>> Diagram of state:

The shape memory alloys do not behave as usual materials do. A shape memory material is essentially characterized by a diagram of state Constraint-Temperature (s,T) (picture 1).
Thanks to this diagram, and according to the constraint (s) and the temperature (T), we can see if we are in an austenite, a martensite domain or in a mixing area.

Picture 1: Diagram of state for the transformation Austenite to Martensite