Certain classes of metallic alloys have a special ability to “memorize” their shape at a low temperature and recover large deformations imparted at a low temperature on thermal activation. These alloys are called shape memory alloys (SMAs). The recovery of strains imparted to the material at a lower temperature, as a result of heating, is called the shape memory effect (SME). The SME was first discovered by Chang and Read in 1951 in the Au-Cd (gold-cadmium) alloy system. However, the effect became more well known after the discovery of nickel-titanium alloys.