Microstructure and Thermoelastic Martensitic Transformation in Ni-Low and -Rich Ni–Ti–Hf–Nb Hightemperature Shape Memory Alloys

Abstract

The paper studies the alloying effect of the quenched Ni-low (Ni_49.5Ti_35.5Hf₁₅)_100–XNb_X and Ni-rich (Ni_50.3Ti_34.7Hf₁₅)_100–XNb_X alloys (X = 0, 15 at.% Nb) on the B2-B19' martensitic transformation, viscoelastic properties and microstructure. Alloying of Ni-low and -rich alloys with Nb, provides the β-Nb phase precipitation within the (Ti, Hf)₂Ni phase. After alloying, the transformation temperature and austenite elastic modulus decrease in Ni-low alloys and increase in Ni-rich alloys, thus making them similar.