Could an amorphous binder Co phase improve the mechanical properties of WC-Co? A study of molecular dynamics simulation

The trade-off effect between strength and fracture toughness typically observed in composites is challenging for the design and development of novel materials. An amorphous state can impede the trade-off effect of strength and fracture toughness, improving the mechanical properties of composites. Choosing the typical tungsten carbide-cobalt (WC-Co) cemented carbides as examples, where the amorphous binder phase was found, the impact of binder phase Co on the mechanical properties was further investigated by molecular dynamics (MD) simulations. The mechanical behavior and microstructure evolution of the WC-Co composite in the uniaxial compression and tensile processes were studied at different temperatures. The results showed that Young's modulus and ultimate compressive/tensile strengths were higher in WC-Co with amorphous Co, and the ultimate compressive/tensile strengths increased by about 11-27% compared to the samples with crystalline Co. Amorphous Co not only restricts the propagation of voids and cracks but also delays fractures. The relationship between temperatures and deformation mechanisms was also investigated, in which the tendency of strength to decrease with increasing temperature was clarified.