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 [<10(1)over bar 0>] direction in the basal (0001) plane from 1 to 25 nm on average when specimens of N51.60Ti48.40 (at%) and Ni51.87Ti41.81Fe6.32 (at%) are annealed at 850 degrees C for 2.5 h. The crystallites of B2 austenite and Ni4Ti3 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 degrees C for 0.5 h. The iron additions reduce the cracking behavior and increase both the crystallization temperature and the density of planar defects. (C) 1998 Elsevier Science B.V.