Characterization and Prediction of Flow Behavior in High-Manganese Twinning Induced Plasticity Steels: Part I. Mechanism Maps and Work-Hardening Behavior

Thermodynamic stacking fault energy (SFE) maps were developed using the subregular solution model for the Fe-Mn-Al-C system. These maps were used to explain the variations in the work-hardening behavior of high-manganese steels, both through experiments and by comparison with the published data. The suppression of the transformation induced plasticity (TRIP) mechanism, the similarity between the shape of the work-hardening rate diagrams for the produced iso-SFE materials, and an earlier onset of stage C of work hardening by decreasing SFE were shown to be efficiently predictable by the given mechanism maps. To overcome the limitations arising from studying the deformation response of high-manganese steels by SFE values alone, for example, the different work-hardening rate of iso-SFE materials, an empirical criterion for the occurrence of short-range ordering (SRO) and the consequently enhanced work-hardening, was proposed. The calculated values based on this criterion were superimposed on the thermodynamics-based mechanism maps to establish a more accurate basis for material design in high-manganese iron-based systems. Finally, the given methodology is able to clarify the work-hardening behavior of high-manganese twinning induced plasticity (TWIP) steels across an extensive range of chemical compositions.