Transmission electron microscopy study of microstructural evolution in nanograined Ni-Ti microwires heat treated by electric pulse

0365169 - FZÚ 2012 RIV CH eng J - Journal Article
Delville, R. - Malard, B. - Pilch, Jan - Šittner, Petr - Schryvers, D.
Transmission electron microscopy study of microstructural evolution in nanograined Ni-Ti microwires heat treated by electric pulse.
Solid State Phenomena. 172-174, č. 6 (2011), s. 682-687. ISSN 1012-0394
R&D Projects: GA MŠMT(CZ) LA10010
Institutional research plan: CEZ:AV0Z10100520
Keywords : transmission electron microscopy * shape memory alloy * martensitic transformation * dislocation slip * nanograins
Subject RIV: BM - Solid Matter Physics ; Magnetism

Transmission electron microscopy and mechanical testing were employed to investigate the evolution of microstructure and functional superelastic properties of 0.1mm diameter as-drawn Ni-Ti wires subjected to a non-conventional heat treatment by controlled electric pulse current. This method enables a finer control of the recovery and recrystallisation processes taking place during the heat treatment and accordingly a better control on the final microstructure. The best functional properties were obtained for heat-treated Ni-Ti wires having a nanograined microstructure (20-50 nm) partially recovered through polygonization and partially recrystallized. Such microstructure is highly resistant against dislocation slip upon cycling, while microstructures annealed for longer time and showing mostly recrystallized grains were prone to dislocation slip, particularly as the grain size exceeds 100 nm.
Permanent Link: http://hdl.handle.net/11104/0200474