Modelling hot deformation of Inconel 718 using state variables

A dislocation density based state variable model has been developed to describe the characteristic flow stress behaviour during hot deformation of polycrystalline superalloy Inconel 718. Model equations have been formulated to describe the role of the evolving microstructures on the macroscopic flow stress response to deformation. Following a peak in the flow stress associated with strain hardening, the model utilises mechanisms associated with dynamic recovery and recrystallisation to explain the gradual decrease in flow stress with continued deformation. Incorporation of these microstructure based state variables also enables prediction of microstructures associated with a range of hot deformation conditions. Model flow stress predictions have been validated against isothermal uniaxial compression tests conducted over a range of temperatures and strain rates relevant to industrial forging conditions.