SHAPE MEMORY ALLOYS: A group of metallic materials that can return to some previously defined shape or size when subjected to the appropriate thermal producer. That is to say, shape memory alloys can be plastically distorted at some comparatively low temperature and, upon exposure to higher temperature, will come again to their original shape. Materials that exhibit the shape memory effect include a number of copper alloy and systems and of gold –cadmium, nickel-aluminium, and iron-platinum. Shape memory property possessed by certain alloys that allows them to return when heated, to their original shape after having been performed, it undergoes a martens tic (or a thermal) transformation a solid state transition that rapidly changes the crystalline structure of the alloy without thermal activation that is readily reversed once an appropriated amount of heat is applied. Among the alloys are copper aluminium nickel, copper-zinc-aluminium, nickel titanium, and iron-manganese silicon.
APPLICATIONS: The shape memory alloys are used in the heat activated fasteners, switches, eyeglass frames, orthopaedic devices, teeth braces and blood clot filters.