Comparative Analysis of Precipitation Effects in Microalloyed Austenite and Ferrite Under Hot and Cold Forming Conditions

Deformation processes of microalloyed steels, both during hot and cold processing, are characterized by complex interactions between fine strain-induced precipitates and deformation activated movement of dislocations. Disperse particles that are either forming during the deformation at elevated temperature or are already present in the material at ambient temperature can significantly affect also other strengthening mechanisms e.g. dislocation and grain size strengthening. In the current work, quantitative and qualitative analysis of the effects of second phase particles in fcc and bcc microalloyed structures subjected to severe plastic deformation (SPD) processing was performed with respect to the inhomogeneity of microstructure evolution and properties. Observed inhomogeneities of deformation mechanisms, work hardening and microstructure refinement of microalloyed ferrite much more pronounced than in the case of microalloyed austenite. Discussion of the mechanical and microstructural reasons of such differences is also presented. Conclusions regarding effects of applied complex deformation history on microstructure morphology and properties were used as a validation of performed computer modelling.