The methods of optical and scanning electron microscopy and x-ray spectrum microanalysis are used to study and to compare the special features of formation of metastable trialuminides under rapid crystallization of superheated melts of the Al – Hf – Sc and Al – Hf – Ti systems. Heating of such melts by over 100°C above the liquidus temperature yields Aln(Hf1–xScx) and Aln(Hf1–x Tix) aluminides with a cubic lattice of structural type L12.