Local microstructural inhomogeneities and casting defects often arise in complex thermal fields, and research how different cooling rates influence microstructures is key to realistic microstructure guidance. IN718 samples were prepared under 0.1 K/s, 1 K/s, 5 K/s, and 10 K/s to investigate this. Five metrics were chosen—secondary dendrite arm spacing (SDAS), grain size (GS), segregation degree (CSSD), microporosity neighbor count (MNC), and average microporosity volume (AMV)—to quantitatively analyze microstructure behavior. Nonlinear asymptotic functions were employed to describe the behaviors with respect to cooling rates ( \(x\) ) of microstructures: \({f}_{\text{SDAS}}\left(x\right)=33.53{x}^{-0.183}\) , \({f}_{\text{GS}}\left(x\right)=60.361{x}^{-0.397}\) , \({f}_{\text{MNC}}\left(x\right)=0.9576{x}^{0.308}\) , \({f}_{\text{CSSD}}\left(x\right)=52.276{x}^{0.032}\) , \({f}_{\text{AMV}}\left(x\right)=3639.404{x}^{-0.896}\) . The study clarified the microstructural coordinated behavior at different cooling rates and the correlation between properties and microstructural coordination, calculated the coupling relationships between various microstructural characteristics. A negative coupling relationship was identified between multi-element segregation and microporosity distribution with SDAS, grain size, and microporosity size, with the coupling strength ranked as: SDAS > grain size > microporosity size. A positive coupling was observed between micro-segregation and microporosity distribution, as well as among SDAS, grain size, and microporosity size. These findings provide valuable insights to study the effect of cooling on microstructure and help to optimization of cooling strategies during the manufacturing of IN718.
