Heterogenous columnar-grained high-entropy alloys produce exceptional resistance to intermediate-temperature intergranular embrittlement

Abstract

High-entropy alloys (HEAs) strengthened by coherent nanoparticles show great potentials for elevated-temperature structural applications, which however, generally suffer from a severe intergranular embrittlement when tested at intermediate temperatures. In this study, we demonstrated a novel “heterogenous columnar-grained” (HCG) approach that can effectively overcome this thorny problem. Different from the equiaxed counterpart which shows extreme brittleness along grain boundaries at 800 °C, the newly developed HCG-HEA exhibits an exceptionally high resistance to intergranular fractures originating from the unique grain-boundary characters and distributions. The presence of heterogenous columnar grain structure drastically suppresses the crack nucleation and propagation along with boundaries, resulting in an unusually large tensile ductility of ~18.4 % combined with a high yield strength of ~652 MPa at 800 °C. This finding provides a new insight into the innovative design of high-temperature materials with extraordinary mechanical properties.