VHCF response of Gaussian SLM AlSi10Mg specimens: Effect of a stress relief heat treatment

•Ultrasonic VHCF tests were successfully conducted on AlSi10 SLM Gaussian specimens.•Annealing for two hours at 320 °C is detrimental for the VHCF response.•The evolution of Si particles during the heat treatment affects the VHCF response.•The performed tests extend the knowledge about the VHCF response of AlSi10Mg SLM parts. The present paper investigates the effect of a stress relief heat treatment (two hours at 320 °C and air cooling down) on the VHCF response of an AlSi10Mg alloy produced through SLM. Ultrasonic tension-compression tests up to 109 cycles were carried out on as-built and heat treated Gaussian specimens with a large loaded volume. Experimental results showed that the investigated heat treatment has a detrimental effect on the VHCF response: VHCF strength reduction is larger than 20% at number of cycles above 108. The microstructural changes induced by the heat treatment (i.e., rupture and spheroidization of the original eutectic silicon network) was shown to be the main reason for the VHCF decrement, thus suggesting that an optimization of the heat treatment parameters is required.