Research on the deformation behavior and microstructure characteristics of 2024 aluminum alloy spun parts in die-less spinning process using ball-crown-shape rollers

Die-less spinning can greatly enhance the flexibility of spinning technology. Nevertheless, the significant wall thinning under variable taper angle conditions severely limits its application, replacing the conventional roller with a ball-crown-shaped roller (BCSR) can effectively suppressing the wall thinning. However, the mechanisms underlying this suppression are unclear and warrant detailed investigation. Microstructural characterization is an effective means to elucidate the mechanism of wall thinning suppression. Therefore, in this study, spinning experiments were conducted using multiple BCSRs and a conventional roller, followed by a systematic analysis of the mechanical properties and microstructure of the workpiece. Electron backscattered diffraction analysis was employed to reveal the origin of these differences at the microscopic level. The results showed that grains in BCSR-spun workpieces retained equiaxed morphology similar to that of the original blank, whereas those subjected to conventional roller spinning exhibited larger elongation. Among the BCSR conditions, rollers with larger radii produced larger grain sizes and lower percentages of low-angle grain boundaries, reflecting reduced deformation. The geometrically necessary dislocation density and tensile strength of the BCSR-spun workpieces were close to those of the original blank. The wall thinning suppression mechanism was clarified: conventional roller spinning induces shear-dominated deformation, whereas BCSR spinning primarily involves bending deformation. The greater circumferential compressive stress generated during BCSR spinning effectively inhibited wall thinning. Furthermore, increasing the BCSR radius reduced sheet bending and tensile stress in the feed direction, while a larger roller–blank contact area increased resistance to deformation and friction of the material, thereby suppressing wall thinning. • Different parameters of ball-crown shape rollers was investigated by experiments. • The microstructural studies of cold die-less spinning forming are currently rare. • Mechanism of non-thinning wall thickness revealed by grain density. • Near-equal wall thickness forming are achieved with ball-crown shape rollers.