Research on the hot processing window for large GH4706 alloy turbine disks

The hot deformation behavior of GH4706 alloy was systematically investigated through compression tests at 1173–1423 K and strain rates of 0.001–10 s⁻¹. Flow stress is highly sensitive to temperature and strain rate: low temperatures and high strain rates cause pronounced work hardening, while high temperatures or low strain rates lead to dynamic recovery and recrystallization, resulting in flow softening and steady-state flow. The classical Hensel–Spittel (HS) model fails to capture energy dissipation under low-temperature, low-strain-rate conditions, so an improved HS model incorporating strain and strain-rate terms in the strain-rate sensitivity factor was developed and fitted via multivariate regression, significantly improving prediction accuracy. Hot processing maps based on experiments and the improved model indicate a stable window at 1223–1423 K and strain rates below 1 s⁻¹. Microstructure analysis confirms predictions: unstable regions show elongated grains with low recrystallization, while high-temperature, low-strain-rate conditions achieve full dynamic recrystallization with refined grains. For large turbine disks, the forming temperature was set at 1253 K ± 20 K and maximum strain rate below 1 s⁻¹, yielding equiaxed grains of grade 4.5~5 in production trials, providing practical guidance for hot working of large GH4706 components.