ABSTRACT
Scandium is a very powerful addition to aluminum alloys. The grain refinement of ingots and castings depends on the concentration of scandium and on the presence of other transition metals, the best results being obtained in combination with zirconium. The grain refinement up to the formation of a non-dendritic grain structure greatly improves the properties of cast metal, including its strength and technological plasticity. The decomposition of scandium supersaturated solid solutions occurs at temperatures above 200°C and facilitates essential hardening in the temperature range from 250 to 350°C. In aging aluminum alloys the main effect of scandium additions is the essentially increased recrystallization temperature. The ability of scandium to form a fine structure in cast metal substantially improves the weldability of many wrought aluminum alloys. The combination of scandium with zirconium increases these effects and the permissible temperatures of heat treatment.
