Solidification behaviour and microstructure of A360-SIC P cast composites

Abstract

In the present investigation, the solidification microstructure of Al based composites was studied. The materials investigated were a commercial A360 aluminium alloy and the corresponding composites reinforced with 10 and 20 vol. % SiC particles. The materials were cast under different conditions for a first set of laboratory tests, aimed at studying the solidification behaviour and the related microstructures. The reinforcement distribution in the cast composites revealed to be governed by the pushing action exerted by the matrix solidification front during casting, giving rise to clustering effects of the SiC at dendrite boundaries, especially in sand castings. Copper mould castings, experiencing reasonably high cooling rates during solidification, showed a very fine microstructure within which the segregational effects of the reinforcement was of limited relevance. SiC particles also revealed to be a site for heterogeneous nucleation of coarse Si crystals in the composites.