Molecular Dynamics Simulation of the Mechanical Behavior of Duplex Stainless Steels with Nanotwin Structure

Twin boundaries as an effective barrier to dislocation propagation can effectively increase the strength of polycrystalline materials with a peak critical twin spacing. Whether such a critical spacing also exists in biphasic structural materials is poorly understood. In this work, the potential deformation mechanisms of nano-duplex stainless steels with different twin spacings are revealed using molecular dynamics simulations. The results show that the existence of a critical twin spacing results in the highest strength and toughness of NDSS, where twinning and lattice incomplete dislocations are appeared inside the crystals, which indicates that multiple dislocation slip systems are activated inside the crystals, and that both γ → ε → α' and γ → α' are the dominant mechanisms of the phase transition simultaneously. The high density of dislocation activity increases the stability of the grain boundary structure, resulting in the strength enhancement.