Phase Diagram And Phase Transformation Of Zr-T(T=Cu,Fe)-Ge And Zr-Cu-Mo Ternaryalloy Systems

Goal of achieving“carbon peak,carbon neutral”for China demands a change of its energy structure from fossil energy to clean energy sources,such as nuclear power,wind power,and solar energy.Zirconium alloys have a small thermal neutron absorption cross section,good mechanical properties,and excellent corrosion resistance,and are widely used as cladding and structural materials for nuclear reactor fuel.The development of nuclear energy requires extending the refueling cycle of fuel groups and increasing the combustion power of nuclear fuel,which demands more higher corrosion resistance and creep resistance of zirconium alloy,the fuel cladding material.Alloying is a key way to improve the corrosion resistance of zirconium alloys.Additional amount of elements such as Ge,Fe,Cu,and Mo can improve the corrosion resistance of zirconium alloys.The role of alloy elements is related to interaction and distribution of alloy elements in zirconium alloys.Studying of phase diagrams related to Zr-Ge and Zr-Mo binary system will benefit the understanding of the interaction of Ge,Fe,Cu,and Mo between Zr matrix,promoting the establishment of thermodynamic database of zirconium alloy materials.The main research contents and achievements of this article include:（1）The phase relationship of the 800℃isothermal section of the Zr-Fe-Ge system was determined by using scanning electron microscopy,and X-ray diffraction.The results show that at 800℃,the Zr-Fe-Ge ternary system consists of 25 single-phase regions,50 two-phase regions,and 29 three-phase regions.The five previous reported ternary compounds,such as Zr₄Fe₄Ge₇,ZrFe₆Ge₆,ZrFeGe₂,ZrFeGe,Zr₂Fe₃Ge in the Zr-Fe-Ge ternary system,were all observed in this work.A new ternary compound Zr₂FeGe₂was discovered.In the solubilities of Zr in the binary Fe-Ge compounds,such as Fe₁₇Ge₃,Fe₁₃Ge₃,Fe₁₃Ge₈,and FeGe₂are observed negligible.（2）The Zr-Fe-Ge ternary as-cast samples were prepared by arc melted.The microstructure of the specimens and composition of the indentified phases were analyzed by scanning electron microscopy/energy spectrometer,and X-ray diffraction.The invariant reaction temperature was obtained by using differential canning calorimetry technique.The liquidus projection surface of the Zr-Fe-Ge ternary system consist of 20 primary phase regions,which include（Fe）,Zr₆Fe₂₃,ZrFeGe,Fe₁₇Ge₃,Fe₃Ge,Fe_1.7Ge,Fe₁₃Ge₈,FeGe₂,（Ge）,ZrFeGe₂,Zr₂Fe₃Ge,ZrFe₆Ge₆,Zr₄Fe₄Ge₇,ZrGe₂,ZrGe,Zr₅Ge₃,ZrFe₂,Zr₃Ge,Zr₂Fe,（Zr）.5 quaternary eutectic reactions,such as L→（Fe）+Fe₃Ge Zr₂+ZrFeGe,L→Zr₅Ge₃+ZrFe₂+ZrFeGe,L→Zr₃Ge+Zr₂Fe+（Zr）,L→ZrFe₆Ge₆+（Ge）+FeGe₂,and L→ZrFeGe+Fe_1.7Ge+Fe₃Ge,respectively,were identified.A new ternary compound Zr₂FeGe₂was found,which precipitated from peritectic reaction L+Zr₅Ge₃→Zr₂FeGe₂.（3）The isothermal section of the Zr-Cu-Ge system at 600°C was determined by electron probe microscopy and X-ray diffraction by using equilibrated alloy and diffusion couple method.The results show that the Zr-Cu-Ge ternary system consists of 19 single-phase regions,39 two-phase regions and 21 three-phase regions at 600℃.There are four ternary compounds,such as ZrCuGe,Zr₃Cu₄Ge₂,ZrCuGe₂,and Zr₂CuGe₄were observed for the Zr-Cu-Ge ternary systemat 600℃.（4）In this work,Six diffusion couples were successfully prepared by immersing Mo into liquid Cu-Zr master alloy or Mo-Zr master alloy immersing into liquid Cu.The phases in the diffusion couple alloy were analyzed by scanning electron microscope（SEM）and energy dispersive spectrometer（EDS）.It is determined that the Zr-Cu-Mo ternary system consists of 11 single-phase regions,19 two-phase regions and 9 three-phase regions at 800℃.