Centrifugal casting of aluminium containing in situ formed TiB2

A method of producing micrometre sized TiB2 particles within an aluminium matrix is the salt reaction method, using KBF4 and K2TiF6 salts. The advantages of this in situ reactive process are a small particle size and good particle/matrix interfacial bonding. However, this method is limited to producing low particulate volume percentage material (< 6 vol.-%). To overcome this limitation, centrifugal casting has been investigated. A series of casts was made to observe the influence of centrifugal acceleration g on final TiB2 distribution. This was done by casting at four different rotational speeds (rev min(-1)). The TiB2 particulate content was concentrated towards the outer radius with a clear interface between this region and the remaining unreinforced aluminium matrix. The final concentration of TiB2 particles increased with increasing rotational speed and particle clustering was found to influence the settling behaviour of the TiB2 particles. The present paper demonstrates that centrifugal casting may be employed to yield a higher volume percentage (> 10 vol.-%)TiB2 reinforced particulate metal matrix composite. Particle volume fraction is a weak function of g, and the final volume fraction may be controlled by the rotational speed. A model has been developed to describe development of the concentration profile of TiB2 particles as a function of rotational speed.