Dislocation-Based Finite Element Modeling of an Off-Axis Twist Extrusion with Variable Helix Angles

This study presents a comprehensive investigation into the deformation behavior and microstructural characteristics of pure aluminum during off-axis twist extrusion with variable helix angle. To accurately predict the material’s deformation characteristics, a combined finite element and modified ETMB (Estrin–Toth–Molinari–Brechet) dislocation-based constitutive model is employed. The modified ETMB model is rigorously validated against experimental observations, demonstrating its reliability and relevance in capturing the complex deformation mechanisms. Moreover, the effects of extrusion conditions and die geometry on the deformation characteristics, dislocation distribution, cell structure, and material strength are analyzed. The results show that the die geometry parameters, such as twist angle, off-axis parameter, and twist zone length, significantly influence the material’s deformation behavior. Increasing the twist angle and off-axis parameter leads to a higher extrusion load and mean equivalent plastic strain while increasing the twist zone length reduces the extrusion load and plastic strain. The study also highlights the role of backward pressure in achieving better die filling and eliminating gaps between the workpiece and the die. The increase in backward pressure leads to a higher extrusion load and mean equivalent plastic strain. The findings enhance the understanding of the TE process and pave the way for optimizing material processing to achieve desired microstructural properties.