This study shows the effect of hot isostatic pressing (HIP) on the porosity and the
microstructure, as well as the corresponding fatigue strength of selectively-laser-melted (SLM)
AlSi10Mg structures. To eliminate the influence of the as-built surface, all specimens are machined
and exhibit a polished surface. To highlight the effect of the HIP treatment, the HIP specimens are
compared to a test series without any post-treatment. The fatigue characteristic is evaluated by
tension-compression high cycle fatigue tests under a load stress ratio of R = 􀀀1. The influence of HIP
on the microstructural characteristics is investigated by utilizing scanning electron microscopy of
micrographs of selected samples. In order to study the failure mechanism and the fatigue crack origin,
a fracture surface analysis is carried out. It is found that, due to the HIP process and subsequent
annealing, there is a beneficial effect on the microstructure regarding the fatigue crack propagation,
such as Fe-rich precipitates and silicon agglomerations. This leads, combined with a significant
reduction of global porosity and a decrease of micro pore sizes, to an improved fatigue resistance for
the HIPed condition compared to the other test series within this study.