Effect of processing parameters on the densification of an additively manufactured 2024 Al alloy

Processability and Optimization of Laser Parameters for Densification of Hypereutectic Al–Fe Binary Alloy Manufactured by Laser Powder Bed Fusion

“…The relative density increased at higher P values (Figure 5), whereas cracks (macroscopically propagating parallel to the powder bed plane) occurred in the built samples when P > 140 W and v > 1.0 m•s −1 (Figure 2a,c). The suitable ranges of P and v for manufacturing dense Al-15%Fe alloy samples are different from the optimized parameters reported for other Al alloys [16][17][18]20,24,27,30]. Figure 8 presents the laser parameter ranges for manufacturing Al-15%Fe alloy samples with high relative densities above 95%, together with the process windows for other types of alloys in the literature [16][17][18]20,24,27,30].…”

“…In general, the optimized P and v should depend on other process parameters (e.g., laser spot size, hatch distance, and powder layer thickness) and could not be compared between different L-PBF machines and materials [43]. However, it is obvious that the window for Al-15%Fe alloy samples is much smaller compared to not only commonly used Al-Si alloys (AlSi10Mg, A356 and A357) [17][18][19] but also high-strength Al alloys [19][20][21][22]44]. One of these studies produced Al-2.5%Fe binary alloy samples under the same conditions (same scan strategy, spot size of approximately 100 µm, hatch distance of 100 µm, powder layer thickness of 30 µm) [42].…”

“…This more limited process window could be attributed to macroscopic cracking when the Al-15%Fe alloy powder is subjected to high laser powers and scan speeds (Figure 2a,c). Similarly, it is known to be difficult to process heattreatable wrought-type Al alloys (Al-Cu, Al-Mg-Si, and Al-Zn-Mg systems) using L-PBF, because those materials are highly sensitive to cracking during solidification [19][20][21][22][23][24][25][26][27][28][29]. The solidification cracks often propagate along the building direction (which likely coincides with the solidification direction) in a process called "hot cracking" [24,45], resulting in poor processability of high-strength Al alloys.…”

“…Thus, a higher laser scan speed would enhance the formation of microscale solidification cracks in the L-PBF process, assisting the process to form macroscopic lateral cracks in the built Al-15%Fe alloy samples, as presented in Figure 2c. Laser power (P) and scan speed (v) for manufacturing the Al-15%Fe alloy samples with high relative densities above 95%, together with the process windows for manufacturing other alloy samples reported in the literature [16][17][18]20,24,27,30].…”

“…Optimization of the laser process parameters, in particular the laser power and scan speed, is required for the densification of Al-Fe alloy samples. In fact, the influence of L-PBF process parameters on porosity and cracking (L-PBF processability) had been extensively studied in the cases of Al-Si-based alloys [10,[16][17][18] and age-hardenable wrought-type alloys (the 2xxx, 6xxx, and 7xxx series) [19][20][21][22][23][24][25][26][27][28][29]. In comparison, similar research for the Al-Fe alloys remains limited [30], although a few reports considered application of the L-PBF process to the Al-Fe-based alloys [31,32].…”