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 degrees 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. (C) 2013 Elsevier B.V. All rights reserved.