Effect of TiO2 particle size on reinforcements, reaction mode and kinetics in Al-TiO2-C system

The Aluminum Matrix Composites were manufactured by in situ reaction of Al powder, TiO2 powder, C powder. The effects of TiO2 particle size on reinforcements, reaction mode, and kinetics were studied. The results show that the reinforcements contain Al3Ti, Al2O3, TiC and AlN in Al-TiO2-C system. Al3Ti is lath-like with a length between 500-2000 mu m, there is a preponderance on quantity when TiO2 particle size is 30 nm, the area account for nearly 11.5%. TiC is granular and agglomerated, granular Al2O3 mainly distribute on Al grain boundary. Also there is a small quantity of AlN, the reaction mode is solid-liquid reaction. With the increase of TiO2 particle size (200 nm), Al3Ti changed from lath to block, and the length was declined sharply to 20-60 mu m. The distribution is uniform, but the area account for nearly 8.9%, compared with the Al-TiO2-C system prepared by 30 nm TiO2, the area ratio is reduced by 2.6%, the quantity is significantly decline. TiC distribution is more uniform, and the Al2O3 particles are melted and become blocky or ring what distribute on the grain boundaries or matrix of Al grains. The quantity of AlN is increased obviously, showing a ring shape, distributed on the alpha-Al grain boundary or phase boundary, the length is about 250 nm, and the reaction mode is solid-solid reaction. The particle size of TiO2 affects the speed of sintering process and the reaction rate. The smaller the particle size of TiO2, the faster the sintering speed. Also, at the beginning of the reaction, the smaller the particle size of TiO2, the faster the reaction the smaller the particle size of TiO2, the faster the reaction rate. However, as the reaction progresses, the influence of the particle size of TiO2 is weakened.