Microstructure Evolution of Semi-solid TiAl3/A356 Composite Prepared by Ultrasonic Vibration

The semi-solid TiAl3/A356 aluminum composite was prepared by ultrasonic vibration treatment (UVT). The effects of UVT temperature, time and power on the microstructure of semi-solid slurry of TiAl3/A356 composite were studied by SEM and XRD. The results reveal that the size of primary alpha-Al particles increases with the decrease of UVT temperature and power. The size of the primary alpha-Al particle decreases first and then increases with the increase of UVT time. When treated at a UVT temperature of 608 degrees C and a UVT power of 1 kW for 60 s, a good primary alpha-Al particle morphology with an average size of 62 mu m and a shape coefficient of 0.8 can be obtained. The mechanism involved in the development of microstructure is the result of the increase of nucleation rates and undercooling caused by cavitation and acoustic streaming. Furthermore, the in situ TiAl3 particles have strong ability to nucleate alpha-Al particles.