Central Damage Mechanism and Criterion of TC11 Titanium Alloy during Hot Rolling Based on Rotating Compression Experiment and Finite Element Simulation

Hot rolling is an efficient near–net–shape forming process for manufacturing titanium alloy shafts. However, central damage during the rolling process presents a critical challenge for meeting the stringent internal quality requirements of high–end equipment. In this study, rotary compression experiments and finite element simulations are combined to investigate the central damage mechanism of TC11 titanium alloy during hot rolling and establish a corresponding damage criterion. First, rotary compression experiments were conducted to simulate the stress states characteristic of hot rolling processes such as cross wedge rolling and skew rolling, with different initial temperatures and area reductions to analyze the effects of process parameters on central damage. Microstructural observation reveals that the deformation incompatibility between the hexagonal close–packed α phase and the body–centered cubic β phase leads to stress concentration at α/β phase interfaces and micro–void nucleation, with higher temperatures suppressing damage initiation while larger reductions promoting damage accumulation. Subsequently, numerical simulations were used to analyze the stress state at the center of the deformed specimen, identifying the primary stress variables driving damage accumulation and propagation as the first principal stress and shear stress. Based on these findings, a damage criterion suitable for the hot rolling process was proposed. The damage threshold for TC11 titanium alloy at an initial rolling temperature of 900 °C was determined to be 3.19. This research provides a theoretical and numerical basis for predicting central damage in the hot rolling of titanium alloys.