Effect of precipitation on the microstructure and the shape memory response of the Ni50.3Ti29.7Zr20 high temperature shape memory alloy

The effect of nano-precipitation on the shape memory characteristics and martensite microstructure of the Ni50.3Ti29.7Zr20 high temperature shape memory alloy was studied. With appropriate heat treatment, the alloy shows excellent dimensional stability during thermal cycling under tension. Fine precipitates are absorbed by martensite variants and do not significantly hinder martensite formation. These alloys demonstrated higher transformation strain, smaller thermal hysteresis and narrower transformation range than samples with larger precipitates, a few hundred nanometers, that interfere with martensite variant growth.