Constitutive modeling of the as cast structure of a large size ingot during open die forging: flow characteristics and microstructure evolution

Large steel ingots exhibit complex as-cast microstructures composed of columnar and equiaxed regions that respond differently to hot deformation. However, most existing constitutive models and recrystallization studies are based on wrought materials, leaving a significant knowledge gap regarding the deformation behavior of as-cast structures during industrial forging.

This PhD project aims to develop physically based constitutive equations that account for the nature of the initial cast microstructure during open-die forging. The influence of key hot-working parameters — including strain, strain rate, inter-pass time, and solutionizing temperature and duration — on microstructure breakdown and recrystallization kinetics will be investigated. Multi-step thermomechanical tests will be carried out using the Gleeble 3800 MaxStrain module to replicate industrial forging conditions. Advanced microstructural characterization using electron microscopy will be performed to quantify recrystallized grain size, phase transformations, and precipitation phenomena. These mechanisms will be incorporated into modeling frameworks using internal variable and crystal plasticity approaches.

The project will generate fundamental knowledge and practical tools for predicting microstructure evolution in large forged components.