Abstract

Shape-memory alloys (SMAs) when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape-memory. This strain recovery can occur against large forces, resulting in their use as actuators. Associated with this behavior is the superelastic or pseudoelastic effect (SE) wherein large and completely recoverable strains are generated mechanically rather than thermally. Whereas the alloys are primarily nonferrous, some ferrous alloys also exhibit shape memory. Applications of SMAs include those as tubes and valves in piping systems for power plants, ships, and the petroleum industry; use as explosive bolts in the aerospace and construction industry; as packaging devices for electronic materials; and as dental materials, prosthetics, and biomedical devices. Shape-memory alloys may be found in sensors in automobiles, in consumer products, and generally in smart materials and adaptive structures.