New approach for modelling strain induced precipitation of Nb(C,N) in HSLA steels during multipass hot deformation in austenite

A new model for strain induced precipitation of Nb(C,N) is developed from the existing model for single pass hot deformation. This new model can be extended to multipass deformation to explain the microstructural evolution during the hot deformation of Nb supersaturated high strength low alloy (HSLA) steels. The key feature of this model is the microband geometry employed, which leads to determination of the local solute concentration at microbands, and hence the potential for carbonitride precipitation on the microbands. The model also validates the need for concurrent growth and coarsening processes, even at the early stages of precipitation. The evolution of the precipitate radius, number density and volume fraction are compared with the experimental results obtained from thin foil TEM micrographs on Fe-30 wt-%Ni alloys ( that are austenitic at room temperature and are similar to HSLA steels in deformation behaviour) subjected to deformation by plane strain compression. The model predictions are in good agreement with experimental results.