PSI - Issue 74

Kristýna Vašáková et al. / Procedia Structural Integrity 74 (2025) 99–105 Kristýna Vašáková et al. / Structural Integrity Procedia 00 (2025) 000–000

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The Al₇Cu₂Fe phase, along with Al₅FeSi and Al₈Fe₅, was also detected in T6-treated LPBF AlSi9Cu3 alloy by transmission electron microscopy, as reported by (Roudnická et al. (2020)). Regarding annealing at intermediate temperatures (250– 350 °C), after 2 hours at 250 °C (Fig. 3d), the network is still present, with more pronounced precipitation inside the α -Al cells compared to the T5 condition. At 300 °C (Fig. 3e), the network is fragmented into discrete particles due to enhanced diffusion of Si, Cu, and Fe along the cell boundaries, leaving behind a homogenous dispersion of particles . At 350 °C (Fig. 3f), the particles formed by the disintegration of the network become coarsened. This behavior is consistent with previous reports on LPBF AlSi10Mg alloys, where the network begins to disintegrate at temperatures around 300 °C and is accompanied by a decrease in hardness (Fiocchi et al. (2021). Although Cu and Fe are undoubtedly present in the cellular network (Fig. 4), the disintegration of the network is primarily governed by the Si content, which is comparable in both AlSi10Mg and AlSi9Cu3 alloys.

Fig. 3: Microstructure of LPBF AlSi9Cu3 alloy in as-built state (a) and heat-treated conditions (b-f).

Tab. 2: EDS point analyses results of LPBF AlSi9Cu3 alloy in T6 condition

Al (at. %)

Si (at. %)

Cu (at. % )

Fe (at. %)

Spectrum 1 Spectrum 2

4.3

95. 7

-

-

74.4

-

17.5

8. 1

Fig. 4: EDS mapping analysis showing the element distribution of the LPBF AlSi9Cu3 alloy in the as-built state.

4. Discussion