HIGH-RESOLUTION ELECTRON-MICROSCOPY OF TH ERMAL EPSILON-MARTENSITE INAN FE-MN-SI-CR-NI SHAPE-MEMORY ALLOY

Polycrystalline samples of the Fe-Mn-Si-Cr-Ni shape memory alloy which contained a 70% fraction of thermal epsilon-martensite, have been stu died by H.R.E.M. Images taken along a [011]gamma//[2110]epsilon axis c learly show, at the atomic level, the layered substructure of the epsi lon-phase. The structure of the epsilon(h.c.p.)/gamma(f.c.c.) interfac e has been analysed from numerically processed images of elementary ep silon-laminate ends. It can be described by a periodic array of 30-deg rees and 90-degrees Shockley partials in a 2:1 ratio. Isotropic elasti city calculations confirmed this model which illustrates the self-acco mmodation properties of thermal epsilon-martensite at the finest scale .