Gs. Hanumanth et Ga. Irons, PARTICLE INCORPORATION BY MELT STIRRING FOR THE PRODUCTION OF METAL-MATRIX COMPOSITES, Journal of Materials Science, 28(9), 1993, pp. 2459-2465
The production of ceramic particle-reinforced metal-matrix composites
by the melt-stirring technique involves two different steps: firstly,
the establishment of particle-melt contact, and secondly, the wetting
of the particles by the melt. The wetting behaviour of metal-ceramic s
ystems has been studied extensively, whereas the contacting problem ha
s been largely neglected. In this paper, a novel in situ thermal metho
d has been used to investigate the kinetics of particle-melt contactin
g, based on melt cooling during and immediately after the particle add
ition. An enthalpy balance relates the amount of cooling and the fract
ion of the particles contacting the melt. For the aluminium alloy (A35
6) with 15 vol % silicon carbide (17 mum diameter), it was found that
only 16 % of the particles contacted the melt after mixing times of 15
min, but contact could be improved to 36 % by adding magnesium to the
melt. The fraction contacting the melt agreed well with the particle
volume fraction calculated independently. Sampling of the froth layer
on top of the melt revealed that a large portion of the particles resi
des there prior to incorporation into the melt.