Deposition and characterization of Ti-Ni-Pd and Ti-Ni-Pt shape memory alloy thin films

Thin films of Ti-Ni-Pd and Ti-Ni-Pt shape memory alloys were produced by a DC magnetron sputtering process. Targets with the following compositions were studied: Ti54Ni16Pd30, Ti54Ni6Pd40, Ti54Ni3Pd43 and Ti54Ni26Pt20. The films were deposited on SiO2/Si substrates at ambient temperature and were crystallized in situ at 550 degrees C for I h. X-ray diffraction data show that the crystal structure of the martensitic phase is orthorhombic (B 19) 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 well defined twin structure at ambient temperature. Transformation temperatures were determined by both DSC and wafer curvature methods. The results indicate that as the Pd content increases to 43 at.% the transformation temperature A(f), austenite finish temperature, increases up to 516 degrees C. For the Ti-Ni-Pt film, at 20 at.% Pt, the austenite finish temperature is 422 degrees C compared to 273 degrees C for Ti-Ni-Pd at 30 at.% Pd. Experimental data also demonstrate that all the films fabricated exhibit the classic shape memory effect.