Microstructure and fracture toughness of a Nb–Ti–Si-based in-situ composite fabricated by laser-based directed energy deposition

Laser-based directed energy deposition (LDED), a significant integrated preparation technique combining material design and production, has been progressively used to manufacture Nb–Ti–Si-based in-situ composites. However, it is commonly known that Nb–Si-based in-situ composites have low room-temperature fracture toughness. Herein, we have designed a novel Nb–40Ti–10Si–5Al–2V (at.%) composite, the microstructure of LDED-built composite is made up of Nbss and γ-Nb₅Si₃, the formation of γ-Nb₅Si₃ precipitate in the Nbss phase with an orientation relationships (ORs) of [1110]_γ//[011]_Nbss, (10 1‾ 0)_γ//(011)_Nbss and (1 2‾ 11)_γ//(200)_Nbss. The composite has Nbss, Nb₃Si and γ-Nb₅Si₃ phases after heat treatment at 1400 °C for 30 h, and δ-Nb₁₁Si₄ precipitate has formed in the Nbss phase with an ORs of [100]_Nbss//[010]_δ, (010)_Nbss//(010)_δ. The composite processing Nb–40Ti–10Si–5Al–2V (at.%) has outstanding toughness (21.62 MPa·m^1/2). It has ascertained that the room-temperature fracture toughness of Nb–Si-based in-situ composite is positively impacted by the high concentration of Ti.