Shape Memory Alloys
A class of smart metallic alloys that can be deformed when cold, but return to their original pre-deformed shape when heated above a transition temperature.
Governing formula
Reversible Austenite (High T) ↔ Martensite (Low T) Phase Shift
SI unit
% (Recoverable Superelastic Strain)
In depth
Operates via thermoelastic martensitic phase transformation. Deforming low-temperature twinned martensite shifts domain boundaries; heating above Austenitic finish temperature A_f triggers a reverse phase change to original high-symmetry austenite.
Examples in the real world
Nitinol (Nickel-Titanium) self-expanding vascular medical stents and superelastic eyeglass frames.