No abstract

We have deposited the Ti-Ni-X films having various compositions while keeping the Ti content to be ~50at% by means of triple-source dc magnetron sputtering. All of the annealed films showed thermoelastic martensitic transformation. Ms temperature of the Ti-Ni-Pd films increased with increasing Pd content, and the highest Ms temperature of ~180°C was attained for the Ti-23%Ni-27%Pd film. On the other hand, Ms temperature of Ti-Ni-Cu films slightly increases as Cu content increases. The transformation hysteresis is decreased rapidly down to 15~20°C by adding Pd or Cu more than 10at%. Both ternary alloy films showed shape memory behavior during thermal cycling tests under various constant stresses. The critical stress against plastic deformation, c, of the Ti-Ni-Cu films is higher than that of the Ti-Ni-Pd films. The recoverable strain of these ternary alloy films is found to be ~2%. Actuation response by Joule's heat induced shape memory effect of Ti-Ni shape memory alloy films was slightly improved by the addition of Pd or Cu into the alloy.