Additive manufacturing of Ti2AlNb alloys: A review of process, microstructure, property relationships

As the latest generation of low-density titanium aluminides, Ti 2 AlNb alloys hold great promise, having high temperature properties close to those of nickel-based superalloys. However, their inherent brittleness and compositional sensitivity present significant challenges for conventional manufacturing techniques. Consequently, additive manufacturing (AM) methods are attracting a lot of attention, taking advantage of their ability to fabricate geometrically complex Ti 2 AlNb structural parts. This work comprehensively reviews recent progress in the AM of Ti 2 AlNb alloys, focusing primarily on powder methods, i.e. electron beam melting (EBM), laser powder bed fusion (LPBF), and laser directed energy deposition (LDED). The relationship between AM process parameters, ensuing microstructures, and the resulting mechanical properties is systematically examined. The microstructural characteristics exhibit significant process dependency: the higher preheating temperatures and slower cooling conditions in EBM promoting O phase precipitation; whereas the rapid solidification characteristic of LPBF results in B2 phase-dominated metastable microstructures; while the layer-by-layer variation in thermal cycles experienced during LDED leads to substantially higher macro-scale microstructural heterogeneity. By examining how energy density, scanning strategy, and post-processing treatment influence phase transformation, grain morphology, and defect formation, we propose strategies to address challenges hindering broader application of AM Ti 2 AlNb alloys. As such, this review seeks to offer new insights for advancing the development of AM-fabricated Ti 2 AlNb components.