Microstructure of Al-2.5Fe Binary Alloy Fabricated by Laser Powder Bed Fusion

Abstract

In the present study, microstructural and crystallographic features of an Al-Fe binary alloy with a near eutectic composition (Al-2.5wt%Fe) fabricated by laser powder bed fusion (LPBF) process were examined. The LPBF processing for the Al-Fe alloy powder was conducted at room temperature using a 3D Systems ProX 200 operating at a laser power of 204 W and a laser scan speed of 0.6 m/s and 0.8 m/s to fabricate cube samples with high relative density above 99 %. The fabricated sample exhibited characteristic microstructure consisting of a number of melt pools in which the regions had locally melted and rapidly solidified by laser irradiation during the LPBF process. Numerous fine particles of Al-Fe intermetallics with a mean size below 100 nm were found within the α-Al matrix in the observed melt pools, whereas relatively coarsened particles were localized around melt pool boundaries. Electron backscatter diffraction (EBSD) analyses revealed a number of columnar a-Al grains with a mean size of approximately 10 μm. The LPBF-fabricated Al-Fe alloy exhibits a high hardness of approximately 90 HV, which is more than twice higher than the conventionally casted Al-Fe alloy.