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

Abstract

•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 ∼21 μm elongated along the building direction were also observed in the α-Al matrix. Numerous nano-sized particles of the metastable Al6Fe intermetallic phase with a mean size <100 nm were finely dispersed in the α-Al matrix. The hardness of the refined microstructure produced by the LPBF process was high at ∼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 α-Al matrix.