Twin boundary-assisted improvement of radiation resistance of iron: Defect evolution, mechanical properties, and deformation mechanism

•Recoverable point defects and unrecoverable clusters lead to hardening and strength reduction, respectively.•Twin boundary can effectively control radiation embrittlement through suppressing cluster defects.•Twin boundary could inhibit screw dislocation formation and hinder edge dislocation migration.•Twin boundary could ensure dislocation density after irradiation for strength reduction. Molecular dynamics (MD) simulations are applied to explore the defect evolution of single-crystal iron (SC Fe) and bicrystalline iron (BC Fe) under irradiation with 100 KeV energy at 673 K, and their mechanical properties and deformation mechanism under uniaxial tension at 300 K. The results show that twin boundary can significantly reduce the peak value of Frenkel defects, and enhance the defect clustering to inhibit the growth of clusters defects. The hardening behaviour is closely related to the fractions of recombinant point defects, while the unrecoverable point defects would transit to voids for the reduction of strength. Twin boundary can capture some small voids and inhibit the coelescence and growth of voids for reduction of strength loss. Additionally, it can effectively enhance the irradiation brittleness resistance through the inhabition of loss of dislocation density after irradiation. The plastic deformations of the SC Fe models depend on the operation of atomic slip system with high dislocation density, while irradiation will lead to the transformation of plastic deformation mechanism into emission and motion of shear dislocation loops (SDLs) with lower dislocation density. The plastic deformation mechanisms of the ∑3 (11–2) BC Fe are phase transformation, and SDLs emission and motion, while those of the ∑11 (332) BC Fe are only SDLs emission and motion. Irradiation hardly affects the plastic deformation of BC Fe. [Display omitted]