Effects of ferrite phase characteristics on microstructure and mechanical properties of thermomechanically-processed low-silicon content TRIP-assisted steels

The effects of ferrite phase characteristics and deformation in α+γ two-phase region on microstructure development and mechanical properties of low-silicon content TRIP-assisted steels was investigated. Laboratory simulation of controlled-thermomechanical processing (TMP) were carried out using an automated hot-compression testing machine and the TMP process parameters were changed in order to generate various microstructures with different ferrite phase characteristics (volume fraction, grain size, morphology). It was found that variation of ultimate tensile strength (TS) was predominantly governed by the changes in the fraction of hard phases of martensite and bainite whereas variation of total elongation (T−El%), in general, coincided with the changes in retained austenite volume fraction(VRA). The optimum combination of strength and ductility (29,800 MPa%) was obtained in the sample deformed to a true strain of −0.15 at 650 °C in intercritical region.