A transmission electron microscopy procedure for in-situ straining of miniature pseudoelastic NiTi specimens

J. OLBRICHT; M.F.-X. WAGNER; A. CONDÓ; A. DLOUHY; CH. GROSßMANN; A. KRÖGER; CH. SOMSEN; G. EGGELER

International Journal of Materials Research

Hanser

Año: 2008 vol. 99 p. 1150 - 1156

1862-5282

The in-situ transmission electron microscopy technique allows direct observations of formation and growth of stress-induced martensite in pseudoelastic NiTi shape memory alloys. The present paper reports on the development of a miniature test procedure for in-situ straining experiments with specimens taken from small components. The deformation of an ultra-fine grained NiTi specimen is characterised by transmission electron microscopy (at early loading stages) and by optical microscopy (at larger strains). A complementary finite element analysis of the complex strain state in the specimen rationalises why the stress-induced martensitic transformation first occurs in the thin foil region of the specimen before spreading towards the outer rim of the specimen.