Mixed crystal and local coarse grain often appeared during radial-axial ring rolling of IN718 alloy

which impeded the satisfaction to the stern service requirement of aircraft engine. This article derived the mathematic model of steady rolling condition and the synergistic radial-axial feeding of ring rolling process based on the constant ring growth speed

and established a multi-physical finite element model of radial-axial ring rolling with adaptive roller control. A unified constitutive model of IN718 alloy based on internal state variables including dislocation density

recrystallization fraction and grain size was employed to investigate the effect of diameter growth speed on the microstructural evolution of radial-axial ring rolling of IN718 alloy by finite element simulation. The results showed that under the steady rolling condition

higher average temperature could be obtained by using higher diameter growth speed

which facilitated the nucleation and growth of the recrystallized grains. Moreover

the rolling time was decreased with the increasing diameter growth speed

the fraction of recrystallization was then decreased since there was insufficient time for growth of dynamic recrystallized grains. As a result

the total fraction of recrystallization was increased at early stage and then was decreased with the increase of diameter growth speed after the diameter growth speed exceeds 4.0mm/s.