Abstract
Martensitic phase transformation from the β to the α'' phase (and vice versa) in a TiNbAl alloy system has been studied by ultrasound spectroscopy. Resonance frequencies and corresponding internal frictions are measured from ambient temperature to 12 K by electromagnetic acoustic resonance (EMAR) and resonant ultrasound spectroscopy (RUS) coupled with laser Doppler interferometry. Both in the cooling and heating processes, we observed a marked decrease in resonance frequency and an increase in internal friction approaching the transformation temperatures. The analysis of temperature dependence in the elastic moduli indicates that lattice anharmonicity in the longitudinal acoustic mode may play a dominant role in the martensitic phase transformations.