Hot deformation and microstructure evolution of GH4706 alloy for use in super-large turbine discs

The hot deformation behavior and microstructural evolution of GH4706 superalloy, a key material for ultra-large turbine disks in heavy-duty gas turbines, were systematically investigated through isothermal compression tests over a wide range of temperatures (900–1150 °C) and strain rates (0.001–10 s −1 ). The true stress–strain curves were corrected for friction effects, and an Arrhenius-type constitutive model incorporating strain compensation was developed. The model demonstrated high accuracy, with a correlation coefficient of 0.948 and an average absolute relative error of 6.72 %. Based on the dynamic materials model and Murty's instability criterion, processing maps were constructed to identify the optimal hot working window: 1010–1150 °C and 0.01–0.8 s −1 . Microstructural analysis revealed that dynamic recrystallization was the dominant softening mechanism, with grain size significantly refined after deformation. The average grain size decreased initially and then increased with rising temperature, reaching a minimum of 13.32 μm at 950 °C. At 1050 °C, grain size varied non-monotonically with strain rate, reaching a minimum of 17.4 μm at 0.1 s −1 . A full-scale turbine disk with a diameter of 2000 mm was successfully forged under the optimized parameters, exhibiting uniform and fully recrystallized microstructures. This study provides critical insights and practical guidance for the thermo-mechanical processing of GH4706 alloy in industrial applications.