High-entropy alloy nanocrystals with low-angle grain boundary for superb plastic deformability and recoverability

High entropy alloys (HEAs) have received widespread attention as structural and functional materials owing to their large atomic lattice distortion and vast compositional space. Recently, nanoscale HEAs have been proven to exhibit exceptional combinations of mechanical properties, thermal stability, and oxidation resistance. The structural and functional stabilities of nanoscale HEAs under practical loading conditions are vital to their applications. Here, based on a grain boundary (GB) design strategy, we introduced custom-designed low-angle GBs (LAGBs) into quinary face-centered cubic HEA nanocrystals, intending to improve the mechanical stability of nanoscale HEAs under external loading through molecular dynamics simulations. Using CuCoNiPdFe and FeNiCrCoCu HEAs as examples, we reveal two distinct LAGB-mediated deformation behaviors of nanoscale HEAs, which stem from the differences in lattice distortion and shear modulus of the materials. In the case of CuCoNiPdFe, the LAGB is composed of separate Shockley dislocations, endowing the material with extraordinary plastic deformability and structural stability. In the case of FeNiCrCoCu, the LAGB contains a series of parallel stacking faults crosslinked immobile dislocation segments, which severely damages the plastic deformability of the material. Based on the atomistic understanding of LAGB structure and migration behavior, we have screened out a range of material systems with small lattice distortion and shear modulus, realizing superb plastic deformability and structural recoverability in HEAs designed with LAGBs. These findings promote the understanding of GB-mediated deformation mechanisms in HEAs and provide insights into the structural and composition design of HEA nanomaterials.