Size effect on fatigue performance of SLM-ed AlSi10Mg alloy: Role of defect size distribution

The size effect on high-cycle fatigue performance of SLM-ed AlSi10Mg alloy was studied with three different highly stressed areas. It shows clear that small size specimens present higher S-N data and small fatigue initiator sizes compared to large specimens. Fatigue cracks were initiated from either lack of fusion (LOF) pores or gas pores. The sizes of fatigue initiators were analyzed based on Gumbel distribution and Frechet distribution, respectively. The LOF defects were equivalent to small cracks and Paris equation was used to reveal the relationship between the fatigue life, applied stress and fatigue initiator size. P-S-N curves were obtained by combining the fatigue initiator size distributions with crack propagation formula. According to the weak-link theory, P-S-N curves of other sizes could be predicted and it was found that Frechet approach could give a better prediction.