Three dimensional atom probe analysis of pre-precipitate clustering in an Al-Cu-Mg-Ag alloy

Journal Article · Fri Mar 13 04:00:00 EST 1998 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(98)00027-X· OSTI ID:619483

Murayama, M; Hono, K ^[1]

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1. National Research Inst. for Metals, Tsukuba (Japan)

Trace element additions in age hardening aluminum alloys often modify precipitation products and kinetics. In the case of Al-Cu alloy, combined addition of trace amount of Mg and Ag leads to precipitation of fine and uniform dispersions of plate-like {Omega} phase on the {l_brace}111{r_brace}{sub Al} planes in addition to the {theta}{prime} precipitates on the {l_brace}001{r_brace}{sub Al} planes. The {Omega} phase shows high thermal stability and resistance to coarsening compared with the {theta}{prime} phase. Thus Al-Cu based alloy with trace additions of Ag and Mg has improved high temperature strength. The structure of the {Omega} phase was studied by Knowles and Stobbs and Muddle and Polmear, and it was concluded that the {Omega} phase has a face centered orthorhombic structure. More recently Garg and Howe suggested that the {Omega} phase formed at 250 C had a tetragonal structure with a = b = 0.607 and c = 0.487 nm using convergent beam electron diffraction, and suggested that {Omega} is a modified form of the equilibrium phase in Al-Cu binary alloy, {theta}. Effectiveness of {Omega} in improving mechanical and thermal properties of Al-Cu-Mg-Ag alloy is due to its uniform dispersion of {Omega} in the final microstructure with a different habit plane of {theta}{prime}. The role of the Mg-Ag co-cluster in the nucleation stage of the {Omega} phase is still unclear, because conventional APFIM study did not provide any information on the morphology of the clusters. Three dimensional atom probe (3DAP) recently developed by Cerezo et al. and Blavette et al. is able to determine positions of individual atoms using a position sensitive detector with almost an atomic resolution, thus it is able to observe morphology of atom clusters embedded in a solid solution. In this study, the authors employed 3DAP for investigating the morphology of the pre-precipitate clusters which appear in the early stage of aging in a Al-Cu based alloy with trace amounts of Mg and Ag.

• OSTI ID: 619483
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 8 Vol. 38; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BASE ALLOYS
COPPER ALLOYS
MAGNESIUM ADDITIONS
METALLURGICAL EFFECTS
MICROSTRUCTURE
NUCLEATION
SILVER ADDITIONS