Microstructure of austenitic-ferritic duplex stainless steel loaded in the Very High Cycle Fatigue regime was investigated using microbeam energy-dispersive X-ray Laue diffraction. Scanning electron microscopy analysis of the surface shows that damage in the form of fatigue cracks is initiated at grain boundaries assisted by slip bands observed in austenite grains. Energy-dispersive X-ray Laue diffraction was then used to scan a damaged area containing both a fatigue crack and slip bands, in order to measure the changes in microstructure. Results from the X-ray data from the austenite grain indicates slip activation of the most favored slip system tilted by 45° with respect to the external loading direction, dividing the grain into two regions on either side of the slip band. In the ferrite phase, in front of the crack, variations in the angle and energy spectra of the diffraction peaks indicate the presence of lattice curvature and a strain gradient. In regions around the crack, diffraction peaks spatially split into several sub-peaks indicating the presence of fine granular areas separated by polarized dislocation walls. Possible reasons for the observed structural evolution are discussed and the advantages of using energy-dispersive X-ray Laue diffraction in fatigue damage analysis are illustrated.

使用微束能量色散 X 射线劳厄衍射研究了在极高周疲劳状态下加载的奥氏体-铁素体双相不锈钢的微观结构。表面的扫描电子显微镜分析表明，在奥氏体晶粒中观察到的滑移带辅助下，在晶界处引发了疲劳裂纹形式的损伤。然后使用能量色散 X 射线劳厄衍射扫描包含疲劳裂纹和滑移带的损坏区域，以测量微观结构的变化。来自奥氏体晶粒的 X 射线数据的结果表明，相对于外部加载方向倾斜 45° 的最有利的滑移系统的滑移激活，将晶粒在滑移带的两侧分成两个区域。在铁素体相中，在裂纹前，衍射峰角度和能谱的变化表明存在晶格曲率和应变梯度。在裂纹周围的区域，衍射峰在空间上分裂成几个子峰，表明存在由极化位错壁隔开的细粒区域。讨论了观察到的结构演变的可能原因，并说明了在疲劳损伤分析中使用能量色散 X 射线劳厄衍射的优势。