Observation of a metastable aluminide ThFe2Al10

Metastable ThFe2Al10 ternary aluminide was observed in the as-cast Al-6.1at.%Th-6.1at.%Fe alloy. It crystallizes into an orthorhombic structure belonging to Pmmn space group symmetry and possesses unit cell with parameters a = 9.076 إ, b = 8.998 إ and c = 5.031 إ. Fe2Al10 (Pmmn) phase can be considered as a metastable state of the equilibrium ThFe2Al10 (Cmcm) compound; its formation should be directly related to the cooling rate of the alloy during casting. After annealing the as-cast alloy at 600 °C for one week the metastable ThFe2Al10 (Pmmn) phase decomposes: the particles of this phase are no longer observed in SEM, and the diffraction peaks associated with this phase disappear in the XRD pattern.