One-way and two-way shape memory effect in single-phase CoNiGa single crystals

On single-phase [1¯23] -oriented single crystals of ferromagnetic Co49Ni21Ga30 (at.%) alloy shape memory effect (SME) and superelasticity (SE) in compression are studied. The value of SME and SE are both equal to −3.2%. SE is observed in the temperature range of T=318–473 K. After realization of SE in [1¯23] -oriented crystals the two-way SME was found. Two-way SME is equal in value to one-way SME, SE and the lattice stain, |ε0|, for the crystals of a given orientation at B2–L10 martensitic transformation (MT) under compression deformation. The physical reason for the existence of the two-way SME in [1¯23] -oriented crystals after realization of SE is associated with the occurrence of internal stress fields due to the appearance of the crystal structure defects at T>423 K