Effect of Dispersoid Size and Volume Fraction on Aging Behavior and Mechanical Properties of TiO₂-Dispersed AA7075 Alloy Composites

TiO₂-dispersed AA7075 alloy composites were produced by mechanical milling followed by hot uniaxial compaction and sintering. The effects of volume fraction and dispersoid size on precipitation kinetics, densification, and hardness of the composites were studied in detail. While the sinterability of the composites decreases with increasing volume fraction of the particulate reinforcement (dispersoid), the same increases with decreasing particle size of the reinforcement. Microstructural analysis using X-ray diffraction and scanning electron microscopy shows an improvement in the distribution of reinforcement with decreasing particle size. The hardness of the composites increases with increasing volume fraction and decreasing TiO₂ particle size. Further, the reinforced composites do not show age hardenability unlike unreinforced AA7075 alloy. Microstructural analysis reveals the formation of MgTiO₃ and ZnO near the TiO₂-AA7075 interface, which suppresses the formation of Guinier-Preston (GP) zone resulting in no age hardenability of the composites.