Micromechanical modeling of the behavior of duplex stainless steels

Abstract The aim of the present paper is the micromechanical modeling of an aged duplex (austenite/ferrite) stainless steel. While the elastic properties of both phases are almost the same, the plastic mismatch between ferrite and austenite is high due to ferrite aging. Accounting for the complex micro and macrostructure of this material, three scales are investigated. The first one corresponds to each single phase. The second scale consists of a percolated (interwoven) network of both phases. The third scale is an aggregate of percolated bicrystals. For the first scale, each phase is modeled as a single crystal. In the second scale, F.E. simulations are performed on a unit cubic cell representing the percolated networks. A mean field model is then fitted in order to represent that bicrystal. This mean field model is used at the third scale to model the behavior of the aggregate of two-phase grains, using a model for multi-phase materials. At this scale, it becomes possible to represent the distribution of average ferrite stresses in each ferrite-austenite bicrystal. These variations are thought to be responsible for the heterogeneous damage nucleation observed in this material.