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??C for 1 h. X-ray diffraction data show that the crystal structure of the martensitic phase is orthorhombic (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 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 Af, austenite finish temperature, increases up to 516??C. For the Ti?Ni?Pt film, at 20 at.% Pt, the austenite finish temperature is 422??C compared to 273??C for Ti?Ni?Pd at 30?at.%?Pd. Experimental data also demonstrate that all the films fabricated exhibit the classic shape memory effect.