Intermartensitic Thermoelastic Transformations in [012]-Oriented Single Crystals of Ferromagnetic Nifega Alloys Under Compressive Loading

The results of investigations of stress-induced intermartensitic transformations in [012]-oriented Ni54Fe19Ga27 (at.%) single crystals are presented as a function of testing temperature and applied stresses. The sequence of intermartensitic transformations L2(1)-14M-L1(0) at D cent < 423 K is observed to change to L2(1)-L1(0) at D cent > 423 K. The interval of superelasticity development is controlled by the high value of alpha(2-1) = d sigma(cr)/dT = 3.1 MPa/K and on the side of high temperatures is limited by the strength properties of the martensite phase; superelasticity is observed during L2(1)-14M-L1(0)-transformations below 353 K. It is experimentally found out that with increasing temperature and externally applied stresses the value of reversible transformation-induced strain is decreased, while the stress hysteresis is increased, and the interval of the forward transformation under loading becomes larger than that of the reverse.