Microscopic Mechanisms of Solute Distribution Patterns Dominating Defect Evolution and Strengthening-Toughening in...

To meet the stringent requirements for the synergy of ultra-high strength and exceptional toughness in drilling equipment for ultra-deep wells, this study employs molecular dynamics (MD) simulations to systematically investigate the intrinsic effects of spatial configurations (Cluster vs. Dispersion) of five transition metal elements (Co, Mo, Ni, Ti, and W) in an iron matrix on micro-defect evolution and mechanical performance. The simulation systems, each containing approximately 54,000 atoms, were initially relaxed under an isothermal-isobaric (NPT) ensemble at 300 K for 50 ps to ensure thermodynamic equilibrium, and were subsequently deformed under uniaxial tensile loading at a strain rate of 5 × 10⁹ s^-1. The results demonstrate that the distribution pattern of solute atoms influences the mechanical response. The cluster configuration generally weakens the matrix strength, a behavior indicative of stress localization and dislocation pile-up at the interfaces; in contrast, the dispersed configuration is associated with a more thermodynamically stable state and enhanced ultimate load-bearing capacity. Specifically, the Fe-Mo dispersed system reaches an ultimate tensile strength (UTS) of 28.32 GPa under the studied conditions, which exceeds the pure Fe benchmark of 24.90 GPa-an enhancement that points toward the formation of denser local atomic ordering and extensive dislocation network hardening. Meanwhile, the Fe-W dispersed system exhibits sustained dislocation activity up to large strains, suggesting that enhanced cross-slip contributing to its relatively high ultimate tensile strain and toughness. Based on these atomistic insights, a "Mo-W composite dispersed" micro-configuration design strategy is proposed as a conceptual direction for further exploration.