Improving fatigue life for additively manufactured AlSi10Mg

While laser powder bed fusion enables rapid and resource-efficient production, challenges such as microstructural defects, porosity, and unfavourable residual stresses compromise the durability of components under dynamic loading. Thus, we investigated methods to enhance fatigue life of AlSi10Mg produced by laser powder bed fusion. To do so, we explore the effects of manual polishing, heat treatment, and deep rolling on the mechanical properties and fatigue performance of AlSi10Mg. Specimens were fabricated and divided into five groups: as-built, as-built with manual polishing, heat-treated and manually polished, as-built with deep rolling, and heat-treated with deep rolling. These groups underwent surface roughness measurements, residual stress analysis, hardness testing, and microscopy. The primary evaluation of fatigue performance was conducted using a rotating bending test rig under a load ratio of R = -1, following the high-cycle fatigue string-of-pearl method. The fatigue tests revealed significant differences among the treatment groups. The as-built specimens exhibited the lowest fatigue life, with cracks initiating from surface defects. While polishing and heat treatment provided moderate improvements, specimens treated with deep rolling exhibited the highest bearable stress amplitudes and the flattest S–N curves, indicating a significant improvement in fatigue resistance. The slope of the S–N curve in this condition is 7.8 times flatter compared to the untreated as-built condition. At a defined number of load cycles of 1E+06, the bearable stress in the “as-built + deep rolling” condition reaches 251 MPa, which is ~8.5 times the stress amplitude tolerated in the untreated as-built condition. Interestingly, combining heat treatment with deep rolling resulted in a decrease in performance compared to deep rolling alone. Our results indicate that surface treatment is critical for improving the fatigue life of additively manufactured AlSi10Mg components. It has turned out that deep rolling is an effective and economical method, as it reduces surface roughness and induces beneficial compressive residual stresses that counteract crack initiation. Furthermore, deep rolling eliminates the need for subsequent heat treatment, which may even be counter-productive, thus saving both time and energy costs. Our results help to exploit the potential of laser powder bed fusion of AlSi10Mg by combining near-net-shape production with effective surface enhancement.