两种780 MPa级热镀锌双相钢的低周疲劳断裂行为

Low Cycle Fatigue Properties of Two 780 MPa Hot-Dip Galvanized Double Phase Steels

本研究以两种780 MPa级热镀锌双相钢为研究对象,通过施加单向拉伸及应变控制的循环载荷,对两种材料的力学性能和疲劳寿命进行了研究。结果表明,高C成分的DP780具有更高的延伸率和n值,其组织中除了铁素体和马氏体之外还含有5%左右的残余奥氏体;对比两种材料的疲劳寿命曲线,发现高C成分DP780的疲劳寿命要高于低C成分DP780的疲劳寿命;残余奥氏体在循环加载过程中发生的马氏体相变对疲劳寿裂纹的萌生和扩展起到了一定延迟作用,使其具有较高疲劳寿命。

In this research,two different 780 MPa grade hot-dip galvanized dual phase steels are selected to cyclic loading test.The results show that DP780 with high C content has higher elongation and n value,and the microstructure contains 5%retained austenite besides ferrite and martensite.Comparing the fatigue life curves of the two materials,it is found that DP780 with higher C content has higher fatigue life than DP780 with lower C content.Martensite phase transformation of retained austenite during cyclic loading will delay the formation and propagation of fatigue life crack,which contributes to higher fatigue life.