A KINETIC-STUDY ON THE NUCLEATION AND GROWTH OF THE AL8FEMNSI2 INTERMETALLIC COMPOUND FOR ALUMINUM SCRAP PURIFICATION

This work presents the results of an experimental investigation on the formation of Al8FeMnSi2 intermetallic particles from Al-Si-Fe-Mn liqu id alloys, in the temperature range from 878 to 973 K. The results of this study show that the formation and segregation of the intermetalli c particles could serve as the basis for the purification of aluminum scrap melts exceeding permissible iron and manganese levels. The rates of nucleation and growth of the intermetallic particles were determin ed using chemical analysis and quantitative optical microscopy measure ments. Kinetic formulae taking into account the effects of undercoolin g and supersaturation on the nucleation and growth rates of the partic les were used to correlate the experimental results. Finally, a thermo dynamic analysis of the system was carried out to determine the enthal py and entropy of formation of the intermetallic compound, and to expl ain the role of the Mn/Fe ratio on the aluminum scrap purification thr ough the segregation of the Al8FeMnSi2 intermetallic compound. (C) 199 7 Elsevier Science Limited.