PSI - Issue 76

R. Fernandes et al. / Procedia Structural Integrity 76 (2026) 43–49

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1. Introduction AlSi10Mg aluminum alloy has excellent mechanical properties combined with low specific height, becoming widely used in high-performance engineering applications, as reports Petrovic et al. (2011). Its benefits use in transport industries, lead to weight reduction and decreasing use of energy, Frazier (2014). The Laser Powder Bed Fusion (L PBF) process allows the production of more complex geometries with faster production times when compared with the conventional processes. A critical factor influencing the performance of L-PBF components is surface quality. Surface and subsurface defects can significantly reduce fatigue life by creating stress concentrations and crack initiation sites, Bereta et al. (2017). To address these challenges, various surface treatments have been investigated, including chemical and electrochemical polishing, Muhammad W. et al. (2023), shot peening, Uzan et al. (2018), ultrasonic shot peening, Maleki, E., et al. (2023) and laser shock peening, being demonstrated improved fatigue performance compared to the as-built condition. Roveda et al. (2023) studied the influence of two different stress relief treatments, conducted at 265 °C and 300 °C. Both treatments were found to enhance fatigue crack growth (FCG) resistance. Also, Fernandes et al. (2024) investigated the impact of low-temperature stress relief at 250 °C on FCG rates. The heat-treated samples exhibited improved FCG resistance, attributed to residual stress relief, with the absence of crack closure in regime II. Given the significant influence of residual stress on crack propagation, shot peening emerges as a promising post processing technique, by introducing compressive residual stresses. Current work aims to address key gaps in understanding the behavior of AlSi10Mg aluminum alloy produced via L-PBF, namely the influence of combined influence on FCG rates of heat treatments and surface treatments, such as shot peening, especially under overload conditions. The study evaluates all four conditions – as-built, as-built shot peened, stress-relieved, and stress-relieved shot-peened specimens. Crack closure was assessed using Digital Image Correlation, and fracture surfaces were analyzed to identify the main mechanisms governing overload behavior.

Nomenclature a

crack length

ΔK stress intensity factor range , maximum and minimum load crack-opening load U load ratio parameter 2. Experimental Procedures and Methodologies 2.1. Material and specimen’s geometry N number of cycles

Experimental fatigue tests were performed using 6 mm thickness CTS specimens, with the geometry and dimensions shown in Fig. 1, produced in AlSi10Mg aluminium alloy powder, with the detailed chemical composition presented in table 1. The specimens were fabricated using a Renishaw AM400 system, using the following conditions: laser operated at a power of 350W, with a hatch distance of 80 µm, a scanning speed of 1800 mm/s, a layer thickness of 30 µm and a rotation incremental angle of 67°. All specimens were produced in the vertical orientation, following the geometrical specifications illustrated in Figure 1.

Table 1. Chemical composition of AlSi10Mg aluminium alloy powder (nominal, % wt.).

Al

Si

Mg

Mn Cu

Ni

Fe

Zn

Pb

Sn

Ti

Bal.

9-11

0.25-0.45

0.45 0.05

0.05

0.55

0.10

0.05

0.05

0.15