On the constitutive modeling and microstructural evolution of hot compressed A286 iron-base superalloy

The hot working behavior of A286 was studied using hot compression tests over temperature range of 950–1100 °C and at strain rates of 0.001–1 s−1. The flow curves of the material over the studied temperatures and strain rates were typical of dynamic recrystallization. However, some points reflected a change in the mechanism of softening with the change of strain rate. The relation between flow stress, deformation temperature and strain rate was examined via power-law, hyperbolic sine and exponential constitutive equations and the hyperbolic sine function was found more appropriate. The peak strain increased with strain rate up to 0.01 s−1 and then unexpectedly decreased at higher strain rates suggesting a change in the mechanism of dynamic recrystallization from a continuous to a discontinuous nature. Microstructure of the hot deformed samples at low strain rates was characterized by wavy boundaries typical of continuous dynamic recrystallization. On the contrary, at high strain rates fully equiaxic grain structure reflected the occurrence of discontinuous dynamic recrystallization.

► Dynamic recrystallization observed from the flow curves obtained at 950–1100 °C.
► Hyperbolic sine function was consistent with the experimental flow stress data than other equations.
► Mechanism of dynamic recrystallization changes at 0.01 s−1.
► Continuous and discontinuous recrystallizations were observed at different regimes.