High strength and ductility high-entropy intermetallic matrix composites reinforced with in-situ hierarchical TiB2 particles

Abstract

The design guided by entropy enables the attainment of superior mechanical properties and further extends the concept of high-entropy alloys to intermetallic systems, thus forming high-entropy intermetallic compounds and even high-entropy intermetallic matrix composites. In this study, a novel high-entropy intermetallic matrix composites incorporating in-situ hierarchical TiB2 particles was successfully synthesized through the spark plasma sintering. This method enables precise control over the microstructure, ensuring uniform distribution of the in-situ formed TiB2 particles within the high-entropy intermetallic matrix. The in-situ formation of TiB2 particles is achieved through a reactive sintering mechanism, which not only contributes to the composite's enhanced mechanical properties but also ensures excellent bonding between the precipitates and intermetallic matrix. The composites were composed of the ordered L12 intermetallic matrix and the hierarchical hexagonal-close-packed TiB2 particles. Due to the L12 intermetallic matrix and the heterogeneous distribution of TiB2 reinforcement, the intermetallic matrix composites demonstrate a high ultimate tensile strength of ∼1400 MPa. The TiB2 play a pivotal role in impeding the propagation of cracks and the collaborate with distinctive disordered interfaces at grain boundaries, ensuring enough ductility. The disordered interfaces, exhibiting an average width in the range of 5 nm–10 nm, possess the capability to delay fracture and promote the strain-hardening rate during plastic deformation. The intermetallic matrix composites overcome the limitations typically associated with conventional intermetallics and offer an excellent strength and ductility balance. These findings are expected to formulate additional strategies for designing in-situ reinforcement-strengthened high-entropy intermetallic matrix composites with exceptional mechanical properties.