PSI - Issue 53

S. Senol et al. / Procedia Structural Integrity 53 (2024) 12–28 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 5. OM images displaying the etched YZ cross sections, displaying (a) the AB sample with the spatters and the rough surface, (b) the R sample, with the line indicating the approximate melt-pool depth formed during re-melting (~200 µm), (c) the EDM sample, displaying the white layer on the top with a thickness of 10 to 20 µm, (d) the M sample, with smooth surface profile. Finally, YZ cross sections are used for nanoindentations. The calculated average hardness ( H ) and modulus ( E ru ) values can be seen in Table 2. The indentations located at a maximum distance of 150 µm from the top surface are employed in determining the average hardness and modulus values across all conditions. Considering the average values and the standard deviations of both H and E ru displayed in Table 2, it can be stated that no considerable differences in H or E ru between different surface conditions are observed, except for the higher hardness of the ’white layer’ observed in the EDM sample. The additional indentation conducted at that region as shown in Appendix C revealed the average H or E ru for the ’white layer’ as 2.54 ± 0.07 GPa and 81.9 ± 2.3 GPa, respectively.

Table 2. The average hardness and E ru values for AB, R, EDM, and M surface conditions. Surface condition AB R EDM

M

Hardness (GPa)

1.92 ± 0.19 80.9 ± 4.6

1.86 ± 0.18 84.0 ± 5.0

2.03 ± 0.19 78.1 ± 4.7

1.92 ± 0.16 78.9 ± 4.7

E ru (GPa)

3.2. Effect on fatigue performance The three-point bending fatigue test results for four surface conditions, namely AB, R, EDM, and M, are shown as an S-N plot in Fig. 6. The best fatigue performance is recorded for the reference conventionally machined condition, M, followed by R, and then by EDM samples, with EDM condition displaying a more scattered behaviour. In comparison, considerably degraded fatigue performance is revealed in the case of AB samples, displaying the lowest fatigue life at all stress levels tested. Nevertheless, it is worth noting that the recorded fatigue performance of the investigated AMC ((Ti+B 4 C)/Al-Cu-Mg) in AB condition is superior to the fatigue performance of AlSi10Mg (Series A, Ra = 8 ± 4 µm) in (Beretta et al., 2020) and similar to AM205 (Ra = 23 ± 2 µm) (Senol et al., 2023). The enhanced fatigue performance of the AB (Ti+B 4 C)/Al-Cu-Mg composite, as compared to AlSi10Mg, despite the lower surface roughness recorded for the latter in (Beretta et al., 2020), can be attributed to the higher yield strength of the AMC parts with high density. This hybrid particle reinforced (Ti+B 4 C)/Al-Cu-Mg composite has a yield strength of 407 ± 10 MPa, while AlSi10Mg is reported to have a yield strength of 229 MPa (both of the reported values are for AB