A single-powder strategy for LPBF and LDED processing of a BCC Nb–Ti–Zr alloy

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Refractory multi-principal element alloys offer high melting temperatures and compositional flexibility for structural applications under extreme conditions. In the Nb–Ti–Zr ternary system, Zr confers corrosion resistance and a low neutron capture cross-section, while Nb stabilizes the body-centered cubic (BCC) phase across a wide composition space, and Ti, the lightest constituent, lowers the alloy density. Here we report the first additive manufacturing of Nb 25 Ti 20 Zr 55 by laser powder bed fusion (LPBF) and laser directed energy deposition (LDED) from a single prealloyed powder. Both routes produced intact builds with sparse pores across much of the processing window, with cracking confined to part of the LPBF range. Electron backscatter diffraction and X-ray diffraction indexed a predominantly body-centered cubic microstructure at Zr contents of 50.4 to 55.5 at.% across both routes. Ti evaporated preferentially, falling 9.5 at.% from the feedstock in LPBF, yet the BCC phase was retained. The LPBF composition was uniform across the processing window. The LDED composition varied with energy density and approached the LPBF value only at the highest energy density. LPBF gave finer grains (96 μm) than LDED (140 μm) at equivalent hardness (H = 2.73 to 2.90 GPa) and Young’s modulus (E = 79 to 83 GPa).