In situ Al-SiOC composite fabricated by in situ pyrolysis of a silicone polymer gel in aluminum melt

In situ aluminum matrix composites were fabricated by the addition of a gelated BS290 silicone polymer precursor to molten aluminum where the polymer gel was pyrolyzed in the melt and produced ceramic phases with chemical composition close to that of SiOC. The results indicated successful incorporation of in situ formed micro-sized particles in the melt, which acted as reinforcement and nucleation sites in the aluminum matrix. Homogeneous dispersion of the in situ formed particles in the matrix was attributed to rapid release of a large amount of gas during pyrolysis, which would disintegrate the particles’ agglomerates. The fabricated composites had mostly equiaxed and much finer grains than their corresponding monolithic cast sample. To improve SiOC particles’ distribution and to remove the structural porosity, both composite and monolithic samples were hot extruded at 400 °C. Hardness, yield strength and compressive strength of the extruded composite sample were found to be about 23, 53 and 18% higher than those of the extruded monolithic sample, respectively. Fractography of the fracture surface of the tensile test samples indicated a ductile fracture mode for both extruded samples. Elastic modulus mismatch was recognized as the main strengthening mechanism for the composite sample.