Ti-Niスパッタ薄膜の結晶化とマルテンサイト変態

抄録

Ti-Ni alloy films were deposited on quartz substrates by sputtering in argon atmosphere, using a sputtering target of an equiatomic TiNi alloy. The composition of the films were determined by electron probe micro-analysis using a calibration line prepared from bulk samples of well-established compositions. Since it was found that the Ti content in a deposited film was less than that of the target material, the film composition was controlled by placing Ti pieces on the target and changing their sizes. In this way it was successful in obtaining films with various compositions. Transmission electron microscope observation showed that the as-deposited films are amorphous when the substrate temperature is kept below 423 K during sputtering, and that they are crystallized when the specimens are heated above 708 K. By the heat treatment at temperatures above 708 K, Ti₂Ni precipitated in the Ti-46.8 at.%Ni and Ti-48.4 at.%Ni films, and Ti₃Ni₄ precipitated in the Ti-51.4 at.%Ni film, but no precipitation occurred in the Ti-50.0 at.%Ni film. The martensitic transformation in these films were investigated by differential scanning calorimetry and electron microscopy. The R-phase transformation occurred reversibly on cooling and heating the films in the electron microscope. It was confirmed by constant load thermal cycling tests that the films show very good shape memory.