为了探究残余奥氏体稳定性对于中锰钢塑性失稳的影响和作用规律，本工作针对中锰钢(0.2C-5Mn-0.5Si-1.5Al，质量分数，%)，设计了预处理加临界退火的热处理工艺，得到2种残余奥氏体，并对其成分、形貌及稳定性进行了分析，进而讨论了残余奥氏体对力学性能的影响。结果表明，珠光体+马氏体+铁素体的多相初始组织退火后能够获得2种不同稳定性的残余奥氏体：源自珠光体具有较高Mn含量的薄膜状残余奥氏体；主要源自于马氏体具有适当Mn含量的块状残余奥氏体。块状残余奥氏体稳定性较差，在塑性变形初始阶段发生相变，有助于消除Lüders应变；薄膜状残余奥氏体稳定性较高，在变形中后期发生相变，有助于获得高强塑性。含双稳定性残余奥氏体的试样不仅保持了高抗拉强度(> 1000 MPa)和高断裂延伸率(> 30%)，而且还具有连续屈服和高强屈比的特点。

Researches have focused on the development of lightweight and high-performance steel materials to ensure automobile safety. Medium manganese steel is a potential candidate owing to its excellent mechanical properties and low production cost. However, the problem of plastic instability (Lüders strain, Portevin-Le Chatelier effect) is one of the main factors restricting the development of medium manganese steel. Therefore, resolving the plastic instability of medium manganese steel is a prerequisite for its development and hence to ensure the benefits of its mechanical qualities. Many studies have found that the stability of retained austenite is directly related to the plastic instability of medium manganese steel. In this work, cold rolled low-carbon medium manganese steel is selected, and multi-stable retained austenite is obtained by designing pretreatment and critical annealing process. The phase transformation of the retained austenite with different stability in each stage of the tensile process and its influence on the mechanical properties are studied. The results show that the microstructure containing pearlite + ferrite + martensite is obtained after pretreatment of medium manganese steel. After annealing, pearlite transformed into filmy retained austenite and ferrite phase; while martensite transformed into blocky retained austenite. Mn content in the filmy retained austenite is higher than that in the blocky retained austenite, making the filmy retained austenite more stable than the blocky one. The blocky retained austenite has poor stability, and phase transformation occurs at the initial stage of plastic deformation, eliminating Lüders strain. In contrast, the filmy retained austenite has high stability, and phase transformation occurs in the middle and late deformation, contributing toward its high strength and plasticity. The specimens containing double-stable retained austenite not only maintain the tensile strength (> 1000 MPa) and high fracture elongations (> 30%), but also have the characteristics of continuous yield and high strength yield ratio.