Impact of laser scanning strategies on microstructure and mechanical properties of Ti2AlNb intermetallic alloy

This study investigates the effects of laser scanning strategies on the microstructure and mechanical properties of the low-ductility Ti₂AlNb intermetallic alloy fabricated via laser-based powder bed fusion of metals (PBF-LB/M). Three bidirectional linear scanning strategies—67° rotation (0-R67), 90° rotation (0-R90), and 45° inclined followed by 90° rotation (45-R90) between adjacent layers—were employed, with all other PBF-LB/M parameters held constant. High-quality alloy samples with <0.01 % porosity, free of visible lack-of-fusion defects and cracks, were successfully fabricated. The as-printed microstructures predominantly consisted of a single B2/β phase, with grain size influenced by the scanning strategy, although texture remained largely unchanged. The 45-R90 sample demonstrated the highest yield strength (980 MPa) and best elongation (13.1 %), attributed to reduced residual stress and a higher, concentrated Schmidt Factor (SF). After heat treatment (HT: solution treatment, water quenching, and ageing), all samples retained the B2/β grain morphology, with α₂ phases forming along grain boundaries and O phases distributed within the grains. The HT 0-R67 sample exhibited the best strength-ductility combination (1066 MPa, 5.47 %), attributed to randomly oriented B2/β-grain boundaries, thin α₂ precipitates, and the lowest average SF of the O phase precipitates. These findings highlight the critical role of laser scanning strategies in tailoring microstructure and optimizing the performance of Ti₂AlNb alloys in both as-printed and heat-treated conditions.