Date of Award


Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

First Advisor

R.A. Fournelle

Second Advisor

Robert F. Brebrick

Third Advisor

Martin A. Seitz

Fourth Advisor

Robert Blumenthal


The morphology and growth kinetics of cellular precipitation and discontinuous coarsening of the cellular precipitate in an Al-29 at. pct. Zn alloy has been investigated at temperatures ranging from 50 to 250°C by light and electron microscopy. At all aging temperatures the alloy was observed to decompose completely by a cellular precipitation reaction which resulted in a fine lamellar structure of aluminum rich and zinc rich solid solutions. The first cell lamellar structure was subsequently decomposed at all aging temperatures by a second cellular or discontinuous coarsening reaction. The discontinuous coarsening reaction occurred at a much slower rate than the first cellular reaction and resulted in a much coarser lamellar structure. Several models for cellular precipitation and the existing theory of Livingston and Cahn for discontinuous coarsening have been used to evaluate the growth kinetics. The Petermann and Hornbogen model appears to describe the results the best. Finally, analysis of the kinetics suggests that both first and second cellular reactions are controlled by cell boundary diffusion in the whole aging temperature range.



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