Latent strain in titanium-nickel thin films modified by irradiation of the plastically-deformed martensite phase with 5 MeV Ni{sup 2+}

• Published in: Acta materialia Vol. 48; no. 3
• Main Authors: Grummon, D.S., Gotthardt, R.
• Format: Journal Article
• Language: English
• Published: United States 09.02.2000
• Subjects: DEFORMATION; ION IMPLANTATION; MARTENSITE; MATERIALS SCIENCE; METALLURGICAL EFFECTS; NICKEL; NICKEL ALLOYS; STRAINS; THIN FILMS; TITANIUM ALLOYS
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(99)00401-2

Lattice damage brought on by heavy ion irradiation is able to alter the displacive transformation characteristics of near equiatomic titanium-nickel. Irradiation of sputtered TiNi thin films can modify thermomechanical response to a depth of more than a micron, and may thus be used to create a perfectly bonded heterophase that deploys materials of sharply differing latent thermal strain on opposite sides of a thin sheet. If the alloy film is first martensitized, and then deformed in tension prior to partial-depth exposure to ion beam damage at temperatures well below A{sub s}, a novel active-passive bilayer results that expresses pronounced bending displacements on subsequent heating. In the present paper, describing experiments on stretched 6-{micro}m thick sputtered Ti{sub 50.2}Ni{sub 49.7} Films irradiated with 5 MeV Ni{sup 2+}, the authors show that ion-induced latent bending can be cyclically reversed in temperature-displacement space, and that appreciable mechanical work can be extracted. Marked effects are observed at doses as low as 5 x 10{sup 13} Ni{sup 2+} cm{sup {minus}2}. The approach, in which nominally planar processing is used, derives mechanical robustness from a naturally diffuse interface between the beam-damaged stratum and the adjacent unmodified shape-memory layer.