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In this work, CALPHAD-based thermodynamic screening was combined with a local-neighbourhood particle swarm optimisation (PSO) algorithm to explore the composition space of Nb-Si-Ti-Hf-Al-Cr alloys for additive manufacturing (AM). The search identified distinct high-fitness compositional regions based on solidification range, phase constitution, and bcc (body-centred cubic) phase fraction. More than 28,000 unique compositions were evaluated and classified into five compositional clusters. Two representative alloys were selected for experimental validation: near-eutectic Nb 70.6 Si 15.8 Ti 10 Al 3.6 and hypoeutectic Nb 68.4 Si 13.7 Ti 15 Al 2.9 alloys (subscripts indicate at% of corresponding elements). Experimental characterisation confirmed microstructures consistent with their near-eutectic and hypoeutectic solidification behaviour, consisting of a bcc Nb solid solution and tetragonal α-Me 5 Si 3 phases. The near-eutectic alloy exhibited higher compressive strength than the hypoeutectic alloy across the 22–1000°C temperature range, with both alloys achieving some of the highest specific strengths reported to date at 1000°C. Laser-remelting experiments used for rapid screening of AM processability identified crack-free processing windows, with a broader window for the hypoeutectic alloy. Rapid solidification led to substantial microstructural refinement in both alloys, accompanied by an α-Me 5 Si 3 → Me 3 Si transformation and a 30–40% increase in microhardness. The results demonstrate how thermodynamic composition screening combined with experimental processability assessment can be used to identify promising Nb-Si alloy compositions for AM.
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Mirontsov et al. (2026) studied this question.