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Unformatted text preview: of alpha particles.
Grain boundaries are common nucleation sites because the excess energy (due to the strain it
exerts on the material due to disorder) is recovered by the nucleation of other grains.
If the material is cooled and then reheated, the final microstructure consists of a dense
distribution of Beta precipitates in the interior of alpha grains.
If it is cooled too quickly, the precipitates are forced into the grain interiors by quenching the
alloy to suppress nucleation on the grain boundaries and then reheating to induce
precipitation at a low temp where nucleation happens predominantly in the interiors of the
There is not enough time for diffusion so the beta phase particles are trapped in alpha phase
so beta particles precipitate out of the alpha....
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- Fall '12