Phase selection in Al–TM–RE alloys: nanocrystalline Al versus intermetallics

Al–TM–RE (TM: transition metal, RE: rare earth metal) and Al–RE alloys were analysed with the aim of studying phase selection under various processing conditions. The metastable phases formed in binary Al-rich systems (notably Al–Sm) are revised for a unified interpretation of the literature. Two groups of alloys had different behaviour as for phase selection. In Al 88 Fe 9 Nd 3 and Al 87 Ni 10 Ce 3 stable intermetallic compounds form as primary phases during solidification. Nanocrystalline Al is formed at high undercooling. This may occur directly in rapid solidification or when fully amorphous materials are suitably annealed. In Al 90 Sm 8 Ni 2 and Al 90 Sm 8 Fe 2 metastable intermetallics form during rapid solidification together with a fraction of amorphous phase, whereas nanocrystalline Al forms on annealing the amorphous phase.