Influence of thermal conductivity on the productivity of Al alloys designed for LB-PBF

One of the main limitations of laser powder bed fusion (LPBF) is its limited productivity, which directly impacts the cost of fabricated components. Here, we investigate how tailoring the thermal conductivity of aluminium alloys can enhance productivity. Several alloys were designed by varying transition element concentrations (Mn, Cr, and V) to decrease thermal conductivity. Lower thermal conductivity results in larger melt pools by reducing heat dissipation through the substrate. These enlarged melt pools enable the use of larger hatch spacings and thicker powder layers while maintaining sufficient overlap between adjacent tracks and preventing lack-of-fusion defects. The build rate of one of the least conductive alloys, Al-0.5Fe-1.2Zr-2Cr (wt%), reaches 63.5 cm³ /h while maintaining a pore volume fraction below 0.5%. This represents a substantial improvement compared with typical build rates reported for AlSi10Mg (20–25 cm³/h), demonstrating that low thermal conductivity alloys offer an extended processing window towards higher productivity. The microstructure of a novel Al-0.5Fe-2Cr-1.2Zr (wt%) alloy, among the least thermally conductive compositions investigated, was characterized in the as-printed condition. EBSD revealed a bimodal grain structure, with fine grains located at melt pool boundaries and coarse columnar grains within melt pool interiors. Coarse faceted Cr-rich precipitates were observed in the fine-grained regions, whereas globular Fe-rich eutectic dispersoids formed within melt pool interiors. Atom probe tomography revealed a highly supersaturated Al matrix, particularly enriched in Cr, intentionally added to reduce thermal conductivity. These extended supersaturations result from out-of-equilibrium solidification conditions and provide opportunities for designing high-productivity aluminium alloys for LPBF.