Orientation dependent stress-induced intermartensitic transformations in Ni50.3Mn28.7Ga21.0 single crystal

Intermartensitic transformations (IMTs) between 10, 14, and 2M martensitic phases induced by the uniaxial compression and tension have been investigated using the same Ni 50.3 Mn 28.7 Ga single crystal. One series of thermomechanical measurements was carried out in a tensile configuration along the [001] c 21.0 direction and another one under a compression load along the [110] direction of the samples cut from the same single crystal. The obtained slopes of the "stress-temperature" phase diagrams of 10M ->14M and 14M ->2M IMTs are in satisfactory agreement with the Clausius-Clapeyron relationship applied for each IMT induced under compression and tension loadings. The results are important for the development of the theory of IMTs in magnetic shape memory alloys as well as for their practical applications given large superelastic strains summed over a sequence of martensite structures and a low twining stress noted uniquely for modulated martensites.