Application of computational thermochemistry to Al and Mg alloy processingwith Sc additions

Thermochemical calculations have been used to discuss various aspects of Al -Mg-Sc alloy processing: alloying of scandium, alloy melting, solidificatio n and heat treatment. The feasibility of replacing expensive scandium by ch eap scandium oxide for alloying into liquid Al is supported by these quanti tative data, whereas the alloying into liquid Mg is found to be unfeasible. Calculations of ternary Al-Mg-Sc phase equilibria are based on an experime ntally supported thermodynamic data set. Liquidus surfaces of both the Al a nd Mg rich corners depict the narrow ranges for complete melting of alloys subject to reasonable temperature limits. The joint solid solubilty limits in both the (Al) and (Mg) matrix are given as a basis for heat treatments. The solidification of one typical Al and one Mg alloy are discussed based o n the equilibrium calculations and also using the Scheil model. (C) 2000 El sevier Science S.A. All rights reserved.