Bao Shun, Feng Han, Song Zhigang, He Jianguo, Wu Xiaohan, Gu Yang
Special Steel Research Institute of General Iron and Steel Research Institute Co., Ltd., Beijing 100081, China.
Materials (Basel). 2024 Jul 9;17(14):3390. doi: 10.3390/ma17143390.
In this paper, the deformation behavior of UNS S32750 (S32750) duplex stainless steel during low cycle fatigue was studied by controlling the number of cycles. The microstructure of the specimens under different cycles was characterized by optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM). The microhardness of the two phases was measured by a digital microhardness instrument. The results showed that the microhardness of ferrite increases significantly after the first 4000 cycles, while the austenite shows a higher strain hardening rate after fatigue fracture, and the microhardness of ferrite and austenite increases by 23 HV and 87 HV, respectively. The two-phase kernel average misorientation (KAM) diagram showed that the continuous accumulation of plastic deformation easily leads to the initiation of cracks inside the austenite and at the phase boundaries. The evolution of dislocation morphology in the two phases was obviously different. With the increase in cycle number, the dislocation in ferrite gradually transforms from dislocation bundles and a dislocation array to a sub-grain structure, while the dislocation in austenite gradually develops from dipole array to an ordered Taylor lattice network structure.
本文通过控制循环次数研究了UNS S32750（S32750）双相不锈钢在低周疲劳过程中的变形行为。采用光学显微镜（OM）、扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和透射电子显微镜（TEM）对不同循环次数下试样的微观结构进行了表征。用数字显微硬度仪测量了两相的显微硬度。结果表明，铁素体的显微硬度在最初4000次循环后显著增加，而奥氏体在疲劳断裂后表现出较高的应变硬化率，铁素体和奥氏体的显微硬度分别增加了23 HV和87 HV。两相的核平均取向差（KAM）图表明，塑性变形的持续积累容易导致奥氏体内部和相界处裂纹的萌生。两相中位错形态的演变明显不同。随着循环次数的增加，铁素体中的位错逐渐从位错束和位错阵列转变为亚晶结构，而奥氏体中的位错则逐渐从偶极阵列发展为有序的泰勒晶格网络结构。
