Microsegregation and Rayleigh number variation during the solidification of superalloy Inconel 718

Ling Wang1,2),Jianxin Dong1),Yuliang Tian1),and Lei Zhang2) 1) School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083,China 2) College of Mathematics and Physics,Nanjing University of Information Science and Technology,Nanjing 210044,China

摘 要：The microstructure and composition of the residual liquid at different temperatures were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectrometer （EDX） associated with the Thermo-calc software calculation of the equilibrium phase diagrams of Inconel 718 and segregated liquid. The liquid density difference and Rayleigh number variation dur-ing solidification were estimated as well. It is found that the heavy segregation of Nb in liquid prompts the precipitation of δ and Laves phase directly from liquid and the resultant quenched liquid microstructure consists of pro-eutectic γ+eutectic,or complete eutectic according to the content of Nb from low to high. The liquid density increases with decreasing temperature during the solidi-fication of Inconel 718 and the liquid density difference is positive. The largest relative Rayleigh number occurs at 1320°C when the liquid fraction is about 40vol%.

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