Root inspired in situ interlocked interface for strength and ductility combination of refractory high-entropy alloys/Ni composites by activated sintering

This work proposed a simple bionic-inspired strategy to in situ construct a root-like interfacial interlocked structure in the refractory high-entropy alloys (RHEA) particle-reinforced Ni matrix composites by activated sintering. The results showed that at the RHEA-Ni interface, Ni element preferred to aggregate inside the RHEA near the interface by grain boundaries (GBs) wetting and far away from the interface by GBs prewetting. Subsequently, the Ni-rich liquid-like film crystallized into Ni₃(Ta, Nb), Ni₂(Ta, Nb) phases due to relatively low Gibbs free energy change (ΔG) and high diffusion rate, in situ forming root-like interlocked structure anchored on the RHEA particle. At the root-like interlocked interface, the Ni-Ta intermetallic compounds (IMCs) and BCC phase, serving as alternating hard and soft oriented phases, enhance the interlocked interface hardness and elastic modulus. The finite element method proved that the root-like interlocked structure reduced the demand for interfacial reaction layer strength and the degree of interfacial stress concentration. Compared to the pure Ni bulk, the 10 vol% RHEA/Ni composite obtains 41.8 % and 93.4 % in ultimate tensile strength (UTS) to 509 MPa and yield strength (YS) to 205 MPa, respectively, while maintaining an acceptable elongation of 15.8 %. This work offers a novel approach to in situ synthesize the bionic configuration interface structure for the enhanced interfacial bonding and optimized interfacial stress distribution of the Ni matrix composites.