Strength response of 1200 MPa grade martensite-ferrite dual-phase steel under high strain rates

摘要

A commercial 1200 MPa grade martensite-ferrite dual-phase steel (martensite volume fraction is 61.3%) was studied by dynamic tensile tests and Nano-indentation tests. Results indicate that the strain rate sensitivity of this DP1200 steel is mainly owing to the increase of martensitic strength. Both (yield strength) R-p0.2 and (ultimate tensile strength) R-m increase with the increase of strain rate. But the degree of work hardening is decreased when strain rate exceeds the critical value (about 600 s(-1)). The above result is mainly caused by the two facts: i) ferrite loses strain rate sensitivity; ii) softening effect of adiabatic heating on martensite. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.