| Based on the conventional method, in this thesis, with the application of high-intensity ultrasound in the reaction among halide salts and molten aluminum, a new preparation method of Al-Ti-B master alloy was put forward. After intensively studied the application parameters of ultrasound, we prepared new Al-1.2Ti-0.5B master alloy under 720℃, with continuous 800w high-intensity ultrasonic vibration for six minutes.Compared with the master alloy prepared by the conventional way, the mean size of TiB2 particles in new Al-1.2Ti-0.5B master alloy is diminished from 2.16μm to 0.57μm and the spread of size distribution is reduced from 0.2μm -3μm to 0.1μm-1μm, much more closer to the ideal state. There are some agglomerated TiB2 particles in the microstructure. In the grain refinement of commercial purity aluminum, new Al-1.2Ti-0.5B master alloy has a quick response, a very good grain-refining result, but fades quickly. New Al-1.2Ti-0.5B mater alloy not only refinedα-Al but also modified eutectic Si in the grain refinement of A356 Al-Si alloy. In the new Al-5Ti-1B master alloy prepared by the new technique within the application of ultrasonic vibration for four minutes, the blocky TiAl3 particles were 10μm-20μm in size and the isolated regularly polygonal TiB2 particles do not cling to each other. The mean size of TiB2 particles is 0.65μm and size distribution is 0.1μm-1.5μm. It has an ideal grain refining performance in the commercial purity aluminum with quick response, low fading. But it can not effectively refine A356 Al-Si alloy.The new preparation method with the application of ultrasound in the halide salts reaction process can really reduce the reaction time and optimize size characteristics of particles. But with different Ti/B ratio, the process parameters are not the same. Also because of the difference of Ti/B ratio, the extent of chances brought by ultrasound to size characteristics of TiB2 particles and grain-refining performance is different. |
