Powder Based on Nano-crystalline NiTi Produced Using High Energy Ball Milling and Subsequent Heat Treatment

Planetary ball milling and subsequent heat treatment were employed for the production of nano-crystalline NiTi-based powder from initial Ni and Ti powder mixture with stoichiometric composition of Ni50Ti50. Characterization of the crystal structure of the milled product using X-ray diffractometry, scanning and transmission electron microscopy showed that increasing milling time decreased the particle and crystallite size but increased internal lattice strain. Milled products with nano-crystalline NiTi and amorphous structures were detected which transformed to the dominant B2-NiTi and minor Ni3Ti and NiTi2 crystal structures upon subsequent annealing as detected by X-ray diffraction and differential thermal analysis.