Mechanical Properties of Nanometric Al₂O₃ Particulate-Reinforced Al-Al₁₁Ce₃ Composites Produced by Friction Stir Processing

Abstract

Aluminum matrix composites reinforced with nanometer sized Al₂O₃ particles were produced from powder mixtures of Al and CeO₂ by the use of friction stir processing (FSP). This approach has combined hot working nature of FSP and exothermic reaction between Al and oxide. In the composites, Al₂O₃ particles (∼10 nm in size) and Al₁₁Ce₃ intermetallic compound were formed in situ by oxide-aluminum displacement reaction. The aluminum matrix of the composites has an average grain size about 400 nm. The composites produced exhibit high strength both at ambient and elevated temperatures. It is mainly attributed to the uniform dispersion of nanometer sized Al₂O₃ particles, which not only contribute significantly to the strength by the Orowan mechanism but also stabilize the fine structure at elevated temperatures.