Experimental Investigation and Thermodynamic Calculation of the B-Co-Zn Ternary System

The 450 °C isothermal section of the B-Co-Zn ternary system has been determined using scanning electron microscopy, electron probe microanalysis and x-ray diffraction. Seven three-phase regions exist in the 450 °C isothermal section, and no ternary compound is found. The experimental results indicate that the maximum solubility of B in β₁, γ, γ₁ and γ₂ is 0.31, 2.54, 0.52 and 2.51 at.%, respectively. The solubility of Zn in Co₂B and CoB is not greater than 0.6 at.%. On the basis of the literature data of the thermodynamic assessment of Co-B, Co-Zn binary systems and B-Zn system obtained in the present work, the phase diagram calculation for B-Co-Zn ternary system was carried out by means of CALPHAD method. The calculated results and the experimental data are in good agreement.