Multiscale crack deflection overcomes intermediate-temperature brittleness via hierarchical fiber-like structure in a dual nanoprecipitation-strengthened high-entropy alloy fabricated by selective laser melting

Abstract

The rapid synthesis of nanoprecipitation strengthened high-entropy alloys through additive manufacture shows great potential for high-temperature applications, but high-temperature intergranular brittleness limits the efficient structural application, especially in intermediate temperature, i.e., 650 - 900 °C. The current study reported a combinatorial structure, i.e., hierarchical fiber-like structure (HFS) and dual-phase nanoprecipitates (DNP) using selective laser melting followed by annealing, exhibiting an exceptional high-temperature strength-plasticity synergy. The L12- and L21-type nanoprecipitates with superior thermal stability promote precipitation strengthening at elevated temperatures. Meanwhile, the presence of HFS persistently contributes to the plasticity through grain boundary sliding accompanied by multiscale crack deflection along with boundaries inhibiting final fracture. The representative plastic anisotropy facilitates the engineering application of this combined structure in more extreme conditions. This current innovative design of high-temperature structural materials is potentially applied to other additively manufactured alloys and opens a pathway for further optimization of thermostable alloy properties.