Calorimetry-assisted analysis of low-temperature Ti2AlN formation in sputtered multilayers

Rapid differential scanning calorimetry (DSC) measurements were performed on Ti, TiN, TiAl, and AlN multilayers that were magnetron sputtered at ambient temperature and had a similar overall composition to MAX-phase Ti2AlN. The DSC yielded thermal scans with exotherms indicating diffusion and crystallization processes during the annealing process, including the formation of Ti2AlN. Multilayer Ti/AlN yielded a distinctly large exotherm in the range of 500–700 °C, in contrast to the other films, and was estimated to have the highest cumulative enthalpy during annealing up to 700 °C. X-ray diffraction measurements and annealing treatments also indicated that all TiAlN films yielded Ti2AlN by 600 °C, with STEM imaging revealing the onset of Ti2AlN-like structural ordering in Ti/AlN by 475 °C. These data collectively show that multilayer films with Ti/AlN chemistry are distinctly reactive, experiencing phase transformation events that facilitate MAX-phase Ti2AlN synthesis at low substrate temperatures.