Influence of thermal treatment on the structure of Ti–Al films

Titanium aluminides based on TiAl and Ti₃Al are potential materials for high temperature aerospace application. Their low density, high temperature creep resistance and strength, high oxidation resistance, make them excellent potential engine materials. It is reasonable to develop processing strategies for protective and high temperature coatings based on them. On magnetron sputtering the Ti–48% Al alloy films, the composition of which corresponds to the target’s one, have been obtained. When annealed, the aluminium atoms have been discovered to diffuse into the substrate. The redistribution and the leveling of the films’ compositions in the volume take place. After annealing the film contains a higher titanium concentration. On sputtering the formation of the Ti₃Al-based metastable phase in the films has been observed. This phase is the main one in the films and has a different morphology on different substrates. It is stable and doesn’t decompose at annealing. During annealing the new intermediate metastable phases, which are stable only within a definite temperature and concentration range, have developed. The structure, kinetics of phase transformation and evolution of the film microstructures depend on the structure and morphology of the substrate.