| Cu-Ni-Si alloys has high electrical conductivity,high thermal conductivity,high strength and high corrosion resistance,which are widely used in electronic industry.The related phase diagram and thermodynamic information can provide theoretical guidance for the design of new copper alloys and the improvement of the properties of alloys.This work combines CALPHAD（CALculation of PHAse Diagrams）,key experiments and a new method for determining the phase transition temperature.The phase diagram thermodynamics of Cu-Zr-Si and Ni-Si-Zr ternary systems in copper alloys were systematically studied.The thermodynamic database of Cu-Ni-Si-Zr quaternary system was constructed and applied to the calculation of phase transformation sequence during solidification process.The main research contents are as follows:（1）The phase equilibria of Cu-Zr-Si system at 750 and 900℃was systematically studied in detail by X-ray diffraction（XRD）and electron probe microscopy（EPMA）,and the isothermal sections at the corresponding temperatures were constructed.At 750℃,four ternary compounds（Cu4Si6Zr3,Cu4Si4Zr3,Cu Si Zr and Cu4Si2Zr3）and eight three-phase equilibria are observed in the system.At 900℃,seven three-phase equilibria are in the system,while the two-phase region Cu3Si+Cu4Si6Zr3at 750℃transforms to the liquid phase+Cu4Si6Zr3 at 900℃.Combined with the experimental data of phase diagram,CALPHAD method was used to optimize and calculate the thermodynamics of this system,and the reasonable thermodynamic parameters to describe the phase equilibria of the system were obtained.（2）The high temperature transformation information（>1750℃）in Ni-Si-Zr system is measured by the high speed pyrometer.The melting points of Ni,Si,Zr is 1455,1414 and 1855℃.There is an eutectic reaction L（?）（Si）+Si2Zr in Si-Zr binary system.In the Ni-Si-Zr ternary system,the invariant reactions L+τ1+τ4（?）τ2,L（?）Ni2Si+Ni Si+τ4,L+τ1（?）Ni Zr+Si2Zr3 occur at 1623±14℃,1137±3℃and 1281±13℃.（3）Isothermal sections of the Ni-Si-Zr system at 750 and 900℃were measured,and the cooling curve and solidification structure of the system were analyzed.Four ternary phases(Ni11Si31Zr8,Ni16Si7Zr6,Ni2Si2Zr and Ni Si Zr)are observed in the system.At the same time,the solution solubility of Si in Ni5Zr and Ni7Zr2 is 7.93-8.35 at.%and 9.34 at.%,respectively.The thermodynamic optimization and calculation of the Ni-Si-Zr system were carried out by CALPHAD method,and a set of thermodynamic parameters were obtained to describe the phase equilibrium of Ni-Si-Zr system reasonably.（4）Based on the calculation results of the ternary system and the thermodynamic data of the binary system and ternary system reported in the literature,a thermodynamic database of the Cu-Ni-Si-Zr system was constructed.According to the thermodynamic database,the solidification structure of Cu-Ni-Si-Zr quaternary alloy was designed and analyzed.The reliability of Cu-Ni-Si-Zr quaternary thermodynamic database is verified by comparing the experimental results with Scheil simulation results.The research results obtained in this work of the Cu-Ni-Si series of copper alloy is an important component of the thermodynamic database.The high temperature（above 1750℃）phase transition temperature determination method has important reference value to determine other system phase diagram.The establishment of the thermodynamic database is important for the copper alloy composition design and provides the theoretical basis of heat treatment process and it also provides a feasible research means for improving the properties and designing copper alloys in the future. |
