Combined effect of surface anomalies and volumetric defects on fatigue assessment of AlSi7Mg fabricated via laser powder bed fusion

In recent years, the fabrication of aluminum alloy parts via laser powder bed fusion has been extensively considered in the biomedical, aerospace, and other industrial sectors, as it provides advantages such as the ability to manufacture complex shapes with high performance associated with lightweight design. However, surface irregularities and sub-surface defects limit the full exploitation of such parts in fatigue-critical applications. Moreover, most of the commonly used metrological methods for surface characterization have proven to be unsuitable for determining important features such as undercuts and sub-surfaces pores. Hence, a comprehensive coupled investigation of metrological methods and cross-sectional analysis were performed in this study to evaluate the effects of surface features and volumetric defects typical of additively manufactured materials. Fatigue tests and fractographic analyses were conducted to support the finite element simulations and proposed fracture mechanics model. The results demonstrate that the standard metrological methods cannot provide all of the data needed to model the fatigue behaviors of additively manufactured materials robustly. Moreover, a statistical model describing the competition between volumetric defects and surface irregularities was developed and validated.