Annealing-Induced Evolution of Band-Like B2 Phase in Hot-Rolled Fe-16Mn-10Al-5Ni-0.86C Steel and Its Role in Strength-Ductility Balance

초록

Controlling the B2 phase in hot-rolled Fe-Mn-Al-Ni-C lightweight steels remains a significant challenge. In this study, the evolution of banded ferrite/B2 structures in hot-rolled Fe-16Mn-10Al-5Ni-0.86C steel was systematically investigated under different annealing temperatures (800 degrees C and 900 degrees C) and holding times. The banded ferrite/B2 phases exhibited a three-stage size evolution during annealing, characterized by initial coarsening, subsequent refinement, and re-coarsening. After 30 min of annealing, the banded structures reached their minimum size at both temperatures. The sample annealed at 800 degrees C (A800) contained the finest banded B2 phase, leading to a high work-hardening rate but reduced ductility due to kappa-carbide coarsening. In contrast, the 900 degrees C annealed sample (A900) developed fine intragranular B2 precipitates within the austenite matrix, achieving the best strength-ductility balance with a tensile strength of similar to 1.20 GPa and an elongation of 11.2%. These results highlight the critical role of annealing parameters in tailoring the morphology of banded B2 and optimizing the mechanical performance of Fe-Mn-Al-Ni-C lightweight steels.

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