Enhanced strength-ductility combinations over a wide temperature range in high-entropy alloys via manipulating the nano-lamellar precipitation behavior

Alloys strengthened by the D0 19 intermetallic phases exhibit considerable promise for high-temperature applications. However, they generally suffer from the inherent brittleness, which seriously limits their widespread use. In this work, we elaborately designed a novel D0 19 -strengthened high-entropy alloy (HEA) featuring the directional lamellar and granular structured (DLGS) precipitation behavior. This new-type DLGS alloy exhibits substantially enhanced strength-ductility synergy over a wide temperature range from room temperature to 900°C in comparison to the conventional non-directional lamellar structured (NDLS) counterpart. Specifically, the DLGS alloy maintains high yield strength of 821, 770, and 670 MPa at room temperature, 700, and 800°C, respectively. More prominently, the ductilities exceed 25 % at all these temperatures, indicating the elimination of the intermediate-temperature embrittlement, which is evident in the NDLS alloys. Systematic microstructural characterizations reveal that temperature-dependent deformation mechanisms are highly correlated with stacking faults (SFs) and deformation twins (DTs) activated at different temperatures. Furthermore, the origins of initiating SFs and DTs in the DLGS alloy are discussed in detail. The introduction of unshearable D0 19 precipitates leads to local stress accumulation at the interface, which further contributes to the formation of SFs and DTs. Meanwhile, these precipitates can also impede boundary mobility and suppress grain growth through the Zener drag effect, thereby increasing the starting temperatures of dynamic recrystallization. This work would offer valuable guidance for designing advanced precipitate-strengthened HEAs with superior mechanical performance toward wide-temperature structural applications.