zhang Zhi Feng , Shi Li Kai
Published: March 2009

An application of the semi-solid alloy Al-6Si-2Mg to produce automobile components
was carried out for farther development of this new alloy. The experiments were done in a
self-developed SSM trial line composed of semi-continuous caster combined with electromagnetic
stirring for feedstock billet production, 6-station induction reheating equipment for restoring
thixotropy of SSM billet and modified die-casting unit for semi-solid thixoforming. The results
show that Al-6Si-2Mg alloy has such a suitable fraction solid and low temperature sensitivity of
fraction solid that the controllability of SSM process is increased greatly. The billets have uniformly
fine microstructure with a higher degree of sphericity and also retain good thixotropic properties.
During thixoforming, the die is filled completely, the microstructure of components is dense, and
the primary phases are near spherical, and the mechanical property after heat treatment has good
performance.
Thixoforming of Steel – Influence of Thermal Parameters
Authors: Cezard Pierre , Bigot Régis , Favier Véronique , Robelet Marc
Published: March 2009

This paper presents experimental results on steel thixoforming. The influence of thermal
effects on the semi-solid response is analysed through the influence of thermal exchanges with tools
and environment. Several rheological experiments such as compression, extrusion or radial filling
test were developed to understand the semi-solid steel behaviour and determine the parameters that
have a major influence on thixoforming. Actually, in our experiments, the temperature of the slug
and consequently the solid fraction were found first order parameters while; the morphology of the
solid phase plays a minor role.
High Volume Fraction Al2O3/Al Composite Thixoforging in Pseudo-Semi-Solid State
Authors: Du Zhi Ming , Cheng Yuan Sheng , Luo Shou Jing
Published: March 2009

In this paper the authors propose a new technology for high volume fraction ceramic/metal
composites—pseudo-semi-solid thixoforging, based on metal semi-solid process combing with
traditional powder metallurgy technology, and explain the differences with other technologies and
characters in detail. At the same time the authors prepare the cup shells with high volume fraction
Al2O3/Al composite by this technology. It proves that it is feasible for the high volume fraction
ceramic/metal composites forming through metallographic analyses and three-point bending tests.
The results show that the tough strength and degree of hardness of the samples with certain plasticity
are high. It will play a very big role in accelerating the ceramics composites and high melt point
materials being used in more fields and tamp the foundation for further studies of this technology.
Inductive Reheating of Steel Billets into the Semi-Solid State Based on Pyrometer Measurements
Authors: Schönbohm Alexander , Gasper Rainer , Abel Dirk
Published: March 2009

The aim of the paper is to demonstrate a control scheme by which it is possible to
reproducibly reheat steel billets into the semi-solid state. Usually a heating program is used to reheat
the billet into the semi-solid state. Our experiments showed that this control scheme leads to varying
semi-solid fractions from one experiment to the next. To gain information about the billet’s state its
temperature is often used since there is a known relationship between the temperature and the liquid
fraction. Direct measurement of the temperature via thermocouples is not feasible in a production
environment, therefore a radiation pyrometer has been used as a contact-less measurement device.
The accuracy of the pyrometer depends heavily on the exact knowledge of the radiation coefficient,
which can vary from billet to billet due to different surface properties and which is subject to change
during the heating process. These uncertainties prohibit the implementation of a closed-loop control
scheme since the exact temperature cannot be measured with the required accuracy. In order to be
independent of the measurement errors the proposed control scheme only relies on the slope of the
temperature. By detecting the distinct change of slope which occurs when the solidus temperature is
crossed, the beginning of the melting process can be determined. The energy fed to the billet from
this point onward determines the resulting liquid fraction. By detecting the entry into the solidusliquidus
interval and then feeding the same amount of energy to each billet, it is guaranteed that the
billet reaches the desired liquid fraction even by uncertain absolute value of the temperature and by
small variations of the alloy composition. For the experiments the steel alloy X210 has been used
and measurement data demonstrate the feasibility of the proposed control scheme.
Study on Static Shear-Rheologic Characteristics of Semi-Solid AZ91D Magnesium Alloy by Reheating
Authors: Ji Ze Sheng , Hu Mao Liang , Zheng Xiao Ping
Published: March 2009

Static shear-rheology for self-made semi-solid AZ91D magnesium alloy slurry was
studied by using the tester and a universal electronic machine. Shear-stress along with cylindrical
surface in the sample was produced by using the tester and then shear-rheologic deformation
happened. It showed that on the condition of the same loading, the longer the loading time and
holding time were, the larger the deforming rate was. When the holding time attained a certain
value, small grains acquired enough energy to grow up or amalgamate with prolonging the holding
time and coarse grains started to melt from intergranular or grain boundaries, but the critical
shear-stress kept a constant. The sample didn’t flow but appeared to instantaneous shear-strains with
starting to load. When the loading exceeded the critical value, the sample started to flow and had
the phenomena of elastic after-working, elastic before-working and remained deformation. The
rheologic characteristics of semi-solid AZ91D magnesium alloy were expressed by the five element
mechanical model: H1—(N1/H2)—(N2/S).
Optimization of the Microstructural Evolution of Al-8%Si in Cooling Slope Device
Authors: Semenov B.I. , Kuschtarov K.M. , Song Joon Hyuk , Ha T.S.
Published: March 2009

An experimental apparatus using cooling slope and thin metal container has been
developed to study controlled rheocasting process. The microstructural characteristics of Al-8%Si
industrial alloy processed by this route were determined statistically. The statistics and quantitative
analysis of the dispersions of particle’s diameters were used for process optimization. Emphasis is
placed on factors which determine the final grain size in a billet. It is suggested that much of the
refinement of the microstructure in the process may be caused by temperature fluctuations in solid
shell formed at cooling slope. The nuclei which could be formed by melting of eutectic phase in
solid shell and transferring by overheated liquid metal to the container mostly survived and
contributed to final globular microstructure of a billet and ring type feedstocks.
Flatness Based Inductive Reheating of A356 Billets into the Semi-Solid State
Authors: Schönbohm Alexander , Gasper Rainer , Abel Dirk
Published: March 2009

An important step in the processing of semi-solid metals is the inductive re-heating of the
feedstock material. The heating should lead to an uniform billet temperature in order to obtain good
forming results. The billet is supposed to be heated to the target temperature as fast as possible and at
the same time it must be guaranteed, that the outer area of the billet does not melt prematurely.
Conventionally the open-loop trajectories consist of simple power over time diagrams and are
generated by extensive experiments. By using an open-loop control scheme it is possible to chose a
desired trajectory for the middle axis temperature of the billet which respects the given constraint on
the heating process. By taking advantage of the flatness property of the system, an open loop
trajectory for the coil current can be calculated which ensures the desired behavior of the axis
temperature. The shape of the trajectory is determined by the shape of the desired trajectory and the
temperature dependent material properties, which have to be known with the needed accuracy. The
losses of the converter and induction coil are estimated online so that the induced power is known.
The trajectory ensures that the billet is heated to a temperature just below the solidus temperature
without overheating of the billet’s surface and with a very homogeneous temperature distribution.
The Experiments have been conducted using A356 aluminum alloy.
Development of Thixoextrusion Process for 7000 Series Al Wrought Alloys
Authors: Yoon Young Ok , Jo Hyung Ho , Lee Jin Kyu , Jang Dong In , Kim Shae K.
Published: March 2009

Thixoextrusion for 7003 and 7075 Al wrought alloys with different content of Cu was
carried out with respect to isothermal holding temperature in the partially remelted semisolid state.
Especially, despite higher extrudability index of 7075 Al wrought alloy compared with the
extrudability index of 7003 Al wrought alloy, the maximum extrusion pressures of 7075 Al wrought
alloy were about the same as the maximum extrusion pressures of 7003 Al wrought alloy at
temperature with the liquid fraction 10% (7003-624, 7075-609). The hardness values of
thixoextruded specimens were higher than that of as-quenched specimens only after partial remelting.
The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures.
The average grain sizes of thixoextruded specimens were smaller than average grain sizes of
homogenized specimens.
Effect of Crystal Orientation on Textures of Electromagnetic Stirred Aluminum Alloy
Authors: Lee Dock Young , Kang Suk Won , Kim Ki Bae
Published: March 2009

Recently, a rheocasting process has been interested to produce a structural part for an
automobile industry and so the slurry-on-demand process to make the semi-solid slurry having a fine
and globular microstructure has been very important to produce a high quality and cost effective part
in the rheocasting process. An electromagnetic (EM) stirrer employing for a slurry making process
was designed and prepared to induce simultaneously both a circumferential and vertical fluid flow of
a melt in order to control a rotation angle of EM stirring of a poured melt. In the present study, the
semi-solid slurry of Al-15%Cu alloy was produced in the EM stirrer and its microstructure and the
orientation distribution function calculated from the pole figure data was examined in accordance
with a various rotation angle of EM stirring between 0˚ (circumferential flow) and 90˚ (vertical flow).
The size and morphology of primary α phase was affected with a rotation angle of EM stirring and the
finest and the most globular primary α phase could be obtained at a rotation angle of EM stirring of
45˚ and 60˚. Also, due to the EM stirring the tendency to random orientation was appeared. Also, the
tendency of random orientation was the most at a rotation angle of 45˚ and 60˚. Therefore, it was
considered that the rotation angle of EM stirring of 45˚ and 60˚ was the most effective to induce the
non-dendritic growth of primary solid phase of EM stirred Al-Cu alloy.
Thixoextrusion Process of AZ31 Mg Wrought Alloy
Authors: Yoon Young Ok , Kim Shae K.
Published: March 2009

Thixoextrusion process has been developed for improving productivity, reducing extrusion
pressure, extending die life and even cost saving due to low energy consumption compared with
conventional extrusion process. The present study focuses on AZ31 Mg wrought alloy to investigate
the potential industrial applications of thixoextrusion process. The maximum extrusion pressures of
thixoextrusion process were very lower than that of hot extrusion process. The average grain sizes of
thixoextruded specimens were bigger than average grain sizes of hot extruded specimens. However,
the grains of the thixoextruded specimens did not show any asymmetry. Also, the microstructures of
thixoextruded specimens did not show any dendrites or rosette-like structures. The values of tensile
strength and hardness of thixoextruded specimens were lower than that of hot extruded specimens.
The specimens manufactured by the thixoextrusion were usually rather soft and their tensile strength
was lower than those of hot extruded specimens. If necessary, their low tensile strength can be
improved through appropriate heat.
Hot Forging of Semi Solidified High Strength Brass
Authors: Choe Kyeong Hwan , Cho Gue Serb , Lee Kyong Whoan , Kim Ki Young , Kim Myung Ho
Published: March 2009

The name “high strength brass” is given to the wrought and cast alloys indicating their
particular virtue of high strength, which can be achieved by additions of Al, Fe, Mn and Sn. Forgings
made from copper base alloys offer a number of advantages over products made by other processes.
However, because for forging more heat must be applied to the ingot which was solidified once, there
are some disadvantages in the economy of energy and time. In this study, we investigated the
microstructures and mechanical properties of high strength brass made by semi solid forging and
compared them with those of conventionally forged product and gravity die casting. No shrinkage or
gas hole was found in semi solid forgings. Fine equiaxed crystals developed at the center of semi solid
forgings, while grains in the corner of semi solid forgings were elongated perpendicular to the
pressure direction. The grains of semi solid forgings were smaller than those of conventional forgings
and gravity die castings. It is suggested that a rapid heat transfer condition due to applied pressure is
responsible for grain refinement. Tensile and yield strengths of semi solid forgings were as high as
those of hot forgings but elongation was positioned between that of conventional forgings and gravity
die castings.
A Study on the Composition Determination of Cu Alloys by Image Processing Technology
Authors: Kim Chan Wook , Kim Hang Goo , Suk Han Gil
Published: March 2009

This study examined the application of color measurement to determining the chemical
composition of Cu alloys such as Cu-Zn, Cu-Sn, and Cu-Al using a color recognition system.
Measured data showed that the hue intensity changed exponentially when Zn, Sn, or Al in the Cu
binary systems and fitted well with an exponential equation within the experimental error. This
indicates that the obtained equations can be used for predicting the compositions of Cu-Zn, Cu-Sn,
and Cu-Al systems by measuring the hue intensity.
Semisolid Casting of Automotive Component: Water Pump Lid
Authors: Wang H. , Xu Jun
Published: March 2009

Water pump lid is selected as the automotive component to be cast using semisolid casting
technology. Semisolid feedstock of alloy A357 was produced by a vertical continuous DC casting
with electromagnetic stirring. Non-dendritic structure was obtained in the feedstock billets. A
6-station induction heating system was developed for feedstock billet reheating. Multi-stage reheating
and well controlled reheating process resulted in a uniform temperature profile in the billet. Semisolid
casting was carried out in a conventional high pressure die casting machine. Die design and casting
parameters were adjusted to be suitable for semisolid casting. Compared with the conventional liquid
melt casting, semisolid casting resulted in a much higher microstructural integrity with reduced
shrinkage porosity.
Opportunities and Challenges for Use of SSM Forming in the Aerospace Industry
Authors: Govender Gonasagren , Ivanchev L.
Published: March 2009

SSM is now considered an established technology to produce high integrity near net shape
components for the automotive industry in particular. Although it is used extensively in the
automotive industry, very little attention has been given to aerospace applications. SSM processing
does demonstrate the potential to replace certain hogout components in commercial aircraft with the
main aim to reduce costs while maintaining high strength to weight ratios. In order to achieve this it
will require developing processes to reliably cast components with consistent properties to meet
aerospace requirements. Since SSM forming is a relatively new process, materials properties data
bases for components produced using this technique is very limited. One of the major challenges is
the generation of a data base of material properties to assist design engineers for design of
components, as well to assess the life expectancy and development maintenance schedules.
Variable-Runner System for Family Mold Filling Balance
Authors: Park Hyung Pil , Rhee Byung Ohk , Cha Baeg Soon
Published: March 2009

It is well known that the family-mold has an advantage to reduce the overall production
cost. However, defects are frequently occurred by an excessive packing the smaller volume cavity
during molding, especially when the volumetric difference between two cavities is not
negligible. Although the size of runner could be optimized by CAE analysis, the filling imbalance is
hardly avoided in the actual injection molding process by various means. In this study, we confirmed
the filling imbalance in a family-mold by the temperature and the pressure sensors, and developed a
variable-runner system for balancing the cavity-filling. We carried out experiments of balancing the
cavity-filling in the family-mold with the variable-runner system, and examined the effect of reduced
cross-sectional area of a runner in the system. We examined the conditions of the shear rate and the
viscous heating in the system with a CAE analysis. We also examined the influence of the injection
speed and types of resins to the balancing-capability of the system in order to help mold designers
easily adopt the variable-runner system to their design.
Microstructural Changes of SKD11 Steel during Carbide Dispersion Carburizing and Subzero Treatment
Authors: Kong Jung Hyun , Sung Jang Hyun , Kim Sang Gweon , Kim Sung Wan
Published: March 2009

Microstructural changes and hardness variations in SKD11 steel have been investigated during the processes of carbide dispersion (CD) carburizing, austenitization, subzero treatment and tempering. The carbon content of the surface region increased up to 3.0% after CD carburizing, and the surface phases consisted of two predominant types of M7C3 carbides (large primary eutectic M7C3 carbide and secondary M7C3 carbide), retained austenite and martensite. After austenitization, the carbon content of the surface region decreased to 2.4%. At the same time, surface hardness was reduced from 900Hv for the CD carburizing condition to 830Hv after austenitization. On the other hand, the hardness at the interior region of the austenitized steel displayed a 100Hv higher value than that of the CD carburizing steel. In spite of removal of the retained austenite, subzero treatment (at -100) of the austenitized steel resulted in a decrease in hardness, probably due to the softening of the martensite matrix. However, tempering (at 200 for 4 hours) of the subzero treated steel raised its hardness up about 70Hv compared to steel tempered without the subzero condition, due to precipitation of fine nano size carbides below 50nm.
Study on Nitriding Mechanism for Aluminum Using Barrel Nitriding
Authors: Okumiya Masahiro , Ikeda Hiroshi , Tsunekawa Yoshiki
Published: March 2009

In a previous study, an aluminum nitride (AlN) layer was formed below the melting point
of aluminum (Al) on the surface of an Al substrate (JIS-A1050) in a barrel with
alumina/aluminum-magnesium alloy powder which activates the substrate in the nitrogen
atmosphere. In this study, the mechanism of formation of AlN in the barrel was examined. AlN
formation requires an incubation period. During the incubation period, a white region on the surface
is observed by the optical microscopy. The Electron Probe Micro Analyzer (EPMA) show that this
region contains magnesium (Mg). It seems that Mg penetrates and diffuses from the filled Al-Mg
powder in the barrel. After that, the nitride is partially generated at the surface of the Al substrate,
and it grows with the substrate surface. The AlN layer thickness increases proportionally with the
square root of time, and it has good adhesion.
Characteristics of TiAl-Doped DLC/TiAlN/TiN Multilayered Coatings Synthesized by Cathodic Arc Evaporation
Authors: Chang Chi Lung , Jao Jui Yun , Ho Wei Yu , Wang Da Yung
Published: March 2009

The combinations of TiAl-doped DLC and TiAlN/TiN layers were designed to deposit on
the tool steels using cathodic arc evaporation in a continuously single batch process. The economic
advantage in depositing the combined coating in one production scale of PVD system is of practical
importance. The TiAl-doped DLC as lubricant coatings were synthesized by using arc plasma
sources mounted with Ti50Al50-target to emit high energy ion plasma to activate the decomposition
of acetylene reactive gases. The results show that the TiAl-doped DLC and TiAlN/TiN combined
coatings retained lower friction coefficient at approximately 0.15 during the steady-state sliding.
The lubricity and wear resistance of TiAl-doped DLC/TiAlN/TiN coatings is then demonstrated to
potentially be applied to the cutting tools with no lubricants.
Tempering Kinetics of S45C Martensitic Steel
Authors: Jung Min Su , Lee Seok Jae , Lee Young Kook
Published: March 2009

The strain change during the tempering of S45C martensitic steel was examined at
different heating rates using a dilatometer. Tempering stages 1 and 3 corresponding to the
precipitations of transition carbide and cementite were observed. Tempering kinetics at each stage
was investigated from the relation between the measured strain and atomic volume change during
tempering. From the tempering kinetic data, continuous heating tempering diagram was constructed
and the tempering kinetic model was proposed as Zener-Hillert type differential equation.
Aging Precipitation Behavior of Cu-Ag-Cr Alloy
Authors: Lei Jing Guo , Liu Ping , Tian Bao Hong , Zhi Xiao , Jing Xiao Tian
Published: March 2009

The Cu-Ag-Cr alloy is a kind of aging hardening copper alloy and has excellent combination properties of high strength and good electrical and thermal conductivity. In the present investigation, the aging precipitation behavior of Cu-Ag-Cr alloy is studied, and the effects of aging processes on the microstructure and properties are discussed. Emphasis is on the correlation between the coherency and coarsening behavior of the Cr precipitates. When the alloy aging at low annealing temperatures, the homogeneous dispersed Cr precipitates are observed to be approximately spherical and keep coherent with Cu matrix in the Cu-Ag-Cr alloy, the coherency is lost between at 450°C~520°C, coherency on coarsening process of Cr precipitates at high annealing temperatures, the radium for coherent / semi-coherent transition of the Cr precipitates is determined from TEM micrographs as 15-45nm. Aging in the intermediate stage, coherent and semi-coherent particles can co-exist(15<r<45nm). The precipitation can be accelerated by cold deformation before aging, the 60% deformed Cu-Ag-Cr alloy aging at 480°C for 1h, the hardness and electrical conductivity can respectively reach to 158HV and 85%IACS.
An Investigation of the Melt-Out and Heat Checking Phenomena in Surface Modified Hot Die Steel for Aluminum Die Casting
Authors: Youn Kuk Tae , Rhyim Young Mok , Lee Jong Hoon , Na Young Sang , Yoo Wee Do , Lee Chan Gyu
Published: March 2009

For hot die steel, failure is mostly caused by heat checking and melt-out on its surfaces
which are in contact with molten metals. In the present research, resistances to melt-out and heat
checking of surface modified H13 hot die steels, such as gas nitriding(GN) and
micro-blasting(MB), were investigated. The evaluation of melt-out behavior was carried out by
measuring the mean depth from the original surface after immersion. To examine the thermal
fatigue resistance, a cyclic thermal shock system consisting of induction heating and water spray
quenching was constructed. The value of Lm is proposed as the index representing the susceptibility
to crack initiation and propagation. The melt-out depth was the lowest for the GN treated surface.
MB-GN and MB-GN-MB treated specimens also showed good resistance to melt-out. In the case of
GN treatment, while the white layer was completely melted out, the diffusion layer still existed
even after immersion for 43 hours. This implies that nitriding significantly reduced the rate of
melt-out. From the total crack number, it is seen that crack initiation was reduced to the extent of
half after surface treatment. This result means that the residual compressive stress and nitrided layer
were beneficial to crack initiation resistance.
The Effect of Ca and Mn Addition on Ignition Temperature, Castability, and Electrochemical Properties of Mg-Alloy by Casting
Authors: Kim Hye Sung , Kim Tae Gyu
Published: March 2009

The effect of Ca and Mn additions on cast ability, ignition temperature, and electrochemical properties has been investigated in the as-cast magnesium alloys. Not only the remarkable improvement of electrochemical properties but also the ignition prevention of magnesium alloys during melting and casting is achieved by small addition of Ca and Mn into Mg. Flow length of the specimens decrease with an increase of Ca content. Serious decrease of flow ability in Mg melt is observed in Mg-1.31wt%Ca alloy. However, flow length of Mg-Ca alloys is negligibly influenced by small amounts of Mn addition. The improved performance of Mg-Ca alloys is attributed to the homogeneous and refined microstructures with extremely electronegative potential of Ca. It is considered from that serious reduction in flow length of Mg-1.31wt%Ca alloy is due to cast from large solidification interval.
Electrical Sliding Wear Property of Cu-Ag-Cr Alloy
Authors: Liu Ping , Jia Shu Guo , Ren Feng Zhang , Tian Bao Hong , Zheng Mao Sheng
Published: March 2009

By means of a vacuum induction furnace, Cu-Ag-Cr alloy were produced. The wear property and mechanism of Cu-Ag-Cr alloy are studied, and its property was compared with a Cu-Ag alloy. The microstructure of the Cu-Ag-Cr alloy before wear tests was analyzed by transmission electron microscopy. Worn surfaces of the Cu-Ag-Cr alloy were analyzed by scanning electron microscope (SEM) and energy dispersive X-ray spectrum (EDS). Wear tests were conducted under laboratory with a special sliding wear apparatus that simulated the tribological conditions of sliding current collectors on contact wires, and alloy wire was slid against a copper-based powder metallurgy strip under unlubricated conditions. The results show that the wear rate of Cu-Ag-Cr alloy increase with the increase in the sliding speed and the sliding distance. Adhesive wear, abrasive wear and electrical erosion wear are the dominant mechanisms under the electrical current sliding processes. At lower sliding speed, adhesives wear and abrasive wear are the major wear damage, while electrical erosion wear and adhesive wear are the major at higher sliding speed. Under the same conditions, the wear resistance of the Cu-Ag-Cr alloy is 2~3 times of the Cu-Ag alloy.