Research Specifications

Mechanical twinning plays a significant role in the plastic deformation of Twinning Induced Plasticity steel (TWIP). The effect of grain size on the twinning nucleation stress, yield stress, twin morphology and deformation mechanisms of Fe-22 wt. % Mn steel have been studied using molecular dynamics simulations. The nanostructure materials with mean grain sizes of 11.1, 14.3, 17.7 and 32 nm are constructed using the Voronoi tessellation method, and the plastic deformation behavior is studied by molecular dynamics simulation. A meta-atom potential is applied to represent the atomic interactions. The result of tensile test showed that the yield strength and twin nucleation stress increase by grain size decreasing. Structural analysis of the samples deformed to 10 and 20% total strain disclosed thicker primary twins in the coarse-grained material in comparison with the fine-grained one. Moreover, a high volume fraction of twins was formed in the coarse-grained sample. Dislocation analysis exhibited that the dislocation structure influenced by the initial grain size. The density of nucleation sites for twins and subsequently the developing twin substructure is affected by the dislocation substructure. It is concluded that with decreasing grain size, deformation of nanocrystalline TWIP steel by mechanical twinning can become difficult.