As-cast Microstructure of A Designed Polycrystalline Ni_3 Al-based Superalloy Is Characterized Using Optical Microscope,scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffraction System,and the Intermetallic Phase Transformations Involved During Solidification Process Are Determined Based on Thermal Analysis Measurements. the As-cast Microstructure Is Mainly Composed of 80.63 Vol% Dendritic and 19.37 Vol% Interdendritic Phases,and the Dendrite Is Identified As Quasi-cuboidal γ’_i Phase Connected by γ-channels Where Ultrafine γ’_Ⅱ Particles Are Distributed,and the Interdendritic Phases Are Determined As γ’-γ Eutectic Structure Consisting of Ye Phase with Dotted Quasi-spherical γ’_e Particles. During Solidification, the Dendrite Firstly Nucleates from Liquid Melt Near 1348 ℃; Subsequently, the Residual Liquidoid Is Transformed into Interdendritic Phases Around 1326 ℃. Afterward, γ’ Phase Will Precipitate from Dendritic Ymatrix with Two-stage Characteristics, Resulting in the Distinct Precipitation of γ’_Ⅰ and γ’_Ⅱ Phases When Approaching to 1190 And 1043 ℃, Respectively. the Corresponding Transformations Involved During the Solidification Process Can Be Translated As:Liquidoid{Dendrite(γ_D)(80.63)%→γ’_Ⅰ+γ(channel)→γ’_Ⅰ+γ’_Ⅱ+γ(channel) Residual liquidoid(19.37%)→Interdendrite(γ’_E-γ_E eutectic)}As-cast As-cast Microstructure of A Designed Polycrystalline Ni_3 Al-based Superalloy Is Characterized Using Optical Microscope, scanning Electron Microscope, Transmission Electron Microscope Equipped with Selected Area Diffraction System, and the Intermetallic Phase Transformations Involved During Solidification Process Are Determined Based on Thermal Analysis Measurements. the As-cast Microstructure Is Mainly Composed of 80.63 Vol% Dendritic and 19.37 Vol% Interdendritic Phases, and the Dendrite Is Identified As Quasi-cuboidal γ’_i Phase Connected by γ-channels Where Ultrafine γ’_II Particles Are Distributed, and the Interdendritic Phases Are Determined As γ’-γ Eutectic Structure Constructed of Ye Phase with Dotted Quasi-spherical γ’_e Particles. During Solidification, the Dendrite For Nucleates from Liquid Melt Near 1348 ° C .; The Residual Liquidoid Is Transformed into Interdendritic Phases Around 1326 Afterward, γ ’Phase Will Precipitate from Dendritic Ymatrix with Two-stage Characteristics, Resulting in Distinct Precipitation of γ’_I and γ’_II Phases When Approaching to 1190 And 1043 ° C, Respectively. The Corresponding Transformations Involved During the Solidification Process Can Be Translated As: Liquidoid {Dendrite (γ_D) (80.63 )% → γ’_Ⅰ + γ (channel) → γ’_Ⅰ + γ’_II + channel Residual liquidoid (19.37%) → Interdendrite (γ’_E-γ_Eutectic)} As-cast