铸造双相不锈钢CD3MWCuN凝固与析出热力学模拟

Thermodynamic Simulation of Solidification and Precipitation of Cast Duplex Stainless Steel CD3MWCuN

利用FactSage 8.2热力学计算软件对铸造双相不锈钢CD3MWCuN的平衡凝固及冷却过程相变以及非平衡凝固偏析和相变规律分别进行研究。计算表明:平衡凝固及冷却过程的相变路径为:L→L+δ→L+δ+γ→L+δ+γ+N2→δ+γ+N2→δ+γ→δ+γ+Cr2N→δ+γ+Cr2N+M23C6→δ+γ+Cr2N+M23C6+σ→γ+Cr2N+M23C6+σ→γ+Cr2N+M23C6+σ+Laves→γ+Cr2N+M23C6+σ+Laves+ε-Cu→γ+Cr2N+M23C6+σ+Laves+ε-Cu+α→γ+Cr2N+M23C6+σ+Laves+ε-Cu+α+π→γ+M23C6+σ+Laves+ε-Cu+α+π。平衡转变过程中析出的金属间相为σ相与Laves相,其中σ相富Cr、Mo,贫Ni、W且不含N,而Laves相富Cr、Mo及W,贫Ni、Cu;基于Scheil-Gulliver cooling模式的非平衡凝固相变路径为:L→L+δ→L+δ+γ→L+δ+γ+Cr2N→L+δ+γ+Cr2N+M23C6→L+γ+Cr2N+M23C6+σ→L+M6C+σ。非平衡凝固过程:高温液相中主要的析出相为Cr2N,元素Fe为负偏析,Cr、Ni、Mo、W、Cu、N及C为正偏析,其中元素Cr、Mo及W在凝固末期的残余液相内偏析严重。

The phase transition during equilibrium solidification and cooling process,non-equilibrium solidification segre-gation and the raw of phase transition of cast duplex stainless steel CD3MWCuN are investigated by FactSage 8.2 thermo-dynamic calculation software.The calculation results indicates that the phase transition path of equilibrium solidification and cooling are asfollows Liquid-+Liquid+8-Ferrite-+Liquid+δ-Ferrite+Austenite-→Liquid+δ-Ferrite+Austenite+Nitro-gen-+8-Ferrite+Austenite+Nitrogen-→δ-Ferrite+Austenite-→8-Ferrite+Austenite+Cr2N-→8-Ferrite+Austenite+Cr2N+M2C-→δ-Ferrite+Austenite+Cr2N+M2C.+Sigma-+Austenite+CrN+M2C.+Sigma-+Austenite+Cr2N+M2Cg+Sigma+Laves-→Aus-tenite+Cr2N+M2sC.+Sigma+Laves+e-Cu-+Austenite+CrN+M2Cg+Sigma+Laves+e-Cu+a-Ferrite-+Austenite+GrN+M2C6+Sigma+Laves+8-Cu+o-Ferrite+Pi-+Austenite+M2C.+Sigma+Laves+e-Cu+a-Ferrite+Pi.The intermetllic phases precipi-tated during the equilibrium transition are Sigma phase and Laves phase,in which the Sigma phase is rich in Cr and Mo,but poor in Ni and W without N,while the Laves phase is rich in Cr、Mo and W,and poor in Ni and Cu.The non-equilibrium solidification phase transition path based on the Scheil-Gulliver cooling model are as follows:Liquid→Liq-uid+8-Ferrite→Liquid+8-Ferrite+Austenite-→Liquid+δ-Ferrite+Austenite+Cr.N→Liquid+8-Ferrite+Austenite+Cr,N+M2sCo-+Liquid+Austenite+Cr2N+M2C6+Sigma-→Liquid+M.C+Sigma.The main precipitated phase is Cr2N during the non-equilibrium solidification process,the alloy element Fe is negative segregation,Cr、Ni、Mo、W、Cu、N and C are positive segregation,among which the elements Cr、Mo and W are very serious in the residual liquid phase at the end of solidification.