采用XRD、SEM、TEM、EBSD、EPMA等表征手段及硬度测试和拉伸实验研究了Mn12Ni2MoTi(Al)钢经过形变热处理后的微观组织及其性能。结果表明,Mn12Ni2MoTi(Al)钢经过65%冷轧及745 ℃两相区退火处理后,其横截面形成了由奥氏体层和铁素体层交替排列的层状条带组织,每个条带均由晶体取向相近的亚微米等轴晶组成;奥氏体条带中含有少量的铁素体晶粒,同样铁素体条带中含有少量的奥氏体晶粒。这种奥氏体/铁素体层状条带结构中的奥氏体晶粒具有黄铜型{110}<112>和Goss型{110}<001>织构,铁素体晶粒主要为旋转立方型{001}<110>和立方型{001}<100>织构。随着退火时间的延长,层状条带特征先增强然后逐渐减弱直至消失,同时奥氏体织构由黄铜型织构逐渐向Goss型织构演化。当材料具有层状条带组织时,同时具有高屈服强度和良好延伸率;当层状条带组织消失时,其屈服强度大幅度下降的同时延伸率也下降。

Lamianate structured metals have recently attracted extensive interests for their outstanding mechanical properties which are produced by synergetic strengthening of different heterogeneous layers. For Mn-rich maraging steels, austenite can precipitate in the martensite matrix due to Mn segregation during heat treatment, and then the austenite and martensite/ferrite duplex steel is produced. Besides, high Mn TRIP steel is regarded as a promising material for next generation automobile steel because of its high strength and good ductility. In this work, the microstructures and properties of Mn12Ni2MoTi(Al) steels produced by thermo-mechanical process were investigated using XRD, SEM, TEM, EBSD, EPMA, hardness tests and tensile tests. The results showed that laminate structures with austenite/ferrite band alternate arranging along the normal direction were formed in Mn12Ni2MoTi(Al) steels, which were processed by 65% cold-rolling and subsequent annealing at 745 ℃. Both of austenite bands and ferrite bands consist of ultrafine equiaxed grains. Moreover, a small amount of ferrite grains and austenite grains were found inside the austenite bands and ferrite bands, respectively. In the austenite/ferrite laminate structures, the austenite bands show the Brass texture of {110}<112> and Goss- type texture of {110}<001>. The ferrite bands show the rotate Cube texture of {001} <110> and Cube texture of {001}<100>. With the increase of annealing time, the laminate structures first become dominant and then disappear gradually, accompanying with the orientation transition of austenite from the Brass texture into the Goss one. The samples with laminate structures have high yield strength and good ductility. Otherwise, when the laminate structures disappear, the yield strength and ductility of the samples will decrease, and the yield strength deceases more.