Tailoring Heterogeneous Structure to Enhance Mechanical Properties of 1020 Steel through Cold Rolling and Subsequent Electric Pulse Treatment

A heterogeneous structure with multiscale distribution of ferrite matrix grain size and high density of nanoscale cementite particles in 1020 steel is fabricated by cold rolling and subsequent electrical pulse treatment (EPT). The total cumulative deformation of cold rolling reaches 82%. The changes in microstructure and mechanical properties of cold‐rolled (CR) samples before and after EPT are studied. The results show that the dislocation density of the CR sample decreases after EPT. In the EPT1 sample, the average grain size is significantly refined to 700 nm, which is about 34% lower than that of CR sample. The ultimate tensile stress (UTS) and yield strength (YS) of EPT1 sample reach 836 and 811 MPa, respectively, and the elongation is 9.5%. Compared with CR sample, the UTS and YS of the EPT1 sample are increased by 3% and 8.4%. The elongation increases with the increase in current density. Fine grain strengthening and the pinning effect of nanoscale cementite particles on dislocations are the main reasons for the increase in strength. Heterodeformation‐induced strengthening improves the work hardening ability through geometrically necessary dislocations generated at the interface of “soft” microcrystalline/ultrafine‐grained ferrite and “hard” nanoscale cementite particles, thereby improving the plasticity.