Effects of dynamic precipitates on the formability and mechanical properties of 2195 Al-Li alloy ribbed cylindrical part during spin extrusion forming

Spinning extrusion forming (SEF) is an effective method to realize the near-net-shape manufacturing of ribbed cylindrical parts, which are important structural components for launch vehicles. However, there are still problems in terms of balancing contour accuracy and mechanical performance during SEF, especially when dealing with 2195 Al-Li alloy due to its sensitivity to SEF temperatures. In the present work, the evolution of dynamic precipitates and grain structures of 2195 Al-Li alloy ribbed cylindrical parts during the SEF process is studied, and their effects on the forming stability and the mechanical performances are discussed. It is found that a large number of Al-Cu-Mg phase and Al-Cu-Mn phase dynamically precipitate at low SEF temperature and are severely tangled with dislocations, which strengthens the material and renders good contour accuracies but lower rib height; higher SEF temperatures precipitate phases that weakly interacts with dislocations and generates fewer low angle grain boundaries (LABs), however, higher number of LABs can be conserved after T8 treatment due to insufficient driving force for static recrystallization. This facilitates the precipitation of T1 precipitates during aging, contributing to a higher mechanical strength, further increasing the SEF temperature would lead to severe enrichment of T1 precipitates along LABs, which compromises the ductility of the finished parts. The present study suggests that at the optimal SEF temperature of 300 °C, the contour accuracy of the finished parts is improved by 73.7%, and their strength/ductility product can be improved by 51.3%, indicating a good combination of formability and mechanical properties. •Different SEF temperatures render distinct dynamic precipitates.•Low temperature yields dynamic precipitates which interacts strongly with dislocations.•High temperature sample maintains more LABs during solution treatment and has higher strength after aging.