Conference proceeding
In Situ Observations by HVEM of the Growth of Theta Prime Precipitates in Al--Cu
Solid to Solid Phase Transformations; Pittsburgh; Pa.; 10-14 Aug. 1981, pp.561-565
10 Aug 1981
Abstract
A solution treated and quenched (100) crystal of Al--3% Cu was thinned and aged in situ in the hot stage of a high-voltage electron microscope at 1 MeV, at 240 deg C. An individual theta ' precipitate was continuously observed during 2 hr growth, during which time it grew continuously with its length and thickness increasing with the square root of annealing time. The rate of growth was compatible with diffusion-controlled growth, though the diffusion coefficient was apparently increased 16 times by the point defects created by the electron irradiation. The observed theta ' precipitate had a very small aspect ratio (17 plus/minus 3) as had other theta ' plates in its vicinity. Other precipitates had the high value of aspect ratio normally found (A > 100). It is suggested that the behavior seen is the result of an enhanced interface reaction at the coherent interface due to easier formation of growth ledges, either by the electron irradiation or due to the proximity of the foil surface--the intersection of the foil surface with the theta ' precipitate could stimulate formation of the required growth ledges. Surface nucleated theta formed late during the reaction and outlined the solute depleted region around each theta ' precipitate. 10 ref.--AA.
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Details
- Title
- In Situ Observations by HVEM of the Growth of Theta Prime Precipitates in Al--Cu
- Creators
- R DohertyG Purdy
- Publication Details
- Solid to Solid Phase Transformations; Pittsburgh; Pa.; 10-14 Aug. 1981, pp.561-565
- Resource Type
- Conference proceeding
- Language
- English
- Academic Unit
- [Retired Faculty]; Materials Science and Engineering
- Identifiers
- 991021889909404721