The Shape Memory Effect
The shape memory effect that Nitinol exhibits was first discovered in a Gold-Cadmium alloy in 1932. However, gold-cadmium is very expensive and difficult to work with, so it never gained popularity. The shape memory effect relies on Nitinol's transition between the martensitic and austenitic states, with slightly different arrangements of their atoms. When Nitinol is cold, it remains in the martensitic state, but when heated, it reverts to the austenitic state. In this process, it goes back to a rigid molecular structure, and most deformities are pushed out.