In situ synthesis of Al-TiCp composites by reacting K2TiF6 and particulate graphite in molten aluminium

Al-TiCp composites have been extensively studied in recent years owing to their attributes as wear-resistant structural materials and to their potential as efficient grain refiners. In the present work, Al-TiCp composites were synthesized in situ by reacting K2TiF6 and graphite in molten aluminium. TiC particles form in increasing numbers with increasing reaction temperatures when Ti is introduced into molten aluminium in the form of a halide salt, to-ether with graphite. Blocky Al3Ti particles form first and then dissolve in the melt with increasing temperatures and holding time. The reduction of K2TiF6 by molten aluminium generates K-Al-F salts which clean the particle surfaces and remove the oxide layer from the surface of the melt. The reaction between carbon and solute Ti is promoted, generating TiC particles, once the graphite particles are incorporated into the melt, thanks to the improved wetting provided by K-Al-F salts. The Al3Ti particles are gradually replaced by TiC particles upon holding the melt further at 1000 degrees C. (C) 2006 Elsevier B.V. All rights reserved.