Effect of Internal Pores on Fatigue Properties in Selective Laser Melted AlSi10Mg Alloy

The mechanical properties of aluminum alloys fabricated by selective laser melting (SLM) were examined with particular focus on their fatigue properties. The SLM aluminum alloys with various amounts of internal porosities were fabricated to investigate the effect of porosity on the fatigue properties. There were no remarkable differences in the microstructures of the SLM alloys. In terms of tensile properties, the tensile strength was significantly higher in the specimen with low porosity and decreased with increasing porosity. In terms of fatigue properties, crack initiations were observed at the internal pores in all specimens with the number of crack initiations increasing as a function of porosity. The fatigue strength decreased with increasing porosity, and porosity had a more significant effect on fatigue strength than tensile strength. The fatigue limit, which corresponds to the size and number of internal pores, changed remarkably in the low porosity regime because the size and number of internal pores changed drastically in this range. Considering the residual stress, these results demonstrate that by considerably suppressing the internal pores in the SLM aluminum alloys, a good fatigue performance can be expected, regardless of the occurrence of fatigue cracks at the internal pores.