通过相变点测定、相图计算、组织观察、XRD分析及EBSD取向成像技术研究了室温下含两种马氏体及奥氏体的18Mn钢在100-500℃间进行温变形时的组织、相结构变化及马氏体逆相变行为. 结果表明, 在300℃以上压缩变形时, TRIP效应消失,马氏体减少, 出现逆相变; 形变加速了扩散型逆相变, bcc马氏体或铁素体以扩散方式转变成奥氏体, 奥氏体不需要重新形核; 形变使奥氏体出现机械稳定化并出现大尺寸的形变孪晶, 抑制了随后冷却过程中的马氏体相变; 压缩形变时,最后残留的马氏体多出现在{110} 和{100}取向的奥氏体晶粒中.bcc马氏体周围难以观察到hcp马氏体. 分析认为, hcp马氏体以切变方式逆相变.

High manganese steels show significant potential for industrial application due to their remarkable TRIP/TWIP effects at room temperature. The study on the TRIP behavior during warm deformation is important in controlling microstructures and properties of high manganese steels. In this paper, the microstructures, phase structures and reverse transformation of martensites to austenite in a high manganese steel which is composed of two types of martensites and austenite were investigated under warm deformation (100—500℃) by means of the determination of transformation temperature, calculation of phase diagram, microstructure observation, XRD analysis and EBSD orientation imaging technique. Results show that during compression above 300 ℃, TRIP effect disappeared and reverse transformation from martensite to austenite was enhanced. The transformation from bcc martensite to austenite was determined to be diffusive and no nucleation of austenite was needed. The warm deformation of austenite leads to the formation of coarse deormation twins and the mechanical stabilization of austenite, which suppressed the subsequent martensitic transformation during quenching. The austeniic grains in which reverse martensitic transformation completed at the latest, show mainly {110} and {100} orientations. In addition, hcp martensite could hardly edetected around bcc martensite, and the transformation of hcp martensite into austenite is regarded to be reversible and diffusionless.