X.L. Meng

Microstructure and martensitic transformation behaviors of a Ti–Ni–Hf–Cu high-temperature shape memory alloy ribbon

The Ti36Ni41Hf15Cu8 melt-spun ribbon undergoes a B2 ↔ B19′ transformation upon cooling and heating. When the Ti36Ni41Hf15Cu8 melt-spun ribbon is annealed at 873 K for 1 h, the spherical (Ti, Hf)2Ni particles with a diameter of 20–40 nm precipitate in the grain interior. The fine (Ti, Hf)2Ni precipitates improve the stability of phase transformation temperatures and cause martensite domains, with (001) compound twins in three orientations dominant instead of (011) type I twins. {111}-, {113}- and (001)//{111}-type boundaries are observed among these martensite domains. When the (Ti,Hf)2Ni precipitates coarsen, (011) type I twins become main martensite structures in the ribbon annealed at 973 K for 1 h.

Microstructure and Shape Memory Behavior of Ti–Nb Shape Memory Alloy Thin Film

Ti–Nb shape memory alloy (SMA) thin film is a promising candidate applied as microactuator in biomedical field. In this study, the microstructure and shape memory behavior of Ti–Nb SMA thin films in different heat treatment conditions have been investigated. Fine ω phases embedded in the β phase matrix suppress the martensitic transformation of the films. As a result, the as-deposited and most of the annealed films consist of the β and α″ dual phases. The annealed Ti–Nb thin film shows excellent superelasticity effect when deformed above the reverse martensitic transformation temperature, that is 3.5% total recovery strain can be obtained when 4% pre-strain is loaded.