In situ TEM study of martensitic NiTi amorphization by Ni ion implantation

The amorphization of an equiatomic martensitic NiTi alloys is followed at room temperature using the Philips EM 400 transmission electron microscope (TEM) on line with the CSNM ion implantor of Orsay (France). During a 390 keV Ni+ ion irradiation, it is observed that the initial martensitic structure does not transform to austenite (B2 structure) before the crystalline-amorphous transition. From a micrographic series of the same part of a thin foil, an estimate of the amorphous volume, as a function of the dose, is made. It turns out that the results are consistent with a cascade overlap mechanism. A comparison is made with the amorphization obtained by 1.5 MeV electron irradiation in a high voltage electron microscope (HVEM). (orig.)