1100 ℃ isothermal section of Nb-W-Zr-C quaternary system

An isothermal section of the Nb-W-Zr-C system at 1 100 ℃ was established by means of multiphase diffusion couples along with electron microprobe analysis and X-ray diffraction analysis. The isothermal section consists of two single-phase regions, α（Nb, W, Zr） and （W, Nb）2Zr and one double-phase region, α（Nb, W, Zr）+)（W, Nb）2Zr.) It is concluded that （W, Nb）2Zr is an interstitial intermediate phase with the face-centered cubic （Cu2Mg） lattices. The maximum solid solubility of carbon in （W, Nb）2Zr phase is determined as about 4.18%C（mole fraction）.The composition ranges of tungsten in the （W, Nb）2Zr phase are 55.41% to 65.98% and the maximum solid solubility of niobium in （W, Nb）2Zr is determined as 7.78%.