TiAu and TiPt high temperature shape memory alloys

Abstract

Equiatomic TiAu and TiPt exhibit thermo-elastic martensitic phase transformation at high temperature. Phase transformation temperatures of TiPt (A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</inf> =1057°C) are about 400°C higher than TiAu (A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</inf> =624°C). However TiAu and TiPt exhibit partial shape memory effect and very low strength (e.g. ∼120MPa for TiAu and ∼20MPa for TiPt) in B2 phase region. So these alloys cannot be used for high temperature applications without improving their shape memory properties and strength in B2 phase region. Zirconium (Zr) belongs to same group IV as titanium (Ti). However atomic radius of Zr (1.58Å) is larger than Ti (1.47Å). So it was expected that partial substitution of Ti with Zr will improve the high temperature strength and shape memory properties of TiAu and TiPt alloys. Then in this study, we shall compare the effect of partial substitution of Ti with Zr on high temperature strength and shape memory properties of TiAu and TiPt high temperature shape memory alloys.