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

16 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

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