[110]TA(1) phonon dispersion relation of the beta(1)-phases in Ni-Co-Al alloys

The present study is mainly concerned with the relation between electron co ncentration and anomalous dip appearing on the [110]TA(I) phonon branch of the beta(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 Pi-phase existing above T-b- temperature, below which Ni3Al precipitates. The obtained results ind icate clearly that the dip is not any precursor of the martensitic transiti on but a reflection of the electronic property in the beta(1)-phase. (C) 19 99 Elsevier Science Ltd. All rights reserved.