Precipitation stability in Al-Cu-Mg-Ag alloys aged at high temperatures
- Monash Univ., Clayton, Victoria (Australia). Dept. of Materials Engineering
A study has been made of the thermal stability of the [Sigma] phase in Al-Cu-Mg-Ag alloys aged at high temperature (200 to 350 C). This phase, which precipitates as thin plates on the [111][sub [alpha]] planes, has been shown to be replaced by the equilibrium precipitate [theta] (Al[sub 2]Cu) after prolonged aging (e.g. 2,400 h at 250 C). Measurements have been made of the thickening behavior of the [Omega] plates and the various orientations and morphologies of the [theta] phase have been characterized. While there is some evidence for the direct allotropic transformation of [Omega] to [theta], it is concluded that a gradual dissolution/re-precipitation mechanism dominates the changes to microstructure at these high temperatures. Although magnesium and silver are known to segregate to the [Omega] phase, they were not detected in association with [theta]. Rather they were found to partition to sites of the S phase (Al[sub 2]CuMg) which forms as a minor precipitates under these aging conditions.
- OSTI ID:
- 5158849
- Journal Information:
- Acta Metallurgica et Materialia; (United States), Vol. 42:5; ISSN 0956-7151
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM BASE ALLOYS
MICROSTRUCTURE
COPPER ALLOYS
ELECTRON DIFFRACTION
EXPERIMENTAL DATA
MAGNESIUM ADDITIONS
PHASE STUDIES
QUATERNARY ALLOY SYSTEMS
SEGREGATION
SILVER ADDITIONS
TRANSMISSION ELECTRON MICROSCOPY
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
COHERENT SCATTERING
DATA
DIFFRACTION
ELECTRON MICROSCOPY
INFORMATION
MAGNESIUM ALLOYS
MICROSCOPY
NUMERICAL DATA
SCATTERING
SILVER ALLOYS
360102* - Metals & Alloys- Structure & Phase Studies