ZrC segregation to the surface of dilute solid solutions of zirconium carbide in niobium carbide

Precipitation of crystalline ZrC in the surface region of dilute ZrC-NbC solid solutions (< 1.0 mot % ZrC) was revealed by electron microscopy, x-ray microanalysis, laser mass spectrometry, and x-ray diffraction. The ZrC precipitation was shown to be a consequence of the diffusional decomposition of the dilute Zr1-xNbxC solid solutions. The boundaries of the solid-miscibility gap in the ZrCy-NbCy, system were calculated. The segregation energy of zirconium carbide was estimated at -33.3 kJ/mol.