Simulation of Micro-/Macrosegregation during the Solidification of a Low-alloy Steel.

Abstract

A model for the solidification of multicomponent steels is presented and used to simulate the solidification of an austenitic steel. Assuming stationary solid phases, conservation of multiple species is considered simultaneously with the solution of the energy and Navier-Stokes equations, with full coupling of the temperature and concentrations through thermodynamic equilibrium requirements. By including finite-rate microscopic solid solute diffusion in the model, the solidus temperature of multicomponent austenitic steels can be accurately calculated. The extension of the model to incorporate a microscopic model of the peritectic transformation is described. A simulation of the austenitic solidification of a steel containing ten elements in a rectangular cavity cooled from the side shows the formation of macrosegregation, channel segregates, and islands of mush surrounded by the bulk melt. The global severity of macrosegregation of an element is found to be linearly dependent on its partition coefficient, although such scaling is not possible locally.