Effect of SI Content on Microstructure and Mechanical Properties of the Spray-Formed SiCp/Al–Si Composites

The effect of the silicon content on the microstructure and mechanical properties of the SiCp/(1–x)Al–xSi (x = 7, 13, and 20 wt.%) composites, produced by spray deposition, are investigated. The average size of the eutectic Si and primary Si in the composite containing 20% Si (3.44 and 7.85 μm) is higher than that in the composites containing 13% Si (2.51 and 5.85 μm) or 7% Si (1.95 and 0 μm). With increasing in Si content, composites demonstrate an increase in the volume fraction of the primary Si and eutectic Si phases, and a decrease in the average distance between Si and Siphase particle. During tensile tests, the as-sprayed composite with a higher Si content shows an increase in elastic modulus, yield strength, and ultimate tensile strength, but a decrease in elongation. Both SiC particle/matrix debonding and Si decohesion are observed in all three composites, while the primary Si particle cracking is dominant in the composites containing 13 and 20% Si. The fracture reveals an increase in brittleness and in the tendency for the primary Si particles to crack, as the Si content increases.