A Unified Constitutive Model for CLAM Steel Coupling Microstructure Evolution and Considering Phase Transformation in a Wide Range of Temperatures

摘要

The thermal deformation mechanical behavior and the microstructure evolution behavior of China low-activation martensitic (CLAM) steel were studied at temperatures ranging from 873 to 1223 K and at strain rates ranging from 0.001 s(-1) to 1 s(-1) by Gleeble-3500 thermal simulation machine. The results show that the material develops dynamic recovery at higher strain rates while exhibiting the obvious characteristics of dynamic recrystallization at lower strain rates. The intersecting phenomena of the true stress-true strain curves occur in the dual-phase temperature region. Compared with the full dynamic recrystallization of austenite, the partial dynamic recrystallization of ferrite has a more significant effect on the flow stress. Single-phase constitutive equations considering the work hardening, the dynamic recovery, and the dynamic recrystallization were established based on the effects of microstructural evolution mechanisms and macroscopic deformation parameters on the mechanical behavior in CLAM steel. Subsequently, the constitutive equation suitable for the thermal deformation of dual-phase in the inter-critical temperature region was established by modifying the iso-strain mixture law. Finally, a unified constitutive model was obtained and the reliability of the model was verified by calculating the error between the predicted stress and the experimental stress over the entire range of temperatures.