Combination of mechanochemical activation and self-propagating behaviour for the synthesis of Ti aluminides

The synthesis of TiAl3 is not easy, since conventional techniques based on thermal treatments provide mixtures of intermetallics, due to the particular thermodynamic stability of the TiAl and Ti3Al phases. The synthesis of the aluminium-rich intermetallic TiAl3 becomes, however, feasible when non-equilibrium processing techniques are properly combined. The methodology we set up for the preparation of the TiAl3 consists of two different stages. During the first stage, reactant powders at the correct composition undergo mechanochemical activation inside a ball mill under inert atmosphere. A self-propagating high-temperature reaction is then induced on the pre-treated powders through thermal ignition. At the end of the reaction, the TiAl3 equilibrium compound is obtained with impurities below 5 wt.%.