Influence of ageing on fatigue properties of graphite reinforced aluminium composites

Impact of age hardening and incorporation of graphite particles reinforcements on fatigue properties of Aluminum metal matrix composites which were fabricated with liquid metallurgical method is explored in this paper. Fabricated fatigue testing specimens were age hardened at temp of 170 °C and 270 °C to improve fatigue strength. Both aged and ascast specimens were characterized to study fatigue properties at operating temperature.Ggraphite particulate and age hardening temperature influences the fatigue strength of composites owing to its higher fatigue life compaed with as cast condition and age hardening at 270 °C. The incorporation of graphite exhibited remarkable improvement in fatigue strength. The detailed study of fractured surfaces of composites under microscope revealed its failure mechanism. It is found that , hardness increased with aging temperature up to 170 °C, beyond which found to be decreased resulted in formation of precipitation near the grain boundaries and enhanced the hardness of composites. But at 270 °C, both precipitate and grain boundaries abrading reduces both strength and hardness of composite. EDS analysis of composites at different phases for particles and interface between matrix and graphite particles is shown rich phase in aluminium matrix and poor at the interface.