Solid State Phenomena
Vol. 127
Vol. 127
Solid State Phenomena
Vols. 124-126
Vols. 124-126
Solid State Phenomena
Vols. 121-123
Vols. 121-123
Solid State Phenomena
Vol. 120
Vol. 120
Solid State Phenomena
Vol. 119
Vol. 119
Solid State Phenomena
Vol. 118
Vol. 118
Solid State Phenomena
Vols. 116-117
Vols. 116-117
Solid State Phenomena
Vol. 115
Vol. 115
Solid State Phenomena
Vol. 114
Vol. 114
Solid State Phenomena
Vol. 113
Vol. 113
Solid State Phenomena
Vol. 112
Vol. 112
Solid State Phenomena
Vol. 111
Vol. 111
Solid State Phenomena
Vol. 110
Vol. 110
Solid State Phenomena Vols. 116-117
Paper Title Page
Abstract: Semi-solid forming (SSF) involves alloys with non-dendrite microstructure that contain spherical
solid particles in the liquid matrix. This process is generally divided into three main steps: feedstock
manufacturing, reheating and forming.
Feedstock has the main effect on the cost and quality of product. Many researches have been carried
out to reduce the cost of feedstock manufacturing. Slope plate is a simple semi-solid process that
can reduce the cost of feedstock. In this study a Cu plate with water and without water circulation
was used to investigate the effect of pouring temperature, cooling rate during casting and
solidification in the mold on the microstructure. Cast ingots with optimized microstructure were
reheated in various time and temperatures in semi-solid region to obtain kinetics of globularization
and solid grain growth.
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Abstract: Reheating process in the semi-solid state is a very important step in the thixoforming
process. In this research semi-solid ductile cast iron and Al alloys (Al-2.5Si, Al356) prepared by
inclined plate method, were reheated to examine the effect of reheating conditions on the
microstructure and coarsening kinetics of the alloys. For ductile cast iron, solid fraction at different
reheating temperatures and holding times was obtained and based on these results the optimum
reheating temperature range was determined. In the case of Al alloys increase of holding time in the
semi-solid state, leads to increase of liquid fraction, solid grain size and improvement of sphericity
of solid particles. In addition, the results show that coarsening kinetics of microstructures of both
alloys during reheating was diffusion controlled and can be mostly treated by Ostwald ripening
theory.
205
Abstract: This paper deals with the examination of the steel grade X210CrW12 and its suitability
for Thixoforming. In the semi-solid state, the microstructure of this steel consists of a homogeneous
distribution of globular particles surrounded by liquid. Additionally, carbides are stabile up to
fraction liquid contents of approximately 40%. After quenching, this steel reveals a globular
austenitic microstructure with eutectic (former liquid phase) at the grain boundaries. Compression
tests permit to determine the influence of different process parameters on the properties and the
material behaviour in the semi-solid state. Their influence on the microstructure was investigated
but not yet highlighted. Further investigations on this steel allow a fine-tuning to establish optimal
process windows of the different thixoforming- and rheoforming- routes.
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Abstract: The structural control of Al-Si alloy, which was not studied among various electromagnetic
processing of materials, was considered applying the alternating current and direct current magnetic
flux density. The main aim of the present study is to investigate the effects of electromagnetic
vibration on the macro and microstructure of Al-Si alloy in order to develop a new process of
structural control in Al-Si alloy. When the electromagnetic vibration is conducted for changing the
shape of primary aluminum, at low frequency (≤ 60Hz), the shape of dendrite is changed speroidal
shape. When the electromagnetic vibration is conducted for changing the shape of eutectic silicon, the
fact that a morphological change of the eutectic silicon from coarse platelet flakes to fine fiber shape
is observed with EMV (Electro Magnetic Vibration) process at high frequency(≥ 500Hz).
213
Abstract: In-situ Al-4.5Cu-5TiB2 composite plates were stir cast with TiB2 particles formed
through mixed salt route. The as-cast samples with 30 volume percent liquid content were rolled in
mushy state down to 2.5 and 5 percent reduction in thickness per pass. The rolled products found to
be defect-free after the first pass were subjected to multiple roll passes in mushy state with identical
experimental conditions, adding up to seven. The wear properties of as-cast and mushy state rolled
composites were also investigated, and correlated with microstructure.
217
Abstract: The success of the thixoforming process depends on the possibility to confer to material,
when it is found in the semisolid state, a microstructure characterized by globular particles of solid
phase surrounded by a continuous film of liquid phase; such microstructure is obtainable through
particular thermo-mechanical treatments. In the present research, in order to optimize the influence of
process parameters in the step in which the thixotropic properties are conferred to the AA7075
aluminum alloy, the statistic technique of the Design Of Experiments (DOE) has been used. The
advantages in the application of such technique are expressible in terms of reduction the times of
development of process and more efficient use of resources. A Central Composite Design factorial
plan with two levels has been realized to allow the evaluation of experimental error and to check the
adequacy of the model. The experimental tests foreseen from the same plan have been therefore
performed. Using the method of the response surfaces (RSM), the function of response has been
formulated, and the analysis of the experimental data has been realized by the linear regression
method. Finally, the analysis of variance (ANOVA) allowed to value the causes of variability of the
results. Statistic test has been performed on the significance of single factors and their interactions.
221
Abstract: Back extrusion technique was employed to characterize phase segregation tendency of
mechanically stirred ZA27 alloy at different deformation rates. Variation of segregation intensity
with ram diameter was found to follow opposite trends at low and high ram speeds. At sufficiently
high ram speeds, small rams are of better performance in minimizing segregation whereas at low
ram speeds, large rams result in less pronounced segregation. In addition, increasing ram speed
invariably decreases segregation degree. Back extrusion at very high shear rates provided via a
Drop Extruder Apparatus capable of displacing ram at speeds in excess of 1m/s results in
production of very homogeneous products in terms of solid fraction as well as size distribution of
globules.
225
Abstract: The evolution of the microstructure of semi-solid Al-Cu alloys has been characterized
during isothermal treatments in the semi-solid state by using in-situ X-ray microtomography
experiments carried out at ESRF, Grenoble. This work is therefore a continuation of previous
experiments reported at the 8th S2P Conference in Limassol. Quantitative data are presented dealing
with changes with holding time of the solid volume fraction, of the solid-liquid interface area and of
the mean and Gaussian curvatures of the solid phase. Discussion of the results is carried out on the
basis of the mechanisms involved in semi-solid systems.
231
Abstract: Magnesium alloy AZ31, which processed by conventional rolling or extrusion, has high
anisotropy of mechanical properties in its strength and elongation at room temperature. We compared
the influence of differential speed rolling with conventional rolling process on microstructure and
mechanical properties of commercial AZ31 sheet. Commercial AZ31 alloy sheets were processed
with conventional and differential speed rolled with thickness reduction ratio of 30% at a various
temperature. The elongation of AZ31 alloy, warm-rolled by differential speed rolling is larger than
rolled by conventional rolling. Besides, grain size and distribution on microstructure of the
conventional rolling were coarsely(~30μm) and inhomogeneously but, that those of the differential
speed rolling were fine(~13μm) and homogeneously.
235
Abstract: In order to produce a high quality and cost effective part in the rheocasting process for an
automobile industry it has been important to develop a slurry-on-demand process, which can
manufacture the semi-solid slurry having a fine and globular structure of primary solid phase. The
morphology of primary solid phase of semi-solid slurry is coarsened and globularized during an
isothermal holding process in a solid-liquid region. Accordingly, in this paper, the microstructural
evolution of semi-solid slurry during the isothermal holding at a various temperature in solid-liquid
region was investigated to examine a coarsening and globularization behavior of primary solid
phase. The semi-solid slurry of Al alloy was produced in a slurry maker using a multiplex-type
slurry cup that we developed recently. A size of primary solid phase was the finer at the higher
holding temperature, but under a constant holding time a roundness degree of primary solid phase
was the lower at the lower holding temperature. Also, a coarsening rate of primary solid phase was
not considered to be affected significantly by a holding temperature even though a little lower
coarsening rate was obtained at the higher holding temperature.
239