Enhancing Strength and Ductility in a Fe‐Mn‐Al‐C Lightweight Steel by Zirconium Addition‐Induced Heterostructure

The extremely insufficient strengths have been widely observed in tensile experiments of annealed Fe‐Mn‐Al‐C lightweight steels due to the shearable of coherent κ carbides. Here, a typical heterostructure is processed by introducing zirconium (Zr) into a annealed Fe‐Mn‐Al‐C lightweight steel after hot/cold‐rolled processing. As Zr content is increased to 0.01 wt%, the microstructure exhibits a heterogenous feature, including soft recrystallized zones (∼78% in area) and hard non‐recrystallized zones (∼22% in area), which is mainly attributed to partial recrystallization caused by Zr‐drag effect and Zener pinning of ZrC carbides. The structural heterogeneity and precipitation of nanoscale ZrC contribute to the high strengths (yield strength: ∼1360 MPa, ultimate tensile strength: ∼1450 MPa). Such strengthening effect in turn enables multistage deformation mechanisms, including planar slip, stacking faults and deformation twinning, which assists further strain hardening and fracture ductility (∼15%).