Synthesis and characterization of Ti/Al reactive multilayer films with various molar ratios

This study describes the fabrication and characterization of the bimetallic Ti/Al reactive multilayer thin films. Reactive films with different molar ratios of Ti and Al (mTi/nAl, m = 1; n = 1, 2, 3) were fabricated by using Magnetron Sputter Ion Plating (MSIP) method. Differential scanning calorimetry (DSC) was used to analyze the phase change temperature and heat flow. The heat of formation of different phases in Ti-Al system was also calculated by using thermodynamic simulation. Here, reaction heat depends on types of phases form. Microstructural features of the as-deposited Ti/Al reactive multilayer films show columnar microstructures with coherent multilayers. After an electrical ignition, all foils exhibit self-propagating reaction. The experimental result shows that 1Ti/1Al reactive foils have higher reaction velocity of 2.6 ± 0.6 m/s compared to other molar ratios at 9 V electrical ignition. Here, 1Ti/1Al and 1Ti/2Al reactive films show only steady reaction propagation, whereas 1Ti/3Al films exhibit both steady and unsteady reaction propagation. The microstructural characterization exhibits two types of diffusion modes of reactants mixing in the periodic layers and grain boundary, which assure even faster diffusion during self-propagating reaction. - Highlights: • Freestanding Ti/Al reactive films with different molar ratios have been developed. • Microstructural features of the as-deposited and reacted films have been characterized. • Reaction propagation and heat flow depend on the molar ratios of the film. • 1Ti/1Al film shows higher reaction velocity compared to 1Ti/2Al and 1Ti/3Al films. • 1Ti/3Al reactive films exhibit both steady and unsteady reaction propagation.