Temperature dependence of twinning stress in Ni49.5Mn38.4Sn12.2 single crystal

Abstract

Temperature dependence of twinning stress associated with type I twin boundaries in the Ni49.5Mn38.4Sn12.2 single crystal has been measured. At room temperature, the twinning stress amounts to 16.6 MPa, exceeding the typical values observed in the archetypical Ni-Mn-Ga alloys; nonetheless, it shows a remarkable sensitivity to temperature decreasing with a slope of 0.2498 MPa/K. This is a level of magnitude more than in Ni-Mn-Ga alloys. The remarkable sensitivity of twinning stress to temperature is primarily associated with the evolution of lattice parameters during heating. The type II twin boundaries in the same single crystal are activated at the twinning stress of 3.4 MPa, roughly one fifth of the twinning stress recorded for the type I twin boundaries. It is demonstrated that by careful compositional adjustments and thermomechanical training, it may be feasible to exercise magnetic field-induced strain due to twin variant rearrangement outside the Ni-Mn-Ga system.