Microstructures and thermomechanical properties of sputter-deposited NiTi(Fe) shape memory alloy films

The influence of iron on the nature of sputter-deposited NiTi(Fe) shape memory alloy films for possible microelectromechanical system applications was studied as a function of annealing conditions. The iron additions only result in the formation of dense intervals of stacking faults along the [101̄0] direction in the basal (0001) plane from 1 to 25 nm on average when specimens of N 51.60Ti 48.40 (at%) and Ni 51.87Ti 41.81Fe 6.32 (at%) are annealed at 850°C for 2.5 h. The crystallites of B2 austenite and Ni 4Ti 3 with a rhombohedral structure are present and their orientation relationship is determined when initially amorphous specimens of iron-free and iron-containing material are annealed at 550°C for 0.5 h. The iron additions reduce the cracking behavior and increase both the crystallization temperature and the density of planar defects.