Microstructural and mechanical characterization of multiphase Nb-based composites from Nb–Ti–C–B system

• Novel multiphase Nb-based composites were prepared using the arc-melting method.
• The derived Nb-based composites exhibit high strength and hardness.
• The derived Nb-based composites maintain the desirable toughness.
• The hybrid boride and carbide effectively strengthen the composites.

The microstructures and mechanical properties of novel multiphase Nb-based composites from Nb–Ti–C–B system have been investigated. The microstructures were characterized using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The composites contain Nb solid solution, (Nb,Ti)B boride and (Nb,Ti)C carbide phases. The hybrid (Nb,Ti)B and (Nb,Ti)C together with Nb solid solution form the network microstructure. The composites exhibit high hardness and strength while maintaining desirable fracture toughness at room temperature. Boride and carbide phases effectively improve the strength and hardness of the composites, while Nb solid solution toughens the composites. Higher boron contents increase the hardness and strength, but decrease the toughness.