Microstructure and room-temperature mechanical properties of Nb/Nb ₅Si₃ alloys fabricated by spark plasma sintering

Using pure Nb and Nb₅Si₃ metal powder as raw material, Nb/Nb₅Si₃ alloys with three different proportions (90:10, 70:30 and 50:50) were fabricated by spark plasma sintering (SPS). The microstructures, relative densities, and room-temperature mechanical properties of the three SPS Nb/Nb₅Si₃ alloys were investigated. It is revealed that the synthesized alloys are composed of two phases of Nb and Nb₅Si₃. The volume fraction of Nb and Nb₅Si₃ in the synthesized alloys is in line with the original ratio, indicating that the volume fraction ratio of Nb to Nb ₅Si₃ is able to be precisely controlled. The SPS Nb/Nb₅Si₃ alloys are nearly fully dense and their relative densities are above 99.66%. With an increasing volume fraction of Nb ₅Si₃, the room-temperature hardness of the bulk SPS alloys increased, meanwhile, the fracture toughness decreased with a little amplitude. The SPS alloy with a Nb/Nb₅Si₃ volume fraction ratio of 50:50 has the highest hardness of Hv879.6, and that with a Nb/Nb ₅Si₃ volume fraction ratio of 90:10 has the highest fracture toughness of 6.9MPa•m^1/2.