Experimental and thermodynamic assessment of the Gd–Zr system

The phase equilibria of the binary Gd–Zr system have been investigated by combining electrostatic levitation of the melt with in situ high energy synchrotron X-ray diffraction. The liquidus line was experimentally assessed between 1500 and 1800 K from the diffraction data. At T=1495±10 K the eutectic reaction L↔bcc-Gd+bcc-Zr is evident. The eutectic composition x=18±2 at% Zr is determined from the in situ diffraction data and confirmed by the analysis of the microstructure of cast alloys. The so far unknown coexistence of bcc-Gd and bcc-Zr is observed for the temperature range 1450 K<T<1495 K. Based on the experimental data an improved Gd–Zr phase diagram is derived and a thermodynamic description of the binary system is presented.