On the control of the scale of nanobainitic microstructures by prior austenite strengthening

Abstract

The bainitic ferrite plate thickness is the most relevant parameter when aiming to obtain a high final strength on the microstructure. Such parameter has been shown to be primarily dependent on the driving force for the transformation and on the yield strength of the austenite prior to the transformation. Based on that statement, in the present study, thermal and thermomechanical treatments have been performed in three different commercial steels. The treatments parameters have been selected in such a way that both the driving force and the yield strength at the isothermal temperature are the same in all cases, aiming to obtain similar microstructures in terms of bainitic ferrite plate thickness. Results: However, significant differences were found among the microstructures, the plate thickness can be up to 100nm higher from one alloy to other. Conclusions: These results indicate that there might be other factors such as the effect of alloying elements on the austenite carbon enrichment and, in turn, on the modification of the austenite yield strength while the transformation advances, that take part and that will be further discussed.