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

Centimeter-sized samples of hypereutectic Al-15 mass% Fe alloy were manufactured by a laser powder bed fusion (L-PBF) process while systematically varying laser power (P) and scan speed (v). The effects on relative density and melt pool depth of L-PBF-manufactured samples were investigated. In comparison with other Al alloys, a small laser process window of P = 77-128 W and v = 0.4-0.8 ms(-1) was found for manufacturing macroscopically crack-free samples. A higher v and P led to the creation of macroscopic cracks propagating parallel to the powder-bed plane. These cracks preferentially propagated along the melt pool boundaries decorated with brittle theta-Al13Fe4 phase, resulting in low L-PBF processability of Al-15%Fe alloy. The deposited energy density model (using P center dot v(-1)(/2)) would be useful for identifying the optimum L-PBF process conditions towards densification of Al-15%Fe alloy samples, in comparison with the volumetric energy density (using P center dot v(-1)), however, the validity of the model was reduced for this alloy in comparison with other alloys with high thermal conductivities. This is likely due to inhomogeneous microstructures having numerous coarsened theta-Al13Fe4 phases localized at melt pool boundaries. These results provide insights into achieving sufficient L-PBF processability for manufacturing dense Al-Fe binary alloy samples.

Automated summary

By systematically varying laser power and scan speed, crack-free macroscopic samples of hypereutectic Al-15%Fe alloy were manufactured with a small laser process window. However, higher scan speeds and laser powers led to the formation of cracks, especially along melt pool boundaries decorated with brittle phase, resulting in reduced processability of the alloy. The deposited energy density model was found useful for identifying optimum process conditions towards densification, but its applicability was reduced for this alloy due to inhomogeneous microstructures with coarsened brittle phases.