Early stages of composite formation by oxidation of liquid aluminum alloys

Microstructure evolution during the early stages in the directed oxidation of molten Al-Mg and Al-Mg-Si alloys is investigated. Continuous heating above the alloy liquidus produces a thin MgO layer then brief rapid growth of a spinel+metal mixture within a temp. range which depends on Mg content and...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1995-03, Vol.78 (3), p.609-622
Main Authors: SALAS, O, VIKRAM JAYARAM, VLACH, K. C, LEVI, C. G, MEHRABIAN, R
Format: Article
Language:English
Subjects:
Applied sciences
Building materials. Ceramics. Glasses
Ceramic industries
Chemical industry and chemicals
Exact sciences and technology
Miscellaneous
Technical ceramics
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Summary:Microstructure evolution during the early stages in the directed oxidation of molten Al-Mg and Al-Mg-Si alloys is investigated. Continuous heating above the alloy liquidus produces a thin MgO layer then brief rapid growth of a spinel+metal mixture within a temp. range which depends on Mg content and heating rate. Initial rapid oxidation terminates abruptly with formation of a dense spinel layer at the surface, leading to a long incubation period of negligible wt gain. Surface MgO regenerates in this regime, while the metal channels slowly advance upward by dissolution of the dense spinel, eventually reaching the MgO and inducing formation of composite nodules. These consist initially of spinel+metal upon which conventional Al sub 2 O sub 3 +metal growth starts after the Mg in the near-surface alloy is depleted to a critical level. 31 refs.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1995.tb08222.x