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 Al88Fe9Nd3 and Al87Ni10Ce3 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 Al90Sm8Ni2 and Al90Sm8Fe2 metastable intermetallics form during rapid solidification together with a fraction of amorphous phase, whereas nanocrystalline Al forms on annealing the amorphous phase.