**4. Conclusions**

(1) Based on the thermal compression experiment, the constitutive model of the material and the mathematical model of recrystallization evolution were derived by analyzing the stress-strain curve of GH4169 and applied to the secondary development of software. A simulation of the microstructure evolution law in the double-open multi-directional forging process was conducted.

(2) The evolution rule of the recrystallization volume fraction and the recrystallized grain size of the GH4169 superalloy double-open multidirectional forging was obtained. Increasing the forging temperature increased the recrystallization volume fraction and reduced the recrystallization grain size. Performing more passes had the same effect and led to more complete recrystallization and a smaller recrystallized grain size. At 1000 ◦C and nine passes, the recrystallization volume fraction exceeded 95%, and the recrystallized grain size reached the minimum size of 3–5.5 μm.

**Author Contributions:** J.L. and Y.J. conceived and designed the experiments; H.X., S.W., and Z.Y. performed the experiments; L.Z. and C.Z. analyzed the data; J.L. and Y.J. wrote the paper.

**Funding:** This project is supported by Natural Science Foundation of Hebei Province, China (Grant No. E2019203005). **Conflicts of Interest:** The authors declare no conflict of interest.
