不同应变幅下高锰钢的低周疲劳性能研究

Study on low cycle fatigue properties of high manganese steel under different strain amplitudes

对铸态高锰钢(120Mn13)进行了常温拉伸及低周疲劳试验,研究了试样在拉伸变形中的动态应变时效,在拉压疲劳变形过程中的循环应力应变行为、循环硬化软化行为及裂纹扩展行为等。结果表明:在拉伸曲线中发现了代表动态应变时效作用的峰状低频A型锯齿和波纹状高频B型锯齿。在不同应变幅下的低周疲劳实验中,试样均先循环硬化,后循环软化直至断裂。随着应变幅的增加,其最大循环拉应力逐渐增加,疲劳寿命却降低。高应变幅下的裂纹多沿晶界扩展,但裂纹偏转次数及二次裂纹数量增多,这是其寿命较低应变幅下相差较小的主要原因。

In this paper,the tensile and low cycle fatigue tests of high manganese steel casting(120Mn13)were carried out at room temperature.The dynamic strain aging in tensile deformation,cyclic stress-strain behavior,cyclic hardening and softening behavior and crack propagation behavior under tension and compression fatigue deformation were studied.The results shown:low-frequency A-type peak sawtooth and shaped high-frequency B-type ripple sawtooth were found in the tensile curve,which represented dynamic strain aging.In the low cycle fatigue experiments under different strain amplitudes,the samples were first cycle hardened,and then cycle softened until fracture.With increasing strain amplitude,the maximum cyclic tensile stress increased gradually,but the fatigue life decreased.The cracks under high strain amplitude mostly propagated along the grain boundary,but the number of crack deflection and secondary cracks increased,which was the key reason for the little difference in fatigue life compared low strain amplitude.