Two‐Directional TiNi Shape Memory Alloy Film

Abstract

A change from a memorized convex to a concave curvature between 10 °C for the martensitic and 50 °C for the austenitic transition is the important feature of a novel two‐directional shape TiNi memory alloy film fabricated by sputtering. The key to two‐directional actuation is Ti 3 Ni 4 precipitate formation attained by an Ni enrichment (55.6 %) in the alloy. The Figure shows the bending of a strip placed over a steaming cup of tea after 0.1 to 0.4 seconds.