铝对超高锰Fe-24Mn-1.0C铸钢的组织和性能的影响

Influence of Al on Microstructures and Properties of Ultra High Manganese Fe-24Mn-1.0C Cast Steel

以超高锰Fe-24Mn-1.0C(无铝)和Fe-24Mn-7.1Al-1.0C(含铝)铸钢为研究对象,采用水韧处理、水韧处理+时效处理的热处理方法,研究铝对不同热处理条件下无铝和含7.1%Al铸钢组织和性能的影响。利用光学显微镜和扫描电镜观察显微组织,利用能谱分析和透射电镜测试观察析出物的成分、形貌;性能检测包括抗拉强度、屈服强度、冲击韧性(V型缺口)、断后延伸率、初始硬度。结果表明,铝的添加提高了铸钢Fe-24Mn-1.0C的层错能(γSFE),但却降低了其抗拉强度、冲击韧性和加工硬化速率。在时效过程中,铸钢Fe-24Mn-1.0C晶界处析出大量针状粗大的碳化物,恶化了其性能(500℃时效2h)。而铝元素增加了奥氏体基体中碳的稳定性,抑制了粗大针状碳化物的析出,析出纳米级的(Fe,Mn)3AlC的κ-碳化物,明显提高了基体的硬度和强度。铸钢Fe-24Mn-7.1Al-1.0C经550℃时效2h后综合力学性能达到最佳值,与常规水韧处理相比屈服强度提高到574MPa(提高40.0%,)抗拉强度为825 MPa,硬度提高到271HB(提高32.2%),断后延伸率为32.0%,冲击韧性为156J/cm2。

Ultra high manganese Fe-24Mn-1.0C(aluminum free)and Fe-24Mn-7.1Al-1.0C(aluminum-containing)cast steels were involved in this work and the effect of Al on the microstructures and mechanical properties of Fe-24Mn-1.0C cast steel were investigated.The microstructures of Al-free and 7.1%Al cast steels after water toughening and water toughening-aging were further analyzed with the help of optical microscope(OM),scanning electron microscopy(SEM),energy dispersive spectrometer(EDS)and transmission electron microscope(TEM).The mechanical properties of the samples such as ultimate tensile strength(UTS),yield strength(YS),total elongation(TE),initial hardness(IH)and impact toughness(V-notch,a k)were tested.The results indicate that addition of Al increases stacking fault energy(γSFE)and decreases UTS,a k and work hardening rate of Fe-24Mn-1.0C cast steel(after water toughening).The mechanical properties of Al-free steel would be deteriorated after aging 2 h at 500℃due to the preci-pitation of coarse needle-like carbides at grain boundaries.However,Al increases the metastable solubility of carbon in austenite and suppresses the needle-like carbide precipitation in the process of aging,and the nano-sized(Fe,Mn)3AlCκ-carbide precipitates in the matrix,which can improve the initial hardness,ultimate tensile strength,and yield strength of Fe-24Mn-1.0C cast steel.The mechanical properties have the best match after aging 2 h at 500℃:UTS is 825 MPa and YS is 574 MPa(increase by 40%),IH is 271 HB(increase by 32.2%),TE is 32.0%,a k is 156 J/cm 2.