Effect of particles on the dynamic recrystallization behavior of Al–V–N micro-alloyed medium carbon steel

Using a Gleeble hot-deformation simulator, we have studied the dynamic recrystallization (DRX) behavior of Al–V–N micro-alloyed steel subjected to two different cooling conditions, i.e., air-cooling (AC) and water-cooling (WC), after solution treatment. The different prior-thermal treatment resulted in distinctively different DRX behavior of the steel. The DRX at a slow strain rate (0.01 s−1) was significantly retarded by dynamic precipitation of fine VCN particles; in contrast, the DRX was accelerated at a fast strain rate (5 s−1) due to coarse AlN particles, which were formed by rapid coarsening of static AlN particles during fast deformation. The activation energy for DRX was 420–480 kJ/mol, which was significantly larger than that of V-microalloyed steel. The peak and critical strains significantly deviated from the conventional exponential function of the temperature corrected strain rate. The grain size was refined from 130 μm to 5–60 μm by DRX and the dynamic precipitation appeared to be effective for grain size refinement.