Laser powder bed fusion of a near-eutectic Al-Fe binary alloy: Processing and microstructure

This study focused on additive manufacturing (AM) of the Al-Fe binary alloy samples with a near-eutectic composition of 2.5 mass% Fe using the laser powder bed fusion (LPBF) process. The melt pool depth, relative density, and hardness of LPBF-fabricated Al-2.5Fe alloy samples under different laser power (P) and scan speed (v) conditions were systematically examined. The results provided optimum laser parameter sets (P = 204 W, v <= 800 mm s(-1)) for the fabrication of dense alloy samples with high relative densities > 99%. Additionally, Pv(-1/2), which is based on the deposited energy density model, was found to be a more appropriate parameter for additively manufacturing Al-2.5Fe alloy samples, and using it to simplify the relative densities of the samples made the determination of a threshold value for the laser parameters required to fabricate dense alloy samples. The microstructural and crystallographic characterization of the LPBF-built Al-2.5Fe alloy samples revealed a characteristic microstructure consisting of multi-scan melt pools that resulted from local melting and rapid solidification owing to laser irradiation during the LPBF process. Furthermore, a number of columnar grains with a mean width of similar to 21 mu m elongated along the building direction were also observed in the alpha-Al matrix. Numerous nano-sized particles of the metastable Al6Fe intermetallic phase with a mean size < 100 nm were finely dispersed in the alpha-Al matrix. The hardness of the refined microstructure produced by the LPBF process was high at similar to 90 HV, which is more than twofold higher than that of conventionally casted alloys that contain the coarsened plate-shaped Al13Fe4 intermetallic phase in equilibrium with the alpha-Al matrix.