Microstructural evolution during aging of an Al-Cu-Li-Ag-Mg-Zr alloy

Journal Article · Wed May 01 04:00:00 EDT 1996 · Acta Materialia

DOI:https://doi.org/10.1016/1359-6454(95)00319-3· OSTI ID:247945

Kumar, K S ^[1]; Brown, S A; Pickens, J R ^[2]

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1. Brown Univ., Providence, RI (United States). Div. of Engineering
2. Martin Marietta Labs., Baltimore, MD (United States)

Using transmission electron microscopy (TEM) techniques, the phases present in an Al-5.4Cu-1.64Li-0.4Ag-0.4Mg-0.16Zr alloy were identified in the naturally-aged condition and after artificial aging to various times along the aging curve. The effect of prior stretching on the identity of strengthening phases in various aging conditions was also examined. In the naturally aged condition, {delta}{prime} (Al{sub 3}Li) and GP zones were present. Prior stretching discouraged the formation of these GP zones. Upon artificial aging, a reversion occurred in both the stretched and unstretched material that was associated with the dissolution of the GP zones and some of the {delta}{prime}. Longer exposures to temperature caused the precipitation of more {delta}{prime}, {theta}{prime} (Al{sub 2}Cu), T{sub 1} (Al{sub 2}CuLi) and S{prime} (Al{sub 2}CuMg), and the latter two of these phases remained in the overaged condition. The {delta}{prime} phase precipitated homogeneously in the matrix and heterogeneously on {theta}{prime} and Al{sub 3}Zr. In the unstretched material, the T{sub 1} phase first precipitated on the subgrain boundaries, then in the interior of the subgrains, leaving a precipitate-free zone that decreased in size with longer aging times. The {theta}{prime} in the stretched material produced streaks and spots of lower intensity (in selected area diffraction patterns) than in the unstretched material, for comparable aging times. Overaging of the stretched material, however, resulted in the dissolution of {theta}{prime} and some {delta}{prime} leaving a matrix consisting of T{sub 1}, S{prime} and minor amounts of {delta}{prime}.

• OSTI ID: 247945
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 5 Vol. 44; ISSN XZ504Y; ISSN 1359-6454
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGING
ALUMINIUM ALLOYS
COPPER ALLOYS
CRYSTALLOGRAPHY
DISSOLUTION
GUINIER-PRESTON ZONES
INTERMETALLIC COMPOUNDS
LITHIUM ALLOYS
MAGNESIUM ADDITIONS
MICROSTRUCTURE
PHASE STUDIES
PRECIPITATION
SILVER ADDITIONS
TIME DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
ZIRCONIUM ADDITIONS