Kinetics of the thin films transformation Ti/Al multilayer→γ-TiAl

Ti/Al multilayer thin films with nanometric bilayer thickness (period) were produced by d.c. magnetron sputtering. The kinetics from the Ti/Al nanolayers to the γ-TiAl alloy is established based on differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. The kinetic study shows that the period (λ) influences the formation of the ordered γ-TiAl phase. For λ = 4 and λ = 20 nm the high diffusivity and reactivity lead to the formation of γ-TiAl in a single step that includes the formation of disordered TiAl followed by an ordering process. On the contrary, for a multilayer with 200 nm period the formation of γ-TiAl is preceded by the formation of Al3Ti. In both cases the activation energies (Ea) calculated can be compared with values reported in literature.