Abstract
Shape memory alloys are one of the new functional materials and they have a unique property which shows the shape recovery phenomena by heating after deformation. Many applications using shape memory effect are developing. TiNi shape memory alloy has excellent material properties among shape memory alloys. These shape memory effects are caused by thermoelastic martensitic transformation and reverse transformation.
The phase transformation temperatures in TiNi shape memory alloy were measured by adiabatic method, DSC and DTA. These temperatures were affected by many factors, such as Ni concentration, thermal cycling and substitution of Ni by third elements. Tini shape memory alloy transformed from martensite phase to parent phase by heating after solution treatment. By thermal cycling or substitution of Ni by third elements, intermediate phase was observed between martensite phase and parent phase. By heating, the CsCl type ordered structure of TiNi parent phase changed to the BCC disordered structure at high temperature.
