Study On The Phase Diagram And Thermodynamics Of The Ni-Al-M(M=Re,Ru,W,Ta,Co),Re-Ru-W And Cu-Cr-Ti Systems In Ni-based Superalloys

Ni-based superalloys are widely used in aerospace,nuclear,energy and power,transportation and other fields because of their excellent high temperature strength,good oxidation resistance,corrosion resistance,creep performance and microstructure stability.Among them,approximately 50%of the hottest parts of aero-engines are made of Ni-based superalloys.With the development of aero engines,the requirements for the working temperature and performance of high temperature alloys for turbine discs are increasing.To design new nickel-based high-temperature alloy materials that meet the performance requirements,the phase diagram and thermodynamic information related to the alloy are critical.In this thesis,the systematic investigation of Ni-Al-M(M=Re,Ru,W,Ta,Co)and Re-Ru-W systems phase equilibria in Ni-based superalloys was carried out based on the CALPHAD(CALculation of PHAse Diagrams)method.By key experiments,the isothermal section at 800? of the Cu-Cr-Ti system was determined by X-ray diffraction(XRD)and scanning electron microscopy(SEM/EDS).The solidification processes and phase transition sequences of several alloys with different compositions were also simulated based on the available thermodynamic database.The main works as follows:(1)A detailed literature data evaluation of the marginal binary and ternary systems of the Ni-Al-M(M=Re,Ru,W,Ta,Co)system was carried out,and based on the experimental data reported in the literature and the thermodynamics of the marginal binary system,the Ni-Al-M(M=Re,Ru,W,Ta,Co)was reoptimized using the CALPHAD method,and a set of accurate descriptions of the Ni-Al-M(M=Re,Ru,W,Ta,Co)system was obtained.Some representative isothermal sections were also calculated,and the thermodynamic parameters obtained in this work can describe the experimental data well.(2)A detailed literature data evaluation of the marginal binary and ternary systems of the Re-Ru-W system was carried out,and based on the experimental data reported in the literature and the thermodynamic description of the Re-W binary system,the CALPHAD method was used to thermodynamically optimize the Re-Ru,Ru-W and ReRu-W systems,and a set of accurate descriptions for the Re-Ru,Ru-W and Re-Ru-W systems was obtained.The isothermal sections at 2000 and 1500? and liquidus surface projection for the Re-Ru-W system were calculated.The calculated results of this work agree well with the experimental data.(3)Detailed literature data were evaluated for marginal binary and ternary systems of the Cu-Cr-Ti system,and a total of 18 key alloys were designed and prepared based on extrapolated 800? isothermal section.By means of XRD and SEM/EDS characterization equipment,the phase equilibria of the 800 ? isothermal section of the Cu-Cr-Ti ternary system were determined,and the ternary compound ?1 was discovered and its solubility range was determined.(4)Based on the above research results and combined with literature data,a thermodynamic database of Ni-Al-Re-Ru-W-Ta-Co seven-membered system was established.Using this database,the solidification process of nickel-based hightemperature alloys with several different compositions and the precipitation of each phase composition were calculated,and the effects of adding different contents of Re,Ru and Ta on the solidification process of the alloy were analyzed.Figure [35] table [6] reference [201]...