Microstructure stability of as-extruded bimodal size SiCp/AZ91 composite

The microstructure stability and micro-hardness of as-extruded bimodal size (micron+submicron) SiCp/AZ91 composites were investigated. Results show that the significant grain refinement appears around micron SiCp at the temperature range of 643-693 K. Compared with monolithic AZ91 alloy and micron SiCp/AZ91 composite, the obvious submicron particle dense zones (SPDZs) are formed in the vicinity of micron SiCp in bimodal size SiCp/AZ91 composite during thermal stability test, which results in the small average grain size and improved microstructure stability. The micro-hardness of bimodal size SiCp/AZ91 composite is higher than that of monolithic AZ91 alloy and micron SiCp/AZ91 composite. The micro-hardness of bimodal size SiCp/AZ91 composite depends strongly on grain size and the lowest micro-hardness appears at 643 K.