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

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Abstract
Three kinds of Ti—Ni sputter-deposited thin film were tensile tested until fracture: Ti—48.3at.% Ni thin films annealed at 773K for 5min, Ti—50.0at.% Ni thin films annealed at 773K for 1h and Ti—51.5at.% Ni thin films age treated at 673K for 1h after solution treatment at 973K for 1h. 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 1.5GPa for the Ti—51.5at.% 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—50.0at.% Ni thin films and 20% for the Ti—48.3at.% Ni thin films. These results indicate that sputter-deposited thin films have sufficient ductility and strength for practical use.