Atomic Transport and Transformation Behavior in Metallic Glasses.
HARVARD UNIV CAMBRIDGE MASS DIV OF ENGINEERING AND APPLIED PHYSICS
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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 andor 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, keta, 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 110 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 keta 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
- Ceramics, Refractories and Glass