Wetting between the dispersoid and the matrix alloy is the foremost re
quirement during the preparation of metal matrix composites (MMC) espe
cially with the casting/liquid metal processing technique. The basic p
rinciples involved in improving wetting fall under three categories: (
i) increasing the surface energies of the solids, (ii) decreasing the
surface tension of the liquid matrix alloy, and (iii) decreasing the s
olid/liquid interfacial energy at the dispersoid matrix interface. The
presence of magnesium, a powerful surfactant as well as a reactive el
ement, in the aluminium alloy matrix seems to fulfil all the above thr
ee requirements. The role played by magnesium during the synthesis of
aluminium alloy matrix composites with dispersoids such as zircon (ZrS
iO4), zirconia (ZrO2), titania (TiO2), silica (SiO2), graphite, alumin
ium oxide (Al2O3) and silicon carbide (SiC), has been analysed. The im
portant role played by the magnesium during the composite synthesis is
the scavenging of the oxygen from the dispersoid surface, thus thinni
ng the gas layer and improving wetting and reaction-aided wetting with
the surface of the dispersoid. The combinations of magnesium and alum
inium seem to have some synergistic effect on wetting.