Experimental Investigations On Phase Diagrams Of Some Ternary Alloys Containing Ta In Superalloys

Novel Co-based superalloys are expected to be ideal materials for high temperature parts of turbine engines due to its high initial melting temperature.However,the high density and poor stability of γ’ phase in novel Co-based superalloys limit its application in aviation field.Alloying is an important research approach to improve the comprehensive mechanical properties of novel Co-based superalloys.Ta is the forming element of γ’ phase in the novel Co-base superalloys,which can improve the solution temperature and stability of γ’ phase,Al,Si,V,Cr,Ni,Nb and Ru can also strengthen γ’ phase,appropriate additions of these alloying elements are beneficial to improving the comprehensive mechanical properties of Co-based superalloy.The phase diagram can provide an important theoretical basis for alloying,so it is necessary to carry out the research on the phase diagrams of important ternary systems composed of Co,Ta,Al,Si,V,Cr,Ni,Nb and Ru.Therefore,in this work,the isothermal sections of Co-Ta-Al,Co-Ta-Si,Ta-V-Cr and Ni-Nb-Ru ternary systems were experimentally determined,and the main research results are as follows:(1)The isothermal sections of Co-Ta-Al ternary system at 1200℃ and 1300℃were experimentally investigated.At 1200℃ and 1300℃,there is one ternary compound TaCo2Al with L21 structure in this ternary system.(2)The isothermal sections of Co-Ta-Si ternary system at 900℃ and 1100℃were experimentally investigated.At 900℃,there are four ternary compounds G,E,V,τ3 in this ternary system,and at 1100℃,there are four ternary compounds G,G ",E,V in this ternary system.(3)The isothermal sections of Ta-V-Cr ternary system at 1200℃ and 1300℃were experimentally investigated,and no ternary compounds were found.At 1200℃,aV2Ta and Cr2Ta(LT)phase form a continuous solid solution of C15 phase.At 1300℃,bcc-(Ta)and bcc-(V,Cr)form a continuous solid solution of bcc phase.(4)The isothermal sections of Ni-Nb-Ru ternary system at 1000℃ and 1200℃were experimentally investigated.There are three ternary compounds τ1,τ2 and τ3 in the two isothermal sections.