Microstructure evolution of Fe-25Mn-3Al-0.5C TWIP steel during monotonic deformation

This study explores the microstructural evolution of a texture-free lightweight TWIP (Twinning-Induced Plasticity) steel during monotonic deformation. Utilizing electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM), we conducted a detailed microstructural analysis on samples subjected to varying levels of deformation at different stages of the strain-hardening curve. The results reveal that the increase in strain hardening at early deformation stage is primarily linked to planar slip and dislocation interactions. Mechanical twins were observed only in the sample strained to 0.4, suggesting that this alloy exhibits a higher critical stress for twinning compared to conventional TWIP steels, attributed to the presence of aluminum, which elevates the stacking fault energy (SFE). Consequently, the delayed nucleation of twinning indicates that it is not the sole mechanism governing the hardening behavior; rather, the interactions between planar slip and dislocations significantly influence the mechanical response of the Fe-25Mn-3Al-0.5C steel. This study enhances our understanding of the deformation mechanisms in advanced TWIP steels, providing valuable insights for their application in lightweight structural materials.