Intermetallic phases in Al-Mn alloys

Abstract

The intermetallic phases present in high-purity and commercial purity Al-Mn alloys(up to 2 Mn) in as-cast and heat-treated conditions were extracted electrolytically in 10% HCL in methanol solution and identified by X-ray diffraction. As iron is known to increase the coarses cast-intermetallic particles and to cause refinement of the grain size after recrystallization, different amounts of iron (up to 0.5%) were added and the resulting intermeta-llic phases were extracted and identified with and wihout hear treatment. The unidentified phase phase. a-Al (Mn, Fe)Si, reported by Sperry and others, was recognized as corre-sponding for ASTM card' number 6-0669 and the conditions favourable for its formation were determined. This phase may be responsible for refining the grain size after recry-stallization in commercial purity alloy as compared to high-purity Al-Mn alloys and may therefore be tried as an inoculant (by adding powdered compound to liquid alloys) for grain refining.