Role of Ti and Y in the nucleation of the primary α-Al of Al7075–Ti–Y natural composites and influence of ultrasonic vibration

Abstract Al7075–Ti–Y natural composites were prepared by using a combination of ultrasonic vibration and casting. The effects of titanium (Ti) and yttrium (Y) on the nucleation of primary α-Al were studied and the influencing mechanism of Y on the TiAl 3 formation was analysed. Furthermore, a reaction kinetics model of TiAl 3 under ultrasonic vibration was established. The results showed that the uniformly distributed TiAl 3 and Al 3 Y nano-particles resulted in grain refinement. Y changed the morphology of TiAl 3 and the appearance of corrosion pits was related to the fact that Y was dissolved within the TiAl 3 structure to form Ti(Al,Y) 3 . The established model revealed that ultrasonic vibration significantly promoted the formation of TiAl 3 , and that ultrasonic time was the main factor affecting its growth.