为了深入探究高强钢的疲劳性能，本工作研究了合金成分为Fe-22Mn-3Al-0.6C的第三代孪晶诱导塑性(TWIP)钢的低周疲劳行为，重点分析了晶粒尺寸对循环应力响应、损伤机制和疲劳寿命的影响。综合考虑应变、应力对疲劳损伤的贡献，本工作从能量的角度评价TWIP钢的低周疲劳性能。结果表明，在低总应变幅(Δε / 2 = 0.3%)下，小尺寸晶粒(8 μm) TWIP钢表现出更好的低周疲劳性能；而在高总应变幅(Δε / 2 = 1.0%)下，大尺寸晶粒(60 μm) TWIP钢表现出更好的低周疲劳性能。通过滞回能模型分析，发现在较高总应变幅下，材料的疲劳机制由应变损伤主导，粗晶材料具有更好的容纳损伤缺陷的能力；而在较低总应变幅下，材料的疲劳机制由应力损伤主导，细晶材料强度更高，具有更优异的抵抗裂纹萌生能力。

Lightweighting for bodies in white has become an important approach for enhancing energy efficiency and reducing emissions within the automotive industry. Among various lightweight materials, high-strength steel has shown considerable potential in terms of cost-effectiveness, safety, and user satisfaction. In particular, Fe-Mn-Al-C twinning-induced plasticity (TWIP) steel, also known as the third generation TWIP steel, has received considerable attention from the automotive industry in recent years owing to its excellent mechanical properties and good formability. During deformation, TWIP steel generates a considerable amount of deformation twinning within its grains, thereby impeding dislocation motion and resulting in high strain hardening rates in TWIP steels. Given that TWIP steels may be subjected to cyclic loading during actual service, the potential for fatigue failure poses a substantial risk during their long-term service, resulting in serious economic losses or human casualties. However, the deformation behavior and microstructure evolution of Fe-Mn-Al-C TWIP steel during low-cycle fatigue remain extensively understudied. Therefore, the study of the fatigue properties of TWIP steels is of considerable importance for their design and application in the automotive industry, warranting increasing attention. Herein, the low-cycle fatigue behaviors of Fe-22Mn-3Al-0.6C steels with different grain sizes were investigated. Steels with grain sizes of 8, 16, and 60 μm were prepared via hot rolling and subsequent heat treatment. After low-cycle fatigue testing, the samples were characterized using SEM equipped with electron channeling contrast imaging components and TEM. The effects of grain size on cyclic stress response, damage mechanisms, and fatigue life of Fe-Mn-Al-C TWIP steel were analyzed. Considering the fatigue damage contributed by strain and stress, the low-cycle fatigue property of TWIP steel was assessed from the perspective of hysteresis energy. Results indicated that the TWIP steel with small grain size (8 μm) exhibited enhanced low-cycle fatigue performance at a small total strain amplitude (Δε / 2 = 0.3%). Conversely, at a large total strain amplitude (Δε / 2 = 1.0%), the TWIP steel with large grain size (60 μm) exhibited enhanced low-cycle fatigue performance. Hysteretic energy model analysis revealed that fatigue damage mechanisms in TWIP steels were dominated by strain damage at large total strain amplitudes, with coarse grains showcasing an improved capacity to accommodate damaged defects. Conversely, at reduced total strain amplitudes, the fatigue mechanism was dominated by stress damage, with fine-grained steels showing enhanced strength and improved resistance against fatigue crack initiation.