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Characterization of precipitates in an aged 7 xxx series Al alloy
Author(s) -
Sha Gang,
Cerezo Alfred
Publication year - 2004
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1702
Subject(s) - alloy , atom probe , precipitation , transmission electron microscopy , materials science , crystallography , ageing , metallurgy , analytical chemistry (journal) , chemistry , nanotechnology , chromatography , biology , meteorology , genetics , physics
Precipitates in a 7050 Al alloy under two‐step ageing treatments were characterized using an energy‐compensated optical position‐sensitive atom probe and transmission electron microscopy. Selected‐area diffraction analyses indicated that the early‐stage precipitates present after a stabilization ageing treatment at 121°C for 4 h have a crystallographic structure similar to η′, but probably rich with defects. After T6 treatment ageing at 121°C for 24 h followed by 12 h at 154°C, η′ and η coexist within the Al matrix. Energy‐compensated optical position‐sensitive atom probe analysis was used to measure the partitioning of Zn, Mg and Cu to the precipitates. Early‐stage precipitates in the alloy after stabilization treatment have a Zn/Mg ratio of ∼1.3 and a (Zn + Cu)/Mg ratio of 1.4. The T6‐aged alloy contained η precipitates with an Zn/Mg ratio of ∼1.2 and a (Zn + Cu)/Mg ratio of 1.3 coexisting with η′ precipitates with a Zn/Mg ratio of ∼0.7 and a (Zn + Cu)/Mg ratio of ∼1. Copyright © 2004 John Wiley & Sons, Ltd.