Chemical Resistance of Refractories to AI and AI‐Mg Alloys

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Abstract
The chemistry of the reaction between molten aluminum alloys and some refractory oxides is discussed. High‐alumina brick containing 85, 94, and 99% Al2O3 periclase brick, and magnesia spinel brick were immersed for 48 hours in three aluminum alloys containing 0, 2.4, and 7.7% magnesium, respectively. All brick were discolored, although most of the discoloration disappeared after reheating at 1000°C in an oxidizing atmosphere. Only the 85 and 94% brick, which contained silica, showed permanently darkened reaction rims. X‐ray diffraction analysis of these darkened areas showed that the alloy containing 7.7% magnesium caused periclase formation in the rim whereas the alloy containing 2.4% magnesium produced spinel. Commercial aluminum caused only a decrease in the mullite content of the darkened area. Magnesia spinel and periclase were unaffected by all the alloys tested.

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