Alloying effect on the microstructure and mechanical properties of hot-Rolled Fe-C-Mn-Si base TRIP steels (Part II); Deformation behavior of retained austenite

摘要

Deformation induced martensite transformation inhot-rolled multiphase steels containing retained austenite wasstudied to elucidate the relationship between the stability ofretained austenite and the flow behavior depending oncompositions and process conditions. The change in volumefraction of retained austenite with strain was studied on twobasically different kinds of kinetics model, treated as a function ofstrain in one model and stress in the other model. It is shown in thepresent study that the latter model (stress) has the clearer physicalmeaning. A new kinetics equation for deformation inducedtransformation was formulated as log fγ= log fγ0 – δ(σ-σYS),with parameter δ characterizing the stability of retained austenite.The increase in plastic stability of retained austenite with theincrease in carbon content in retained austenite can be explained bythe increase in the mechanical driving force for martensite transformation.