The microstructural evolution and enhanced mechanical properties of in-situ Ti(C, N)-reinforced CoCrFeNiTi high-entropy alloy composites fabricated via mechanical alloying and spark plasma sintering

A new metal-matrix composite, fine Ti(C, N) particles reinforced CoCrFeNiTi high-entropy alloy (HEA), were successfully fabricated via mechanical alloying and spark plasma sintering process. Graphite carbon nitrides (gC3N4) particles and equiatomic CoCrFeNiTi HEA powders were used as the original materials. The microstructural investigations have been carried out with scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM), and the results reveal that the increase in strength can be ascribed to grain refinement and dislocation strengthening, particularly the fine Ti(C, N) particle strengthening. The fracture modes of composites are mainly combination of brittle fracture with ductile fracture. An interesting microstructural feature is that the fine HEA grains are distributed within Ti(C, N) particles forming a core-shell structure, which further improves the fracture toughness of the composites. The final composite (Ti(C, N)/ CoCrFeNiTi HEA) shows exhibits the best combination of compressive strength and fracture toughness, which are 2965 MP and 12.4 MPa m1/2, respectively. The present study not only expands the application field of g-C3N4 but also provides a new idea for the preparation of composites reinforced with Ti(C, N) particles.