Application of computational thermochemistry to Al and Mg alloy processing with Sc additions

Thermochemical calculations have been used to discuss various aspects of AlMgSc alloy processing: alloying of scandium, alloy melting, solidification and heat treatment. The feasibility of replacing expensive scandium by cheap scandium oxide for alloying into liquid Al is supported by these quantitative data, whereas the alloying into liquid Mg is found to be unfeasible. Calculations of ternary AlMgSc phase equilibria are based on an experimentally supported thermodynamic data set. Liquidus surfaces of both the Al and 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 on the equilibrium calculations and also using the Scheil model.