The isothermal section of Fe-Ni-Zr ternary system at 1198K was experimentally determined using diffusion triple technique together with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results indicate that there are seven binary intermetallic phases, Fe2Zr, FeZr2, NiZr2, NiZr, Ni10Zr7, Ni7Zr2, and Ni5Zr, found in the ternary system, the binary compounds NiZr2 and FeZr2 show a homogeneity range and form a continuous solid solution, namely (Fe, Ni)Zr2. Five three-phase sections, γ(Fe,Ni) + Ni7Zr2 + Ni5Zr, γ(Fe,Ni) + Ni7Zr2 + Ni10Zr7, γ(Fe,Ni) + Fe2Zr + Ni10Zr7, (Fe,Ni)Zr2 + Fe2Zr + Ni10Zr7, and (Fe,Ni)Zr2 + NiZr + Ni10Zr7, exist in the isothermal section. No ternary compound is observed.
