<p>The effect of step aging on the phase composition and succession of reverse martensitic transformations of a NiTi-based alloy containing 55.6 wt.% Ni is studied. Metallographic and x-ray diffraction analyses of the alloy are performed, and the temperatures of the reverse martensitic transformation are determined after one-and two-stage aging. It is shown that decrease of the temperature of the second aging stage leads to precipitation of an additional volume fraction of intermetallic compound Ti₃Ni₄ and increase in the shape recovery temperatures. Increase of the temperature of the second stage results in dissolution of the Ti₃Ni₄ particles formed in the first stage and decrease in the shape recovery temperatures. The use of stage aging makes it possible to correct accurately the response temperatures of functional articles from titanium nickelide.</p>