Enhancing the strength-ductility synergy of nanoprecipitate strengthened steel via tuning of silicon content

Addressing the strength-ductility trade-off remains a critical challenge in engineering metallic materials. This study systematically investigates the effect of Si on Cu-rich nanoprecipitate-strengthened steel, demonstrating that an increase in silicon content not only enhances the precipitation of Cu-rich precipitates through reducing lattice misfit but also regulates the martensitic matrix dislocation. When the Si content increases from 0.5 to 2.5 wt%, the yield strength increases from 964 MPa to 1137 MPa, the tensile strength from 1012 MPa to 1221 MPa, and the uniform elongation from 6 % to 9 %. Quantitative strength analysis reveals that the primary contributor to this strength improvement is the high-density Cu-rich precipitates, which provide an additional 116 MPa based on the shearing mechanism. Furthermore, the higher dislocation density in the martensitic matrix enhances the work hardening capacity during plastic deformation , while the combination of a high proportion of screw dislocations and low-lattice-misfit precipitates reduces stress concentration, collectively improving the uniform elongation. The present strategy, which synergistically optimizes matrix dislocation and nanoprecipitates, offers new insights into the development of precipitate-strengthened steels.