Vibrational behavior of the β phase near martensitic transformation in Cu–Al–Ni shape memory alloys

The vibrational behavior of the metastable β phase near the martensitic transformation (MT) in a single-crystalline Cu–27.96 at.% Al–3.62 at.% Ni shape memory alloy (SMA) has been studied by resonant ultrasonic spectroscopy (RUS). This technique allows to determine simultaneously all the elastic constants Cij of anisotropic materials and also the internal friction Q−1(Cij) associated to some particular elastic constant Cij. The evolution of the resonance frequencies with temperature has been studied and shows that the C′ and C44 elastic constants are the magnitudes which control the vibrational response of the β phase near the martensitic transformation. The internal friction value Q−1 associated to different resonance modes and their evolution has been measured and correlated to the elastic behavior of the alloy.