The combined influence of defects and various heat treatment levels on high cycle fatigue performance of additively manufactured AlSi10Mg alloy

In the present work, the impact of defect geometry, size and position on the high cycle fatigue (HCF) properties was studied on AlSi10Mg alloy manufactured by Laser Powder Bed Fusion (LPBF). Different types and variations of heat treatment were applied on fatigue testing specimens from several building platforms. To investigate the influence of porosity and its characteristics on fatigue crack initiation, propagation and fatigue life, specimens were tested in the state of as built, after three types of annealing with various impact on supersaturated eutectic Si, and after two types of T6 heat treatment resulting in dissolution of Si network and reprecipitation of Si particles (total of 6 configurations of heat treatment). Fatigue crack growth and propagation mechanism together with defect evaluation were determined by fractographic analysis, while the influence of heat treatment on microstructural transformations was analyzed using light and scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD). Based on the results, maximum stress intensity factor was determined, and the prediction of fatigue limit was established for each material state. The synergistic effect of heat treatment and defects properties on high cycle fatigue is discussed.