Atomic Transport and Transformation Behavior in Metallic Glasses.
Abstract
Glasses, metallic or non-metallic, are in states which are configurationally frozen and less stable than some crystallized state. Upon annealing glasses may relax configurationally without transforming and then phase separate and/or crystallize. In this paper we survey the atomic transport behavior in metallic glasses as manifested by their flow, relaxation and transformation behavior. The rate constant for flow, k(eta), of a glass may be regarded as a product of a 'jump' factor and a configurational excitation factor. The activiation energy for jumping or iso-configurational flow, of a metallic glass is only a small fraction, of order 1/10 or less, of the apparent activation energy for flow of the fully relaxed melt in the glass transition range. In configurationally relaxed metallic glasses, the rate constants for phase transformations scale as k(eta) and appear to be controlled by the rate of impurity redistribution. In some configurationally unrelaxed systems, the indicated rates of diffusive transport persist for periods much longer than those expected for configurational relaxation. Some possible explanations for this behavior are discussed. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1976
- Accession Number
- ADA034512
Entities
People
- David Turnbull
- Frans Spaepen
Organizations
- Harvard University