Formation and fine-structures of nano-precipitates in ZIRLO

Transmission electron microscopy and energy dispersive X-ray spectroscopy have been used for crystallographic and compositional characterization of nano-precipitates distributed within the α-Zr matrix of the ZIRLO alloy. Intermetallic nano-particles with the C14 Laves-phase structure were found to be the dominant precipitate phase typically larger than 60 nm in sizes, which is assigned to the Zr(Fe,Nb)2 formula with Fe and Nb being mixed on the second sublattice sites in the bracket. Stacking faults were also observed in the ternary Laves phase, together with dislocations presenting on prism planes of the matrix solid solution. Besides, some fine spherical β-Nb particles about 30 nm in size were also found to precipitate within the α-Zr grains, with the α/β interface being crystallographically coherent.