Micromechanical modeling of the behavior of duplex stainless steels

The aim of the present paper is the micromechanical modeling of an aged dup lex (austenite/ferrite) stainless steel. While the elastic properties of bo th phases are almost the same, the plastic mismatch between ferrite and aus tenite is high due to ferrite aging. Accounting for the complex micro and m acrostructure of this material, three scales are investigated. The first on e corresponds to each single phase. The second scale consists of a percolat ed (interwoven) network of both phases. The third scale is an aggregate of percolated bicrystals. For the first scale, each phase is modeled as a sing le crystal. In the second scale, F.E. simulations are performed on a unit c ubic cell representing the percolated networks. A mean held model is then f itted in order to represent that bicrystal. This mean field model is used a t the third scale to model the behavior of the aggregate of two-phase grain s, using a model for multi-phase materials. At this scale, it becomes possi ble to represent the distribution of average ferrite stresses in each ferri te-austenite bicrystal. These variations are thought to be responsible for the heterogeneous damage nucleation observed in this material. (C) 1999 Els evier Science B.V. All rights reserved.