ABSTRACT
The shape memory effect and superelasticity are related to a thermoelastic martensitic transformation (austenite → martensite) which can be produced either by cooling or be stress induced [1-5]. Martensite formation can be initiated by cooling the material below Ms, defined as the temperature at which the martensitic transformation begins. Mf is the temperature at which martensitic transformation finishes. The transformation is reversible, As being the temperature at which the reverse austenitic transformation (martensite→ austenite) begins upon heating and Af the temperature at the end of the reverse austenitic transformation. In Fig. 1 can be observed the microstructure of the martensite in a orthodontic archwire.
