Mechanical Properties and Fracture Behavior of DP1180 Duplex Steel at High Strain Rate

Quasi-static and dynamic tensile tests were conducted on DP1180 duplex cold-rolled steel at different strain rates （0.1, 1, 10, 50, 100, 200, 500, 1 000 s⁻¹）. The mechanical properties, fracture behavior, and microstructure evolution laws of the material were studied. The results show that with the increase of strain rate, the tensile strength, yield strength, percentage elongation after fracture, and percentage uniform elongation of DP1180 duplex steel all increased. At high strain rates （100-1000 s⁻¹）, the strain rate sensitivity of the yield strength was greater than that of the tensile strength. With the increase of strain rate, the tensile fracture cross-section changed from a fault-like shape to a tearing shape, the number of transverse microcracks increased, and when the strain rate reached 1 000 s⁻¹, it transformed into a micro-pore aggregation fracture pattern. With the increase of strain rate,, the number of large-sized dimple at the fracture surface increased, and a deeper hole formed by martensite fragmentation appeared at the center of thedimple. At high strain rates, the martensite plates were fin and the dislocation density was large. Dislocation strengthening and martensite deformation were the main reasons for the increase in the strength and plasticity of the steel.