Managing both high strength and thermal conductivity of a laser powder bed fused Al-2.5Fe binary alloy: Effect of annealing on microstructure

The microstructure of Al-2.5Fe (wt%) binary alloy samples additively manufactured by laser powder bed fusion (L-PBF) was systematically characterized, and its change due to subsequent annealing at 300 degrees C and 500 degrees C was examined. The as-fabricated samples featured homogeneous distribution of numerous fine particles of the metastable Al6Fe phase in the solidification microstructure where melt pools formed, and a relatively coarsened cellular structure was observed around the boundaries between the melt pools formed at different locations (melt pool boundaries). After the annealing at 300 degrees C, a slight growth of the nano-sized Al6Fe phase occurred, and coarsened plate-like.-Al13Fe4 phases were locally formed in the cellular structure at melt pool boundaries. Annealing at 500 degrees C induced a pronounced transformation of the metastable Al6Fe phase to the stable.-Al13Fe4 phase in the microstructure where melt pools formed, although no significant change in the microstructure of the a-Al matrix was detected. The thermal conductivity and tensile properties of as-fabricated and subsequently annealed specimens were measured. The as-fabricated specimens exhibited a high tensile strength of similar to 320 MPa and a thermal conductivity of similar to 150 W m(-1) K-1. Annealing at 300 degrees C improved the thermal conductivity to similar to 185 W m(-1) K-1 without a loss of tensile strength, whereas annealing at 500 degrees C significantly decreased the tensile strength. These results are utilized to discuss a balance between mechanical properties and thermal conductivity, which provided novel insights for managing both high strength and thermal conductivity of L-PBFbuilt Al-Fe binary alloys by controlling microstructure.

Automated summary

The microstructure of Al-2.5Fe binary alloy samples fabricated by laser powder bed fusion was characterized, and subsequent annealing at different temperatures affected the distribution and growth of phases within the microstructure. Annealing at 300 degrees C improved thermal conductivity without compromising tensile strength, while annealing at 500 degrees C significantly decreased tensile strength. These results highlight the balance between mechanical properties and thermal conductivity in Al-Fe binary alloys fabricated by L-PBF.