Competition mechanism of dynamic recrystallization and recovery and microstructure evolution of TC4 alloy during warm deformation
Hao Su, Tiexin Liu, Jie Kang, Lei Li, Rigu Su, Bo Lv, Chunlei Zheng, Fucheng Zhang
Abstract
As a key aerospace material, TC4 alloy has attracted significant attention for its warm deformation combining advantages of cold/hot forming. However, the lack of process-microstructure-property integration during deformation induces processing instabilities, which narrow the processing window. This study systematically investigated the warm deformation behavior of TC4 alloy in the α+β dual-phase region (650–800 °C, 0.1–5 s −1 ) using a thermomechanical simulator, elucidating the temperature-strain rate dependence of the competitive mechanisms between dynamic recrystallization (DRX) and dynamic recovery (DRV), along with their governing effects on microstructural evolution. The results demonstrate that flow stress significantly decreases with increasing temperature and decreasing strain rate, accompanied by enhanced DRX capability, with the most intense DRX activity observed at 800 °C. In 650–700 °C, 1–5 s −1 , DRV dominates, where work hardening coexists with localized softening induced by adiabatic heating. In 750–800 °C, 0.1–0.22 s −1 , DRX is fully activated, resulting in fine equiaxed α grains. At 800 °C, acicular structures partition and refine the β-phase, inhibit grain coarsening, promote DRX, and thereby enhance processability. The dynamically constructed processing maps based on strain accumulation effects reveal an optimal processing window at 775–800 °C, 0.1–0.22 s −1 , where the power dissipation efficiency ( η ) exceeds 0.18, effectively avoiding ASBs and microcracks. This study provides theoretical foundations and process optimization strategies for warm deformation of TC4 titanium alloy.