This study aims to elucidate the fundamental superplastic deformation mechanisms and microstructural evolution of a fine-grained Inconel 718 sheet, which is crucial for optimizing its superplastic forming process window. Within the range of 910-970 °C and strain rates of 6×10 -4 to 4×10 -3 s -1 , the alloy exhibits superior superplastic elongation of up to 750%, strain rate sensitivity ( m ) values of 0.33-0.44, and a true activation energy close to that of lattice self-diffusion. The flow stres