Shape memory materials - On the kinetics of precipitation in Cu-Al-Be alloys

The effect of aging on the martensitic transformation of a Cu-Al-Be eutecti c alloy was detected by Differential Scanning Calorimetry and thermoelectri c power measurements. Precipitates of a(2) and gamma(2) phases were identif ied, by transmission electron microscopy, depending on the aging temperatur e. The size of gamma precipitate was studied at 370 degrees C. The thermoel ectric power measurements show two stages during aging, the first one is at tributed to a vacancy diffusion process, and the second to precipitation pr ocess (also detected in calorimetry). The precipitate nature was analyzed b y electron and optical microscopies. A time-temperature-transformation (TT- T) diagram has been constructed from these results. The peritectoid reactio n alpha+gamma(2) --> alpha(2) was deduced to be close to 275 degrees C.