ABSTRACT

The effect of retained austenite stability on microstructure evolution and mechanical properties of a new cold-rolled medium-manganese steel (0.12C, 7.69Mn, 1.45Si, 2.76Al wt-%) under intercritical annealing Q&P process at different partitioning temperatures was investigated. The evolution of retained austenite was characterized and statistically analysed using SEM, TEM, EBSD, and XRD techniques. The results show that the stability of retained austenite depends to a large extent on the applied heat treatment and is mainly attributed to the retained austenite content and morphology, whose carbon content is not the main influence. More retained austenite content and the formation of heterogeneous austenite structures (granular, massive, lamellar) are observed at a partitioning temperature of 150°C. The retained austenite of different morphologies has different stabilities and can sustain the TRIP effect at different strain stages, obtaining the best comprehensive mechanical properties with 34.5% elongation and the product of tensile strength and elongation is up to 43.5 GPa·%.

摘要

研究了不同分配温度下临界退火 Q&P 工艺下残余奥氏体稳定性对新型冷轧中锰钢 (0.12C, 7.69Mn, 1.45Si, 2.76Al wt-%) 显微组织演变和力学性能的影响。使用 SEM、TEM、EBSD 和 XRD 技术对残余奥氏体的演变进行表征和统计分析。结果表明，残余奥氏体的稳定性在很大程度上取决于所采用的热处理，主要归因于残余奥氏体的含量和形貌，其碳含量不是主要影响因素。在 150°C 的分配温度下观察到更多的残余奥氏体含量和异质奥氏体结构（粒状、块状、层状）的形成。