Ordered sigma-type phase in the Ising model of Fe-Cr stainless steel

A lattice-based Ising model is presented which describes precipitation of an ordered phase at high temperature. It is based around the Ising model of mixed ferromagnetism (FM) and antiferromagnetism (AFM), which gives a qualitative description of the FeCr phase diagram. In addition to spin and species, a third index labels the precipitate phase and serves to produce its additional entropy. Thus the FM-AFM Ising model is adapted to produce precipitation of a sigma-type phase at high temperature, as observed in FeCr, in a form suitable for kinetic Monte Carlo simulations. In addition, the anomalous asymmetry observed in the miscibility gap of materials such as FeCr is also described, as is the finite low-temperature solubility and the onset of the stainless property for high-Cr content steel.