Microstructure evolution of inconel 718 alloy during ring rolling process

Microstructure determines the comprehensive mechanical properties and service life of ring parts. In this study, ring rolling process is considered as a multi-pass process which is parted into four phases, and the microstructure evolution model is then established based on the characteristics of this multi-pass process by combining with a 3D coupled thermo-mechanical FE model. By contrasting with experiment results, the microstructure evolution model is actually proven can be competently applied to predict the microstructure of the formed ring. Also through comprehensive analysis on distribution of recrystallization fractions based on the microstructure evolution model, conclusions can be summarized as following. (1) It is inaccurate to predict the microstructure by regarding the ring rolling as a single-pass deformation. The ring rolling process should be parted into different phases, and for each phase, the singlepass microstructure evolution model is adapted. (2) Different with single-pass deformation, due to the high temperature dwelling phase during ring rolling process, meta-dynamic recrystallization (MDR) is another important grain refinement mechanism besides dynamic recrystallization (DR). (3) MDR has different distribution trends with DR, which is benefit not only for grains refinement but also for microstructure uniformity. (4) Rolling penetration is obviously improved with feed rate increases, whereas, unduly high feed rate leads to recrystallization fraction decrease in outer layer area, which is adverse to microstructure uniformity.