  In this paper, the Fe-20Ni-25Cr alloy that is used for fuel cladding or
pressure vessels with various grain boundaries (GBs) was investigated by
employing molecular dynamics simulations. The bi-crystals comprised of
{\Sigma}3(111), {\Sigma}3(112), {\Sigma}9(114), {\Sigma}11(113),
{\Sigma}19(116), and {\Sigma}17(223) types GBs were considered to
systematically examine the interplay between irradiation defects, irradiation
microstructure evolution under stress, and irradiation mechanical properties
with irradiation intensity, coincidence site lattice parameter, tilt angle, and
GB thickness. It is found that irradiated vacancies and interstitials are
annihilated by competitive GB absorption and recombination. Bias absorption of
interstitials is observed for most bi-crystals except {\Sigma}3(111) and
{\Sigma}11(113) at 15 keV incident energy, and results in abundant residual
vacancies clusters in grain interior. In addition, different GBs exhibit quite
diverse irradiation defect sink ability, and the number of residual vacancies
is inversely related to the GB thickness, where {\Sigma}3(111) and
{\Sigma}11(113) GBs with narrow GB thickness are weak in defect absorption and
the others are strong. Furthermore, uniaxial tensile simulations perpendicular
to the GB reveal that all of the mechanical performance of bi-crystals
deteriorates after irradiation, which originates from dislocation propagation
facilitated by irradiation defect clusters. In particular, regardless of
whether the irradiation is applied, the maximum tensile strain, toughness, and
Youngs modulus are monotonically correlated with GB tilt angle, while the
ultimate tensile strength is stable for larger GB CSL parameter. Finally, on
the basis of the evolution of the irradiation defects, microstructures, and
mechanical performances, we proposed guidelines of rational design of
irradiation-resistant Fe-Ni-Cr alloy.
