Abstract
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) Rp0.2 and (ultimate tensile strength) Rm 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.
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