The key advantage of high-Mn steels – the combination of high strength and high ductility – is achieved by locally adapting the microstructure during deformation. The modification of the stacking sequence of atomic layers results in the formation of twins or martensite. The structure and stability of the resulting planar defects including grain boundaries are strongly influenced by changes in the local composition.
We carefully study with DFT the energetics and diffusion barriers of substitutional and interstitial atoms in the vicinity of stacking faults, grain boundaries and interfaces. Our investigations are taking the sensitive interplay of chemical, structural and magnetic degrees of freedom into account. The results are compared with atom probe tomography and transition electron microscopy measurements. We will in particular use the examples of C interaction with stacking faults and increased Mn concentrations at grain boundaries to outline the impact of the local chemistry on the performance of these steels.