Experimental determination of intermetallic phases, phase equilibria, and invariant reaction temperatures in the Fe-Zr system

The phase diagram of the binary Fe-Zr system was redetermined by differential thermal analysis (DTA), electron-probe microanalysis (EPMA), x-ray diffraction (XRD), and metallography in the whole range of compositions. The stable intermetallic phases of the binary system are the cubic and the hexagonal polymorphs of the Fe2Zr Laves phase and the Zr-rich phases FeZr2 and FeZr3. While the cubic polymorph of the Laves phase is the stable structure at the stoichiometric Fe2Zr composition, the hexagonal C36-type polymorph of the Laves phase is a high-temperature phase that is found at Zr concentrations as low as 26.6 at.%. The Zr-rich phases FeZr2 and FeZr3 have small homogeneity ranges of about 0.5 at.%. FeZr2 is a high-temperature phase, stable between 780 and 951 degreesC. FeZr3 decomposes peritectoidally at 851 degreesC. The frequently reported phase Fe23Zr6 (Fe3Zr) is found not to be an equilibrium phase of the binary system.