Deformation Characteristics and Microstructure Evolution of GH4169 Alloy Bars with δ-phase in Flexible Skew Rolling

Flexible Skew Rolling (FSR) is a novel near-net-forming process for forming bars and shaft parts. This work relates to forming the GH4169 bars with FSR technology. Firstly, the finite element (FE) model was established to analyze the metal deformation characteristics in the FSR process. Furthermore, the rolling experiments was carried out. The initial microstructures of GH4169 alloy bars with and without δ-phase were obtained by Solution Treatment (ST) and Aging Treatment (AT), respectively, and the δ-phase effect on microstructure evolution of GH4169 alloy bars during FSR process was studied. The FE simulation results show that the metal spiral moves forward under the action of the rolls, completing the radial compression and axial extension. The experimental results show that the δ-phase has an important influence on the microstructure evolution of GH4169 bar. It was found that for ST workpieces and AT workpieces, the dynamic recrystallization (DRX) fraction in the middle is greater than that in the surface. This is because the surface temperature of workpiece is lower than the middle, which is not conducive to DRX. Comparing the middle part of ST and AT workpieces, it can be found that the \(\delta\) phase accelerates the DRX process. DRX has been completed in the middle part of ST workpiece, and the grain size is refined from 87 μm to about 5 μm. In addition, \(\delta\) phase also has a significant effect on the morphology of core defects. The bars obtained have good accuracy, and the diameter deviation is within ± 0.04 mm.