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

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 degrees 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 similar to 18.4 % combined with a high yield strength of similar to 652 MPa at 800 degrees C. This finding provides a new insight into the innovative design of high-temperature materials with extraordinary mechanical properties. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrated a novel heterogenous columnar-grained (HCG) approach that can effectively overcome the severe intergranular embrittlement issue of high-entropy alloys (HEAs) at intermediate temperatures. The newly developed HCG-HEA exhibits exceptionally high resistance to intergranular fractures and shows a combination of high tensile ductility and yield strength at 800 degrees C. This finding provides a new insight into innovative design of high-temperature materials with extraordinary mechanical properties.