Large-sized thin-walled tubular parts with high stiffened ribs are key lightweight structural components used in transportation. To address the challenges of integral forming, a novel local shear forming (LSF) technique that combines the advantages of spinning and shear forging (SFG) is proposed. Finite element (FE) simulations and experimental work have revealed the distinct deformation mechanisms of local shear forming in contrast to those of conventional shear forging or spinning. During local shear forming, the surface material of the billet undergoes sequentially axial upsetting deformation, primary shear deformation, reverse shear deformation, circumferential tensile deformation and radial displacement to form the rib. Gradient plastic deformation is observed through the thickness of the formed wall rather than near the wall surface. The effects of local loading include reduction of the secondary shear deformation zone, reduction of circumferential constraint in the loading zone, material circumferential transfer, and expansion-shrinkage deformation of the billet. The former two decrease the rib thickness and promote radial transfer of the material. The latter two result in a significant strengthening of the formed rib and wall. Moreover, tearing and buckling are suppressed, which enhances the relative wedge thickness up to 50% of the wall thickness of the billet. The aspect ratio of the formed rib can be as high as 3 for the high strength 2A12 alloy and 6 for the highly ductile 1A30 alloy. Shear deformation in the rib promotes recrystallization in the subsequent T6 heat treatment and refines the microstructure. Corrosion resistance is not degraded though microstructural change. Local shear forming shows good potential for forming tubular parts with an external rib structure.

The present study evaluated the β recrystallization behavior and deformation microtexture evolution of TB6 titanium alloy (Ti-10V-2Fe-3Al) taking place during isothermal compression. The hot deformation tests were carried out in the temperature range below the β phase transition temperature and spanned a wide strain rate range of 0.0001~1 s−1. Microstructure evolution on β phase, including its recrystallization behavior and microtexture formation, is sensitive to the strain rates, whereas the average grain size of equiaxed α phase exhibits a slight increase with the strain rate decreasing. Moreover, β recrystallization is not homogeneous among the prior β grains, and is characterized by: (I) enriched β sub-grains, (II) sporadically or chain-like distributed recrystallized β grains with a grain size far less than the prior β grains, and (III) wave-shaped β grain boundaries. The β recrystallization is inadequate and its orientation takes on the inheritance characteristic, which makes the β microtexture significant after deformation. At a lower strain rate, the high activity of the {11−2}<111> and {12−3}<111> slip systems induced the crystal rotation around <101>, but such crystal rotation did not destroy the Burgers orientation relationship (BOR), which could be accounted for by the generation of a strong microtexture of <001>//RD. The divergences on β recrystallization fraction, the operation of slip systems, and initial crystal orientations explain the different microtexture components with varied intensities under different deformation conditions.