Precipitation hardening characteristics of Al-Si-Fe/SiC particulate composites

The effect of age-hardening on the microstructure and mechanical properties of SiCp/Al-Si-Fe particulate composites have been studied. 5 and 15% SiC additions were used for the production of two grades of composites. The composite samples were solution heat-treated at 500 °C for 3 h and quenched in warm water at 65 °C. The samples were then aged at 100, 200 and 300 °C for various ageing times between 1 and 11 h. The microstructure obtained reveals a dark ceramic and white metal phases, which resulted into increase in the dislocation density at the particles-matrix interfaces. The mechanical properties measured included: tensile strength, yield strength, hardness values and impact energy. The composites produced exhibited maximum mechanical properties at peak ageing at various ageing temperatures. These increases in mechanical properties during ageing are attributed to the formation of a coherent and uniform precipitation of the second phase in the matrix of the metal. This result shows that a substantial improvement in mechanical properties has been achieved in the reinforced metal matrices produced after age-hardening.