Composition and stability of [Omega] phase in an Al-Cu-Mg-Ag alloy. [Al-3. 9Cu-0. 5Mg-0. 5Ag]

Journal Article · Thu Jul 01 04:00:00 EDT 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02646587· OSTI ID:6269703

Chang, Y C ^[1]; Howe, J M ^[2]

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1. Aeronautical Research Lab./CSIST, Taichung (Taiwan, Province of China)
2. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to determine the stability and composition of the [Omega] phase in an Al-Cu-Mg-Ag alloy. It is shown that the [Omega] phase can nucleate at isothermal aging temperatures up to 470 C in the [alpha] + [theta] phase region of the Al-Cu phase diagram. Furthermore, [Omega] precipitates formed by aging solution-treated and quenched samples at 130 C were found to exist after reversion treatments at temperatures close to the [theta]-phase solvus. The TEM/EDS analysis of relief-etched [Omega] precipitates shows that the composition of [Omega] phase is statistically the same as that of [theta]-Al[sub 2]Cu phase in a binary Al-Cu alloy, with Ag and Mg below the limits of detectability. These results indicate that the [Omega] phase is probably a metastable (111) variant of the equilibrium [theta] phase.

• OSTI ID: 6269703
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 24:7; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
AGING
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
CHEMICAL COMPOSITION
COPPER ALLOYS
DIAGRAMS
ELECTRON MICROSCOPY
HEAT TREATMENTS
MAGNESIUM ADDITIONS
MAGNESIUM ALLOYS
MICROSCOPY
PHASE DIAGRAMS
PHASE STUDIES
SILVER ADDITIONS
SILVER ALLOYS
SPECTROSCOPY
STABILITY
TRANSMISSION ELECTRON MICROSCOPY
X-RAY SPECTROSCOPY