Applications of advanced transmission electron microscopic techniques to Ni–Ti based shape memory materials

In the present contribution some recent results of advanced transmission electron microscopy applications on Ni–Ti based shape memory materials will be reviewed. These will include the precipitate growth in binary Ni51Ti49 in which lens-shaped Ni4Ti3 precipitates are grown and which induce particular strain fields in the surrounding matrix influencing any ensuing martensitic transformation. Special image treatment methods are used to measure the actual lattice deformations close to these precipitates. Also the crystallisation process occurring in Ti50Ni25Cu25 melt-spun ribbons is investigated in which the focus is on the domain, interface and surface structure of micron-sized spherical B2 particles growing inside the amorphous material. When particles grow larger, martensite plates as well as small planer defects are observed.