Monte carlo-method simulation of the deformation-induced ferrite transformation in the Fe-C system

Abstract

A Monte Carlo (MC) technique has been used to model deformation-induced ferrite transformation (DIFT) in an Fe-C binary system on a mesoscale. The effects of strain rate, strain, and recrystallization of the matrix on DIFT are investigated. Increasing the strain rate slightly retards the onset of DIFT. The volume fraction of ferrite increases gradually as the strain increases before the volume fraction of ferrite reaches its saturation value. After the volume fraction of ferrite becomes saturated, it oscillates around its saturation value. The recrystallization of austenite slightly retards the onset of the DIFT. Although the recrystallization of austenite reduces the equilibrium volume fraction of ferrite significantly, it cannot completely suppress DIFT. The stress concentration has been shown to induce the nucleation of ferrite near the grain boundaries and phase boundaries. The significance of the reverse transformation has been investigated. We found that there is a temporal oscillation of the volume fraction of ferrite and the stored energy after they arrive at their saturation values. We conclude that this oscillation and the effect of the strain rate on DIFT are both brought about by the reverse transformation from induced ferrite to undeformed austenite. The diffusion behavior of carbon atoms in the systems is different for different strain rates. The simulation shows that the dynamic recovery of austenite cannot occur in the system during deformation under the present conditions. The results of the simulation show that, other than the oscillation of the equilibrium volume fraction of ferrite and the unusual diffusion behavior of carbon atoms, the simulation agrees well with the corresponding experimental results. The temporal oscillation of the volume fraction of ferrite and stored energy and the unusual diffusion behavior are two new phenomena that have not been reported by other researchers.