Effect of crystal quality on twinning stress in Ni–Mn–Ga magnetic shape memory alloys

0546337 - FZÚ 2022 RIV BR eng J - Journal Article
Musiienko, Denys - Nilsén, Frans - Armstrong, Andrew - Rameš, Michal - Veřtát, Petr - Colman, R.H. - Čapek, Jaroslav - Müllner, P. - Heczko, Oleg - Straka, Ladislav
Effect of crystal quality on twinning stress in Ni–Mn–Ga magnetic shape memory alloys.
Journal of Materials Research and Technology-JMR&T. Roč. 14, Sept. (2021), s. 1934-1944. ISSN 2238-7854. E-ISSN 2214-0697
R&D Projects: GA MŠMT(CZ) EF16_019/0000760; GA ČR(CZ) GA21-06613S; GA MŠMT(CZ) LM2018096; GA MŠMT(CZ) EF20_079/0017754
Grant - others:OP VVV - SOLID21(XE) CZ.02.1.01/0.0/0.0/16_019/0000760; OP VVV - MSCA-IF IV FZU(XE) CZ.02.2.69/0.0/0.0/20_079/0017754
Institutional support: RVO:68378271
Keywords : magnetic shape memory * twinning stress * crystal mosaicity * microstructure * single crystal * Ni–Mn-Ga
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 6.267, year: 2021
Method of publishing: Open access

Low twinning stress (TS) is a prerequisite for magnetic shape memory functionality. We compare Ni50Mn28Ga22 single crystals from four different producers to reveal the effect of crystal quality on the TS. Near the reverse martensite transformation, the TS is generally low, about 1 MPa, regardless of mosaicity of up to 1.7° and chemical composition deviations of up to 2 at.% of Mn. Pure type I and type II twin boundaries occur in crystals with smooth chemical composition gradients. The temperature dependences of TS follow linear trends for type I twins and type II twins, enabling a very low TS down to 2 K for the latter. An intermediate slope appears for mixed type I/type II twin boundaries in a crystal with sharp local chemical deviations. We conclude that the crystal quality affects the magnitude of the TS indirectly, through its impact on the character of the twin boundaries. The effect is weak near the martensite transformation temperature and strong at low temperatures.
Permanent Link: http://hdl.handle.net/11104/0322885