Evaluation of Strengthening Mechanisms in Novel Fully Ferritic Advanced High-Strength Steels

New steel alloying concepts are designed in order to produce a fully ferritic, low-alloy steel with high (1 GPa) ultimate tensile strength (TS). A simulated hot-deformation process of the Ti-Mo-V-Nb and Ti-Mo-V steels is designed for that purpose, and the strengthening mechanisms of the steels are evaluated after the isothermal dwell at three different temperatures (590, 630, and 680 degrees C). The TS and the yield strength (YS) of the test alloys are estimated via hardness meas-urements. Results show that the estimated TS of over 1000 MPa and YS of over 900 MPa can be achieved in both steels, although the contribution of different strengthening mechanisms to the YS varies between the steels. The effect of the dislocation strengthening can especially compensate the reduced effect of the precipitation strengthening at all tested coiling temperatures (CTs). Based on the results, a CT range of 590-630 degrees C with the 1800 s dwell time seems to be a potential process window for the studied steels after the present thermome-chanically controlled processing (TMCP) route.