Analysis of grain boundary movement analogous to dislocation movement – both with a matrix having precipitates

In the present investigation it has been shown exemplarily for an austenite microstructure containing carbonitrides that the specific restraining force of a grain boundary due to the distribution of precipitates can be described by a modified Orowan's law, so that the grain boundary movement is considered to be analogous to the dislocation movement. This is achieved by using a modified restraining force F r (corresponding to the cubic geometry of the particles), a detailed thermodynamic analysis of the precipitates (in this case, carbonitrides) and selected relation for the interparticle spacing L a . The specific restraining force and the interparticle spacing depend on temperature within the austenite range. Each temperature is attached to a couple ( F r / L a ). The plot F r against shows straight lines for each steel and from their average slope, a shear module G' of grain boundaries, which is about 64300 N·cm −2 , is obtained. Hence, it is possible to describe the specific restraining force of a grain boundary with the help of Orowan's law or as it is conventionally done by using Zener's modell. At a critical temperature T *, which is different for each steel, the specific restraining force is equal to the driving force of the grain boundary. The corresponding values of L a are also different for each steel and the steel which is the most resistant to grain coarsening is allowed to have the greatest value of L a which still retains the capacity of impeding grain coarsening.