Investigation on fatigue strength of sand-blasted DMLS-AlSi10Mg alloy

Fatigue resistance of Direct Metal Laser Sintered (DMLS) AlSi10Mg alloy after sand-blasting was investigated in the present study. A preliminary characterization of the samples was carried out in order to identify material microstructure, surface roughness and superficial residual stresses. It was found that the applied post-processing treatment was responsible for a strong decrease in average surface roughness as compared to the as-built condition and induced compressive residual stresses on the samples surface. Axial fatigue tests were performed in both finite and infinite (i.e. 2x106 cycles) life regimes and the obtained results were compared with literature values for the same alloy after various post-treatments, including heat treatment, machining, polishing and shot peening. A general positive effect of the applied sand-blasting on fatigue resistance was observed. This, coupled with the improvements of surface finishing, encourages the use of sand-blasting as a simple and effective post-treatment. Finally, observations of the fractured surfaces allowed also the identification of porosities located on the surface as the main crack initiation sites. Once the crack has started, it moves along a large flat area, as typical of fatigue propagation, with a small final overload region.