Improvement of a Ti50Pd30Ni20 high temperature shape memory alloy by thermomechanical treatments

Shape memory alloys (S}~) have been of considerable interest the past years as possible functional materials, now actually being used for various practical applications. To the present, the most useful among SMA is the TiNi alloy, because of its unique combination of excellent shape memory (SM) characterestics and sufficient ductility. However, the practical usage of TiNi is limited by temperature to about 373 K, due to the temperature range of thermoelastic martensitic transformation (MT). Presently, there is a strong need to develop high temperature SMA to be used for various actuators in aircraft and automobiles, pipe coupling, etc. Among several metallic systems with a high temperature interval of MT, NiA1 and TiPd alloys seem to be most attractive. In fact, the poor ductility at ambient temperature and the transformation from martensite to NisA13, instead of the reverse transformation upon heating (1), are still the serious problems which restrict the development of SMA based on the first alloy....