The effect of thermomechanical controlled processing on recrystallisation and subsequent deformation-induced ferrite transformation textures in microalloyed steels

摘要

The evolution of texture components for two experimental 0.06 wt% C steels, one containing 0.03 wt% Nb (Nb steel) and the second containing both 0.03 wt% Nb and 0.02 wt% Ti (Nb-Ti steel), was investigated following a new thermomechanical controlled process route, comprising first deformation, rapid reheat to 1200 A degrees C and final deformation to various strains. Typical deformation textures were observed after first deformation for both steels. Following subsequent reheating to 1200 A degrees C for various times, the recrystallisation textures consisted primarily of the alpha-//RD texture fibre with a weak gamma-{111}//ND texture fibre, similar to deformation textures, indicative of the dominance of a strain-induced boundary migration mechanism. The texture components after finish deformation were different from the rough deformation textures, with a strong alpha-//RD texture fibre at the beginning, and then the strong peaks move to (111) and (111) textures due to the deformation-induced ferrite (DIF) transformation. The effect of Ti on the recrystallisation textures and deformation textures has also been analysed in this study. The results illustrate that Ti significantly influences the gamma-{111}//ND texture fibre. Finally, the textures after deformation and recrystallisation in the austenite were calculated based on the K-S orientation relationship between the austenite and ferrite. This allowed the understanding of the mechanism of recrystallisation between first and final deformation and the DIF textures during phase transformation.