A novel continuous dynamic recrystallization model to reveal grain refinement mechanism in constraining ring rolling of thin-walled conical structure with inner ribs

Abstract

Constraining ring rolling (CRR) is an integral and near net-shape forming approach to fabricate the seamless ring aluminum components in aerospace field. The service property of the formed ring components mainly depends on the microscopical grain texture. However, investigation and modeling of microstructure evolution in this complex hot working processes are not appropriately performed, which hinders further control of the forming quality of components during CRR. In this study, by analyzing the characteristics of CRR process and deformation modes in different characteristic zones of typical thin-walled conical ring with inner transverse ribs (TWCRITRs), a continuous dynamic recrystallization (CDRX) model of aluminum alloy that considers the influence of thermal deformation history was firstly proposed. The developed CDRX model was integrated into the finite element (FE) to predict microstructure evolution throughout the entire hot working process. The optimal parameters of the CRR process were obtained with the uniformity and fineness of microstructure as the goal, guiding the subsequent forming experiment. The predicted shape and microstructure agree well with the experimental results. It is found that the grain refinement mechanisms of 2A14 Al-alloy TWCRITRs during CRR include CDRX and thin grain cutting CDRX. Due to the low-angle grain boundaries (LAGBs) being pinned by the upper and lower high-angle grain boundaries (HAGBs), the recrystallization efficiency in the thin grain cutting CDRX is higher than that in the traditional CDRX mechanism. The shear deformation at thin-wall and complex deformation at the corner promotes the occurrence of thin grain cutting CDRX mechanism with a higher recrystallization efficiency. Eventually, the mechanical properties of manufacturing TWCRITRs met the requirements. All of these provide additional insights into the shape and microstructure controlled CRR process for TWCRITRs.