Orientation Dependence of One-Way and Two-Way Shape Memory Effect in CoNiGa Single Crystals

摘要

Orientation dependence of the one-way and two-way shape memory effect (SME) was studied in [001]- and [135] -single crystals of the Co_(49)Ni_(21)Ga_(30) (at. %) alloy. Two-way SME was obtained by creating internal oriented stress fields due to the training on cooling/heating through martensitic transformation (MT) temperatures under compression stress, σ_(ext). It is shown that the value of the one-way SME, ε_(OWSME), and two-way SME, ε_(TWSME), depends on the crystal orientation. In the [001]- oriented crystals ε_(OWSME)~= 4.2 (± 0.2)%, in [135] -oriented crystals ε_(OWSME)~= 3.8 (± 0.2)%. In [001]- oriented crystals maximum value of ε_(TWSME) equal to 4.3 (± 0.2)% is observed after training under σ_(ext)= 175 MPa, in [135] -oriented crystals ε_(TWSME)= 3.8 (± 0.2)% after training under σ_(ext)= 250 MPa. The value of ε_(TWSME) is equal to the ε_(OWSME) and lattice strain ε_0 for the corresponding orientation at B_2-L1_0 MT: ε_0 [001]= 4.5%, ε_0 [135]= 3.8%.