VHCF response of as-built SLM AlSi10Mg specimens with large loaded volume

It is well known in the literature that fatigue is particularly critical for Additive Manufacturing (AM) parts, because internal defects originating during the AM process represent a critical site for crack initiation. In the literature, the High-Cycle-Fatigue (HCF) response of AM parts has been extensively investigated; however, there are few results on the Very-High-Cycle-Fatigue (VHCF) behavior of AM parts, even if the number of machinery components that may sustain VHCF is rapidly increasing in the last years.
The present paper investigates the VHCF response of an AlSi10Mg alloy produced through Selective Laser Melting. Ultrasonic tests are carried out on Gaussian specimens with a large loaded volume and show that fatigue failures in VHCF originate from surface and sub-surface defects with the same mechanism of HCF failures. P-S-N curves and fatigue strength at 10^9 cycles are finally estimated to show the effect of defect size on the VHCF strength.