The structure and bending properties of squeeze-cast composites of A356 aluminium alloy reinforced with alumina particles

In the present work, variations in the microstructure, mechanical propertie s and fracture character of Al2O3/A356 composites fabricated by squeeze cas ting at different solidification cooling rates were investigated. Experimen tal results showed that when the solidification cooling rate decreased, the crystalline grain size of the matrix alloy and the eutectic silicon phase increased gradually, but the bending strength and the elastic modulus decre ased. For Al2O3/A356 composites fabricated by squeeze casting, solidificati on occurred first in the interstices between particles and the particle sur face was the substrate for the heterogeneous nucleation of the eutectic sil icon phase. Fracture surfaces of the Al2O3/A356 composites showed brittle f racture characteristics and broken and cleaved Al2O3 particles were observe d on the fracture surfaces of the composites. (C) 1999 Elsevier Science Ltd . All rights reserved.