THE EVOLUTION OF SOLID POWDERS IN LIQUID ALUMINUM AT LOW TEMPERATURE AND THE EFFECTS OF ULTRASOUND ON IT

摘要

This research investigated the evolution of solid Ti powders in liquid Al at low melting temperature of 730 ℃. In situ Al_3Ti particles were synthesized due to the reactive diffusion between solid Ti powders and liquid Al. These Al_3Ti particles were blocky in morphology and smaller than 5 μm in size. It was found that the formation of Al_3Ti particles underwent the processes of nucleation, growth and rupture. Accordingly, a reaction-peeling model was suggested to illustrate the formation mechanism of small blocky Al_3Ti particles. In addition, the effects of high-intensity ultrasound on the diffusion reaction between solid Ti powders and liquid Al were studied. Ultrasonic fields in the Al melt could generate instantaneous high pressure and interparticle collisions, both of which could accelerate the formation rate of Al_3Ti particles significantly. An ultrasound assisted in situ method was proposed for producing in situ Al_3Ti/Al composites in this research.