A quantitative understanding on the influence of nano-twins spcaing on mechanical behavior of nano-stainless steels: a molecular dynamics simulation

Abstract

In order to break the limit between strength and ductility in duplex stainless steel material, we can seek for breakthrough from so-call defect project. Even the mechanism of TWIP and TRIP have proved to enhance the strength and ductility of duplex stainless steel, however the mechanism of deformation of those need to be elaborated. After using molecular dynamics simulations to stretch and compress nano-stainless steels,  we found that the duplex stainless steel is highly sensitive to the nano-twin spacing. The 𝛾→𝜀→α phase transition mechanism is dominant when S_ntbs< S_t; If S_ntbs> S_t, the 𝛾→𝜀→α phase transition mechanism is dominant (S_ntbs-- the Nano twin boundary spacing, S_t-- critical value). In compression, the main thing is the 𝛾→α phase transition mechanism; Meanwhile, with the change of nano-twins spacing, the tension-compression asymmetry effect is amplified. This work provide a micromechanical understanding for design the excellent mechanical properties of the stainless steels by optimizing material structure.

Keywords: Nano-duplex stainless steel, Molecular dynamics simulation, Nano-scale dislocation behavior, Nano-twins, Mechanism of deformation