This article deals with the microstructural strengthening mechanisms
of aluminium by means of hard α-Al
$_{2}$
O
$_{3}$
alumina fine
particles. A broad of understanding views covering materials preparations,
elaboration process, characterization techniques and associated microstructural
characteristic parameters measurements is given.
In order to investigate the
microstructural characteristic parameters and the mechanical strengthening
mechanisms of pure aluminium by hard fine particles, a set of
Al-(α-Al
$_{2}$
O
$_{3}$
) alloys samples
were made under vacuum by high fusion temperature melting, the high frequency
(HF) process, and rapidly solidified under ambient temperature from a mixture
of cold-compacted high-pure fine Al and α-Al
$_{2}$
O
$_{3}$
powders. The
as-solidified Al-(α-Al
$_<FORMULA>_{2}$
O
$_{3}$
) alloys were
characterized by means of X-ray diffraction (XRD) analyses, optical microscopy
observations and Vickers microhardness tests in both brut and heat-treated
states. It was found that the as-solidified HF Al-(α-Al
$_{2}$
O
$_{3}$
) alloys with
compositions below 4 wt.% (α-Al
$_{2}<FORMULA>_O<FORMULA>_{3}$
) are single-phase
microstructures of the solid solution FCC Al phase and over two-phase
microstructures of the solid solution FCC Al and the Rhombohedral
α-Al
$_{2}$
O
$_{3}$
phases. The optical micrographs reveal the presence of a grain size refinement
in these alloys. Vickers microhardness of the as-solidified Al-(α-Al
$_{2}$
O
$_{3}$
) is increased by
means of pure fine α-Al
$_{2}$
O
$_{3}$
alumina particles.
These combined effects of strengthening and grain size refinement observed in
the as-solidified Al-(α-Al
$_{2}$
O
$_{3}$
) alloys are
essentially due to a strengthening of Al by the α-Al
$_{2}$
O
$_{3}$
alumina particles
insertion in the (HF) melted and rapidly solidified alloys.
