OXIDE FILM ON EQUIATOMIC TiNi SHAPE MEMORY ALLOY
(Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China)
Abstract: By means of scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, the oxide layers on equiatomic TiNi shape memory alloy oxidized in the temperature range from room temperature to 800℃were studied. The results showed that the thin oxide film naturally formed at room temperature contains Ti element in TiO2state and part of Ni element in Ni2O3state, leaving other Ni still in metallic state; The thin oxide films formed at 300~500℃are characterized by enriched Ti and depleted Ni, both in completely oxidized state. Thick scaling layers were formed above 700℃, which are proved to be composed of an outer TiO2layer dissolved by small amount of Ni and an inner pure Ni3Ti layer.
Key words: TiNi shape memory alloy oxidation surface modification