The relation between lattice parameters and very low twinning stress in Ni.sub.50./sub.Mn.sub.25+x./sub. Ga.sub.25-x./sub. magnetic shape memory alloys

0467366 - FZÚ 2017 RIV GB eng J - Journal Article
Straka, L. - Drahokoupil, J. - Pacherová, Oliva - Fabianová, Kristina - Kopecký, Vít - Seiner, Hanuš - Hänninen, H. - Heczko, Oleg
The relation between lattice parameters and very low twinning stress in Ni₅₀Mn_25+x Ga_25-x magnetic shape memory alloys.
Smart Materials and Structures. Roč. 25, č. 2 (2016), 1-6, č. článku 025001. ISSN 0964-1726. E-ISSN 1361-665X
R&D Projects: GA ČR GB14-36566G
Grant - others:AV ČR(CZ) M100101241
Institutional support: RVO:68378271 ; RVO:61388998
Keywords : magnetic shape memory alloys * single crystal * structure * twinning stress * temperature dependence
Subject RIV: BM - Solid Matter Physics ; Magnetism; BI - Acoustics (UT-L)
Impact factor: 2.909, year: 2016

In search for the origins of the extraordinary low twinning stress of Ni-Mn-Ga 10M martensite, we studied the temperature induced changes in lattice parameters of Ni 50 Mn 25+x Ga 25−x (x = 2.7–3.9) single crystal samples and compared them with twinning stress dependences. The alloys exhibited transformation to five-layered (10M) martensite structure (cubic to monoclinic) between 297 to 328 K and exhibited magnetic shape memory effect in martensite. The structural changes were monitored using X-ray diffraction in the temperature range 200–343 K. The 10M structure was approximated by monoclinic lattice, a = b > c, γ > 90 ◦ with the coordinates derived from the cubic unit cell of the parent L2 1 phase. The lattice parameters γ and c/a correlate well with the universal linear increase of twinning stress of Type 1 twins with decreasing temperature. On the contrary, the twinning stress is not affected by differences between a and b.
Permanent Link: http://hdl.handle.net/11104/0266512