Formation of in-situ Al3Ti particles from globular Ti powders and Al alloy melt under ultrasonic vibration

The formation process of Al3Ti was studied based on the in-situ reaction between globular solid Ti powders with almost uniform size and 2024 Al melt under ultrasonic vibration. The microstructures of the Al3Ti/Al composite were examined at different reaction time. The reaction mechanism was analyzed based on the phase diagram and empirical reaction kinetics. Moreover, the effects of ultrasonic vibration on the formation of Al3Ti were discussed. The results show that the Al3Ti formed a layer around the unreacted Ti particle and was ruptured as the reaction continuing. An empirical reaction kinetics model of in-situ Al3Ti was established. The kinetic exponent n is determined to be 0.86, which is much higher than that of the standard diffusion-controlled growth (n = 0.5). The ultrasound assisted reaction follows an interface-controlled growth which means a higher reaction rate. The comprehensive effects of instantaneous pressure, high-intensity shock waves and local high-temperature caused by acoustic streaming and cavitation, are responsible for the high reaction rate and fine Al3Ti particles during the reaction process under ultrasonic vibration. (C) 2015 Elsevier B.V. All rights reserved.