Thermo-kinetic understanding of the correlation between bainitic transformation and mechanical properties for bainitic steels

Abstract

Phase transformations are feasible approaches for tailoring microstructures to achieve desired mechanical properties. However, the direct link between phase transformations and mechanical properties remains poorly studied. Here, using the theory of generalized stability (GS), we theoretically and experimentally correlate the bainitic transformation with the mechanical property of bainitic streels from a thermo-kinetic perspective. We established a quantitative relationship between the thermodynamic driving force and the yield strength, and explored the underlying physical correlation between the GS and the ductility. It is demonstrated that the thermodynamics-kinetics trade-off in the bainitic transformation inherently leads to the mutually exclusive relation between the yield strength and the uniform elongation. Specifically, a higher driving force generally results in an increased yield strength, while a larger GS tends to yield improved uniform elongation. Our findings provide fundamental insights into the relationship between the thermo-kinetics of bainitic transformation and mechanical properties, offering potential guidance for designing bainitic transformations to directly achieve superior mechanical performances.