Surface quality and fatigue behavior of L-PBF AlSi10Mg in as-built condition

Abstract

Parts of complex geometry are increasingly fabricated by powder bed fusion (PBF) of AlSi10Mg. Since post fabrication surface finishing may be restricted due to unacceptable cost increase or/and geometrical inaccessibility of the part surfaces, the resulting fatigue performance of AlSi10Mg parts is often insufficient. Fatigue properties depend heavily local surface roughness which is affected by processing parameters and printing strategy. A direct aging treatment is often applied to improve material ductility while partially relieving residual stresses due to the powder melting and solidification process of L-PBF fabrication. This contribution investigated the fatigue performance of as-built AlSi10Mg together with the near-surface quality affected by fabrication. Three sets of specimens oriented in different directions with respect to build direction were fabricated in an industrial AM system. A significant directional effect of the fatigue response was determined. The quality of the as-built surfaces in the different specimens was characterized in terms of surface roughness and near surface microstructure on etched metallographic sections to explain the fatigue data of L-PBF AlSi10Mg. The directional nature of residual stresses and the contribution on fatigue behavior is also invoked as a contributing factor.