PSI - Issue 54

R.F. Fernandes et al. / Procedia Structural Integrity 54 (2024) 300–306 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Nomenclature Strain amplitude Strain at fracture Effective stress Ultimate tensile stress Yield stress ∆ Stress range b y-intercept of the linear regression Slope of the linear regression E Young’s modulus ‡ Experimental number of cycles N f Number of cycles to failure ’ Predicted number of cycles R Stress ratio C

The most widely studied metal AM process is Laser Powder Bed Fusion (LPBF), which is based on the layer-by layer approach. It utilizes a laser beam that melts powder previously spread, ensuring high-quality densification of the component (Kumar, 2021). The ability to using aluminum alloys through the LPBF process presents new alternatives in the field of design, facilitating the reduction of components weight, based on the topology optimization. AlSi10Mg, with its promising properties including excellent weldability, high strength, low density, and corrosion resistance, is a convincing option for the LPBF process. The combination of these benefits keeps AlSi10Mg alloy processed by LPBF especially attractive for aerospace and automotive industries (Shakil, 2021; Yan, 2019). The LPBF process leads to a significantly finer microstructure in the AlSi10Mg, because of rapid heating and cooling rates during manufacturing, enhancing the mechanical properties of the material. However, this process is also associated with defects, including pores and lack of fusion, along with residual stresses, which have a detrimental effect on the fatigue behavior of the parts (Lehner, 2023; Yang, 2018). In order to control this effect, various heat treatments have been studied to improve the mechanical and fatigue behavior, including conventional ones, such as T6 and stress relief at 300 ºC. However, these kind of heat treatments have a huge impact in the mechanical properties of the material, as observed by the authors (Fernandes, 2022), and confirmed by other studies (Mfusi, 2019; Růžičková, 2022; Xu, 2023; Zhang, 2018) . This behavior is caused by Si precipitation from the supersaturated Al matrix, affecting the Al-Si network generated during the process. Temperatures higher than 260-270 ºC will lead to the Si precipitation (Fiocchi, 2021). This shows the importance of a proper heat treatment for this material. Considering the notch effect on the fatigue behavior, some studies were performed. Nicoletto (2020) investigated the impact of surface roughness on AlSi10Mg alloy, for both unnotched and notched specimens, with different building directions. The author concluded that the sensitivity to build direction is significantly affected, for both unnotched and notched specimens, reaching different notch fatigue factors, Kf. Maleki (2022) conducted a study on the impact of heat and surface treatments on notched components. The hybrid treatment involving heat treatment T6 and laser shock peening had the most significant effect on pore closure. Furthermore, when combined with electro-chemical polishing, it proved to be the most effective treatment for improving fatigue life. Based on this, the authors aimed to explore a simplified and optimized heat treatment with temperatures below the Si precipitation to enhance the fatigue strength of the material. The principal objective of this study was to investigate the impact of this heat treatment on the fatigue behavior of both unnotched and notched specimens. Additionally, the fatigue life was predicted using a model based on the SWT parameter.