Effect of Thermal Ageing Characteristics of Al-Si-Fe/Sic Particulate Composite Synthesized by Double Stir Casting

The effect of thermal ageing on the microstructure and properties of 10wt% and 20wt%SiC particulate reinforced Al-Si-Fe matrix composite, produced by double stir casting route, have been studied. The composite samples were solution heat-treated at 500oC for 3 hrs and aged at 100, 200, and 300oC with ageing time between 60 and 660 minutes. The ageing characteristics of these grades of composite were evaluated using hardness values, impact energy, tensile properties and microstructure. The tensile strength, yield strength, hardness values increased as the percentage of silicon carbide increased in the alloy with decreased impact energy in both the as-cast and thermally age-hardened samples. The increases in hardness values and strength during thermal ageing are attributed to the formation of coherent and uniform precipitation in the metal lattice. It was found that both grades of composites showed acceleration in thermal ageing compared to the monolithic alloy. However, the 20wt%SiC reinforced composite showed more acceleration compared to 10wt%SiC reinforced composite.