Recoverability of large strains and deformation twinning in martensite during tensile deformation of NiTi shape memory alloy polycrystals

0511881 - ÚJF 2020 RIV GB eng J - Journal Article
Chen, Y. - Molnárová, O. - Tyc, O. - Kadeřávek, Lukáš - Heller, Luděk - Šittner, Petr
Recoverability of large strains and deformation twinning in martensite during tensile deformation of NiTi shape memory alloy polycrystals.
Acta Materialia. Roč. 180, č. 11 (2019), s. 259. ISSN 1359-6454. E-ISSN 1873-2453
R&D Projects: GA MŠMT EF16_013/0001794
Institutional support: RVO:61389005
Keywords : NiTi * superelasticity * shape memory alloy * tensile test * large deformation * Martensitic transformation * deformation twinning * transmission electron microsopy
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 7.656, year: 2019
Method of publishing: Limited access
https://doi.org/10.1016/j.actamat.2019.09.012

It is concluded that the plastic deformation of NiTi wires is initiated by deformation twinning in oriented martensite, accompanied by dislocation slip in austenite and/or martensite in extent depending on the test temperature and total strain. The deformation twinning is found to play an ambiguous role in NiTi deformation. When it proceeds at low temperatures (T <= 20 degrees C) beyond the yield point, it raises recoverable strain up to 13%, while at high temperatures (T >= 50 degrees C) when it proceeds already within the plateau range as intermediate step of the stress induced B2=>B19'=>B2(T) martensitic transformation, it restricts the recoverability of transformation strains. The repeated deformation twinning in oriented martensite enables low temperature deformation of NiTi wires with specific microstructure up to similar to 50% strain and causes severe microstructure refinement during the mechanical and thermomechanical processing of NiTi.
Permanent Link: http://hdl.handle.net/11104/0302125