Effect of martensite ageing on the orientation dependence of the B2-phase yield stress and the shape memory effect in Ti–40Ni–10Cu alloy single crystals

For the [001]- and [123]-oriented single crystals of the Ti–40Ni–10Cu alloy, it was shown for the first time that martensite ageing at 250 MPa leads to a strong orientation dependence of the B2-phase yield stress under tension, which is weakly manifested in the initial crystals. The maximum increase in the B2-phase yield stress by 350 MPa compared with the initial state was found in the [001]-oriented crystals. At external tensile stresses of 100 MPa, the shape memory effect in [001]-oriented crystals was 4.0 $\pm$ 0.2% in the initial state and increased to 5.0 $\pm$ 0.2% after martensite ageing, while in [$\bar{1}$23] orientation, on the contrary, it decreased from 8.7 $\pm$ 0.2% to 5.4 $\pm$ 0.2%.