Hot deformation behavior of GH4945 superalloy using constitutive equation and processing map

Abstract

The hot deformation behavior of GH4945 superalloy was investigated by isothermal compression test in the temperature range of 1000–1200 °C with strain rates of 0.001–10.000 s⁻¹ to a total strain of 0.7. Dynamic recrystallization is the primary softening mechanism for GH4945 superalloy during hot deformation. The constitutive equation is established, and the calculated apparent activation energy is 458.446 kJ/mol. The processing maps at true strains of 0.2, 0.4 and 0.6 are generally similar, demonstrating that strain has little influence on processing map. The power dissipation efficiency and instability factors are remarkably influenced by deformation temperature and strain rate. The optimal hot working conditions are determined in temperature range of 1082–1131 °C with strain rates of 0.004–0.018 s⁻¹. Another domain of 1134–1150 °C and 0.018–0.213 s⁻¹ can also be selected as the optimal hot working conditions. The initial grains are replaced by dynamically recrystallized ones in optimal domains. The unsafe domains locate in the zone with strain rates above 0.274 s⁻¹, mainly characterized by uneven microstructure. Hot working is not recommended in the unsafe domains.