Concurrent Precipitation of AIN and VN in Microalloyed Steel

The precipitation kinetics of AIN and VN in microalloyed steel is investigated numerically with the thermo-kinetic software MatCalc. To mimic the heterogeneous precipitation of AIN along austenite grain boundaries, a new model is utilized, which takes into account the fast short circuit diffusion along grain boundaries and sluggish bulk diffusion inside the grains. It is demonstrated that the precipitation of VN inside the grains can be more rapid than the precipitation of AIN at the grain boundaries. However, the thermodynamically more stable AIN can overgrow and dissolve the existing VN again. The computed results are compared to experimental results from literature and good agreement is observed.