SCANDIUM IN ALUMINIUM ALLOYS: PHYSICAL METALLURGY, PROPERTIES AND APPLICATIONS
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Abstract
The use of scandium as an alloying element in aluminium has gained an increasing interest even though scandium is difficult to extract, which makes the metal very expensive. The three principle effects that can be obtained by adding scandium to aluminium alloys are (i)grain refinement during casting or welding, (ii)precipitation hardening from Al3Sc particles and (iii)grain structure control from Al3Sc dispersoids. Addition of scandium in combination with zirconium is particularly effective, and the reason for this is linked to the recently discovered core/shell structure of the Al3(Sc,Zr) dispersoids. The effects that can be obtained from a Sc addition are to a large extent dependent on the alloy system to which it is added, and an overview of some effects in all the major classes of wrought aluminium alloys is given. Industrial use of Sc-containing aluminium alloy is so far limited to a few aerospace applications and to sporting equipment, further use is dependent on a price reduction of scandium.