Contribution to the Zr-Rich Part of the Zn-Zr Phase Diagram

摘要

The reaction of zinc vapor with Zircaloy-4 and nuclear grade zirconium was investigated with various analytical techniques: optical metallography, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Based on the results, the Zr-rich part of the Zn-Zr phase diagram was revised. A eutectoid decomposition of (beta Zr) occurs at 718 + - 6 deg C with a composition of x_(zr) = 0.865; this temperature is lower than the previously accepted 750 deg C eutectoid. The solubility of Zn in (alpha Zr) was determined to be at chi_(zn) = 0.0236, a maximum at 725 deg C. The intermetallic phase ZnZr_2 was observed to occur in samples heat treated at 712 deg C and 725 deg C, but not in those heat treated at 700 deg C and 775 deg C.