agglomerate and collect in between the larger aluminumparticles.
Additives are often added to reduce the electrical attraction of the
SiC particles [10]. The compacted and sintered composite is often
rolled or extruded into final shape. The powder metallurgy
method of producingAl/SiCMMC is more costly than the casting
method of production.
Spray forming is another method of producing Al/SiC
MMCs. This method involves spray atomization of molten
aluminum and injection of SiC particles into the stream of
molten aluminum particles (Fig. 1a). The spray is collected on a
plate where it is quickly solidified [11]. In this process segregation
due to gravity is avoided. Interfacial reactions between
SiC and aluminum are minimized due to the short time the SiC
particles are in contact with the molten aluminum. However, the
mechanical properties of composites produced by this method
have not been impressive [12]. This is due to different cooling
rates and improper collision angles causing that many of the
particles to not be engulfed by the molten aluminum during their
flight. The result is that, particles are not strongly bonded to the
matrix [13].
Here we present a new method based on centrifugal atomization
of the molten matrix while injecting SiC particles just prior
to atomization (Fig. 1b). This method has two advantages. One is
that it reduces particle agglomeration by creating a pre-combined
powder metallurgy MMC with evenly dispersed particles, which
does not require mixing.
The second is that it reduces the SiC particles contact time with
themolten aluminum, therefore, the reaction times areminimized.