Metastable phases in vapour-deposited Al-Ru alloys

Vapour deposition of two Al-Ru alloys containing 10 and 15wt% Ru resulted in the formation of supersaturated solid solutions. Electron microscopy and electron diffraction techniques have been used to characterize this as-quenched structure and also those formed on subsequent decomposition. Elevated-temperature (650–800 K) annealing treatments resulted in the formation of a metastable intermediate phase. Electron diffraction evidence suggested that this phase can be assigned a simple cubic structure either of the Mo₃N₂-type witha=0.42 nm or of the Mg₂Zn₁₁-type witha=0.84 nm. Further annealing led to the formation of the equilibrium AI and AI₆ Ru phases. The morphology and structural features of transformation products and the crystal structure details of the metastable intermediate phase have been discussed.