The influence of the prior formation of a continuous precipitate upon the growth kinetics of the cellular reaction has been evaluated in an Al-17.9 wt. % Ag alloy. The continuous precipitate, in the form of intragranular plates of the γ′ transition phase, was shown to have reduced the upper bound of the driving force for the cellular reaction from the silver content of the untransformed alloy to that corresponding to the coherent solvus. When this reduction (≥ 98 %) is taken into account, the growth of cells is found to be controlled by cell boundary rather than by volume diffusion on the basis of both the Turnbull and the Cahn theories of the cellular reaction. Changing the mode of heat treatment from the usual quenching-and-aging to that of isothermal transformation reduces both the rate of growth of cells and the proportion of cellular structure formed by about an order of magnitude and increases the interlamellar spacing by 50-100%. These effects appear to result from a further decrease in the driving force. This decrease is attributed to a higher rate of introduction of misfit dislocations into the broad faces of the γ′ plates constituting the continuous precipitate, and thus to smaller values of the coherent solvus. © 1968.
H. I. Aaronson and J. B. Clark, "Influence Of Continuous Precipitation Upon The Growth Kinetics Of The Cellular Reaction In An Al-Ag Alloy," Acta Metallurgica, vol. 16, no. 6, pp. 845 - 855, Elsevier, Jan 1968.
The definitive version is available at https://doi.org/10.1016/0001-6160(68)90104-1
Materials Science and Engineering
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01 Jan 1968