Effect of deformation parameters on microstructural evolution during hot compression of Nb-V-Mo microalloyed steel

The flow behavior of Nb-V-Mo microalloyed steel at different deformation parameters was investigated using isothermal compression tests. The microstructures of the specimens after deformation were observed through the use of a metallographic microscope. The results indicated that the deformation temperature had a significant effect on the grain size of the deformed specimen and the average size of grains increases with corresponding increase in temperature in the range of 800 °C-1100 °C. The dislocations and substructures of the specimens after deformation were characterized using TEM. The bulged grain boundary was observed through TEM when the specimen was deformed at 1100 °C and 1 s-1. The effect of the strain rate on the dynamic recrystallization behavior was investigated using electron backscatter diffraction (EBSD). The EBSD results indicated that the fraction of low-angle grain boundaries decreased with a corresponding decrease in strain rate, and the average sub-boundary misorientation increased with a decreasing strain rate. The continuous dynamic recrystallization mechanism was determined through EBSD analysis.