Abstract:Martensitic transformation, mechanical and thermomechanical properties of a Ti-rich Ti₅₂Ni₂₃Cu₂₅ melt spun ribbon annealed at a temperature below the crystallization temperature were studied by XRD, DSC and DMA. After annealing the initially amorphous ribbon at 400 ℃ for 10 h, the ribbon is fully crystallized and exhibits one-stage B2↔B19 phase transformation with the temperature hysteresis of 14 ℃. The annealed ribbon is composed of B2, B19 and B11-TiCu phase with (001) preferential orientation. On the stress―strain curves, the rearrangement of the martensite variants and stress-induced martensitic transformation are observed below the M_f temperature and above the A_f temperature, respectively. The annealed ribbon exhibits up to 1.6% superelastic shape recovery with small stress hysteresis of 25 MPa. No flat stress-plateau is associated with the superelasticity. The annealed ribbon shows a well-defined shape memory effect during thermal cycling from −60 to 100 ℃. The transformation strain and recovery strain increase with increasing the applied external stress. Under the external stress above 150 MPa, the shape recovery strain is not sensitive to it and keeps stable at about 1.74%.

Key words: Ti-Ni-Cu alloy; melt spinning; shape memory properties; superelasticity; dynamic mechanical analysis