Simultaneously improving the strength and ductility of extruded bimodal size SiCp/AZ61 composites: Synergistic effect of micron/nano SiCp and submicron Mg17Al12 precipitates

AZ61 matrix reinforced by micro- and nano-scaled SiC particles fabricated via semisolid stirring assisted ultrasonic vibration was subjected to extruded at different speeds (0.1, 0.5 and 2.5 mm/s) with a constant temperature of 280 ℃. The effect of extrusion speed on the microstructure and tensile properties of the extruded composite was investigated. Grain size, precipitates fraction and texture were found to be greatly affected by the extrusion speed, resulting in tensile properties showing superior strength and ductility as the extrusion speed being of 0.1 mm/s. The improved strength and ductility were ascribed to the synergistic effect of micron/nano SiCp and submicron Mg17Al12 precipitates. The strengthening mechanism of extruded composites was also discussed.