A mechanical spectroscopic study was made of the mobility of defects in the frozen β-phase of a shape memory alloys as a function of temperature. The microstructures and their evolution during over-heating treatments were also characterized. Heat treatments were performed in situ in a transmission electron microscope by using a heating stage. Internal friction and modulus defect measurements were correlated with the microstructural observations by transmission electron microscopy. The behavior of the internal friction spectra, corresponding to over-heating in the β-phase, was considered and microscopic mechanisms were proposed that were responsible for the evolution when the material was not in thermal equilibrium. In particular, the dislocations became mobile between 750 and 800K, where the L21 atomic order changed to the B2 order. A relaxation peak was observed in the equilibrium β phase domain, which was examined in detail by isothermal measurements as a function of frequency. The activation enthalpy of the peak was determined to be 3.05eV, and possible microscopic mechanisms responsible for the peak were considered

Diffusion Processes in Cu–Al–Ni Shape Memory Alloys Studied by Mechanical Spectroscopy and in Situ Transmission Electron Microscopy at High Temperatures. M.L.Nó, A.Ibarra, A.López-Echarri, E.H.Bocanegra, J.San Juan: Materials Science and Engineering A, 2006, 442[1-2], 418-22