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| Influence of Diameter Growth Speed on Microstructural Evolution During Radial-Axial Ring Rolling of IN718 Alloy |
| TANG Xuefeng1 , WANG Baoyu2 , WANG Xinyun1 |
| (1. School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China; 2. School of Mechanical Engineering, Beijing University of Science and Technology, Beijing 100083, China) |
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Abstract 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.
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2020, 
