Fabrication of TiNiCu Alloy Foil by Diffusion Heat-Treatment and Its Shape Memory Properties

New technique for fabricating TiNiCu ternary shape memory alloy foils was proposed. These alloy foils were obtained by using diffusion heat-treatment of laminated pure Ti, Ni, and Cu foils in vacuum. The alloy foils were subjected to a series of the heat-treatments at 1123K for varying holding times and compressive forces. These alloy foils were then examined using scanning electron microscopy and energy dispersive X-ray spectroscopy. The alloy foil heat-treated for 777.4ks with 405kPa compression formed significantly fewer voids than the alloy foil heat-treated for 777.4ks with 180kPa compression. The composition distributions of the alloy foil, which was heat-treated for 777.4ks with 405kPa compression, were found to be devoid of any discernible bias. The alloy foil, which was solution treated at 1273K for 0.9ks in argon atmosphere, was measured with differential scanning calorimetry (DSC), and then their shape recovery motions were observed during the heating and cooling processes. The endothermic and exothermic peaks were clearly obtained on the DSC curves of the alloy foil at heating and cooling process, respectively. Furthermore, the DSC curves showed typical characteristics of thermoelastic martensitic transformation. The alloy foil, which was curled at room temperature, demonstrated a recovery to its original flat shape after the heating process.