In situ TEM study of deformation twinning in Ni-Mn-Ga non-modulated martensite

0395811 - FZÚ 2014 RIV GB eng J - Journal Article
Zárubová, Niva - Ge, Y. - Heczko, Oleg - Hannula, S.-P.
In situ TEM study of deformation twinning in Ni-Mn-Ga non-modulated martensite.
Acta Materialia. Roč. 61, č. 14 (2013), s. 5290-5299. ISSN 1359-6454. E-ISSN 1873-2453
R&D Projects: GA ČR(CZ) GAP107/11/0391; GA MŠMT(CZ) LM2011026; GA ČR GAP107/12/0800; GA AV ČR IAA100100920
Institutional support: RVO:68378271
Keywords : Ni-Mn-Ga * in situ TEM * magnetic shape memory * deformation twinning * twinning dislocation
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 3.940, year: 2013

The straining of non-modulated (NM) Ni–Mn–Ga martensite was studied by in situ transmission electron microscopy (TEM). Initially, the self-accommodated NM martensitic structure consists of internally twinned domains. During straining, the detwinning process starts within these domains. The internal twin variant more favorably oriented to the stress grows at the expense of the other one. In the detwinned, single-variant domain, a new twin variant can form, gradually replacing the existing variant via the twinning process. Both processes—detwinning and new twinning—proceed by the same mechanism, namely by the movement of twinning dislocations along the twin boundary. Lattice dislocations are also created in the detwinning process. While the boundaries between the internal twins are coherent and mobile, the boundaries between the internally twinned domains are incoherent, strained and not mobile. Possible reasons for this discrepancy are discussed.
Permanent Link: http://hdl.handle.net/11104/0223728