Stress-strain curves of sputter-deposited Ti-Ni thin films

Three kinds of Ti-Ni sputter-deposited thin film were tensile tested until fracture: Ti-48.3at.%Ni thin films annealed at 773 K for 5 min, Ti-50.0 at.% Ni thin films annealed at 773 K for 1 h and Ti-51.5 at.% Ni thin films age treated at 673 K for 1 h after solution treatment at 973 K for 1 h. They showed deformation due to the rearrangement of martensite variants and to the stress-induced martensitic transformation below and above the martensitic transformation temperature, respectively. The yield stresses of the thin films are 1.5 GPa for the Ti-51.5 at.% Ni thin films, 650 MPa for the Ti-50.0at.%Ni thin films and 1.1GPa for the Ti-48.3at.%Ni thin films. The maximum elongations were obtained around the martensitic transformation temperatures and amount to 40% for the Ti-50.0 at.% Ni thin films and 20% for the Ti-48.3 at.% Ni thin films. These results indicate that sputter-deposited thin films have sufficient ductility and strength for practical use.