Structure and properties of sputtered TiAl-M (M = Ag, Cr) thin films

The aim of this work was to study the influence of two additional elements - silver and chromium - on the structure and mechanical properties of TiAl-M (M = Ag, Cr) thin films synthesised by sputtering. The films were studied in the as-deposited condition (metastable state) and after successive annealings performed in order to obtain the stable (gamma-TiAl)-based intermetallic phase. The experimental techniques used in this work for chemical and structural characterisation were electron probe microanalysis, transmission electron microscopy/electron diffraction, X-ray diffraction and differential scanning calorimetry. The mechanical analysis consisted of the determination of hardness and ductility. To do this, a new tensile test procedure able to evaluate the ductility of thin films was developed. The results showed that, contrary to the as-deposited state, the addition of silver or chromium does not lead to a significant improvement in the mechanical properties, hardness and ductility of the heat-treated films (gamma-TiAl structure). However, they did contribute to a better understanding of the role of silver and chromium on the structure of these titanium aluminides. (C) 1999 Elsevier Science S.A. All rights reserved.