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Evolution of surface characteristics of two industrial 7xxx aluminium alloys exposed to humidity at moderate temperature
Author(s) -
Schwarzenböck Elisabeth,
Hack Theo,
Kolb Max,
Engel Christian,
Heidenblut Torsten,
Maier Hans Jürgen
Publication year - 2019
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.6652
Subject(s) - alloy , materials science , x ray photoelectron spectroscopy , precipitation , scanning electron microscope , microstructure , transmission electron microscopy , humidity , surface layer , aluminium , oxide , metallurgy , layer (electronics) , chemical composition , aluminium alloy , analytical chemistry (journal) , chemical engineering , chemistry , composite material , environmental chemistry , nanotechnology , thermodynamics , physics , organic chemistry , meteorology , engineering
This study analyses the evolution of surface characteristics of two industrial high‐strength 7xxx aluminium alloys with a focus on alloy composition and environmental parameters. Based on storage and transport conditions of as‐machined products, the effect of humidity—as liquid and vapour phase—on the natural oxide layer has been studied. The evolution of the natural oxide layer has been analysed by scanning electron microscopy and X‐ray photoelectron spectroscopy. The growth behaviour of the surface layer is dominated by environmental conditions, while microgalvanic activity depends mainly on the alloys' chemical composition and differs significantly for tested alloys. Scanning transmission electron microscopy images demonstrated that the long‐term exposure at moderate temperatures affects the microstructure near the surface, which differs for the analysed alloy compositions. An anomalous precipitation of zinc‐rich particles at the surface and along the precipitate‐free zone is observed for the alloy with higher Zn/Mg ratio and lower Cu content.