In-situ TEM straining of tetragonal martensite in a Ni-Mn-Ga alloy

0399987 - FZÚ 2014 DE eng A - Abstract
Zárubová, Niva - Ge, Y. - Heczko, Oleg - Hannula, S.-P.
In-situ TEM straining of tetragonal martensite in a Ni-Mn-Ga alloy.
Microscopy Conference 2013. Regensburg: Regensburg University, 2013 - (Rachel, R.). s. 648-649
[Microscopy Conference 2013. 25.08.2013-30. 08.2013, Regensburg]
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 : in-situ TEM straining * martensitic transformation * Ni-Mn-Ga shape memory alloy
Subject RIV: BM - Solid Matter Physics ; Magnetism

Large strains achieved in Ni-Mn-Ga shape memory alloy by applying magneto-mechanical forces are caused by reorientation of martensite variants. The detailed mechanism of the reorientation process was investigated in the present study by straining the tetragonal martensite in-situ in a transmission electron microscope (TEM). The self-accommodated martensitic structure consists of internally twinned domains. During straining, detwinning process occurs within these domains, i.e. the internal twin variant more favorably oriented to the external stress grows at the expense of the other one. The process proceeds by the movement of twinning dislocations along the twin boundary. The planes of the twin boundary are {202) planes. The Burgers vector of the twinning dislocations was determined from the periodicity of the TEM contrast on the reorienting martensite plates, and was found to be very close to 1/12 <101].
Permanent Link: http://hdl.handle.net/11104/0227177