Study On The Phase Relation Of Zr-Cr-Cu Ternary System

Zirconium alloy has the low absorption cross section of thermal neutron,high conductivity,high thermal conductivity and good corrosion resistance,et al,and are widely used in military-industrial,complex submarine and pressurized water reactor nuclear power plant,such as the cladding tube material of uranium fuel or structural materials.Cr and Cu are the important alloying elements added to the zirconium alloy.Study on the phase relation of the Zr-Cr-Cu ternary system are critical to the alloy design,processing optimization and new zirconium alloy development.In this dissertation,the phase equilibrium and thermodynamic database of the Zr-Cr-Cu ternary system were built via the combination of phase equilibrium experiements,first principles calculation and calphad assessment.This dissertation mainly contains the following work:(1)Using pure Zr,Cr and Cu,10 alloy samples were prepared via the vacuum non-consumable arc melting followed by homogenization heat treatment at 580 oC.The isothermal section of the Zr-Cr-Cu ternay systmer at 580 oC were built.This isothermal section contains nine three-phase regions,eighteen two-phase regions and and ten single-phase regions.No ternary compound was found.The solubility of Cr and Cu in in the ?-Zr are around 0.16% and 0.23%,respectively.The existence of the CuZr phase may be probably due to that the dissolving of Cr in the CuZr phase increases its stability.(2)Using TOPAS sofeware,Rietveld refinement was carried out on the X-ray diffraction spectra of the sample which is located in the Laves_C15(?-ZrCr2)single phase region.It was revealed that the Cu atom was preferred to occupy the site position of the atom Cr.(3)Under the framework of density functional theory,the formation enthalpies of the end-members of the intermetallic compounds in the Zr-Cr-Cu ternary system were predicted using the VASP software package.The Gibbs free energy of the end-members of the Laves_C15 phases were obtained by using softwares of ATAT and VASP.(4)The LIQUID,BCC,FCC,HCP phases were described using the substitutional solution model while the intermetallic compounds were desctibed using the sublatticel model.The thermodynamic parameters of the Zr-Cr-Cu ternay system were obtained using the pandat software.The calculated phase diagram agree reasonably with the experimental ones.