Formation process of Ti-Al intermetallics during solid-liquid reaction between titanium and aluminum foils

The formation process of Ti-Al intermetallics from the elemental titanium and aluminum foils has been investigated. In order to study the reactive process of the solid-Ti/liquid-Al bonding, different processing conditions were employed. The microstructures and phase formation of the obtained samples were characterized by electron probe microanalyzer (EPMA) equipped with an energy dispersive spectroscopy (EDS) X-ray diffraction instrument (XRD) and differential scanning calorimetry (DSC). The results show that annealing above the Al melting point results in the self-propagating high-temperature synthesis (SHS) reaction between solid Ti and liquid Al; according to a modified effective heat of formation model applied to the Ti-Al system, TiAl3 is predicted to the appear as the first phase in the raction, as well as subsequent formation of TiAl between Ti and TiAl3 layers; Ti-3 Al would be formed between Ti/TiAl interfaces and TiAl2 would be formed between TiAl/TiAl3 interfaces; the solid-state reaction is dominated by the competing diffusion among Ti/alpha-Ti/Ti3Al/TiAl/TiAl2/TiAl3 couples, and eventually a multilayered sheet of Ti3 Al and TiAl is achieved.