The relation between lattice parameters and very low twinning stress in Ni50Mn25+xGa25-x magnetic shape memory alloys

L. Straka, J. Drahokoupil, O. Pacherova, K. Fabianova, V. Kopecky, H. Seiner, Hannu Hänninen, O. Heczko*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

15 Citations (Scopus)

Abstract

In search of the origins of the extraordinary low twinning stress of Ni-Mn-Ga 10M martensite, we studied the temperature induced changes in lattice parameters of Ni50Mn25+xGa25-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 the 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, gamma > 90 degrees with the coordinates derived from the cubic unit cell of the parent L2(1) phase. The lattice parameters gamma 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 and thus a/b twins seem to play no role in a - c twin boundary motion resulting in magnetically induced reorientation.

Original languageEnglish
Article number025001
Number of pages6
JournalSmart Materials and Structures
Volume25
Issue number2
DOIs
Publication statusPublished - Feb 2016
MoE publication typeA1 Journal article-refereed

Keywords

  • magnetic shape memory alloys
  • single crystal
  • structure
  • twinning stress
  • temperature dependence
  • NI-MN-GA
  • FIELD-INDUCED STRAIN
  • TEMPERATURE-DEPENDENCE
  • SINGLE-CRYSTALS
  • WALL-MOTION
  • MARTENSITE
  • BOUNDARIES
  • NI2MNGA
  • CRYSTALLOGRAPHY
  • INTERFACES

Cite this

Straka, L., Drahokoupil, J., Pacherova, O., Fabianova, K., Kopecky, V., Seiner, H., ... Heczko, O. (2016). The relation between lattice parameters and very low twinning stress in Ni50Mn25+xGa25-x magnetic shape memory alloys. Smart Materials and Structures, 25(2), [025001]. https://doi.org/10.1088/0964-1726/25/2/025001