Cu-13.2Al-3Ni (wt%) single crystal studied by isothermal mechanical spectroscopy

The internal friction has been measured under isothermal conditions over a large frequency range (10-3 to 40 Hz) in a Cu-13.2Al-3Ni (wt.%) single crystal at temperatures between 293 and 473 K, including the martensitic transformation. On one hand, atypical behavior was revealed in the martensitic state. Indeed, the damping level measured at low frequency, below Ms, is much more important when it is determined under cooling conditions than on heating. On the other hand, a high damping level was observed in a very narrow temperature range during direct transformation. This last effect was ascribed to the nucleation process of the martensite, whereas a freeze in interface motion could be responsible for the thermal asymmetric behavior.