ACTA

Mechanical Stabilization of Martensite: Comparison of Ni-Mn-Ga and Cu-Ni-Al Shape Memory Single Crystals

M. Vronka^{a, b}, L. Straka^{a, c}, H. Seiner^c, M. Karlík^b, O. Heczko^a
^aInstitute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czech Republic
^bCzech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Materials, Trojanova 13, 120 00 Prague, Czech Republic
^cInstitute of Thermomechanics of the Czech Academy of Sciences, Dolejskova 5, 182 00 Prague, Czech Republic
^dCharles University, Faculty of Mathematics and Physics, Institute of Physics, Division of Optoelectronics and Magneto-optics, Ke Karlovu 5, 121 16 Prague 2, Czech Republic

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Newly developed formalism, regarding 2H modulated Cu-Ni-Al system as non-magnetic equivalent of Ni-Mn-Ga 10M modulated martensite provides the way to compare behaviour of these two shape memory alloys. Here we study the mechanical stabilization by mechanical stress in the single crystals of Ni_50.7Mn_27.7Ga_21.6 (at.%) and Ni₄₆Mn₂₄Ga₂₂Co₄Cu₄ exhibiting 10M and non-modulated martensite structures, respectively, and for comparison in Cu_69.4Ni_3.4Al_27.2 2H martensite. The resulting shift of reverse transformation temperature was almost 50 K in the Cu-Ni-Al 2H martensite and about 6 K in Ni-Mn-Ga non-modulated martensite. In contrast, the shift was <1 K in 10M Ni-Mn-Ga martensite. From the comparison it follows that the negligible stabilization in modulated 10M Ni-Mn-Ga can be due to its deep twinning hierarchy and very high mobility of twin boundaries.

DOI:10.12693/APhysPolA.134.627
PACS numbers: 81.30.Kf, 62.20.fg, 61.50.-f, 65.40.-b