超级贝氏体组织中残余奥氏体的TRIP效应研究

针对超级贝氏体组织中残余奥氏体的应力诱发相变及对钢的力学性能影响，设计试验钢60Mn2SiCr，经900 ℃完全奥氏体化保温30 min，在260 ℃盐浴炉中等温处理12 h后，将试样在疲劳试验机上进行加载试验；利用扫描电镜(Scanning electron microscope, SEM)、透射电镜(Transmission electron microscope, TEM)、X射线衍射仪(X-ray diffracmeter, XRD)和拉伸试验机等仪器设备对加载前后的样品，分别进行显微组织形貌观察和相组成的定性定量检测分析以及力学性能测试；结果显示，等温处理后样品的显微组织为超级贝氏体(贝氏体铁素体BF+残余奥氏体AR)，残余奥氏体体积分数为9.4%，其含碳量为1.296%；经加载后试样显微组织中残余奥氏体体积分数下降至6.1%，含碳量达1.439%；钢的强塑积提高近20%。这说明等温处理获得超级贝氏体组织的钢，经施加载荷给予应力作用，显微组织中残余奥氏体发生转变，即超级贝氏体组织中的残余奥氏体能够通过相变诱发塑性(Transformation induced plasticity, TRIP)效应的产生，提高钢的力学性能。

Study on TRIP Effect of Retained Austenite in Super-bainite Microstructure

The loading test of the new developed 60Mn2SiCr super-bainitic steel which is previously austenitized at 900 ℃ for 30 minutes and then isothermal treated at 260 ℃ for 12 h in a salt bath furnace is carried out on the fatigue testing machine for the research of the phase transformation of retained austenite induced by stress in super-bainite microstructure and its effect on the mechanical property of the steel. The microstructure morphology, phase composition and mechanical property of the loaded sample are analyzed comparing with the one without loading test by the scanning electron microscope(SEM), transmission electron microscop(TEM), X-ray diffracmeter(XRD) and tensile testing machine. The results show that the microstructure of the experimental steel after isothermal transformation is the typical super–bainite microstructure(BF+AR). The volume fraction of retained austenite is 9.4% and the average carbon content is determined as 1.296%. However, after the loading test, the volume fraction of retained austenite drops to 6.1% and the carbon content increases to 1.439%. Meanwhile, the product of tensile strength and ductility increases nearly 20%. This illustrates that the mechanical property of the steel is improved obviously by the loading stress owning to the transformation induced plasticity(TRIP) effect of retrained austenite in super-bainite microstructure.