Investigation of the orientation dependence of marforming on superelasticity and shape memory effect in equiatomic TiNi single crystals under compression

Abstract

The shape memory effect (SME) and superelasticity (SE) after marforming (deformation in the martensitic phase at 203 K, followed by annealing at 713 K, 0.5 h) were studied in the equiatomic TiNi crystals under compression. Marforming was carried out along [0 0 1]B2 and [0 1 1]B2 directions of B2-phase after strain of ε = 1.5ε0 (ε0 is the lattice deformation, which depends on the crystal orientation). SME and SE after marforming were studied along [0 0 1]B2 direction. It was shown that the maximum stress level of B2-phase σcr(B2) = 750 MPa, the lowest values of mechanical Δσ = 100 MPa and thermal ΔTh = 32 K hysteresis and the maximum temperature range of SE ΔTSE = 77 K were observed when marforming under compression was realized along the [0 0 1]B2 direction.