Interatomic Distances of the Hexagonal Omega Structure in Ti-V Alloys: Neutron Diffraction Study and Analysis of Bonding Related Regularities

AURELIO, G.; A. FERNÁNDEZ GUILLERMET

SCRIPTA MATERIALIA

Pergamon

Año: 2000 vol. 43 p. 665 - 669

1359-6462

The name omega (V) phase refers to an AlB2-type structure which appears as a high-pressure (P) modification in the elements of the Ti group, i.e., Ti, Zr, and Hf [1, 2]. In relatively dilute alloys of Ti, Zr and Hf with other transition metals, this phase can be formed by a diffusionless transformation and retained metastably at room temperature and atmospheric pressure (RTAP) by quenching the bcc structure, which is usually the stable high-T phase in these alloy systems [3]. Recently, there has been a renewed interest in the characterisation of the V phase in the Zr-Nb system [4, 5, 6, 7] and in the interpretation of the structural data in terms of theoretical [8, 9, 10, 11, 12] and phenomenological [10,13, 14, 15, 16] pictures of the chemical bonding in this phase. The purpose of the present work is to obtain new experimental data on another V-forming binary, viz., the Ti-V system. Quenched alloys with up to 18%V will be studied using a neutron diffraction (ND) technique. With this information an analysis will be made of the composition dependence of three interatomic distances (IDs) in the V unit cell, and a comparison will be reported with the Zr-Nb results [4, 5, 6, 7]. The present work extends theanalysis started by Benites et al. [17] in their ND search for possible atomic-ordering phenomena in the Ti-V V phase.