Ti過剰Ti-Ni合金スパッタ蒸着薄膜の結晶化に伴う析出物の生成とマルテンサイト変態への影響

Abstract

The crystallization temperature and composition dependece of morphology of precipitates and precipitates effect on martensitic transformation of sputter-deposited Ti-rich Ti-Ni alloy films were investigated.For the investigation by the electron microscopy on precipitates morphology behavior, the deposited amorphous films were crystallized and concurrently aged by holding at various temperatures between 693 K and 823 K. The following schemes were observed depending on Ti-rich Ti-Ni alloy films composition and heat-treatment temperature: (a) Precipitate-free; (b) Plate-like precipitates exist in the B2 phase; (c) Plate-like precipitates and spherical Ti2Ni precipitates coexist in the B2 matrix; (d) Ti2Ni precipitates exist in the B2 matrix; (e) Ti2Ni precipitates with and without orientation relationship to the matrix.Then, for investigating composition and crystallization temperature dependence of B2⇔R transformation temperatures the amorphous films were crystallized by holding at various temperatures, 723 K, 773 K and 973 K, for 3.6 ks. For investigation of precipitates effect on the martensitic transformation behavior, the sputter-deposited amorphous films were crystallized and concurrently aged by holding at various temperatures, 695 K and 723 K. The specimens were analyzed with differential scanning calorimetry (DSC) and the following was found. The martensitic transformation behavior changed depending on crystallization temperature and composition. The B2⇔R transformation temperatures of the thin films crystallized at temperatures between 723 K and 773 K were the lowest at Ti-48.5 at%Ni and plate-like precipitates lowered the B2⇔R transformation temperatures.The R⇒B19′ transformation temperatures were lowered by distribution of fine Ti2Ni precipitates of Ti-47.0 at%Ni∼Ti-48.5 at%Ni sample crystallized at low temperatures.