Microstructure evolution and metastable phase formation in laser-ablation-deposited films of Ti5Si3 intermetallic compound

Thin films of Ti62.5Si37.5 composition were deposited by the pulsed-laser ablation technique on single-crystal Nad substrates at room temperature and on ′single-crystal′ superalloy substrates at elevated temperatures. Both vapour and liquid droplets generated by pulsed-laser ablation of the target become quenched on the substrate. Amorphization had taken place in the process of quenching of vapour-plasma as well as small liquid droplets on NaCl substrates at room temperature. In addition to the formation of Ti5Si3, a metastable fcc phase (a 0 = 0.433 nm) also forms in micron-sized large droplets as well as in the medium-sized submicron droplets. The same metastable fcc phase nucleates during deposition from the vapour state at 500°C and at 600°C on a superalloy substrate as well as during crystallization of the amorphous phase. The evolution of the metastable fcc phase in the Ti-Si system during non-equilibrium processing is reported for the first time.