Metallurgical defects have a critical influence on the anisotropic fatigue resistance of additively manufactured parts under cyclic loading. Here X-ray computed tomography (CT) has been used to characterise the defect population for laser powder bed fusion processed AlSi10Mg alloy and correlated with the tensile and high cycle fatigue (HCF) properties of specimens loaded both parallel and perpendicular to build direction. Despite similar tensile strengths, those tested perpendicular to the build direction exhibit a higher elongation and a higher fatigue strength (114 MPa) than those tested parallel to it (45 MPa). The near surface defects preferentially act as the fatigue crack initiation site for almost all the tested HCF specimens. The large oblate (pancake-shaped) defects were found to orient primarily within the build plane giving a larger projected area within this plane leading to a highly anisotropic fatigue strength. Extreme value statistics were used to predict the likely defect population in the critical near surface region of fatigue samples based on X-ray CT measurements. Finally, a fatigue performance assessment diagram considering these extreme value defects was established using the Kitagawa-Takahashi diagram.

冶金缺陷对循环载荷下增材制造零件的各向异性疲劳强度有关键影响。在这里，X 射线计算机断层扫描 (CT) 已被用于表征激光粉末床熔融加工的 AlSi10Mg 合金的缺陷群，并与平行和垂直加载的试样的拉伸和高周疲劳 (HCF) 特性相关联。尽管拉伸强度相似，但垂直于构建方向测试的那些表现出比平行测试的那些 (45 MPa) 更高的伸长率和更高的疲劳强度 (114 MPa)。近表面缺陷优先作为几乎所有测试 HCF 试样的疲劳裂纹起始点。发现大的扁圆（煎饼状）缺陷主要在构建平面内定向，在该平面内提供更大的投影面积，从而导致高度各向异性的疲劳强度。基于 X 射线 CT 测量，使用极值统计来预测疲劳样品临界近表面区域中可能的缺陷群。最后，使用 Kitagawa-Takahashi 图建立了考虑这些极值缺陷的疲劳性能评估图。