Preparation and theoretic study of semi-solid Al2Y/AZ91 magnesium matrix composites slurry by ultrasonic vibration

Semi-solid Al2Y/AZ91 magnesium matrix composites slurry was prepared by ultrasonic vibration, effect of ultrasonic vibration temperature and time on microstructure of semi-solid slurry was investigated. The results showed that with the ultrasonic vibration temperature decreasing the solid volume fraction of semi-solid slurry increased. The best ultrasonic vibration temperature was 600 degrees C. With the increase of ultrasonic vibration time, the average grain diameter of primary a-Mg particles decreased firstly, then increased, the average shape factor increased gradually and decreased slightly after 90 s, and a few rosette dendrites were observed after 120 s. The best semi-solid slurry with average grain diameter of 75 mu m and shape factor of 0.7 were gained after the melt was treated by ultrasonic vibration for about 60 s at near liquidus temperature (600 degrees C). At last, the microstructure evolution mechanism of semi-solid magnesium matrix composites slurry was analyzed by the theories of thermodynamics and kinetics.