Modeling of variant-interaction during bainitic phase transformation

In our research, we develop a thermodynamically consistent multi-scale model for phase transformations from austenite into n possible bainite variants. Each material point of the macroscopic configuration represents a polycrystal which describes the mesoscopic configuration. The microscopic configuration consists of an agglomeration of variants which is attached to each single crystal of the mesoscopic configuration. In addition, the model allows simulation of the macroscopic effects of volume change due to phase transformation as well as transformation-induced plasticity (TRIP). In this paper we present the results of recent work in the context of this model, which is concerned with the extension of the model for an effect of variant-interaction between the different crystallographic variants of bainite. For this reason we make use of the theory of transformation hardening. Thereby we are able to include an effect of preferential variant formation. This leads to the simultaneous formation of a selection of variants while the evolution of crystallographic unfavorable variants is handicapped or even completely suppressed. This extension of the model aims for the fact that in general not every crystallographic variant of bainite forms within a single austenite grain. (paper)