Structural transformations in Ti-Ni-Cu shape memory ribbons

Ti-Ni-Cu shape memory alloy ribbons produced by melt-spinning were investigated in order to assess the crystallinity and the influence of further crystallization on the martensitic transformation. The as-quenched ribbons are partially crystalline, with grains in the range of microns and typical martensitic structure. As result of heating the ribbons, a peak develops around 460°C and, on further cooling, the physical evidence of the martensitic transformation reflected in the DSc peak is increased several times. Both the crystallization and the martensitic transformation have been investigated as a function of the heating and cooling rates. It is concluded that a significant part of the Ti-Ni-Cu shape memory alloy ribbons produced by meltspinning fully crystallizes only after a heat treatment that leads to a full martensitic transformation and the shape memory effect.