Electropulsing strengthened 2GPa boron steel with good ductility

Highlights: ► The boron steel with ultra-high strength could be made by electropulsing. ► The steel also has good ductility. ► The fine lath-martensitic contributed to tensile properties improvement. ► The fine lath-martensitic resulted from the effects of the electropulsing. -- Abstract: For the purpose of further enhancing the mechanical properties of a boron steel used in the automotive industry, the electropulsing is applied to strengthen the steel. The results show that the steel exhibits unexpected high strength and ductility. The engineering ultimate-tensile-strength and fracture strain are about 2022 MPa and 0.246, respectively. The microstructure examinations indicate that the martensitic was refined greatly during the electropulsing strengthening process. The fine martensitic with high-density dislocation makes the steel with good mechanical properties. The amazing results can be attributed to the thermal and athermal effects of the electropulsing. Due to the effect of rapid heating during electropulsing, a large overheating could be obtained, which could result in the high nucleation rate of austenite. Moreover, the pulse current itself can increase the austenite nucleation rate by decreasing the thermodynamic barrier. Finally, the fine lath-martensitic with high-density dislocation formed during the subsequent quenching process.