SOLIDIFICATION OF AN AMORPHOUS PHASE IN RAPIDLY SOLIDIFIED AL-FE-SI ALLOYS

The focus of this work is the 'amorphous' phase formation in Al-Fe-Si alloys. Depending on the concentration of iron and silicon the phase appears either as an intercellular constituent or as a primary phase with globular morphology. Thus the 'amorphous' phase acts like a normal crystalline phase. The globular morphology of the 'amorphous' phase suggests the possibility of a metastable liquid miscibility gap. However, there is no thermodynamic evidence to support a positive heat of mixing for the liquid phase. Another possibility suggests crystallization of a phase structurally different from liquid, but at the same time being neither crystalline nor quasi-crystalline. A possible structural relationship between the 'amorphous' phase, the cubir α-(Al,Fe,Si) phase and the quasi-crystalline phase is discussed.