ABSTRACT
The first information on the shape memory effect (SME) of certain alloys was reported in the 1930s. Swedish physicist A. Olander discovered the pseudoelastic behavior of AuCd alloy in 1932 [1]. AuCd alloy can be plastically deformed in the cold state and can recover its undeformed structure at higher temperatures in heating process. The special characteristic of this material is known as SME, and the alloy showing the same characteristic is called shape memory alloy (SMA). In 1938, 186Greninger and Mooradian reported on the presence of martensite phase (CuZn) in copper, which is the most responsible phase for SME. Ten years later, Kurdjumov and Khandros proposed the basic of reversible transformation of martensite in SMA in 1949, and thermoelastic martensite transformation was also observed in other alloys such as InTi and CuZn, which were proved by Chang and Read in 1951 [2]. In the 1960s, Buehler and his colleagues discovered the economical SME that is NiTi alloy in the Naval Ordnance Laboratory, United States, which caused great interest in the area of shape memory materials. The name of this Nitinol alloy is Nitinol, which is the abbreviation of “Nitinol Naval Ordnance Laboratory.” Leaf and Wallbom first noticed that NiTi and other phases of NiTi have better SME in one phase [3].
