This research investigated the influence of heat treatment and precipitation on the phase transformation temperatures of sputter-deposited nickel-titanium films. Films 5 to 10 microns thick were subjected to isochronal and isothermal heat treatments in vacuum. Four-point resistance measutements were made and the TP, TR, Ma, and Mc temperatures identified. The correlation between transformation temperatures and the film's microstructure was studied using transmission electron microscopy. Existence of Ti2Ni and Ti11Ni14 precipitates was seen to adversely influence the phase transformation temperatures. It was concluded that precipitate-free film is preferable for mechanical actuator applications.
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