Microstructure Evolution During Eformation--Enhanced Transformation in
低碳微量铌钢形变强化相变的组织演变

The microstructure evolution during deformation enhanced transformation of supercooled austenite in Nb-microalloyed steel has been investigated by means of hot compression simulation experiment. The effect of Nb on the strain enhanced ferrite transformation has been studied and the transformation kinetics and orientation of Nb-microalloyed steel has also been analysed. The experimental results showed that the deformation-enhanced transformation is a dominated factor at the deformation temperature between A3 and Ar3. The transformation incubation period of Nb-microalloyed steel was prolonged and therefore the higher strain was needed to accomplish the transformation. The transformation kinetics curves moved to high strain parallelly, and can be divided into two stages: at the first stage the solute Nb dragged the ferrite transformation and led to a long incubation period; at the second stage the fine Nb(C, N) particles not only produced many favorable nucleation sites for ferrite transformation, but also inhibited the grain growth of ferrite. The microstructure evolution is a nucleation dominated process, in which the interchange between <001>nd <111>exture appeared.