Microstructural Variations in Laser Powder Bed Fused Al-15%Fe Alloy at Intermediate Temperatures

The samples of the Al-15Fe (mass%) binary alloy that were additively manufactured by laser powder bed fusion (L-PBF) were exposed to intermediate temperatures (300 and 500 °C), and the thermally induced variations in their microstructural characteristics were investigated. The L-PBF-manufactured sample was found to have a microstructure comprising a stable θ-Al₁₃Fe₄ phase localized around melt-pool boundaries and several spherical metastable Al₆Fe-phase particles surrounded by a nanoscale α-Al/Al₆Fe cellular structure in the melt pools. The morphology of the θ phase remained almost unchanged even after 1000 h of exposure at 300 °C. Moreover, the nanoscale α-Al/Al₆Fe cellular structure dissolved in the α-Al matrix; this was followed by the growth (and nucleation) of the spherical Al₆Fe-phase particles and the precipitation of the θ phase. Numerous equiaxed grains were formed in the α-Al matrix during the thermal exposure, which led to the formation of a relatively homogenous microstructure. The variations in these microstructural characteristics were more pronounced at the higher investigated temperature of 500 °C.