The structure of centrifugally cast composite casting
Jacek Jackowski, Paweł Szymański
Quarterly No. 1, 2012 pages 66-71
DOI:
keywords: dispersion composites, centrifugal casting, gradient structure
abstract The most frequently used methods for manufacturing composite castings with an internal structure composed of a metal matrix and solid particles of the reinforcing phase are gravitational casting (into disposable or permanent moulds), pressure die casting, squeeze casting and centrifugal casting. The diphase character of the composite suspension designed for casting leads to the fact that its gravitational casting is delimited, among others, by a minimum thickness of the casting walls. The process of casting composite suspensions using the centrifugal method is unavoidably accompanied by migration of the reinforcing phase particles. It means that during the casting process, the particles move with respect to the liquid metal matrix. Therefore, experimental tests have been made with a view to manufacturing composite castings with the method of centrifugal casting. The tests were aimed at answering whether thin-walled castings may be manufactured using this method and checking the effect of the method on the behavior of the particles present in the cast suspension. The tests have been performed using a standard composite material with an aluminum alloy matrix including silicon carbide particles. The cast part was a small turbine with a blade thickness of about 1 mm. The casting moulds were made from a gypsum mass which was poured in a device composed of an induction furnace and a mechanism, referred to as a caster, that ensured rotation of the mould around a vertical rotation axis. The castings obtained in such way were evaluated with regard to matching the required shape and achieving a uniform distribution of the reinforcing phase in the composite material samples cut from various points of the casting and its gating system. It was found that the casting conditions allow one to obtain thin-walled castings, however, migration of the reinforcing phase particles in the cast suspension is significant. Hence, further research of the conditions of applying the method appeared necessary.