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In present work the cyclic stability of superelasticity was studied in the stress-free and stress-assisted aged [001]-oriented Ni49Fe18Ga27Co6 (at. %) single crystals. It was experimentally shown, that studied single crystals are managed to undergo 50 000 cycles without destruction and they possess high cyclic stability of superelasticity from 10 to 20 000 cycles: both the critical stress level of martensite formation and the value of stress hysteresis do not change with the increase of cycles number. In the stress-assisted crystals the oriented arrangement of nanosized particles and the training (100 loading/unloading cycles) induce two-way shape memory effect with the maximum reversible strain εrev = 5.5%. The following increase of cycles number up to 50 000 leads to the reversible strain reduction to 0.7%. [ABSTRACT FROM AUTHOR]

Orientation dependence of the one-way and two-way shape memory effect (SME) was studied in [001]- and [1̅35] -single crystals of the Co49Ni21Ga30 (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, σext. It is shown that the value of the one-way SME, εOWSME, and two-way SME, εTWSME, depends on the crystal orientation. In the [001]-oriented crystals εOWSME = 4.2 (± 0.2)%, in [1̅35] -oriented crystals εOWSME = 3.8 (± 0.2)%. In [001]-oriented crystals maximum value of εTWSME equal to 4.3 (± 0.2)% is observed after training under σext = 175 MPa, in [1̅35] -oriented crystals εTWSME = 3.8 (± 0.2)% after training under σext = 250 MPa. The value of εTWSME is equal to the εOWSME and lattice strain ε0 for the corresponding orientation at B2-L10 MT: ε0 [001] = 4.5%, ε0 [1̅35] = 3.8%. [ABSTRACT FROM AUTHOR]