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Abstract: 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 109 cycles are finally estimated to show the effect of defect size on the VHCF strength. Research highlights: Ultrasonic VHCF tests on AlSi10Mg Gaussian specimens produced through SLM. Identification and analysis of critical AM defects inducing VHCF failure. Statistical estimation of models for the prediction of the VHCF response of AM parts. Statistical prediction of effect of defect size on the VHCF response of AM parts. [ABSTRACT FROM AUTHOR]

High-energy ball milling was carried out to disperse SiC nanoparticles (ex-situ reinforcement) and fragments of oxide (in-situ reinforcement) in an Al2618 alloy matrix. Nanocomposite powders were consolidated by hot rolling at 600 °C. Samples produced using ball milled powder showed a weak response to ageing treatment as demonstrated by thermal and microstructural analyses and by hardness tests. Repeated plastic deformation of powder induced by ball milling led to high density of crystal defects which are believed to be responsible of an extension of solid solubility, thus reducing the driving force for precipitation during ageing. Tensile tests were performed at room temperature and at 120 °C on solution treated and peak-aged samples. The nanocomposites showed a remarkably high yield strength and an impressive ability in keeping high mechanical properties even at high temperature. Serrations were noticeable in stress-strain curves both before and after ageing, which are ascribed to the dynamic strain ageing mechanism. [ABSTRACT FROM AUTHOR]

• Size-effect on the VHCF response of SLM AlSi10Mg has been investigated. • AlSi10Mg specimens with increasing risk-volume have been tested. • Size-effect strongly affects the VHCF response of SLM AlSi10Mg specimens. • Size-effect is relevant for horizontal and vertical building orientation. • Size-effect is larger for AM parts than for traditionally built parts. This paper experimentally investigates the effect of the specimen volume (size-effect) on the Very-High-Cycle-Fatigue (VHCF) response of SLM AlSi10Mg specimens. Tension-compression tests are carried out on hourglass and Gaussian specimens with different risk-volumes produced in horizontal and vertical direction. Experimental results show that size-effects significantly influence the VHCF response regardless of the building orientation. Furthermore, size-effects are more evident for SLM specimens than for traditionally built specimens, pointing out that the design of SLM components cannot rely on the results obtained by testing traditionally built specimens. [ABSTRACT FROM AUTHOR]