The isothermal sections of the Co-Ni-Zn ternary system at 450 degrees C and 600 degrees C have been determined experimentally using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray diffraction. Three tri-phase regions have been confirmed at 450 degrees C and 600 degrees C, respectively. Three continuous solid solutions regions, i.e. alpha-Co/alpha-Ni, gamma-Co5Zn21/gamma-Ni4Zn22 and gamma(2)-CoZn13/delta-NiZn8, exist in the sections. The solubility of Co in beta(1)-NiZn is up to 15.0 at.% at 600 degrees C, and 16.5 at.% at 450 degrees C. The maximum solubility of Ni in beta(1)-CoZn and gamma(1)-CoZn7.8 is 10.5 at.% and 8.1 at.% at 600 degrees C, and 11.8 at.% and 5.5 at.% at 450 degrees C, respectively. No true ternary compound was found. The X-ray powder diffraction patterns of the Co-Zn intermediate phases beta(1) and gamma have been obtained experimentally. The results obtained by cell refinement revealed that both Co-Zn compounds beta(1) and gamma belong to the cell type of cubic, and their lattice parameters are 0.63360 and 0.89412 nm, respectively. (C) 2012 Elsevier B.V. All rights reserved.