Effects of multi-directional forging process on coarse crystalline phases and mechanical properties of 2195 Al–Cu–Li alloy

The 2195 Al–Cu–Li alloy, extensively used in aerospace applications such as rocket tank transition rings, suffers from coarse crystalline phases formed during casting. These phases act as stress concentrators, reduce precipitation-hardening efficiency, and impair strength and uniformity, especially in large ingots. This study investigates the refinement of such phases via multi-directional forging (MDF), using samples extracted from large ingots intended for large ring billets. Four MDF process parameters were evaluated: forging temperatures of 450 °C and 500 °C, upsetting–drawing cycles of four upsetting/three drawing (4U3D) or seven upsetting/six drawing (7U6D), and single-step deformations of 55% or 65%. Lowering the forging temperature from 500 °C to 450 °C accelerated the fragmentation of coarse phases, reducing their average size by 16%, but also promoted recrystallization, leading to grain coarsening. Increasing the upsetting–drawing cycles from 4U3D to 7U6D nearly doubled the effective strain but only slightly reduced coarse phase size (by 14%) while increasing process complexity. In contrast, increasing single-step deformation to 65% was most effective, producing fine, uniformly dispersed coarse phases (average size ∼15 μm, area fraction 1.5%) and achieving optimal microstructural uniformity across both core and edge regions. The area fraction and size of coarse phases significantly degraded elongation in a linear manner but had minimal effect on tensile strength. The optimal process (500 °C/65%/4U3D) reduced coarse phase average size to no more than 12.1 μm and area fraction to no more than 1.8% even in edge regions, yielded elongation above 8% in all regions and satisfying performance requirements for large-scale Al–Cu–Li alloy ring components.