Properties and applications of TiNiCu shape-memory-alloy thin films

The shape memory behavior of TiNiCu thin films with 0–37.3 at% Cu and 44.6–55.4 at% Ti is overviewed from the viewpoint of practical application. Films annealed at 873 K for 1 h exhibit attractive properties such as (1) single-stage transformation, (2) relatively high transformation temperatures, (3) small temperature hysteresis, (4) stable shape memory effect, (5) sufficient recoverable strain, (6) reliable mechanical properties, and (7) composition insensitivity of transformation temperatures. Fabrication of TiNiCu thin films from an alloy target verified the feasibility of mass production by sputtering. Some applications such as a polyimide/TiNiCu film actuator are proposed to facilitate the practical use of TiNiCu films.

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► The shape memory behavior of TiNiCu films (0–37 at% Cu, 45–55 at% Ti) was overviewed.
► The optimum annealing conditions are 873 K and 1 h.
► They exhibit stable shape memory behavior over a wide composition range.
► Fabrication using an alloy target suggests the feasibility of mass production.
► A simple polyimide/SMA film actuator facilitates the use of TiNiCu films.