Microstructure and mechanical properties of Nano-ZrO2 and Nano-SiO2 particulate reinforced AZ31-Mg based composites fabricated by friction stir processing

Friction stir processing (FSP) has been applied to fabricate 10 similar to 20 vol% nano-sized ZrO2 and 5 similar to 10 vol% nano-sized SiO2 particles into an Mg-AZ31 alloy to form bulk composites under the FSP parameters of advancing speed of 800 rpm and pin rotation of 45 min/min. The microstructures and mechanical properties of the resulting composites were investigated. The clustering size of nano-ZrO2 and nano-SiO2 particles, measuring average similar to 200 nm was relatively uniformly dispersed, and the average grain size of the both Mg alloy of the composites varied within 1.0 similar to 2.0 mu m after four FSP passes. No evident interfacial product between ZrO2 particles and Mg matrix was found during the FSP mixing in AZ31-Mg/ZrO2. However, significant chemical reactions at the AZ31-Mg/SiO2 interface occurred to form the Mg2Si phase. The mechanical responses of the nano-composites in terms of hardness and tensile properties are examined and compared.