Reversible deformation in nanocrystalline TWIP steel during cyclic loading by partial slip reversal and detwinning

Mechanical responses of nanostructured twinning induced plasticity (TWIP) steels have attracted attention owing to their ultra high strength and ductility. A set of molecular dynamics simulations were carried out to characterize and track the atomic structure of Fe-22Mn (wt. %) nanocrystalline TWIP steel during reverse loading (tension-compression). The results show that intrinsic stacking faults and deformation twins which were formed during forward tensile loading up to total strain of 5.8% were eliminated upon subsequent reverse compression loading up to strain of 0.0 %. The current study provides the first simulation evidence of detwinning in nanocrystalline TWIP steel during the reverse loading. The atomic structure and dislocation analysis show that the observed detwinning is due to the dependence of shear stress acting on the trailing and leading partial dislocations on the loading direction. The results show that the Schmid factor of the trailing partial dislocations in compression loading are larger than leading partial dislocations one. The reversible deformation by detwinning could allow for reversible plastic deformation, storage of energy and mechanical damping in micro or nano devices.