The effects of aging on the hardness and fatigue behavior of 2024 Al alloy/SiC composites

The material tested in this work is 2024 aluminum alloy reinforced with particulate silicon carbide (SiCp). The material was produced by a squeeze-casting technique, which gives rise to composites with a uniform distribution of SiCp throughout the matrix. The effects of the percentage of additives on the microstructure, hardness and fatigue strength of the material produced are discussed. The effects of the age-hardening process are also considered. The results show that reinforcement and cold working before artificial aging have accelerated the reaction kinetics of the precipitation-hardening process of the composite. The peak hardness of these composite materials is found to be comparable to or slightly higher than that of the unreinforced alloy. On the other hand, fatigue tests showed that the limit of the fatigue strength is improved by the presence of SiCp and by artificial aging at 170°C. This limit has been increased by 100% for Al alloy/5 wt.% SiCp composites compared to that found for unreinforced alloys.