Abstract:The behavior of ceramic particles at the solid/liquid interface and the distribution of particles in metallic matrix composites was studied with a zone unidirectional solidification method. Two kinds of partice dispersed composites, Al₂O_3P/Al-12.6%Si-Sr and Al₂O_3P/Al-12.6%Si-Sr-Ca containing Al₂O₃  particles in volume fraction 2%~5% were used. In the Al₂O_3P/Al-Si-Sr composites, the particles were pushed by the solidifying front, and did not uniformly distribute in the solid. But in the Al₂O_3P/Al-Si-Sr-Ca composites, the particles were engulfed by the solidifying front and uniformly distributed in the solid. The particles engulfing into the solid was realized only by Sr and Ca addition at the same time. As the interfacial energy between solid and particle was decreased in this case, the Al₂O₃ particles acted as the substrates of heterogeneous nucleation for the Si phases, which made the particles to be engulfed.

Key words: metallic matrix composites; solidification; particle size distribution