Nitinol is an alloy that consists of approximately 50% titanium and 50% nickel. The distinctive feature of nitinol is characterized by this reversible solid phase transition, known as martensitic transformation. The alloy material forms a crystalline structure capable of changing from one form to another. Temperature change and/or strain induce this transformation.
Above its transformation temperature, nitinol is super elastic and thus can resist some degree of deformation when a load is applied. Once the load is removed, it returns to its original shape. Below its transformation temperature, nitinol is subject to the thermal shape memory effect. After deformation, it will remain in this state until it is heated above the transformation temperature so that it returns to its original shape.