Mechanical characterisation of γ-TiAl thin films obtained by two different sputtering routes

In this study (TiAl)-based films were magnetron sputtered using two different methods: two targets (Ti+Al) and a γ-TiAl target. In both cases, the as-deposited films had to be heat treated in order to obtain the intermetallic γ-TiAl. The effect of the addition of chromium on the structure and mechanical properties was studied. The films were submitted to ageing treatments and the resulting structures and mechanical properties were also studied. To get more insight into the films, the residual stresses were also evaluated. After heat treatment (HT), the films sputtered from two targets are constituted by a single γ-TiAl phase while in the films produced with one target it is possible to observe the presence of the α2-Ti3Al phase. Under annealing, the as-deposited compressive stresses give rise to low tensile stresses. The 18 h HT leads to a pronounced increase in hardness in the films obtained by using two targets. The hardness of the films produced using one target increases gradually with the HT holding time. In all cases, ductility and hardness exhibit inverse trends.