Phase Formation and Interfacial Phenomena of the In-Situ Combustion Reaction of Al-Ti-C in TiC/Mg Composites

Abstract

Phase evolution and interfacial characteristics through the combustion reaction of Al-Ti-C system were investigated, in terms of the reaction mechanism. The phase formation in the reaction system at 650, 660, and 670°C by in-situ high temperature X-ray diffraction (HT-XRD) showed the formation of the solid Al₃Ti phase, along with melting of the Al at 660°C. Microstructural analysis of the Al-Ti-C system after holding at 670°C was carried out to identify the reaction mechanisms, which were the formation and growth of the Al₃Ti phase by dissolving Ti in molten Al. This phase occurs with further contact with C, and would initiate the combustion reaction to produce a more thermodynamically stable TiC phase. Mg-infiltrated 3.04 mm in the Al-TiC substrate was compared to 5.42 mm in the Al-Ti-C system, at the same time and temperature from the infiltration test. The apparent activation energy obtained for Al-TiC system was 350.84 kJ/mol, which was higher than that of the Al-Ti-C system (307.31 kJ/mol). The formation of the Al₃Ti phase in the Al-Ti-C system was also observed from the crystal structural analysis on the infiltrated area; therefore, the in-situ combustion reaction in Al-Ti-C system promoted the wetting of Mg.