Experimental investigation and thermodynamic assessment of phase equilibria in the Nb–Si–Zr ternary system

• The sections of Nb–Si–Zr system at 1373, 1473 and 1573 K were determined.
• Large solubilities of Nb in αZr5Si4, Zr3Si2 and Zr2Si phases were observed.
• The thermodynamic assessment of Nb–Si–Zr ternary system was carried out.

In this study, the phase equilibria of Nb–Si–Zr at 1373 K, 1473 K and 1573 K were experimentally determined by means of back-scattered electron (BSE), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that there were five three-phase regions and sixteen two-phase regions in the studied isothermal sections, and no any ternary compounds were found. The solubility of Si in the Nb–Zr side is very small. Large solubilities of Nb in αZr5Si4, Zr3Si2 and Zr2Si phases were observed, otherwise the solubilities of Nb in ZrSi2, αZrSi and Zr3Si phases are relatively small. Based on the present experimental results, the thermodynamic assessment of Nb–Si–Zr system was carried out using the CALPHAD (Calculation of Phase Diagrams) method. The current calculated phase diagrams are in reasonable agreement with the present experimental data.