The Effect of Heat Treatment on the Shape Memory Effect and Superelasticity in NiMnGa Single Crystals

摘要

It was shown in Ni_(53)Mn_(25)Ga_(22) single crystals that the annealing at 1273 K for 1 h followed by slow cooling, at which the (L2i+y)-structure is formed, provides the increase of crystals plasticity as compared with the brittle initial L2_1-single crystals. The increase of critical stresses by more than 2 Times (up to σ > 150 MPa), at which the cooling/heating cycles under stress are accompanied by sample destruction, is observed. Moreover, the value of thermal hysteresis is increased by 1.5 Times and the perfect curve of superelasticity is observed at T=423 K.