Eur. Phys. J. B (2013) 86: 49
https://doi.org/10.1140/epjb/e2012-30744-3

Regular Article

Twinning in shear and uniaxial loading in five layered martensite Ni-Mn-Ga single crystals^*

Aalto University, School of Chemical Technology, Department of Materials Science and Engineering, Vuorimiehentie 2 A, 02150 Espoo, Finland

^a e-mail: ilkka.aaltio@aalto.fi

Received: 13 August 2012
Received in final form: 13 November 2012
Published online: 11 February 2013

Abstract

Five-layered martensite Ni-Mn-Ga single crystals are known for their exceptionally mobile twin boundaries allowing a shape change under mechanical stress and by magnetic field. The mechanically measured twinning stress has usually been studied in uniaxial mode, however the twinning and detwinning is generally accepted to be resulted by the shear component. We have studied the twinning behavior at uniaxial and shear stress. In addition we have applied the shear stress at different angles in relation to the expected twinning direction . The results show that the onset of twinning lays at similar stress levels in both uniaxial and shear modes.