Nanoparticles induced intragranular and dislocation substructures in powder bed fusion for strengthening of high-entropy-alloy

In recent years, high entropy alloys (HEAs) have attracted considerable attention because of their excellent mechanical and functional properties. Despite this, as-cast high entropy alloys cannot meet the requirements for structural parts with high strength. Powder bed fusion (PBF) technology and nanoparticle additives are expected to enhance the overall properties of HEAs. We present here an AlN nanoparticle-reinforced high-entropy alloy matrix nanocomposite fabricated by powder bed fusion with excellent mechanical properties. Experimental results demonstrate that the addition of 1 wt% AlN nanoparticles results in an increase in the density of dislocations and subgrain boundaries within the HEA, in turn increasing its yield strength, ultimate tensile strength by 27.7%, 23.9% respectively, while elongation decreases slightly. In addition, the fracture toughness of the AlN/FeNiCrCo composite is greater than that of FeNiCrCo HEA because of the well-balanced combination of strength and ductility. The formation of the substructure of HEA grains was investigated using molecular dynamics (MD) by investigating the effects of rapid melting and solidification during SLM of AlN/FeNiCrCo composite. It is found that during the rapid solidification process, a large number of subgrain boundaries and dense dislocation network structures are formed in the grains due to the heat transfer and the difference in lattice structure between nanoparticles and HEA. These findings agree with the experimental results. The substructures contribute significantly to the composite's strength while maintaining its ductility, which allows it to be more suitable for practical applications.