[110]TA1 phonon dispersion relation of the β1-phases in Ni–Co–Al alloys

Abstract The present study is mainly concerned with the relation between electron concentration and anomalous dip appearing on the [110]TA 1 phonon branch of the β 1 -phase (B2-structure) in Ni–Al alloys. By substituting Co for Ni, the dip-position shifts toward the Brillouin zone center. In addition, we prove that the dip appears also in the equilibrium β 1 -phase existing above T b -temperature, below which Ni 3 Al precipitates. The obtained results indicate clearly that the dip is not any precursor of the martensitic transition but a reflection of the electronic property in the β 1 -phase.