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Accelerated growth of oxide film on aluminium alloys under steam: Part I: Effects of alloy chemistry and steam vapour pressure on microstructure

  • Din, Rameez Ud
  • Gudla, Visweswara C.
  • Jellesen, Morten S.
  • Ambat, Rajan
Publication Date
Jan 01, 2015
Online Research Database In Technology
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Aluminium alloys were treated with steam of varying vapour pressures which resulted in the growth of aluminium oxyhydroxide layers of an average thickness of ~450–825 nm. The microstructure and composition of the generated layers were characterised by GD-OES, FEG-SEM, GI-XRD and TEM. The thickness of the oxide layeras well as the compactness increased with steam vapour pressure. The increase in vapour pressure also resulted in a better coverage over the intermetallic particles. Oxide layer showed a layered structure with more compact layer at the Al interface and a nano-scale needle like structure at the top. The kinetics of formation of film understeamwas rapid; approx. 350nm thick layers were generated within 5 s of steam treatment, however increase in thickness of the oxide retarded further growth. The enrichment or depletion of different alloying elements at the surface of aluminium as a result of alkaline etching pre-treatment influenced the thickness and growth of theoxide. Moreover the steam treatment resulted in the partial oxidation of second phase intermetallic particles present in the aluminium alloy microstructure.

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