Theoretical Investigation of Anomalous Properties of BCC Ti, Zr, and Hf Alloys.
Abstract
A model for anomalous self-diffusion in the bcc-phase Group IV B transition metals, Ti, Zr and Hf is proposed. The model is based upon the identity of the activation complex for vacancy diffusion in the bcc lattice and the smallest unit (omega embryo) of a hexagonal phase, the omega phase, found in these metals and their alloys in a metastable state. The coefficient for self-diffusion is calculated as a function of temperature by means of a phenomenological expression for the free energy of formation of an omega embryo, and by means of a more fundamental approach based on Kikuchi's Cluster Variation method. The two methods of calculation for the self-diffusion coefficient of Zr give excellent agreement with experiment, the observed curvature of the Arrhenius plot being reproduced perfectly.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1977
- Accession Number
- ADA042108
Entities
People
- D. De Fontaine
Organizations
- University of California, Los Angeles