Achieving strength-ductility synergy in M50 bearing steel via electroshock treatment: experiments and atomic simulation

• EST can achieve the synergistic improvement of strength- ductility of M50 bearing steel. • Interaction transformation mechanism of edge dislocations and screw dislocations is clarified. • EST has a selective regulation effect on high-energy dislocations and low-energy dislocations. • Contributions of thermal and athermal effects to the dislocation density evolution were quantitatively evaluated. To achieve the synergistic enhancement of strength and ductility of bearing steel, a high-energy transient electroshock treatment (EST) process is proposed in this study. The evolution law of EST process parameters on microstructure and mechanical properties of M50 bearing steel is investigated in detail. The results show that when the EST parameter is 110.74 A/mm 2 –100 ms (EST6), the fracture elongation and impact toughness of M50 bearing steel are increased by approximately 7.02% and 26.91%, respectively, and the tensile strength is enhanced by about 32.94 MPa. Quasi-in-situ EBSD characterization results indicate that EST reduces the density of statistical storage dislocations (SSD) by about 19.35%, and increases the density of geometrically necessary dislocations (GND) density by about 12.75%. Moreover, the GND distribution is more uniform, which favors the alleviation of local stress concentration. When the ratio factor ( γ ) of the dislocation component percentage approaches 1, the strength and ductility of M50 can be synergistically optimized. The molecular dynamics (MD) simulation results reveal that the athermal effect generated by EST can promote the reduction of dislocation density under appropriate EST parameters. Simultaneously, EST tends to promote the motion and annihilation of high-energy dislocations. The contribution of athermal effect to the reduction of dislocation density was quantified through the contribution ratio factor of athermal effect ( m ). When the EST parameter is EST6, the contribution ratios of athermal and thermal effects are 7.08% and 92.92%, respectively. The strength-ductility-toughness of M50 bearing steel is improved under the combined effect of the above effects.