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 Å, b = 8.998 Å and c = 5.031 Å. The ThFe2Al10 (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. ► A metastable ThFe2Al10 phase was observed in as-cast Al-6.1at.%Th-6.1at.%Fe alloy. ► The metastable ThFe2Al10 aluminide is orthorhombic, belongs to Pmmn space group. ► Its unit cell parameters are a = 9.076 Å, b = 8.998 Å and c = 5.031 Å. ► The ThFe2Al10 (Pmmn) phase is as a metastable state of ThFe2Al10 (Cmcm) phase.