Calorimetric study of the oxidation of Al–Mg alloys for the prediction of healing of the double oxide film defect
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Abstract
The oxidation of Al alloys containing 0.3–4.5 wt% Mg in an atmosphere with a very low oxygen partial pressure (<0.5 ppm, to depict the atmosphere within a double oxide film defect) was studied using differential scanning calorimetry and scanning electron microscopy. The results showed that a newly formed Al2O3 layer held in an Al–Mg melt first transformed to MgAl2O4 spinel and then to MgO. This mechanism was the same for all the Al alloys containing 0.3–4.5 wt% Mg, but the kinetics of the transformations were different and depended on the Mg content of the melt. The results also suggest that the two layers of a double oxide film defect that is held in an Al melt containing 0.3–4.5 wt% Mg can heal (i.e. bond to each other) if held in the liquid metal for a long enough period of time.
Keywords
Differential scanning calorimetry Double oxide film defect Bifilm Al–Mg alloys Healing MgAl2O4 MgOReferences
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