Synergistic enhancement of the strength and ductility of high-entropy alloy at high temperatures via multiple heterogeneous microstructure modulation

Abstract

High-entropy alloys (HEAs) commonly exhibit significant strength deficiencies and intermediate temperature brittleness (ITB) in the temperature range of 650–750 °C, which greatly restricts their practical use in safety engineering. In this study, a novel coherent face-centered cubic (FCC)/L1₂ HEA with multiple heterogeneous microstructures, including grain size and L1₂ precipitates was developed. The newly designed HEA demonstrates outstanding mechanical properties across a broad temperature spectrum (25–750 °C). At ambient temperature, the HEA displays a remarkable tensile strength of up to 1700 MPa and a tensile ductility of 15.9%. Notably, the HEA exhibits an impressive yield strength of 1 GPa in the intermediate temperature range, with minimal loss of ductility under high tensile stresses. The presence of the primary L1₂ phase effectively stabilizes the grain boundaries (GBs), inhibiting crack propagation and oxygen diffusion along them. This mechanism prevents the formation of brittle phases at the GBs, thereby protecting the GBs and mitigating the issue of ITB. As a result, the HEA exhibits an intermediate temperature tensile strain surpassing 14%. The heterogeneous structural modulation strategy offers valuable insights into the tailored design of high-performance HEAs for advanced high-temperature structural applications in urgent demand.