Numerous studies have demonstrated the viability of lightweight Fe-Mn-Al-C steels for exhibiting an improved balance of high strength and high ductility in automotive applications. However, their high-cycle fatigue behaviour has been scarcely studied. This work examines the effect of κ-carbides formed during the aging treatment on the high-cycle fatigue performance of an austenitic Fe-29Mn-8.7Al-1C (wt. %) steel. The material is studied in solution-treated, under-aged, and peak-aged conditions. High-cycle fatigue tests and analysis of fatigue fracture surfaces were performed using SEM and EBSD techniques. The results indicate satisfactory high-cycle fatigue performance in the aged material, somewhat better than for high Mn steels. Fatigue crack formation and growth occur predominantly via a quasi-cleavage mechanism along the [1 1 1] crystallographic planes, which is also a plane for planar glide and the formation of persistent slip bands during plastic deformation. The nanoscale intragranular κ-carbides in the aged samples interact with the gliding dislocations, resulting in the shearing of nanoscale κ-carbides in a weakly coupled regime. The resistance of particles to shearing is determined by their size, volume fraction, and antiphase boundary energy (γ), which vary during the aging process. The aged Fe-29Mn-8.7Al-1C steel significantly improves the fatigue strength as the formation of persistent slip bands is delayed due to an additional energy barrier related to the shearing of the κ-carbides. This improvement peaks in the under-aged condition and decreases with further aging time.

中文翻译：

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κ-碳化物对Fe-Mn-Al-C轻质钢高周疲劳行为的影响

大量研究证明了轻质 Fe-Mn-Al-C 钢在汽车应用中改善高强度和高延展性平衡的可行性。然而，它们的高周疲劳行为却很少被研究。这项工作研究了时效处理过程中形成的 κ-碳化物对奥氏体 Fe-29Mn-8.7Al-1C (wt.%) 钢高周疲劳性能的影响。该材料在固溶处理、欠老化和峰值老化条件下进行了研究。使用 SEM 和 EBSD 技术进行高周疲劳试验和疲劳断口分析。结果表明，时效材料具有令人满意的高周疲劳性能，略好于高锰钢。疲劳裂纹的形成和扩展主要通过沿 [1 1 1] 晶面的准解理机制发生，该晶面也是平面滑移的平面，并在塑性变形过程中形成持久滑移带。老化样品中的纳米级晶内 κ-碳化物与滑动位错相互作用，导致纳米级 κ-碳化物在弱耦合状态下发生剪切。颗粒的抗剪切能力由其尺寸、体积分数和反相边界能 (γ) 决定，这些在老化过程中会发生变化。时效后的 Fe-29Mn-8.7Al-1C 钢显着提高了疲劳强度，因为与 κ-碳化物剪切相关的附加能垒延迟了持久滑移带的形成。这种改善在老化不足的情况下达到顶峰，并随着进一步老化而减弱。