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 3.04mm in the Al-TiC substrate was compared to 5.42mm 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.