Effect of Zr content on mechanical properties of Ti–Ni–Zr shape memory alloy films prepared by dc magnetron sputtering

To further understanding of the effect of Zr content on the shape memory behavior of ternary Ti–Ni–Zr alloy films, ternary alloy films were deposited with various Zr contents using triple source dc magnetron sputtering. Deposited films annealed at 700 °C showed martensite transformation accompanied with shape memory behavior. Martensitic transformation start (Ms) temperature of the ternary alloy film was found to increase with increasing Zr content for a Zr content higher than 10 at%. The highest Ms temperature attained was ∼170 °C for a Zr content of 19.5 at%. Critical stress against plastic deformation was found to increase with increasing Zr content up to 10 at%. Although further increase of Zr content caused embrittlement, the Ti32.3Ni48.2Zr19.5 film showed a shape memory effect with a recoverable strain of ∼1.3% under a constant stress of 250 MPa. This indicates that the Ti–Ni–Zr alloy film is a promising candidate for cantilever type micro-actuators.