Deposition and characterization of Ti–Ni–Pd and Ti–Ni–Pt shape memory alloy thinfilms

Abstract

Thin films of Ti–Ni–Pd and Ti–Ni–Pt shape memory alloys were produced by a DCmagnetron sputtering process. Targets with the following compositions were studied:Ti54Ni16Pd30,Ti54Ni6Pd40,Ti54Ni3Pd43 andTi54Ni26Pt20. The films weredeposited on SiO2/Si substrates at ambient temperature and were crystallized in situ at550 °C for 1 h. X-ray diffraction data show that the crystal structure of the martensitic phase isorthorhombic (B19) for all films and texturing is present in the Ti–Ni–Pt films.TEM micrographs show that both Ti–Ni–Pd and Ti–Ni–Pt films have a welldefined twin structure at ambient temperature. Transformation temperatureswere determined by both DSC and wafer curvature methods. The results indicatethat as the Pd content increases to 43 at.% the transformation temperatureAf, austenite finish temperature, increases up to516 °C. For the Ti–Ni–Pt film, at 20 at.% Pt, the austenite finish temperature is422 °C comparedto 273 °C for Ti–Ni–Pd at 30 at.% Pd. Experimental data also demonstrate that all the filmsfabricated exhibit the classic shape memory effect.