Roles of Mn content and nanovoid defects in the plastic deformation mechanism of Fe–Mn twin crystals from molecular dynamics simulations

In this study, the roles of alloying element Mn and nanovoid defects in the deformation behaviour of Fe–Mn twin crystals are investigated with molecular dynamics (MD) tensile test simulations. The results for the supercells with various Mn contents (5–30 at% Mn) show that Mn addition can reduce the elastic constant and improve the strength of twin crystals. In addition, with increasing Mn content, the plastic deformation mechanism transitions from martensitic transformation to dislocation slip. The mechanical properties of supercells containing 20 at% Mn, i.e. the elastic constant and critical stress of plastic deformation, decrease as the nanovoid diameter increases from 20 to 60 Å. The effect of twin boundaries (TBs) on plastic deformation is analysed in detail, revealing that TBs can effectively block the transmission of dislocations through twins, thereby improving the strength of the material. Graphical abstract Representative snapshots of the interactions between dislocations and TBs and the dislocation nucleation mechanism on the TB plane