Abstract
Al–Sc master alloy was prepared by the powder metallurgy route from the initial composition of Al90(Sc2O3)10 mixture. Aluminum powder was mechanically alloyed with addition of Sc2O3, which is much less costly than the metallic Sc, and fine Sc2O3 particles became uniformly dispersed in the matrix of Al. During consolidation by SPS at 873 K for 3.6 ks of mechanically alloyed powder mixture, Sc2O3 was decomposed and Al3Sc and Al2O3 are formed by solid-state reaction. Subsequently, SPS billets were hot-extruded at 773 K with a reduction of 1/12. Obtained extruded P/M material of Al–Sc master alloy was added to Al–4.5%Cu alloy melt and cast into the copper mold in order to attest its grain refining effect. Apparent grain refining was attained in the ingot of Al–4.5%Cu–0.55%Sc alloy and thus effectiveness of extruded P/M material from mixture of Al90(Sc2O3)10 as the Al–Sc master alloy was clearly attested. However, break down of covered oxide film of each powder particle by large plastic deformation is considered to be necessary to complete melting of added Al–Sc master alloy in the Al alloy melt.
