Abstract: The hot compression test was conducted on a Gleeble-3500 thermo-simulation machine over the range of temperatures from 900 ℃ to 1 100 ℃ and strain rates from 0.01 s-1 to 5 s-1 to study the dynamic recrystallization behavior of Nb-Ti microalloyed steel. The analysis of flow curve and the microstructure observation showed that the flow curve does not show the typical dynamic recrystallization characteristic, but the dynamic recrystallization has occurred under the condition of high temperature and low strain rate. The Arrhenius model of flow curves was used to calculate the deformation activation energy. The critical stress and strain were determined by using the method of work hardening and a constitutive equation. The reason for the high modeled values for critical stress was analyzed, and the quantitative relationship between the critical stress, strain and Z parameter was established so that the critical conditions equations of dynamic recrystallization were obtained: σc=0.335Z0.144,εc=0.005 9Z0.079. The relationship between the strain at maximum softening rate and the deformation conditions was established by analyzing the θ-ε curves. Furthermore, the volume fraction of dynamic recrystallization was calculated based on these critical values and the results showed that the model has a good agreement with the data directly obtained from the flow curves.
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2018, Vol. 32 
