采用EBSD、TEM、XRD和万能试验机等对比研究了4种Fe-30Mn-10Al-xC (x=0.53、0.72、1.21、1.68，质量分数，%)低密度钢固溶处理后的微观组织与力学性能。结果表明，随着C含量的增加，奥氏体的体积分数逐渐增多，显微结构由铁素体/奥氏体双相组织逐渐演变为单相奥氏体组织，钢的强度不断增加，而延伸率则先增加后减小。统计分析表明，奥氏体的应变协调能力高于铁素体，双相钢随着奥氏体含量的增加，延展性明显增加，强度略微增加；而对于单相奥氏体钢，随着C含量的增加，屈服强度明显增加，延展性变差，加工硬化能力显著降低，这是由于钢中κ′碳化物的析出造成的。

The lightweight Fe-Mn-Al-C steels (so-called low-density steels) have received great attentions as promising candidate for automobile structure applications due to their excellent combination of density reduction, mechanical properties and corrosion resistance. In previous studies, most examinations of the Fe-Mn-Al-C alloys focused on the deformation mechanisms and the relationship between the microstructure and mechanical properties. It is well known that chemical composition, especially C content, which enhances strength as the interstitial element and reduces the density of steels, plays an important role in the control of microstructure and performance. However, the influence of C element in the alloy with high Mn content is barely studied. In this work, the effects of C content on microstructure and mechanical properties of four Fe-30Mn-10Al-xC (x=0.53, 0.72, 1.21, 1.68, mass fraction, %) alloys were studied by EBSD, TEM, XRD and universal testing machine. The results show that with the increase of C content, the amount of austenite gradually increases and the ferrite/austenite dual-phase microstructure transforms into single phase austenite. In addition, the strength increases monotonously, while the elongation increases and then decreases ultimately with increasing C content. Statistical analysis reveals that the strain coordination capacity of austenite is higher than that of ferrite. Therefore, with the increase of austenite content, the ductility of the dual-phase steel remarkably increases, while the strength increases slightly. For single austenite steels, the yield strength increases but the elongation and work hardening ability decrease with increasing C content, which is related to the precipitation of κ′ carbides.