Nickel-Titanium shape memory alloys belong to a class of smart materials. The alloy is capable of remembering its pre-set shape and reverts back to its shape upon thermal or stress cycling. The alloy among other group of alloys is popular because of its low density and high electrical resistivity.
This material is very much used in mechanical and also bio-medical applications such as cardio-vascular stents, orthodontic arch-wires etc. and applications such as robot micro-grippers, aircraft fuselage coupling etc
A tensile curve for the tensile test performed on the alloy is shown below.