Microstructural damage and fracture mechanisms of selective laser melted Al-Si alloys under fatigue loading

•Microstructural Failure mechanisms in selective laser melted Al alloys.•Comparison of mechanical properties of selective laser melted AlSi12 and AlSi10Mg.•Very high-cycle fatigue testing of selective laser melted Al-Si alloys. Employment of selective laser melted materials for industrial applications has grown in the recent years owing to improvements in machine systems and scanning techniques to result in near full-density parts; however, there are still limitations when their industrial application, particularly under cyclic loading, is concerned. This study investigates the chain from processing to post-process stress-relief to structural investigations in terms of microstructure and three-dimensional defect analysis by micro-computed tomography, and their corresponding behavior under quasi-static, high-cycle fatigue as well as very high-cycle fatigue for AlSi12 and AlSi10Mg alloys. Microstructure and damage mechanisms have been investigated as a function of in-process and post-process thermal treatments. Their corresponding influence on mechanical behavior revealed that there do exist differences in damage mechanisms in high-cycle fatigue and very high-cycle fatigue where the role of microstructure and small porosity respectively determines the damage mechanism in the two regions. The process parameters determining the required set of material behavior under quasi-static and cyclic loading have been identified.