A novel process for the precise forming of Y-shaped Al–Cu alloy ring forgings with fine microstructure and excellent mechanical properties

The Y-shaped 2219 Al–Cu alloy transition ring is a critical load-bearing component in launch vehicle propellant tanks. Traditional manufacturing methods, which involve machining rectangular rings into Y-shaped ones, suffer from low material utilization and disruption of metal flow lines. This study proposes a novel mold-constrained mandrel expansion process, integrating constrained forming with warm deformation, to precisely form Y-shaped Al–Cu alloy rings with fine microstructure and excellent mechanical properties. In this process, a constrained circular mold and mandrel are used to form a cavity, allowing the billet to flow into the cavity and take shape with high precision. Forming at warm temperature enhances the stored energy and promotes recrystallization, resulting in an equiaxed fine-grain structure. A constitutive recrystallization model for 2219 Al–Cu alloy under warm deformation was developed, and the grain refinement parameter range was determined. Finite element simulations using Deform-3D were employed to optimize the forming process, yielding an optimal billet shape and processing parameters to ensure uniform and sufficient deformation, as well as full cavity filling. Using this optimized process, Y-shaped Al–Cu alloy rings were successfully produced with complete cross-sectional filling, low anisotropy, and excellent mechanical properties. Material utilization was doubled, the average grain size ranged from 81 μm to 134 μm, and the three-directional ultimate tensile strength was 465–480 MPa with an elongation of 10–14 %, all of which exceed the required mechanical property standards.