| Zr alloy is an important cladding material for nuclear reactor. The widely used Zr-based alloys are mainly based on Zr-Nb and Zr-Sn system. Sn, Fe, Cr, and Ni are important alloying element for Zr-based alloy. They have a significant impact on the performance of the alloy. The study of phase diagrams is important to the development and application of new materials design and performance. In this work, we determined the isothermal sections of several Zr-based alloys by using X-ray diffraction analysis and scanning electron microscopy methods. Generally, the recrystallization temperature and hot extrusion temperature of commercial Zr alloy is580℃and650～700℃. Therefore, the isothermal section at700℃and580℃were chosen to investigate the Zr-based alloys system. For the Sn-Fe-Ni ternary system, we choose500℃as the experimental temperature. The achieved results were as follows:(1) The isothermal sections of the Zi-Fe-Cr ternary system at700℃and580℃were established. Three binary phase (Fe2Zr, Cr2Zr, and FeZr3) and a ternary phase (Fe,Cr)2Zr were found to stably exist at700℃. The composition ranges of Fe and Cr in ternary phase (Fe,Cr)2Zr is10.9～62.3at.%and3.2～55.1at.%, respectively. In addition, the oxygen stabilized phase Fe23Zr6were also observed in several Cr-rich alloys. Binary phases FeCr, Fe2Zr, Cr2Zr and FeZr3and a ternary-phase (Fe,Cr)2Zr were found to present in Zr-Fe-Cr ternary system at580℃. The composition range of (Fe,Cr)2Zr was at10.9～62.3at.%Fe and3.2～55.1at.%Cr. Similar to the case in the isothermal section at700℃, Fe23Zr6was observed to present as oxogen stablilized phase at580℃.(2) The isothermal section of the Zr-Nb-Cr ternary system at700℃was established. There are four ternary-phase regions, nine two-phase regions and five single-phase zones in Zr-Nb-Cr system at700℃. The cubic Cr2Zr and Cr2Nb form substitute solution at this temperature.High temperature Cr2Nb, with hexagonal structure, was observed in a narrow composition range at the research temperature.(3) The isothermal section of Fe-Ni-Sn system at500℃was established. This study confirms the existence of five binary compounds, namely, FeSn, FeSn2, Ni3Sn, Ni3Sn2, Ni3Sn4and a ternary phase (Fe,Ni)3Sn2. The study verified the crystal structure of (Fe,Ni)3Sn2was consistent with the high temperature phase Ni3Sn2with hexagonal structure. Therefore, we confirmed that both of the hexagonal crystal structure and orthogonal crystal structure of Ni3Sn2were existed in the Fe-Ni-Sn ternary system at500℃. The maximun solubility of Ni in FeSn was11.4at.%. |
