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Abstract
Microstructural evolution in thermomechanical processing is of great importance to obtain good final properties for high strength low alloy steels. This work presents a microstructure based physical model to describe the microstructural evolution of Nb microalloyed steels under controlled rolling. Several factors of dislocation density, recovery, recrystallisation and precipitation have been coupled in the model. The dynamic recrystallisation (DRX) behaviour of Nb microalloyed steels has been investigated to derive the model. The recrystallisation is described as a nucleation grain growth process, and critical radius of subgrain has been used to estimate the occurrence of dynamic recrystallisation. Predictions of microstructural evolution under various hot rolling conditions using this model agree well with reported experimental results. The correlation among evaluation time, DRX rate and recrystallisation grain size can be effectively predicted by this model under different deformation conditions of hot rolling.
This work was supported from National Natural Science Foundation of China (grant no. 50774008) and from Ministry of Education of China (grant no. 20070008049).