Thermodynamics And Phase Diagram Investigation On The Ni-base Superalloys Related Binary Systems

Nickel-base single crystal superalloys are widely used in aerospace engines and industrial gas turbines due to their excellent creep and fatigue properties.Material design is a guide to the development of Ni-base superalloys,and thermodynamic and kinetic information is critical for successful material design.In this work,fundamental research on material thermodynamics was carried out for the binary system of Ni-base superalloys.The alloy components mainly involved 10 elements,including Al,Co,Cr,Hf,Mo,Ni,Re,Ru,Ta,W,etc.And 21 Ni-base binary alloy systems are investigated in this work,including Cr-Re,Cr-Ru,Cr-Ta,W-Re,WRu,Hf-Re,Hf-W,Hf-Cr,Hf-Mo,Hf-Al,Cr-W,Cr-Mo,Re-Ru,Mo-W,Hf-Ta,Ru-Ta,W-Ta,Mo-Ta,Hf-Ni,Hf-Co,Hf-Ru,Hf-Ru.For engineering applications,the purpose of this work is to complete the thermodynamics database for Ni-base superalloys and to form the basis of the thermodynamics database for Ni-base multielement superalloys extrapolated to engineering accuracy.In this work,the CALPHAD(CALculation of PHase Diagram)method and the firstprinciples data calculated by this work are used to conduct thermodynamic modeling and thermodynamic parameter optimization for the Ni-base superalloys related binary system.In addition,the influence of interaction parameters on TCP phase,miscibility gap and ordered phase region are explored by this work.A total of 21 binary alloy systems were investigated by literature review and the evaluation of thermodynamic database.The main research of this work are as follows:(1)First-principles data of TCP phase were calculated,including ? phase of Cr-Re,CrRu,W-Re,W-Ru system,? phase of W-Re,Hf-Re system,and Laves phase of Hf-Re system.A unified thermodynamic model for TCP phase were established.The end-member of TCP phase were described by the calculated first-principles data.And the Gibbs energy of pure component end-member of TCP phase were unified to construct a self-consistent thermodynamic database;(2)To obtain more reliable thermodynamic parameters of the solution phase of Cr-Re,CrRu,Cr-Ta,Cr-Mo,Cr-W,W-Re,W-Ru,Hf-Re,Re-Ru,Mo-W and Mo-Ta system,the model parameters of the constant term of the solution phase were optimized based on the firstprinciples data calculated in this work.The experimental data of enthalpy of mixing at 1473 K for the Mo-W system were gotten by this work;(3)The effects of interaction parameters on the phase regions,including Hf-X(X=W,Cr,Mo)system which containing TCP phase,Hf-Ta system which contain miscibility gap,and HfX(X=Ni,Co,Ru)system which contain B2 phase,were explored combined with thermodynamic analysis;(4)In addition,the following work was done for the binary systems not mentioned above to build a complete Ni-base superalloys thermodynamics database: For the Ru-Ta system,since without publicly reported thermodynamics database,thermodynamics model of the high temperature phase was established by this work.And the thermodynamics database was built based on the phase diagram experimental data;For the W-Ta system,the order-disorder model was used to describe the order phase at low temperature.For the Hf-Al system,thermal vacancy was introduced into bcc phase and fine-tune the parameters of the system for collation of database.