Aluminum alloys, such as aluminum-silicon-magnesium (Al-Si-Mg) alloy, are characterized by high strength to weight ratio and suited for various automotive, aerospace and tooling applications. Additive manufacturing technique, such as selective laser melting (SLM) has been extensively studied. In the present work, a selective laser melted (SLM) AlSi10Mg alloy was subjected to a high cycle fatigue test to elucidate the effect of microstructural characteristics and sub-microscopic defects. The microstructure of the processed materials revealed scan tracks on the scanning surface and solidified melt pool/melt pool tracks on the surface in the build direction. The influence of grain morphology, microtexture, pores, and cellular structure on the deformation behavior of processed materials under cyclic loading was investigated. Load controlled axial fatigue test was conducted at a stress ratio of 0.1 and 25 Hz frequency. Fractography revealed crack initiation occurred, typically, due to the pores and the Si particles in surface or sub-surfaces. The cellular structures in the microstructure played a significant role in influencing the fatigue crack path, depending on its location in the microstructure. Dislocations in the cellular matrix and dislocation fringes in the cellular boundaries observed through transmission electron microscopy affirmed the influence. Anisotropy and shielding gases were observed to exhibit no significant impacts on the fatigue life of the processed material.

Keywords: Al-Si-Mg alloys, Selective laser melting, fatigue analysis, additive manufacturing