Effect of Heat Treatments on Morphology and Transformation Temperatures of Sputtered Ti-Ni Thin Films

¹ The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihoga-oka, Ibaraki, Osaka 567, Japan
² School of Sci. & Eng., Teikyo University, Utsunomiya, Tochigi 320, Japan
³ Metal Economics Res. Inst., Mori Bldg. II, 4-2-12 Toranomon, Minato-ku, Tokyo 105, Japan
⁴ Department of Materials Science and Engineering, Kanazawa Institute of Technology, 7-1 Ohgigaoka, Nonoichi, Kanazawa-South, Ishikawa 921, Japan

Abstract

Morphology and martensitic transformation temperatures of sputter-deposited Ti _51.5 Ni _48.5 thin films were investigated by carrying out transmission electron microscopy (TEM) of those films before and after annealing at several different temperatures. The thin films were prepared by RF magnetron sputtering. TEM observations showed that the as-deposited thin films were all amorphous and contained no crystalline phases even after annealing at lower temperatures than 370°C. However, they were crystallized into a B2 type order phase by annealing at higher temperatures than 400°C. The grain size was about 1-2 μm and not sensitive to annealing temperature. Subgrain boundaries and plate-shaped defects were observed in the specimens annealed at 400°C and 500°C, respectively, and Ti₂Ni precipitates were in the specimen annealed at higher temperatures than 600°C. M_stemperature for the B2 →B19' martensite transformation decreases with decreasing annealing temperature. On the contrast to M_s, T_R temperature for the B2 → R phase transformation was hardly affected by annealing temperature.