الفهرس 
LITERATURE SURVEYOnly 14 pages are availabe for public view
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Abstract
The mechanical properties of eutectic composites have
received considerable attention during the past decade.
This is because of their potential advantages in many
applications, particularly at elevated temperatures.
The present work was devoted to study the effect of the
microstructure and micromorphology of the dispersed
phase of the Al-Ni eutectic alloy on the stress-rupture
properties.
The experimental work included the redesign and construction
of an electric resistance furnace in which the
as-cast Al-Ni eutectic alloys were prepared under
controlled Argon atmosphere. Heat treatment was carried
out on some of the as-cast rods to yield Al3Ni in
spherodized shape. Directional solidification was
performed on other rods to produce rod-like and lamellar
Al~Ni composites. This was accomplished on a directional
solidification apparatus which was especially modified
to satisfy the required conditions. The prepared Al-Ni
eutectic alloys were metallographically examined. Stressrupture
tests were performed at 573°K on specimens
representing the different alloy structures as well as
the directionally solidified Aluminium representing the
matrix of the composites. A stress-rupture testing
machine was especially constructed for this purpose.
The machine was equipped with a split electric resistance
furnace, temperature control system, system for determination
of the rupture time, and electric circuit for
detecting the breakdown of the supply current. The
stress-rupture tests were carried out at different
stress levels and the elapsed times to rupture were determined, Elongation of the fractured specimens was
measured. Macro and micro examination of the fractured
specimens were also carried out to study the fracture
mechanism.
The experimental results revealed that;
(1) The nature and morphology of the dispersed phase,
Al 3Ni, was different according to the preparation
technique used in the production of the Al-Ni
eutectic alloys in this work. The Al 3Ni phase
exhibited a feather-like appearance in the as-cast
alloys, globular shape in heat treated alloys,
aligned rod-like in composites directionally solidified
at high growth rates and lamellar at low growth
rates.
(2) The prepared Al-Ni rod-like eutectic composites
showed a colony structure. This was expected due
to the commercial purity of the materials used.
However, no colony structure was observed in the
lamellar structure, This may be attributed to the
low growth rate used leading to a higher G/R ratio
that suppressed colony formation.
(3) Stress-rupture properties of the unidirectional
solidified composites were superior to those of
the conventional cast and globular alloys, as
indicated by longer rupture times and lower percentage
elongation at rupture/rupture time for the
same stress. This is due to the more effective
strengthening of the aligned dispersed phase in
the composites