Microstructure Evolution of Ti-3.3Al-2.8Mo-1.2V Alloy and its Mechanism in Spin Forming

The spinning process is a primary method for producing large-section seamless titanium alloy cylinders, with microstructural characteristics playing a significant role in determining mechanical performance. The spinning process of a Ti-3.3Al-2.8Mo-1.2V alloy tube was examined to analyze stress-strain distribution, microstructural evolution, and texture development. The results show that, during spinning, strain increases from the hemispherical region to the conical region, while decreasing from the surface toward the inner areas. Addi tionally, stress in the rolling direction (RD) is higher than in other directions. After spinning, the microstructure predominantly consists of a basketweave structure, with a minor presence of Widmanstätten morphology. The average grain size increases, and the lamellar structure width decreases gradually from the hemispherical region to the conical region. The β-phase grain fraction decreases due to Mo diffusion and lattice distortion. Grain refinement is facilitated by discontinuous dynamic recrystallization (DDRX); however, the rate of refinement remains slow due to grain growth during air cooling, leading to coarse grains. A {0001} basal texture forms, predominantly in the rolling direction (RD). The {0001} pole in the pole figure of the grains shifts from the RD toward the circumferential direction (CD) as the location moves from the hemispherical to the conical region, with multiples of uniform distribution (MUD) increasing.