Microstructures and defect structures in ZrCr2 Laves phase based intermetallic compounds

Microstructures of Zr–Cr binary alloys based on the ZrCr2 Laves phase are characterized by optical and scanning electron microscopy, electron probe analysis, X-ray diffraction, transmission electron microscopy, and density measurement. Eutectic compositions corresponding to the reactions of liquid→Cr solid solution+ZrCr2 and liquid→Zr solid solution+ZrCr2 exist at approximately 20.5 at.%Zr and 72 at.%Zr, respectively. The ZrCr2 Laves phase has the solid solution range between 31 at.%Zr and 34 at.%Zr, and more extends in Cr-rich side of stoichiometry. Alloy stoichiometry and heat treatment affect the phase stability and microstructure of the ZrCr2 Laves phase. Atomistic defect structures introduced in Cr-rich and Zr-rich sides of stoichiometry are of the anti-site type and a mixture of the anti-site type with the vacancy-type, respectively. The determined defect structures are discussed, on the basis of the geometrical model, i.e. the atomic size factor.